Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Intermittent engine stopping 1975 +8

Thanks also Druid9

I had not considered a possible fault with the ignition, but this would certainly allow the power to be cut, while leaving the lights on.

The ony item which does not backup the ignition fault is the lack of problems when still cold and when idling.

She only seems to cut out when she has warmed up, and is running >1500rpm

I am leaning towards a faulty coil (especially since she sometimes has trouble firing), and will check voltages and resistance overnight.

I think PaulF's suggestion of swapping the coil is also a wise approach, and may eliminate / confirm a cuplrit.

Add distributor points and condenser to the list of ignition components to change.

ETA: apologies just seen you have electronic ignition

If the engine stops then the Tacho will go to zero as there are no revs!!!! Always remember to start simple and by elimination move up the complexity scale. Firstly go around making sure all the electrical connections and leads are in good condition and secure, as stated above swap the coil, check the rotor arm for any arcing, check the vacuum is working, I would also add check the spark plugs are in good order and the lead connections are tight. Engine heat can cause some strange happenings that are difficult to trace but simple to cure. If the car is standing with the engine at running temperature does it stall when you rev to 1500 or is it only when you are driving?

For clarification you state:

"When she stops, the tacho drops to 0 (which suggests the coil power is unpowered), but then in a fraction of a second the tacho comes back, and the engine restarts (similar to a clutch start)."

The Tacho will drop to 0 when the engine stops but then you say the Tacho comes back and the engine starts, the Tacho should only "come back" when the engine has started not the other way round is this correct?

Thanls britmog,

Sorry but my explanation of the stopping/starting was perhaps a little misleading, since the 0 revs on the tacho will always occur when the engine has stopped. However I was attempting to explain the precise error, where the tacho drops to 0 rpm (no power from coil), and then immediately comes back on, causing the abrupt re-start.

As an extra update for everyone, I have been researching the XR700 ignition module, and also giving myself a crash course in coils and ballast resistors over the last couple of days.

Based on research and the helpful suggestions above, and with fingers crossed, I decided the easiest option yesterday was to pick up a new ballast resistor and standard coil pack.

Last night I also checked the actual resistances and voltages, and found the following :
> ballast resistor showing 2.4 ohms (should be around 1.6 ohms) NOT OK
> coil secondary showing around 13000 ohms OK
> coil primary more difficult to detect and less determined NOT OK

Based on these results last night I installed the new ballast resistor and the new coil, and then measured the following :
> ballast resistor 1.6 ohms
> primary coil 1.1 ohms
> secondary coil 13600 ohms
> voltage behind ballast resistor 12 V
> voltage past ballast resistor 6-7 V

These figures appreared to be in accordance with the recommended tolerances, and therefore at around midnight (and with fingers crossed again) we decided to fire her up.

She showed charging at 14.4 V at the battery (previously only 13.3 V), and was also maintaining the above voltages at the coil.

We then went for a half hour spin around our local steeets, and she reached normal operating temperatures and 100kph/3000 rpm without missing a beat !!!

Based on the above I am thinking that the original engine stop/start fault was caused by an old ballast resistor and an old coil, causing unreliable voltages. I am not sure why she was still able to idle, but at least the fault seeems to be fixed for now.

Thank you once again to everyone for your assistance and knoweldge and suggestions, and happy motoring !!!

Regards, Barney

Actually, that is quite astute, Richard. As Rover/LR Plus 8s are aging, I am finding the damnedest things failing. The condenser is (wrongly) called by LR a "capacitor". And it is not a condenser
either. People too often think it is something to eliminate static on their radio, (better done on Morgans with suppressant spark plug wires). I prefer the mildly more expensive ballast resistors
that never fail and merely cost a few pounds more. They both reduce voltage as should happen with a proper ignition design. The classic experience is running for a 15 minutes or so on a cold
engine and then stalling. I have yet to hear of a car so inflicted restarting itself, but I imagine that can happen. Barney, did you depress the clutch or put the gearbox in neutral just before, when till
turning even the slightest? Fascinating.

This little cylindrical thing you call a condenser and LR calls a capacitor and I can't figure what to accurately call rusts out without a easily visible sign unless you upend it, or test, or change it
(preferably to the much better ballast resistor.) What I can confirm, is that the symptoms match a Plus 8 running without a ballast resistor OR a functional thingie described. As owners begin to
constantly test the issue, the overcharge destroys everything down the line, the coil, the amplifier, the distributor itself. A simply 3 quid component failure fault inevitable costing many 100s of
pounds And this is on top of the fact that these V8 distributors are all very substandard and too delicate, IMHO. Sadly, I have nothing to recommend for Plus 8s since they ended the Mallory
Unilite.

I have no idea from the information given whether this is the issue. We would need a image of the ignition area for that and more tests from you. But there is a cheap shot-in-the-dark solution.
Barney see if you have a canister thingie or a ballast resistor. If a cannister, go buy a ballast resistor at any any auto store,https://www.dcpowersolutions.com.au/ballast-resistor, remove the
little effing canister and wire in the ballast resistor. IF the coil is not destroyed by now (yet) you may have found your fix. If not, start changing, testing, things down the line.. Everything you need to
howto is on gomog. Want images?

Lorne

Thanks gomog,

In response to the technical details of the engine stop/start, it was occurring under the following conditions :
> engine at operating temperature (probably 10 mins after starting)
> engine revs at >1500 rpm, and especially around 1800-2000 rpm
> she was however able to idle

When the engine stop/start occurred, it was during normal driving, with the clutch out and in gear. The tacho would drop to 0 rpm (engine stop), but then would immediately power up again, causing the tacho to jump as the engine turned on again (like a clutch start)

I did think about checking whether the engine would do the stop/start when not driving and at 1500 rpm. However the replacement of the ballast resistor and coil last night appears to have achieved the recommended impedences and voltages, and more importantly she is running again.

As I mentioned originally, I have a steep learning curve when it comes to all the mechanical and electrical issues with carby / distributer engines. Although I now have picked up some info re the coils and and ignition modules, distributer timing does appear to be more complicated, and I will leave this until I need to learn more.

Thanks again, Barney

My guess is that the coil was faulty. If you open one up you will find it has two coils of wire. The secondary coil is wound with very fine wire. If there is a break anywhere in that coil the brken ends will move apart when it gets hot but come back together as it cools. It doesn't need to move much. As the coil ages the continual expansion and contraction will eventually cause the breakage, so it is always a good move to change the coil when faced with a similar fault that you had.

You are welcome.


Hmmm.. The lower the engine revs the fewer times the ignition system is doing its job and the fewer times the fault is being accessed. If it is a overcharged, the lower rpm means the
fewer times it is creating great heat. Be careful. If this is the situation, the coil will quickly get hot enough to burn your skin. That is I never want you to try!


My complete question was: Did you press in the clutch during those incident? Merely curious.


BRAVO! It all makes perfect sense. One minor addendum to our sleuthing. If you have long pivoting bonnet stays, (popularized by the aftermarket) make sure the one on the passenger side (on a RHD) does not touch
the ballast resistor. That will over charge the ignition system as I described. Happened to me once....in only 20 minutes of driving, just outside of Bristol. I burned out the coil and the distributor's photo-optic unit in that time only.

As I mentioned originally, I have a steep learning curve when it comes to all the mechanical and electrical issues with carby / distributer engines.


Easy peasy. Get the old strobe ignition light, onewith no bells and whistles, and two extensions for your socket wrench along with a 5/8 (IIRC) or 15mm socket. That is all you need.

You LEARN very quickly. I predict sorting your Morgan, one problem at a time, will very enjoyable for you. So many new owners of older cars, especially Morgans, get fixated fixing them! Very soon you will start taking apart the obstinate family dishwasher.

gmg

Thanks very much gomog

It certainly has been a challenge over the last couple of weeks, and no doubt we will have the opportunity to experiences new issues in the future.

Despite the possibility of needing to do some detective work to sort out problems, I do love the basic design of the Morgan (no radio, no unecessary electonics, and no roof)

Just a small V8 in a light weight frame makes it a ball of fun to be out driving on our glorious sunny days in the mountains and coast roads around the Sunshine Coast !!!