no start after warm/hard stumble under hard acceleration

[stevenjoseph82]

I've posted my hard starting problem already, now on to another problem probably tied in. 89 GP 3.1L, and on occasion it will stumble so hard I it was like throwing the breaks on. I've heard the possible fuel return line clog, and now I'm hearing a possible injector problem. What I want to know is how I can check if the return line is clogged and how to check if an injector is bad.......i have no clue how to check the fuel return line and any help will be appreciated.

[JS91Z34]

Hook up a fuel pressure guage to the schrader valve on the fuel rail itself and record fuel pressure. If fuel pressure reads normal with engine off, Then start the engine. If fuel pressure goes through the roof, then check the FP regulator. If that seems fine or if you have replaced it, then check for a restriction, irregular bend, or a pinch or kink in the line.

[stevenjoseph82]

Sounds easy enough. I just gotta get a FP gauge or find a friend with one. Thanks for the help. Hey, I was wondering if that beretta with the 2.8 you were talking about on my other post was doing the same thing as my car here. One thing I didn't mention was that it will start back up right after you park it. It's just when you let it sit an hour or so, before it has time to completely cool. I was also wondering if that return line is blocked, then is it possible that the reason my car stumbled on hard acceleration is because it's flooding. Call me crazy, but if the excess gas can't circle back around to the tank, then would it be pushing more throught the injectors? That's just a theory.

[JS91Z34]

Sounds easy enough. I just gotta get a FP gauge or find a friend with one. Thanks for the help. Hey, I was wondering if that beretta with the 2.8 you were talking about on my other post was doing the same thing as my car here. One thing I didn't mention was that it will start back up right after you park it. It's just when you let it sit an hour or so, before it has time to completely cool. I was also wondering if that return line is blocked, then is it possible that the reason my car stumbled on hard acceleration is because it's flooding. Call me crazy, but if the excess gas can't circle back around to the tank, then would it be pushing more throught the injectors? That's just a theory.

 

 

Yes and no. it would be pushing more to the injectors as one would think but you would also have the ECM trying to compensate for a rich condition. The ECM would be narrowing the injector pulse width to maintain the 14.7 to 1 air/fuel ratio. If it couldn't do that enough it would set a code in the ECM. Anything is possible with any type of fuel system. I dealt with vapor-lock in two of my own cars, and both were port-fuel injection(fords). That beretta had a kink in the return line causing the fuel inside the rail to go nowhere. the car began to run like crap and would eventually die. The fuel would absorb so much heat and cause the fuel to boil and wah-lah you got vapor lock. I've heard it is next to impossible to vapor-lock an in-tank fuel pump. If that fuel has nowhere to go, seriously what do you think will happen? If your car is in fair to good shape, you can rule out vapor-lock. The next thing I would look at on your vehicle would be the crank sensor and/or ignition module. It WILL cause the same problem. I've dealt with vapor-locking in a car that was said impossible to do. I replace both crank sensor and module every 30,000 miles regardless. Just as a precaution because I do alot of traveling out of state and I don't want my Z34 breaking down in unfamiliar territory. Check your crank sensor and/or ignition module and let me know what happens

[1trucavalier]

an uplugged or bad MAT sensor does the same thing! it will be hard to start and will absolutely not stay running without your foot on the gas. My pigtail connector somehow came off giving the same symptoms. Not sure if the n/a 3.1L have it but check it out its free!