Fuel pump not priming - car slow to start - why?

[naughtika]

you could've just unhooked it at the FPR and direct to the plenum

 

[TME_Steve]

Just read the last page. All your cars doing have something wrong. Changing ecu parameter etc to run richer at cranking is just making a problem. If the car is prefect it won't do it. Boost leaks and fuel pressure dropping are still my suggestions

 

[Kaldek]

you could've just unhooked it at the FPR and direct to the plenum

That's what I did.

 

[Kaldek]

Just read the last page. All your cars doing have something wrong. Changing ecu parameter etc to run richer at cranking is just making a problem. If the car is prefect it won't do it. Boost leaks and fuel pressure dropping are still my suggestions

Sure, but there's a lot of cars doing it, so the problem has to be fairly consistent.

 

[AKKO]

Sure, but there's a lot of cars doing it, so the problem has to be fairly consistent.

Other than age and poor / questionable maintenance, what does yours have in common with those?

 

[Kaldek]

I haven't compared all the info yet. The free version of survey monkey doesnt let you export data. Have to do it by hand.

Anyway you guys seem to be giving me a pretty hard time considering I'm the only person bothering to investigate it. How about some support rather than throwaway statements.

 

[trotty]

I'm starting to think maybe a leaky injector or oring. Can u smell fuel in engine bat at all?

 

[Kaldek]

Nope no smell. Fuel rail holds pressure for hours too. But I have considered it and we may end up back there after other tests are done.

 

[AKKO]

Wasn't having a go mate, if the issue is consistent as you say there should he something common between the vehicles with the problem. Your own words.

 

[Kaldek]

@TME_Steve no plans to alter ECU settings in particular, but I need ECUflash just to look at what those settings are.

 

[TME_Steve]

No problem my end and I'm not having a go either but if there are cars that don't do it, it means there is something different/wrong with those that do have this problem. If you can hold fuel pressure for hours I'd be thinking you have a boost/ vacuum leak. Does the brake booster hold pressure overnight also?

 

[naughtika]

can someone please try this..

while the key is on 'ON' position, can you please unplug the crank sensor's connector and see if your fuel pump primes? and does it do the same thing when you plug the connector back?

 

[Kaldek]

It will prime initially while cranking (I.e. starter motor running) but the pump will then turn off in the absence of an engine rotation signal from the crank sensor.

An oscilloscope will show you crank sensor pulses, but so will evoscan by checking for an rpm reading while cranking.

If you have spark though, your crank sensor must be working. Also if the crank sensor wheel has no TDC notch (can't recall), then it needs the cam sensor also in order to trigger spark. Some vehicles use the cam sensor for injector trigger only.

 

[Kaldek]

Interesting result today, post removal of the FPR solenoid. The car had been sitting for five days and it was cold. Jumped in, just turned that key straight to start and she fired up straight to a stable cold idle speed.

Could we have found the problem? Nah, needs more tests. I won't call it until I've had no stumble on at least five starts.

 

[trotty]

I'm sure in Facebook
I said to clamp off return line and see if it drops pressure overnight

 

[Kaldek]

Sorry mate I missed that one. Will do that too.

 

[Kaldek]

I'm sure in Facebook
I said to clamp off return line and see if it drops pressure overnight

OK @trotty I had the line clamped and pressure fell to 0 overnight.

I might not have clamped it enough, but give me your thoughts.

 

[trotty]

Injector leaking or fuel pump releasing pressure overnight.

 

[Kaldek]

Injector leaking or fuel pump releasing pressure overnight.

Let's say that is the case, which I agree is a possibility. The problem I have with these failure types is the single following fact: The car always starts/fires with only a short cranking time needed, then the revs drop briefly and it comes back suddenly after a few seconds.

Also:

• Priming the fuel rail by bypassing the pump relay does not stop the problem
• Another start attempt immediately after the low idle will be perfect. The problem only ever occurs once.

It just seems...well...EFI sensor related. I spoke to Paul Danner (probably the world's best EFI diagnostics guy) and his first suggestion was to check ECT and IAT accuracy. I need to make sure I have log data from a bad start - I thought I had one but now I can't find it.

 

[trotty]

If that's the case I would possibly suggest the idle stepper control (ISC)motor. Upon first crank it's slow to get into fast idle causing the stutter/low idle. But upon second crank it's already in position so no stumble. Maybe give it a clean.