vapour lock?

[jb]

Yesterday my car stopped running.
I had been coming back to London from the west not slowly but not super fast either.
It was a very warm day. The oil was still at 180 or maybe a bit above. I then got into stop start traffic for at least half an hour. The temp probably got up to about 210 certainly not much more.
I thought I had just stalled but then it would not start. It caught but immediately died each time I tried.

About half an hour later I tried again and it started so I continued but a bit later I got caught in traffic again and the same thing happened.
I don't think the oil was particularly hot this time but the outside temperature was still very warm. Again I left it and it started ok after about an hour and I got home with no more problems with it running like nothing had ever happened.

I don't know what is going on but I suspect that the fuel had vaporised and wonder if the fuel pump is the problem. It could be so many things especially as it is the early CIS.

Any ideas?

[mean_in_green]

Fuel pump relay? Easy swap test to start with.

[jb]

I am not sure that I would be able tell anything from that as it seems to work fine except when it doesn't.
When my fuel pump failed 8 years ago it just stopped working totally.
This seems different as it mostly works and only seemed to stop when hot and stuck in traffic.
Unfortunately I do not remember whether the pump made a noise or not when it wouldn't start.

[mycar]

I don't see me being a lot of help, it being CIS but isn't vapour lock a caburetor problem ?

[jb]

Maybe - what do I know.
We get it on the plane sometimes when it is hot and the only solution is to take the covers off and wait a bit. That has a carb though so maybe you are right.
I just thought it sounded similar.
Chris Turner would know what to do but unfortunately I am no longer able to reach him.

[fetuhoe]

CIS systems can suffer from vapour locks and this happens when the residual pressure in the fuel lines falls and a hot engine bay allows the fuel in the lines to boil.

The most common cause of this problem is a leaky check valve on the fuel pump but the accumulator can also be a probelm as can dirty injectors that leak and drain the lines. You can change the check valve with the pump in place.

You really need to carry out a residual pressure test and you need a minimum of 2.0 bar after 10 minutes and 1.7 bar after 20 minutes.

[Bruce M]

On some years there is a fuel pump cut out mechanism involving a wire connection to the fuel meter which de-energises the fuel pump relay if the metering flap touches the “rest” position. It’s a safety cut out if the engine stalls but with age, you can get false “signals”. With the key in start position, it should bypass the cut out allowing it to restart but if you have a duff one-way valve or fuel accumulator, the pressure in the fuel lines drops & the fuel boils, causing hot start problems (as suggested above).

[jb]

Thank you for your responses.

Looking back though my invoice file I can see that I replaced the accumulator in 2007 - 60K ago.

The fuel pump went in 2010 (45k ago) and Chris put in a generic pump which I think was for a CIS Audi and it must have the check valve internally as there is no external check value fitted at the moment. If I knew which pump it was I would just replace it as it only cost £120 then.
I still have the failed original which can maybe rebuilt or KMI injection do one but I am not sure how much that will be.
The pressures were tested in 2014 and were ok (ish) then.

I have been chasing a brief hesitation under load for ages which is fairly infrequent but could be down to a failing pump.

I replaced the fuel filter earlier this year and when I cut it open it was full of green stuff so perhaps the fuel pump has been similarly affected.

Also I did get a later WUR with a vacuum connection in 2014 and had it rebuilt and configured by KMI but I never fitted it as the car ran so well as it was.

I do not now know who to take it to if I get stuck as I have always gone to Chris Turner previously and although Tuthills have done a lot of work for me I do not think they are as clued up on CIS as Chris was.

[Nick Moss]

The CDI box can fail at high temps

[Lightweight_911]

I think Jason's got one of Johny Hart's modern CDI+ units fitted ...

[jb]

Yes Andy is right Nick.
I have a CDI+ box fitted but thanks anyway.

[jb]

I think I am going to drain the fuel tank and clean or replace the in tank filter
How much fuel do you think is left in there?
Having decided to drain it I needed to reduce the level so I went to the beach - about 130 miles round trip
Everything worked perfectly but I encountered no real traffic jams




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[210bhp]

And the ambient temperature wasn’t as hot?


Regards
Mike

[jb]

True
I know there is a problem which I have to address but today all I wanted to do was reduce the amount of fuel to be drained!
I am hoping to get by with two 10 litre cans

[scalino65]

Hi Jason. Possibly a bit of a red herring suggestion, but as electrical gremlins can cause all sorts of weird ones, but have a look at the contacts in the dizzy cap and give them a scrape/light sand if they're covered in crap. Similarly rotor arm. I had some odd hesitation recently that I chased through fuel pump, earthing,spark plugs, etc which disappeared immediately when I cleaned up the contacts. Just a thought.
Otherwise, I hope all is well with you and the family.
Best
Will