Starting woes continue...

[Adnan]

Hi,

Last week I had shared my car's odd behavior with you all. To recap, she starts fine cold, or within five minutes of shutdown but give her twenty to thirty minutes and she isn't happy about it.

I added a fuel line check valve per Bruno's site and for good measure, replaced the fuel filter. All electricals seem fine. So far, I can get her going with extended cranking but the idle is rough. Yesterday, I added some throttle and after a few seconds, she smoothed out and purred like normal after that. Flooding?

Leaky injector? If that's the case, she should not start when cold since the system has lost fuel pressure, right? If one injector is leaking, won't the engine at least start with five cylinders? That first time, she refused to fire at all.

Jeff, to your question, the roughness only lasts a few seconds and power is perfect when running normally. No codes are set. Is there an easy test for injectors or do I need to pull the entire fuel rail? Do those Mustang injectors drop right in (I have a set at hand) without requiring DME changes?

Dukester has suggested that the pressure relief valve diaphragm may have ruptured; I'll check that out tonight.

Any other ideas?

Many thanks,
Adnan
'91 535i

[BFEINZIMER]

Where did you get the check valve, I need one.

[Adnan]

...it's a kit for the 750i

Adnan

[Jeff N.]

Cold start OK. Short term warm start OK. Mid-term warm start no good.

Leaking injectors would certainly cause that. If your power is OK during drive, that suggests your FP is OK. Does your MPG 'surge' on a flat 40 MPH drive? If so, that would suggest that your mixture is off (the surge in the gauge is the closed loop feature trying to move the mixture to stoich).

Mustang injectors flow just a bit more than stock, about 3% IIR. You can drop them right in and it will run fine. You'll observe on your trip computer your mileage going "up" a bit but that's just due to the slightly shorter injector pulse to compensate for the extra fuel flow.

I'd say go for the injector swap and see what that does. It's not too hard, maybe 2 hours at a reasonable pace.

[mamilapon]

I'll go with injectors too!