andy boardman

Hi - another problem with the car..

The car is proving more and more diffciult to start. When cold it cranks fine and sometimes with the lightest of feather on throttle it fires first time - most times with or without throttle it will not fire for 10 secs or so. It settles to perfect idle immediately after starting and runs fine. When hot it starts OK but does start to take longer after standing for an hour or so.

Having skimmed through the archives etc and read about falling fuel pressure etc I have replaced the fuel control valve on the pump in the rear but no difference (is there anything else that may be causing pressure loss in the system? - no leaks apparent). I have thought my way through the normal issues of fuel and spark and have got the following to do when the parts arrive:
1) it is due a full service so plugs, caps, rotors, air (& oil) filter on order
2) new fuel filter unit on order also
3) have cleaned injectors with fuel additive
4) will clean earth points on coils whilst doing electrical service

From the manual I have read that the fuel air sensor (lambda probe?) controls the mixture at start up - could this be the culprit and if so how does one decide whether it is or not without the expense of replacing it?

All help gratefully received. (It would appear from my posting about rear window demister units that no one has had any problems with these units only me.....!)

Thanks.............Andy

Mike Schmidt

Besides the check valve by the fuel pump, there are a couple of other things that might be causing the fuel pressure to drop. It could be that a fuel injector is leaking. The fuel pressure regulator or a fuel pressure damper could be bad as well. To check the pressure regulator and dampers, pull the vacuum line off of them and check for any signs of fuel. Check them with a vacuum tester to make sure that they are able to hold a vacuum too.

WallyP

Some comments on your problem:

A dirty fuel filter will almost never cause problems in cranking the car. The first symptom of a dirty fuel filter is poor running at full throttle.

The pump only runs for a couple of seconds when you first hit the starter, then quits until the engine cranks. Try hitting the starter for two or three short bursts, then hold it for five or ten seconds. If the short bursts help, then the problem might be fuel pressure leakage.

There are few places that can cause fuel leakage. The injectors can leak, the fuel pressure regulator can leak, the fuel pressure dampeners can leak, and the fuel pump check valve can leak. Any other leak will cause fuel leakage outside the system, with odor and fire risk.

If the injectors, the fuel pressure dampeners, or the diaphragm of the fuel pressure regulator leaks, the fuel ends up in the intake system. This causes a very rich mixture on hot cranking (flooding) and a very lean mixture on cold cranking.

If the pressure regulator or the pump check valve leaks, there will be no symptom other than a lean mixture on cranking, as the leakage is internal to the fuel system.

Don't forget that the Temp II sensor on top of the engine can cause either hot or cold cranking problems.

andy boardman

Thanks guys for the swift response - next weekend I shall play and try and go through things logically.

Mike / Wally - what you say about the fuel pressure dampner / regulator and injectors does make sense - there are times when the car behaves in exactly that way - too lean when cold would be why it doesn't like to fire unless a little throttle is added and lazy when standing for an hour or so when hot, mo extra throttle required. I have tried the key cycle to see if the pump needs to pressurise the system and it does not seem to mae much difference perhaps then the temp2 sensor is the place to start?!

Thanks for the help - I will let you know what transpires......(PS Wally - I hear what you have to say about workshop manuals......!)

Andy