I've got a theory and would like to see if anyone agrees...

My motor ('89 L98 in a Monte) suddenly became hard to start and unwilling to idle after being driven for a while. No codes but the exhaust smelled rich. A local shop took a look and told me that the fuel pressure was dropping quickly even with both fuel lines pinched shut.
The injectors were the prime suspect but they've only got a few thousand miles on them. I removed the upper intake this morning and found a snootful of fuel in there.
The new suspect is the fuel pressure regulator diaphragm. Any thoughts?

 

Sounds right to me.

 

well, if you pinched BOTH fuel lines, you wouldn't get ANY fuel (fuel pressure) to the rails/injectors. But yes, fuel in the plenum is a ruptured diaphragm. Take the plenum off and the fuel pressure regulator and replace the diaphragm...Replace this. (click on pic)

 

You can test it by pulling the vacuum line to the AFPR. If fuel pours out you have your answer.

 

yep, your regulator is bad

 

Bump... Post up your findings on this as I had the same thing happen to me yesterday, and had not considered my AFPR as a possible culprit. My L98 TPI 350 started fighting me on startup whereas it was fine 2 days earlier.

 

Thanks to everyone for the confirmation.
F-Body Demon was right on the money. Gas is coming out of the regulator's vacuum port. omnipotentgoku; it's time to get to work!

 

Crazy.. do I pull that line while the ignition is off?

 

no, just start your car like normal (if it'll idle) and then unplug the vacuum line to the pressure regulator, if gas squirts out, your diaphragm is ruptured...

 

Its your fuel pressure regulator man, Follow my thread about my fuel pressure regulator here man :> https://www.thirdgen.org/forums/tpi/...lace-fuel.html

 

crap.... no dice brothers... I pulled the vacuum line from the plenum to see if it would leak while it was idling, but it didnt! now im really confused and not sure what to try. The biggest symptom is my car is blowing off excessive white smoke when starting the car, and its still fighting me to start as though it was carb'd.

This started happening when I was looking into a problem with my fan (set to always run) stopped running. I thought it might have been a relay of some sort but did not know which was the fan relay. I also changed out all of my fuses (because I found some fuses that were incorrect amp) as a possibility, but no dice.

Ah.. I just read the post... would it make a difference that I unplugged the end of the line on the plenum rather than the end of the line on the FPR?

 

You would be better off to pull the end on the FPR - at least it won't need to fill the tube before a leak may be observed. I read recently that if you smell a heavy odor of fuel in the tube that you may have a leak; mine smells heavily of fuel but no visible leak - perhaps it's a small leak/perhaps it's just old and crusty and everything stinks like gas (hey, it's a V8).

...Worst case scenario..Perhaps you have an exhaust valve that is no longer opening? If you don't want to get to deep, disable the injectors 1-by-1.

 

Well I ended up changing the diaphragm, but this didn't help really. The one in their was not ripped... So I still am like ???

New line of thought...

The cold start injector. I am pretty sure I had this disabled in the prom when i had it burned. Could this be a source of fuel ?

 

well if its disabled, then just get a block-off kit for the cold start and be done with it...