Sergei

Hi!
Can anybody help me to find the problem part.
The car wouldn't start or starts really bad (at least 5 minutes of attempts) after it stays for more than 10-15 minutes after driving. If it stays for more than approximately 2 hours after driving than everything is just OK.

tonyj

May be the temperture sensor is bad and is always telling the ECU to run the cold start injector. When it is cold it needs the help but when warm the CS injector floods the engine.
Next time try holding the gas pedal to the floor when trying to start when warm. If flooding is the problem this should help it start.

Tony
'91 100Q 5spd

Sergei

Thanks for reply! The problem is that holding the gas pedal doesn't help. Could it be something else? May be some other valve, 'cause when car finally starts, I hear some kind of clap and the motor runs really rough and I need to press gas pedal several times to reach 3000 rpm to get motor idle smooth. Any suggestions?

birdmanmt

I would bet a lot of money that it's the check valve on the fuel pump. Easy to change and costs about $27 for the part. It keeps the fuel system pressurized after you shut the car off. The reason it works after about two hours is the cold start valve is then activated. I just changed it on my car which had the same symptoms.

Hatterasman

I think the pump runs for a few seconds each time the key is turned to run. I've been told that you turn the key on wait 10 seconds then turn off and repeat this several times before trying to start to diagnose a bad check valve.

Hatterasman

I was just thinking about your post and it seems to me it's probably not the fuel pump check valve because it starts ok after two hours. I'd look to a bad Fuel Pressure Regulator or leaking injectors.

birdmanmt

I had the exact same symptom's and problem's with my 87 5000csTQ. Would start fine cold and if it was warm at all, it would take forever to finally start if i sat there and cranked it(30minutes+) which usually ended up in needing a jump. If i just let it sit for 2+ hours it would then start just fine. You can test it with a fuel pressure guage. It bolts into the return fuel line(s) and it will tell you instantly if the check valve is keeping the system pressurized. Leaky injectors are easy to diagnose too, just pull a plug or two and see if there's excessive fuel pooling in the cylinder after the engine is shut off. Good Luck!