Talk Morgan Forums Morgan Sports Cars Morgan Aero 8, 2012< Plus 8, SuperSports, Coupe & Aeromax Hot start .... vapour lock

Appolgies if i seem to be carpet bombing the forum with posts - I'm (I hope) at the steepest part of the learning curve with my 'Mog at the moment, 3 weeks into ownership. Rapidly knocking things down as sorted, but still some niggles to get to grips with.

The car starts on the nail from cold and runs perfectly .... However. If its left to stand for 20 mins once warmed up it takes a very long crank to get it to fire up.

It always goes, but it can be 10 seconds or more cranking before it fires.

I'm pretty sure this is down to vapour lock - is it a known "thing" ?. Does anyone have a fix ?.

I've got a 2015 Aero Coupe, which I guess is going to be the same engine and fueling set up and it always starts immediately hot or cold.

I just googled it which made the following suggestions...

Crankshaft or Camshaft Position Sensors: As these sensors age, internal thermal expansion breaks down their circuitry when hot. They fail to send precise rotational signals to the ECU until cooled or subjected to extended cranking.

Fuel Pressure Leakdown / Leaking Injectors: If an injector drips or the fuel pressure regulator bleeds off pressure into a hot intake tract, a temporary rich or vapor-locked condition occurs, delaying immediate ignition firing.

Quick question as I am not that experienced on S5 and I know it was quite different due to the boot arrangement.

I have an S2 and a Coupe (yes I know, greedy). And the S2 has no issues. The Coupe can be fussy. The breather has been adjusted a few times and had several recalls. Is you starting issue perhaps related to the tank not breathing and so pulling back once switched off. So the restart is a bit starved? Not claiming any skills in this area but I did have that hot start issue after one of the “improvements”.

If it was a vapour lock I would be looking at the insulation around the pressure fuel feed from tank but nearest the engine.

Just before you try the hot restart next time, open the petrol filler cap (there's sometimes a rush of pressure in/out equalisation) and then try the hot start test

I have been messing around with the tank / breather to deal with fuel filling problems (see my other thread). Will definately try the "cap off" test next time it's warm.

I'm pretty confident about the one way breather valve (it's new a week ago) and changing it did not make any difference.

I have had issues with exhaust cam sensors (they put the EMS light on) but ive replaced both of them and the EMS light cleared itself after 5 drive cycles.

I'm planning to add an inline fuel pressure guage and if all else fails a "cooldown" fan, Regardless of the starting issues the engine bay gets incredibly heat soaked - I've even added some insulation on the bonnet stand rod as its too hot to touch comfortably. I suppose it recent UK temps have been a bit extreme, but it's done it again today @ 21C ambient.

Accepting your point concerning heat this is common. Several people have added additional bonnet louvres to reduce heat when standing. Several have also added them because they are pretty. Whoops did I say that out loud. I have never seen evidence of the impact when moving but after you have parked you can feel it through the vents.

The S2 and Coupe do both get a load of heat soak and high under bonnet temperatures at rest. As the car heats up the gearstick can become pretty hot to handle as I had a metal ball knob fitted, I disliked the factory one. Additionally the footwell surrounds and the chassis frame below the door can get pretty warm as well. Great in winter!

If it is really hot I tend to pop the bonnet knobs at the windscreen end which lets the heat out faster and does not really show. Never had anyone look or touch as they get nothing but love.

On the Coupe the breather valve for the tank goes to a pipe which exits down past the tank to the road. On mine it was kinked at one point and so the pressure could not release. Just as a check did you test that one? The cut off triggers constantly when filling following my last service and adjustment at Williams. Uttlerly pisses me off, not to mention I can no longer go more than 90 miles before risk of running out of petrol. It seems to be a magic combo of breather, angle of the neck mounting on body.

I've tried the cap removal when hot now - no change. Next up I've got a capillary adjustable thermo-switch and 2 slimline 6" rad fans.

The plan is to have a activation switch inside the car to enable the aux fans, then the thermo-switch to actually turn the fans on / off.

Position of the fans is planned to be underneath the 2 triangular mesh covered vents to the side of the headlamp cowls. When on they will blow hot air out. The only other slight concern I have is that the fans don't "windmill" excessively in normal driving. We will see ..........

I suspect that if fuel tank vacuum build up relative to vent restrictions were the case, then I might expect the engine to falter under acceleration, given the high fuel delivery demands...?
Using no more than logic, the idea of making use of a fuel pressure gauge to monitor the situation seems a worthwhile next step...?

Another thing I'd not mentioned.

My car has a Global Telematics Thatcham immobilizer fitted.

It's a "key present" system, so you basically disarm it and start engine immediately.

I also wonder if this were not there the OEM systems would run the fuel pump for a second or two to pressurize the rail before cranking ?. I don't seem to be hearing others saying they have the same problem so maybe the OEM BMW / MMC system is sound after all ?.