Won't idle.....

Posted by: TBM

Won't idle..... - 11/01/19 04:43 PM

Now I seem to have a solution to the poor starting, I've got another interesting problem.

On the last three occasions, after I filled the petrol tank (I usually go almost 'brimful') she refuses ti idle. Starts fine, but when I get to a roundabout/junction/trafficlight etc the revs drop and then she stalls.

Starts again fine, and runs OK until the next junction etc. This happens for about 20 miles, and then she cures herself.

Initially I was thinking that tank debris was being stirred up and blocking the idle jet, but the problem is far too uniform and self rectifying for that.

My next thought is a slightly blocked breather vent in the fuel cap. My thinking is that there is much more chance of a vacuum occuring in the tank when she's full, and this affects the fuel flow. At high revx the draw of the fuelpump is strong enough to overcome the vacuum, and when she stalls, it gives the tank a second or two to equalise pressure so she starts OK. Once a couple of litres have been burnt off, the space is too great for a vacuum to occur.

Does that sound plausible? Any other suggestions? I will give the fuel cap a blow through with the airline, although am tempted to buy a lockable one....
Posted by: Paul F

Re: Won't idle..... - 11/01/19 06:57 PM

Does the carburettor have a solenoid operated anti-run-on valve?

Experienced similar symptoms on our 1985 car with a loose connection on this valve - but cannot see why this would be linked to filling the tank as in your case. A zero cost option is to check the wire to the carburettor - if there is one.

Do you get a whoosh of air when you remove the cap? If not, unlikely to be your blocked breather option (stress on unlikely - so still possible).

The self rectifying bit is mystifying.
Posted by: TBM

Re: Won't idle..... - 11/01/19 07:07 PM

No, carb is a basic twin choke Weber - nothing electrical on it.

The 'slightly blocked' breather idea came to me on the way home, and by the time I got home, she was back running perfectly.

However, if it was blocked enough to get the 'whoosh' I think I'd struggle to get her running at all - I once had fun with a bike - on the way to a bike rally, she cut out. Took the tank bag off, got my tools out, checked plugs, fuses etc and all seem fine. She'd then start, I'd get 10 miles down the road and same problem. This happened four times until I realised the tankbag was blocking the cap breather......
Posted by: Graham, G4FUJ

Re: Won't idle..... - 11/01/19 10:28 PM

It does sound like a breather problem.
Posted by: John V6

Re: Won't idle..... - 12/01/19 09:30 AM

+1. It does to me too.
Posted by: Gambalunga

Re: Won't idle..... - 12/01/19 09:35 AM

It is not going to be your problem but in general terms it is not recommended to "brim" the tank when you fill it. Most recommend to stop at the first cut of of the bowser.

In the case of cars that are fitted with carbon canisters the overfilling of the fuel tank can cause raw fuel to contaminate the carbon canister. This can cause problems. In theory the fuel should be blocked from entering the canister by a valve but this may not always work or it may jam. The raw fuel in the canister may provide too rich a mixture until it is purged because the canister is normally purged of fumes by a connection to the intake manifold.
Posted by: Richard Wood

Re: Won't idle..... - 12/01/19 01:48 PM

Had this on a small capacity single cylinder bike in freezing conditions. The petrol cap breather hole was blocked by ice.
Posted by: IvorMog

Re: Won't idle..... - 12/01/19 02:14 PM

I might have missed some of your earlier posts and threads so forgive me if you've already covered this.

Have you had the carb rebuilt or at least thoroughly cleaned since you've had the car

There are all sorts of things that could cause those symptoms in the carb such as sticky floats or gummed up jets etc.

At least if the carb has been rebuilt you can rule out carb issues.
Posted by: TBM

Re: Won't idle..... - 12/01/19 02:53 PM

Yep, carb was cleaned out by Allon White when it first happened.

The uniformity of the problem and then the 'self repair' points me away from the carb,
Posted by: britmog

Re: Won't idle..... - 12/01/19 04:14 PM

Rule number 1:

Never fill the fuel tank beyond the first shut off of the fuel pump on any vehicle of any age.

Such a common mistake to get an extra half gallon into the tank.
Posted by: TBM

Re: Won't idle..... - 12/01/19 04:28 PM

Originally Posted By britmog
Rule number 1:

Never fill the fuel tank beyond the first shut off of the fuel pump on any vehicle of any age.

Such a common mistake to get an extra half gallon into the tank.


Can I ask why?

I always brim my bike tanks and usually the cars. In fact, with the Morgan, if I rely on auto shut off I tend to get a blow back with chucks petrol over the back of the car.
Posted by: britmog

Re: Won't idle..... - 12/01/19 07:22 PM

Can restrict expansion in the fuel tank, also can cause issues with the vapor recovery system. Certainly the M3Ws do not like being filled to the brim, they stutter and stall for the first 5 to 10 miles. Its sort of the same principle as not letting it go below half full too often if it has an internal fuel pump.
Posted by: TBM

Re: Won't idle..... - 12/01/19 07:49 PM

Originally Posted By britmog
Can restrict expansion in the fuel tank, also can cause issues with the vapor recovery system. Certainly the M3Ws do not like being filled to the brim, they stutter and stall for the first 5 to 10 miles. Its sort of the same principle as not letting it go below half full too often if it has an internal fuel pump.


Don't think any of my vehicles have a vapour recovery system smile

The M3W sounds rather frustrating! If you can't fill the tank properly and only use half a tank, then you'd be spending more time in the petrol station than driving. Sounds like a bit of a design fault - my BMW K75 has an internal fuel pump and can fill it brim full and run till near empty with no issues - gives a useful 200 miles between fill ups.
Posted by: britmog

Re: Won't idle..... - 13/01/19 04:02 PM

Everyone to their own.
Posted by: Gambalunga

Re: Won't idle..... - 13/01/19 04:44 PM

Originally Posted By TBM
Originally Posted By britmog
Rule number 1:

Never fill the fuel tank beyond the first shut off of the fuel pump on any vehicle of any age.

Such a common mistake to get an extra half gallon into the tank.


Can I ask why?

I always brim my bike tanks and usually the cars. In fact, with the Morgan, if I rely on auto shut off I tend to get a blow back with chucks petrol over the back of the car.

If you look down the filler of most modern bikes you will find a tube that extends part of the way in to the tank. This is specifically designed to leave some space above the "full" level and to discourage you from overfilling the tank. There is a small air bleeder hole in the top of said tube and if you slowly insisted I suppose you could fill the tank right up but normally the would be a litre or more of air space in the top of the tank. USA models have a breather tube that runs to a carbon canister but unless something is changed in the most recent Euro spec the EU models vent through the fuel cap. You get a nice vacuum build up in the tank if someone accidentally fits a USA spec fuel cap to an EU fuel tank smile Don't ask me how I know wink
Posted by: TBM

Re: Won't idle..... - 13/01/19 05:31 PM

Originally Posted By Gambalunga
If you look down the filler of most modern bikes


That'll be it. My 'youngest' bike is over 20yrs old smile
Posted by: sospan

Re: Won't idle..... - 13/01/19 09:05 PM

On my 2002 Plus8 I overfilled by going past the first pump cut off. This caused the ecu to detect a “evap cannister fault” that triggered the MIL light. I reset it with the Maxiscan and since then stopped adding fuel at the first pump cutoff. Fault has never returned. No actual engine problems, just the fault code registering.
Posted by: TBM

Re: Won't idle..... - 14/01/19 07:19 AM

Back to the drawing board.....

Started fine this morning, first 20 miles (mixture of fast road and 30mph stuff) all fine.

Got to MK and third roundabout in she stalled at idle and continued to do so at each one till I got to work (starts immediately after each stall). Removed the fuel cap when I got to work, started fine, but wouldn't idle. She will idle with about 1/3 choke.

Any thoughts? Done about 50 mile so far on this tank full.
Posted by: TBM

Re: Won't idle..... - 14/01/19 07:25 AM

Didn't help my frustration that I also lost 'dip beam' half way to work! Hopefully just a lose connection somewhere. Side and Main are still ok so I don't think it's related to the problem above!
Posted by: TBM

Re: Won't idle..... - 14/01/19 07:51 AM

Wonder if it's problems with the vacuum pipe?
Posted by: Gambalunga

Re: Won't idle..... - 14/01/19 07:55 AM

The dip beam problem could be the switch on the steering column stalk. Some people fit relays for the headlights to reduce the current running through the switch and thereby protecting it.

Have you checked the fuel filters? It may be that you have had some dirty or water contaminated fuel at some time.

I'm not familiar with the Weber but I would have thought there should be a small filter on the fuel input plus a filter in the fuel line. If there is a drain plug on the fuel float bowl you could try draining it in case there is water or sediment in the float bowl.
Posted by: TBM

Re: Won't idle..... - 14/01/19 08:05 AM

Originally Posted By Gambalunga
The dip beam problem could be the switch on the steering column stalk. Some people fit relays for the headlights to reduce the current running through the switch and thereby protecting it.


I upgraded to Halogens a couple of weeks ago, so that may well be the case - possibly burnt the switch out. I'll check tonight. I have a spare relay so will pop that in and bypass the switch pro tem.

Originally Posted By Gambalunga
Have you checked the fuel filters? It may be that you have had some dirty or water contaminated fuel at some time.


It was all done by Allon White just before christmas - new filter and carb clean, but if refilling the tank is stirring up debris then it'll block up again. I'll fit a new filter and clean the gauze on the fuel pump. If it was a bike, I'd whip the tank off and give it a flush and a treatment!

At least I can now discount the 'uniformity' of the problem - that was probably just coincidence!
Posted by: John V6

Re: Won't idle..... - 14/01/19 09:19 AM

Try cleaning out the idle jet.
Posted by: TBM

Re: Won't idle..... - 14/01/19 09:23 AM

Originally Posted By John V6
Try cleaning out the idle jet.


Just 'googled' and they look are fairly accessible and easy to remove, so will have a crack at that too.
Posted by: CooperMan

Re: Won't idle..... - 14/01/19 09:37 AM

Originally Posted By TBM
Back to the drawing board.....

Started fine this morning, first 20 miles (mixture of fast road and 30mph stuff) all fine.

Got to MK and third roundabout in she stalled at idle and continued to do so at each one till I got to work (starts immediately after each stall). Removed the fuel cap when I got to work, started fine, but wouldn't idle. She will idle with about 1/3 choke.

Any thoughts? Done about 50 mile so far on this tank full.



TBM, looking at the age of your Mog, I would suggest you replace your Condenser as they are known to fail erratically when hot (assuming you're still on points & condenser ignition)
Posted by: Graham, G4FUJ

Re: Won't idle..... - 14/01/19 09:41 AM

Beat me to it Jon! smile
Posted by: TBM

Re: Won't idle..... - 14/01/19 09:49 AM

Originally Posted By CooperMan
TBM, looking at the age of your Mog, I would suggest you replace your Condenser as they are known to fail erratically when hot (assuming you're still on points & condenser ignition)


Good call.

I'll get that sorted as well. Ultimately will change to an electronic but that'll in a couple of 'pay days'!
Posted by: Gambalunga

Re: Won't idle..... - 14/01/19 11:27 AM

Yes. I wondered about an electrical problem but discounted it because it starts again straight away. So long that I haven't had to worry about points ignition that I forgot about the condenser. They cost so little that it is worthwhile changing it if only to eliminate that as the source of the problem.
Posted by: TBM

Re: Won't idle..... - 14/01/19 11:37 AM

Originally Posted By Gambalunga
Yes. I wondered about an electrical problem but discounted it because it starts again straight away. So long that I haven't had to worry about points ignition that I forgot about the condenser. They cost so little that it is worthwhile changing it if only to eliminate that as the source of the problem.


That's what's been frustrating me - if she struggled to start, then it would be easier to diagnose, but she springs back into life virtually instantly - on occasions I've just dropped the clutch and bumped her back into life very easily.

My plan so far:

Change Fuel Filter
Clean fuel pump gauze
Remove and clean idle jets.
Replace Condenser (or if I can sneak it past the Mrs, buy an electronic ignition and new coil smile )
Posted by: Paul F

Re: Won't idle..... - 14/01/19 01:06 PM

That looks like a good solid plan.
Posted by: britmog

Re: Won't idle..... - 14/01/19 03:32 PM

For the sake of being boorish, carry out each corrective measure separately or you will never know what the actual problem was.
Posted by: TBM

Re: Won't idle..... - 14/01/19 05:37 PM

Originally Posted By britmog
For the sake of being boorish, carry out each corrective measure separately or you will never know what the actual problem was.


I think I'll start with cleaning the fuel systems - the problam is that the issue is fairly sporadic so might take weeks
On the 25 mile journey home tonight the problem continued almost immediately I put the choke in and persisted all the way home. I found that if I pulled the choke out about 2cm prior to each potential stop, she would keep running (albeit a slightly quicker tickover).

Just jerry rigged the headlights to bypass the broken column switch which took about an hour (I'm working on the drive in the dark!), started her up to turn her round on the drive and she's ticking over normally again!!!

The fact that she'll run on choke still makes me lean more towards a fuelling issue, rather that electrical but I'm baffled by her ability to 'self fix'. Usually a blocked jet in a bike means a carb strip and fettle.....
Posted by: Paul F

Re: Won't idle..... - 14/01/19 06:20 PM

Sounds like a small bit of crud flapping about in the idle jet - assuming that your choke trick is engaging the fast idle which (IIRC) is main jet.

If the car has had little use prior to your giving it a good home, then there could well be issues in the fuelling system. There may even be deterioration of some of the pipes. A friend had an issue with an MG Midget that kept losing power - transpired the fuel hose near the tank had broken down inside but still looked in good order from the outside.

Good luck.
Posted by: TBM

Re: Won't idle..... - 14/01/19 06:28 PM

Yes, I'm pretty sure that's the main problem - tank crud. Thankfully the main run of fuel pipe is copper, and everything under the engine bay is new, but I'll have a look at the last bit between tank and copper.

I've read about a 'fix' where a bit of stainless fly screen mesh is fitted over the tank pick up pipe - however the bits must be pretty tiny if they're getting through the filter and the fuel pump gauze so I doubt they'd be stopped by the mesh.

I might see if I can get a better quality filter than the plastic ones being fitted.
Posted by: britmog

Re: Won't idle..... - 14/01/19 08:19 PM

When she idles without the use of choke, etc. the revs are at the normal level aren't they? Just making sure that the accelerator stop screw has not shifted or is loose. Also just check that the accelerator cable is moving freely and everything returns to where it should on de-acceleration.
Posted by: CooperMan

Re: Won't idle..... - 14/01/19 08:30 PM

Originally Posted By TBM
Originally Posted By CooperMan
TBM, looking at the age of your Mog, I would suggest you replace your Condenser as they are known to fail erratically when hot (assuming you're still on points & condenser ignition)


Good call.

I'll get that sorted as well. Ultimately will change to an electronic but that'll in a couple of 'pay days'!


TBM, don't pay silly money for some of the electronic conversions on the market

I use one by Accuspark that gets rid of the points & condenser, fits inside the existing Dizzy cap and uses your existing coil, only about £30, half an hour to fit and you can still set the timing up with a basic timing light
Posted by: TBM

Re: Won't idle..... - 14/01/19 08:37 PM

Originally Posted By britmog
When she idles without the use of choke, etc. the revs are at the normal level aren't they? Just making sure that the accelerator stop screw has not shifted or is loose. Also just check that the accelerator cable is moving freely and everything returns to where it should on de-acceleration.


When idling on the choke, she is idling faster than usual. I did originally consider that the idle screw was slowly unscrewing but I'm pretty sure it's not - I set it up nicely (and the idle mixture screw) a couple of weeks ago when she was running nicely. I've just gone out and checked - it looks like it's still in the same place, but have wound it on about 1/8 of a turn so the screw is perfectly vertical - will be easier to check if it's moved.
Posted by: TBM

Re: Won't idle..... - 14/01/19 08:40 PM

Originally Posted By CooperMan
TBM, don't pay silly money for some of the electronic conversions on the market

I use one by Accuspark that gets rid of the points & condenser, fits inside the existing Dizzy cap and uses your existing coil, only about £30, half an hour to fit and you can still set the timing up with a basic timing light


Yep - I was originally looking at Aldon stuff but then remembered simonbbc who I used on my Land Rovers about 10 years ago - have got a new Powerspark unit, non ballast coil and rotor for under £60! Can easily sneak that past the Mrs.... smile smile
Posted by: tmg513

Re: Won't idle..... - 14/01/19 09:34 PM

It could be a worn needle valve allowing the carb to flood slightly. Have a look at its tip and make sure it's perfectly conical.
Posted by: TBM

Re: Won't idle..... - 14/01/19 09:41 PM

Originally Posted By tmg513
It could be a worn needle valve allowing the carb to flood slightly. Have a look at its tip and make sure it's perfectly conical.


The card has only done 600 miles from new, so shouldn't be worn. If the other fixes don't work, I'll start digging deeper.
Posted by: britmog

Re: Won't idle..... - 14/01/19 10:09 PM

So the idle issues have occurred since you "set up" the idle mixture screw and throttle screw a few weeks ago?
Posted by: TBM

Re: Won't idle..... - 14/01/19 10:21 PM

Originally Posted By britmog
So the idle issues have occurred since you "set up" the idle mixture screw and throttle screw a few weeks ago?


No, they've been occurring since I bought her in Novemeber.

Last time it happened (before this most recent event) I wound the tickover right up to try and stop her from stalling. When she cleared herself the idle was really high, so I reduced the idle and set the mixture. Had two clear weeks, until the latest fill up....
Posted by: Ray

Re: Won't idle..... - 14/01/19 10:39 PM

Have you tried the Italian tune up.... Some times it does work.
Posted by: Gambalunga

Re: Won't idle..... - 14/01/19 11:08 PM

Originally Posted By TBM
The card has only done 600 miles from new, so shouldn't be worn. If the other fixes don't work, I'll start digging deeper.

I assume that is automatic predictive text error and you actually meant "The car has only done 600 miles from new". If so it means it has been sitting unused in a garage for an awful long time. In a case like this you can get corrosion in the fuel tank due to condensed water. I have never done it but I believe that the fuel tank can be removed from under the car. It might be an idea to keep in mind the possibility of removing it and giving it a good flush and maybe a treatment or alternatively put a new tank in the budget.

The fact that it is cutting out at idle tends to eliminate the possibility of an actual fuel line blockage or it would be running lean or cutting out under load. If you have an exhaust leak that is heating the fuel line or the fuel line has bee routed too close to the exhaust it could be causing vaporisation in the fuel line.

If it is a fuel problem it is either too rich at idle (black exhaust smoke or plugs fouling) or too lean. Fuel level too high or too low or either the needle jet, the float, or the idle jet giving problems.

Have you fitted new plugs, plug caps and leads? The old ones could well be faulty. Losing the spark through a faulty plug lead is not uncommon. If still original they have probably deteriorated over the years.

A new condenser, new plugs, caps and plug leads won't cost a fortune and will pretty much eliminate ignition problems (check for any poor, corroded, or loose wiring connections too.

If that is not the problem you have to chase down the possibility of a fuelling issue.

When you get it all sorted you will have a wonderful low mileage classic.
Posted by: +8Rich

Re: Won't idle..... - 14/01/19 11:20 PM

Originally Posted By Gambalunga
Originally Posted By TBM
The card has only done 600 miles from new, so shouldn't be worn. If the other fixes don't work, I'll start digging deeper.

I assume that is automatic predictive text error and you actually meant "The car has only done 600 miles from new". If so it means it has been sitting unused in a garage for an awful long time. In a case like this you can get corrosion in the fuel tank due to condensed water. I have never done it but I believe that the fuel tank can be removed from under the car. It might be an idea to keep in mind the possibility of removing it and giving it a good flush and maybe a treatment or alternatively put a new tank in the budget.

The fact that it is cutting out at idle tends to eliminate the possibility of an actual fuel line blockage or it would be running lean or cutting out under load. If you have an exhaust leak that is heating the fuel line or the fuel line has bee routed too close to the exhaust it could be causing vaporisation in the fuel line.

If it is a fuel problem it is either too rich at idle (black exhaust smoke or plugs fouling) or too lean. Fuel level too high or too low or either the needle jet, the float, or the idle jet giving problems.

Have you fitted new plugs, plug caps and leads? The old ones could well be faulty. Losing the spark through a faulty plug lead is not uncommon. If still original they have probably deteriorated over the years.

A new condenser, new plugs, caps and plug leads won't cost a fortune and will pretty much eliminate ignition problems (check for any poor, corroded, or loose wiring connections too.

If that is not the problem you have to chase down the possibility of a fuelling issue.

When you get it all sorted you will have a wonderful low mileage classic.


Peter, reading that back I think TBM maybe meant that the carb has only got 600 miles on it from new so has been replaced recently.
I maybe wrong.
Posted by: pandy

Re: Won't idle..... - 15/01/19 12:09 AM

Won't idle ?

Get it a job with the council hide
Posted by: morgan_75

Re: Won't idle..... - 15/01/19 02:58 AM

A vacuum leak would cause poor idle and make it impossible to tune low speed. A blockage in the idle circuit will also make it impossible to tune. You might not notice either of these at higher engine speeds.
Posted by: TBM

Re: Won't idle..... - 15/01/19 07:05 AM

Originally Posted By Ray
Have you tried the Italian tune up.... Some times it does work.


Funny you should say that - first time it happened I was in the Cotswolds, it lasted for a couple of days and I was getting VERY frustrated - took a very fast blat up the M5 to Worcester to see my folks, and it cleared..... (I reckon it was as soon as she caught sight of the Malverns!)
Posted by: TBM

Re: Won't idle..... - 15/01/19 07:09 AM

Originally Posted By +8Rich
Originally Posted By Gambalunga
Originally Posted By TBM
The card has only done 600 miles from new, so shouldn't be worn. If the other fixes don't work, I'll start digging deeper.

I assume that is automatic predictive text error and you actually meant "The car has only done 600 miles from new". If so it means it has been sitting unused in a garage for an awful long time. In a case like this you can get corrosion in the fuel tank due to condensed water. I have never done it but I believe that the fuel tank can be removed from under the car. It might be an idea to keep in mind the possibility of removing it and giving it a good flush and maybe a treatment or alternatively put a new tank in the budget.

The fact that it is cutting out at idle tends to eliminate the possibility of an actual fuel line blockage or it would be running lean or cutting out under load. If you have an exhaust leak that is heating the fuel line or the fuel line has bee routed too close to the exhaust it could be causing vaporisation in the fuel line.

If it is a fuel problem it is either too rich at idle (black exhaust smoke or plugs fouling) or too lean. Fuel level too high or too low or either the needle jet, the float, or the idle jet giving problems.

Have you fitted new plugs, plug caps and leads? The old ones could well be faulty. Losing the spark through a faulty plug lead is not uncommon. If still original they have probably deteriorated over the years.

A new condenser, new plugs, caps and plug leads won't cost a fortune and will pretty much eliminate ignition problems (check for any poor, corroded, or loose wiring connections too.

If that is not the problem you have to chase down the possibility of a fuelling issue.

When you get it all sorted you will have a wonderful low mileage classic.


Peter, reading that back I think TBM maybe meant that the carb has only got 600 miles on it from new so has been replaced recently.
I maybe wrong.


Correct - it's the carb.

However, although she's done about 82000 in total, she's only done about 600 in the last 6 years, so I think there will be a lot of crud in the tank getting stirred up.

I've have priced up a replacement tank as a last resort!
Posted by: TBM

Re: Won't idle..... - 15/01/19 07:14 AM

First of all, a big thank you for all the help and advice - very much appreciated.

Frustratingly, she started perfectly last night after I'd got the headlights working, and she did the 25 miles commute to work without issue......
Posted by: TBM

Re: Won't idle..... - 15/01/19 07:15 AM

Originally Posted By TBM
First of all, a big thank you for all the help and advice - very much appreciated.

Frustratingly, she started perfectly last night after I'd got the headlights working, idling nicely and then this morning she did the 25 miles commute to work without issue......
Posted by: John V6

Re: Won't idle..... - 15/01/19 08:48 AM

You have obviously scared her into action.
Posted by: CooperMan

Re: Won't idle..... - 15/01/19 09:02 AM

TBM, are your fuel hoses the later Ethanol resistant ones ? if you're still on basic rubber ones they will be gradually dissolving from the inside

I may be worth fitting a cheap clear plastic fuel filter in the line (near the carb) and see what it collects
Posted by: TBM

Re: Won't idle..... - 15/01/19 09:09 AM

Originally Posted By CooperMan
TBM, are your fuel hoses the later Ethanol resistant ones ? if you're still on basic rubber ones they will be gradually dissolving from the inside

I may be worth fitting a cheap clear plastic fuel filter in the line (near the carb) and see what it collects


They are new - fitted by Allon White in the last couple of months.

There's a fuel filter just before the fuel pump, and there's also the gauze in the pump.

I'll see if I can find a clear one - most of them are the white plastic. I might get one of the clear glass 'cleanable' ones.
Posted by: TBM

Re: Won't idle..... - 15/01/19 09:31 AM

Originally Posted By John V6
You have obviously scared her into action.


She's very lucky she was expensive, and I've 'calmed' with age. A couple of my bikes have large fist dents in the tank where frustration has got the better of me.......
Posted by: tmg513

Re: Won't idle..... - 15/01/19 10:07 AM

Originally Posted By TBM
Back to the drawing board.....

Started fine this morning, first 20 miles (mixture of fast road and 30mph stuff) all fine.

Got to MK and third roundabout in she stalled at idle and continued to do so at each one till I got to work (starts immediately after each stall). Removed the fuel cap when I got to work, started fine, but wouldn't idle. She will idle with about 1/3 choke.

Any thoughts? Done about 50 mile so far on this tank full.

Since this wasn't after you'd just filled it, if she'll idle with choke could this point to to a weak mixture? Could a gasket have failed/perished on the carb and caused an air leak?
Posted by: TBM

Re: Won't idle..... - 15/01/19 10:55 AM

Originally Posted By tmg513
Originally Posted By TBM
Back to the drawing board.....

Started fine this morning, first 20 miles (mixture of fast road and 30mph stuff) all fine.

Got to MK and third roundabout in she stalled at idle and continued to do so at each one till I got to work (starts immediately after each stall). Removed the fuel cap when I got to work, started fine, but wouldn't idle. She will idle with about 1/3 choke.

Any thoughts? Done about 50 mile so far on this tank full.

Since this wasn't after you'd just filled it, if she'll idle with choke could this point to to a weak mixture? Could a gasket have failed/perished on the carb and caused an air leak?


She ran fine this morning! Very frustrating.
Posted by: Gambalunga

Re: Won't idle..... - 15/01/19 11:00 AM

Does it have vacuum boosted brakes? The problem could be air intake from a poor connection, leaking vacuum line or a leaking diaphragm.
Posted by: TBM

Re: Won't idle..... - 15/01/19 11:07 AM

Originally Posted By Gambalunga
Does it have vacuum boosted brakes? The problem could be air intake from a poor connection, leaking vacuum line or a leaking diaphragm.


No, non servo.
Posted by: britmog

Re: Won't idle..... - 15/01/19 03:40 PM

How full was the tank for the well behaved 25 mile drive? Hope she remains well behaved for you.
Posted by: TBM

Re: Won't idle..... - 15/01/19 04:35 PM

Originally Posted By britmog
How full was the tank for the well behaved 25 mile drive? Hope she remains well behaved for you.


I'm about 100 mile into the tank, so just over 2/3ish full.

Fingers crossed!
Posted by: TBM

Re: Won't idle..... - 15/01/19 08:41 PM

Left work, went to the shops to get some dinner, then back to work for a meeting. No issues, idled beautifully.

Drove home 25 miles. No issues, idled beautifully.

Will wait for the fun to start again next fill up.....
Posted by: britmog

Re: Won't idle..... - 15/01/19 09:21 PM

Don't overfill tank and see how she performs.
Posted by: TBM

Re: Won't idle..... - 15/01/19 09:54 PM

Originally Posted By britmog
Don't overfill tank and see how she performs.


I'll try! As I said previously, if I wait for 'auto' shut off I get a big blow back out of the filler all over the back of the car. I have to do it slowly by sight - but I'll stop as soon as I can see petrol in the tube and see what happens.
Posted by: tmg513

Re: Won't idle..... - 15/01/19 10:30 PM

Originally Posted By TBM
Originally Posted By britmog
Don't overfill tank and see how she performs.


I'll try! As I said previously, if I wait for 'auto' shut off I get a big blow back out of the filler all over the back of the car. I have to do it slowly by sight - but I'll stop as soon as I can see petrol in the tube and see what happens.

Mine can overflow like that if I wait for the click. I always fill it right to the brim and have never had a problem.
Posted by: TBM

Re: Won't idle..... - 16/01/19 07:53 AM

Originally Posted By tmg513
Mine can overflow like that if I wait for the click. I always fill it right to the brim and have never had a problem.


Glad it's not just me:)
Posted by: Graham, G4FUJ

Re: Won't idle..... - 16/01/19 08:27 AM

Originally Posted By tmg513
Originally Posted By TBM
Originally Posted By britmog
Don't overfill tank and see how she performs.


I'll try! As I said previously, if I wait for 'auto' shut off I get a big blow back out of the filler all over the back of the car. I have to do it slowly by sight - but I'll stop as soon as I can see petrol in the tube and see what happens.

Mine can overflow like that if I wait for the click. I always fill it right to the brim and have never had a problem.

Same with my '76.
The '93 is different (early Zetec) and is even slower to fill. I don't brim it.
Posted by: TBM

Re: Won't idle..... - 16/01/19 09:26 AM

The auto shut off was originally created so that you didn't have to stand and hold the nozzle while filling the tank - potentially you could go off and do other things while filling (like have a fag smile ). I'm sure you remember the old pumps having that little clip so you could lock the handle in place (now removed in the UK).

I think it's entered 'folklore' a little that it's to do with cars/tanks/emission systems - although that's not to say that some cars don't like being brimmed.
Posted by: Graham, G4FUJ

Re: Won't idle..... - 16/01/19 09:53 AM

Many modern cars have a flexible inner tank (plus the likes of carbon canisters / vapour recovery). Those inner tanks should not be overfilled (my last few "moderns" all had warnings in the handbook about stopping after the second auto shutoff).

Just another thought - you possibly have a recirc line (excess fuel returned to fuel tank). May be worth a check.
Posted by: Ray

Re: Won't idle..... - 16/01/19 09:54 AM

Originally Posted By tmg513
Originally Posted By TBM
Originally Posted By britmog
Don't overfill tank and see how she performs.


I'll try! As I said previously, if I wait for 'auto' shut off I get a big blow back out of the filler all over the back of the car. I have to do it slowly by sight - but I'll stop as soon as I can see petrol in the tube and see what happens.

Mine can overflow like that if I wait for the click. I always fill it right to the brim and have never had a problem.
. You soon learn not to stand behind the back panel, unless you enjoy paddling in petrol.
Posted by: TBM

Re: Won't idle..... - 16/01/19 10:15 AM

Originally Posted By Graham, G4FUJ
Just another thought - you possibly have a recirc line (excess fuel returned to fuel tank). May be worth a check.


No - thankfully just a single line.

The fact that she's playing up hot and cold, start of a journey and end of a journey, full tank and 3/4 tank and then fixing herself, points me towards a 'mechanical' issue rather than an electrical issue.

That said, when I have the problem, she the fact that she stills runs perfectly above idle, and accelerates well, and will idle with a little choke makes me think that the fuel pump, fuel line and carb is OK.

I'm going back to my original thought (prior to the cap breather) that due to lack of use, the tank is full of crap and teeny bits are making through the filter and fuel pump gauze and gumming up the idle jet. I might get a spare to carry round so I can try a quick roadside swap next time it happens.

Hopefully, with time and a few filters, everything will get flushed through!
Posted by: tmg513

Re: Won't idle..... - 16/01/19 10:33 AM

Originally Posted By TBM
Originally Posted By Graham, G4FUJ
Just another thought - you possibly have a recirc line (excess fuel returned to fuel tank). May be worth a check.


No - thankfully just a single line.

The fact that she's playing up hot and cold, start of a journey and end of a journey, full tank and 3/4 tank and then fixing herself, points me towards a 'mechanical' issue rather than an electrical issue.

That said, when I have the problem, she the fact that she stills runs perfectly above idle, and accelerates well, and will idle with a little choke makes me think that the fuel pump, fuel line and carb is OK.

I'm going back to my original thought (prior to the cap breather) that due to lack of use, the tank is full of crap and teeny bits are making through the filter and fuel pump gauze and gumming up the idle jet. I might get a spare to carry round so I can try a quick roadside swap next time it happens.

Hopefully, with time and a few filters, everything will get flushed through!

Mine's got a drain plug on the bottom of the tank. Might be worth draining it when you get low to see what comes out.
Posted by: TBM

Re: Won't idle..... - 16/01/19 11:01 AM

Originally Posted By tmg513
Mine's got a drain plug on the bottom of the tank. Might be worth draining it when you get low to see what comes out.


Good plan, thank you. Worth sacrificing a few litres. I can give her a good 'sloshing' before hand too.
Posted by: sospan

Re: Won't idle..... - 16/01/19 02:38 PM

I had a fuel problem on my 1993 4/4. It was the pump. While renewing it I decided to check the whole system. I drained the tank using the drain plug. Filtered the fuel and saw crud in it. So, I flushed the tank. Next I fitted a serviceable glass filter between tank and new pump, put new flexible pipes. New filter under the bonnet. Used Millers additive in the first few tankfulls to hopefully flush clean the solid pipes and injectors. Car went really well after that.
The lesson, I think, is that the car was 20+ years old so the fuel system was due for a bit of refurb. Luckily the tank had the drain plug which meant draining/flushing was easier. As a check I put 1 gallon into an empty tank and looked at the gauge on the dash. I then knew where the safety margin was! Mind you the gauge would fluctuate a lot on cornering. If draining the tank it would be a nice touch.
Just to edit......I flushed by draining, filtering and using the filtered fuel to slosh round thetank. As far as I could see the interior was good and no crud after the 3rd flush.
Posted by: TBM

Re: Won't idle..... - 16/01/19 08:18 PM

Anyone know the idle jet size on the Weber twin choke carb?

Thinking about getting a spare for a quick roadside swap if it happens in future? I could just whip the original out and clean it, but knowing me I'll drop it and it'll roll down a drain so if I have a spare at least I can get home!
Posted by: tmg513

Re: Won't idle..... - 16/01/19 08:36 PM

Originally Posted By TBM
Anyone know the idle jet size on the Weber twin choke carb?

Thinking about getting a spare for a quick roadside swap if it happens in future? I could just whip the original out and clean it, but knowing me I'll drop it and it'll roll down a drain so if I have a spare at least I can get home!

Whip the jet out, it'll be engraved on the side. If the engine's been modified at any point it may have been re-jetted.
Posted by: jbk

Re: Won't idle..... - 17/01/19 03:56 PM

Back in the dark ages I had a similar idling problem, turned out be a shard of fibreglass in the idle jet, you could see right through the jet and it was not until I blew through it against the direction of flow that it lightly stuck into my finger. That was a Ginetta with a fibreglass fuel tank, but you might get a similar effect with a grain of sand, give it a blow, worth a try?
Posted by: morgan_75

Re: Won't idle..... - 18/01/19 01:44 AM

your slow running jets should be 50/45
Posted by: Richard Wood

Re: Won't idle..... - 18/01/19 09:19 AM

Over the years I've had a couple of cars when first purchased that wouldn't idle properly or for a period of time before stalling.

On a newish Sunbeam Imp Sport with twin Strombergs, I discovered the plastic float in one of them was leaking so full of petrol, in turn causing over rich carb. New float and perfect idle.

On an early 911S rough idle just needed distributor tweak to correct poorly set up ignition timing.
Posted by: TBM

Re: Won't idle..... - 22/01/19 07:42 AM

Been running fine all weekend. Fitted a new fuel filter and popped out one of the idle jets (the one on the opposite side to the engine) and gave it a blow through - it's a 55. Will get a spare for emergency roadside swapouts.

Checked the history that came with the car, and she had a full fuel tank clean by Allon White about 8 years ago, so I imagine it's just a bit of surface rust (hence small particles that are clearing themselves). It all depends if she's been kept with a full tank of fuel or not. It might explain why she plays up with a full tank - slight corrosion on the upper surfaces which gets dislodged when full.
Posted by: tmg513

Re: Won't idle..... - 22/01/19 08:16 AM

Originally Posted By TBM
Been running fine all weekend. Fitted a new fuel filter and popped out one of the idle jets (the one on the opposite side to the engine) and gave it a blow through - it's a 55. Will get a spare for emergency roadside swapouts.

Checked the history that came with the car, and she had a full fuel tank clean by Allon White about 8 years ago, so I imagine it's just a bit of surface rust (hence small particles that are clearing themselves). It all depends if she's been kept with a full tank of fuel or not. It might explain why she plays up with a full tank - slight corrosion on the upper surfaces which gets dislodged when full.

A small gas lighter refill cannister is really handy for blowing through jets.
Posted by: CooperMan

Re: Won't idle..... - 22/01/19 09:02 AM

tmg, good tip that !
Posted by: Calypso Red

Re: Won't idle..... - 23/01/19 08:23 AM

I had similar issues with a 1986 4 seater which had a mechanical fuel pump. I had already checked it was pumping fuel ok by turning the engine over with the fuel line in a jar. Eventually, a friend who was a professional mechanic told me that mechanical fuel pumps can work intermittently when they are on the way out rather than packing up altogether. The flap valves jam or leak. I changed the fuel pump, problem sorted!
Posted by: TBM

Re: Won't idle..... - 23/01/19 08:28 AM

Originally Posted By Calypso Red
I had similar issues with a 1986 4 seater which had a mechanical fuel pump. I had already checked it was pumping fuel ok by turning the engine over with the fuel line in a jar. Eventually, a friend who was a professional mechanic told me that mechanical fuel pumps can work intermittently when they are on the way out rather than packing up altogether. The flap valves jam or leak. I changed the fuel pump, problem sorted!


It had a new fuel pump fitted by AW in June last year - however, I have had problems with mechanical fuel pumps in my Land Rovers caused by wear on the camshaft. Had to resort to electrical in the end.
Posted by: TBM

Re: Won't idle..... - 09/02/19 10:40 AM

SUCCESS!

Finally, all the ducks lined up smile

Once I got her started this morning (took a while, but she had been sat for three weeks) and idled OK. Half way to breakfast she started playing up again and still playing up when I got home. Whipped the idle jet out, gave her a spray of carb cleaner and she started up perfectly and idled beautifully!

Thanks for all the help and advice, it's been much appreciated. Hopefully in time, all the rubbish in the tank will work its way through, and in the meantime, I can fix it in minutes. smile smile
Posted by: Paul F

Re: Won't idle..... - 09/02/19 01:14 PM

Originally Posted By TBM
SUCCESS!

Finally, all the ducks lined up smile

Once I got her started this morning (took a while, but she had been sat for three weeks) and idled OK. Half way to breakfast she started playing up again and still playing up when I got home. Whipped the idle jet out, gave her a spray of carb cleaner and she started up perfectly and idled beautifully!

Thanks for all the help and advice, it's been much appreciated. Hopefully in time, all the rubbish in the tank will work its way through, and in the meantime, I can fix it in minutes. smile smile


That is great news. Sounds like the long term fix is to put lots of miles on her. Win Win.
Posted by: +8Rich

Re: Won't idle..... - 09/02/19 02:36 PM

Great news TBM your perseverance has paid off - shouldn't be too long before all the bits get flushed.
Posted by: tmg513

Re: Won't idle..... - 09/02/19 03:36 PM

Originally Posted By TBM
Hopefully in time, all the rubbish in the tank will work its way through, and in the meantime, I can fix it in minutes. smile smile

That surely depends upon what the rubbish in the tank is. If it's rust unless you seal the tank the problem's going to keep recurring.