Misfire and fuel vapoursiation

[antonyj]

Still trying to find the cause of what seems to be a heat soak induced misfire or rough running.
When I have run the car and then stop and leave it for a while, on restart it runs rough.
The fault general clears after a mile or two and runs fine.

Checked the leads, extenders, swapped dizzy cap , rotor arm ok.

I have changed the ignition amp for a new one (Lucas)

Today it is still happening and a few people have suggested fuel vapourisation , so can anyone help to explain how it would occur and how to stop it.
On monday I am going to check pipe work and the filter and pump.

I cant understand how mine would be suffering from it all of a sudden and it doesnt seem to be common on the griff in general.

Any guidance and suggestions greatly appreciated.

Ant

Edited by antonyj on Thursday 26th October 14:35

[wadgebeast]

Which car is this in?

[leorest]

wadgebeast said:

Which car is this in?

antonyj said:

griff...

[GreenV8S]

Could be fuel evaporation cause by heat soak, or any other problem caused by heat soak. I would expected fuel evaporation to clear within a few seconds though rather than a few minutes. The problem is that the air temperature around the top of the engine can be above the boiling point of petrol, causing fuel to boil within the fuel rail when the engine is switched off. When the engine is started, the fuel pump circulates fuel through the rail and cools it down quite quickly, so it's typically only a problem immediately after starting. You can reduce the problem by lagging the fuel rail, which is a good idea anyway.

[antonyj]

Thanks for that Pete, so by the sound of it it isnt vapourisation.

Any other ideas from my description?

[rev-erend]

Anthony - second Peter's idea of lagging.

Alumimum foil is quick and cheap - to prove it that is the problem - a more permanent solution could be sought if that is the issue.

Also - the fuel pump circulates fuel whether it's needed or not - so the excell is returned to the tank.

So - the fuel gradually gets warmer.

You could also try topping up with fuel after a run - nice cold tank full of cold fuel.

[leorest]

I had something similar on the old X1/9 about ten years ago.
If you switch off once everything is up to temp and leave it for 20 minutes or so you could start it and get about a quarter of a mile up the road before it would splutter and die. At this point it would refuse to re-start no matter how long you churned it over on the starter but if you waited about twenty minutes for the top of the engine to cool a bit then it would start on the button.
Re-fitting the carb cooling fan (which a previous owner had removed and put in the boot!) completely solved the problem.

Something simple like Peter said about lagging the fuel rail may work wonders. Otherwise if the fuel pump is not pushing the volume it should ('cause it's a bit old and tired) then it would take longer to cool the rail as less excess fuel will be being pushed through the return back to the tank, taking the excess heat with it!

[antonyj]

Cheers guys , you can understand when I say though, it must be something causing the fuel vapourisation, or all griff would suffer?

[antonyj]

I have some of the material that lines the inner wings left over.
The drivers side got replaced when the manifolds were off.

Would this be ok on the fuel rail?
I could cable tie it in place.(neatly)

[wild skinner]

I have seen this problem many times and 95% of them were e.c.u's over heating. Is your car an early griff?, try putting your e.c.u on the footwell floor before a run.

[wild skinner]

I see your car is an early griff. Has it had the bulkhead mod done? this is basically a mod to the body where the exhaust manifolds leave the engine. If, when looking at the engine from over the wing and the bodywork two inches away from the manifold is straight, then you do indeed need the mod.

[stevieturbo]

leorest said:

I had something similar on the old X1/9 about ten years ago.
If you switch off once everything is up to temp and leave it for 20 minutes or so you could start it and get about a quarter of a mile up the road before it would splutter and die. At this point it would refuse to re-start no matter how long you churned it over on the starter but if you waited about twenty minutes for the top of the engine to cool a bit then it would start on the button.
Re-fitting the carb cooling fan (which a previous owner had removed and put in the boot!) completely solved the problem.

Something simple like Peter said about lagging the fuel rail may work wonders. Otherwise if the fuel pump is not pushing the volume it should ('cause it's a bit old and tired) then it would take longer to cool the rail as less excess fuel will be being pushed through the return back to the tank, taking the excess heat with it!

R5 Turbos, and my old Mini turbo suffered a similar problem. The R5 turbo had a cooling fan for the carburettor. My car should have had a heat sheild under the carb....but alas it never did.
I always had to make sure I didnt switch off very soon after a good rake, as the heat soak would leave me stranded for a good 30 mins.

I think it unlikely thats the problem with his Griff, as I assume its fuel injected ??

[antonyj]

Well, the problem is fixed and it wasnt fuel vapourisation........


It was a bloody spade terminal in number 4 injector cap.
It was connecting/disconnecting under a heat induced movement in the loom.

Now it has been put into the cap properly the problem has gone.