1989 IROC Z 305TPI LB9 , AT. COMPLETLY STOCK.

Cranks over fine, takes very long to start, or no start. Stars FINE when I first squirt Carb Spray, into a fitting on the Intake Plenum and then crank over. Once it runs for a few minutes it starts PROPERLY. Problem only occurs after sitting about 8 hours, or so.

Key on engine OFF fuel PSI 20-25. Cranking PSI the same. Running PSI 33-37. System holds pressure OK. No change in fuel PSI reading when I pinch off the Fuel return hose, at the fuel rail. When I apply vacuum to the fuel pressure regulator vacuum fitting the fuel pressure lowers barely 1 pound.
Once it starts and runs for a few minutes, engine running fuel PSI is 36. AND then it starts UP PROPERLY.
A couple years ago I installed 8 new fuel injectors, overhauled the fuel pressure regulator, replaced all fuel rail O Rings, and installed a new fuel filter. I removed said filter and confirmed that is is NOT plugged or restricted.

The factory Specs say the Fuel pump is bad, because PSI is below 40.

I would hate to install new fuel pump (especially given the questionable quality they are) and still have the problem.

What say youse? Thanks, Mikeceli

 

Anyone?

 

What kind of voltage are you getting at the pump? It's either weak pump or crappy electrical. Hotwire kit and new pump fixes both.

 

Change the pump. Check valve is probably bad. Happened in my 91 TA Vert and now my 94 TA Vert is doing the same thing.
I went with Delco/Delphi pumps, and did it (am going to do it,) the right way. Dropped/dropping the tanks. Not a bad job.....Even at 71 years old.

 

ya, it sort of sounds like you answered your own question. that pesky fuel pump. has it ever been replaced before? if not, then super highly suspicious, just like that girl you posted, looks AI generated to me!

EDIT: You have no ignition problem. Once fuel is in there, you have no problem. You confirmed nothing clogged. vapor lock? its a word i hear, but honestly dont really know exactly what it is

 

Vapor lock is when your fuel starts boiling in the lines. Return style fuel systems largely eliminated the issue.

 

So the battery voltage drops to 10V cranking the engine. I'm installing a new one..."Just because". Was about 10V at the pump, cranking, also. Sounds like I am gonna order a pump. Delphi, because I do not want a noisy pump.

 

I installed a new battery and ordered the Delphi FE0110 fuel pump. I decided on Delphi, because I do not want a loud pump, for me and the next owner.

Thanks, I will be back after the pump install.

 

BTW - did you check your pressure relief valve located near the bottom of the gas tank. they are notorious for cracking. good idea on the battery.

 

Would this be said valve? How do I check it? Thanks!

 

I have used a couple Bosch pumps with good results. Nice and quiet, no problems for 50k miles so far on the Camaro.

 

I telephoned Bosch, they said no listing for the 5.0 TPI, engine.

 

yes, that is the valve. do a visual inspection and look for cracks. you can also take it off (but risk breaking it) and probably put finger on one end and blow on other or something like that. I think is sort of a check valve, if enought pressure builds in tank it will open. often people will smell gas in its area. they have exact duplicates at Hawks if you just want to replace it.

looks like your gas tank may have been off at some point in its life

 

What makes you say that?

THE FUEL TANK VENT VALVE has nothing to do with my 20PSI fuel pressure, correct?

Thanks.

 

missing leather straps. all I know is it probably keeps the tank pressurized to some degree.

 

bETWEEN THE METAL STRAPS AND TANK? Good catch, I will make some.

 

bETWEEN THE METAL STRAPS AND TANK? Good catch, I will make some.

 

yes, I dont know if it is rubber or leather, haven't been down there in a while. too busy building my new garage to play with my toys lately.

 

OP here...PROBLEM SOLVED.

I installed a new Delphi FE0110 Fuel Pump and Carter PD1 Fuel Pulsator. Fuel pressure is 40-42 PSI and the IROC Z Vert starts properly on command.

As always, Thank You All !

 

Ooooo, thats a good feeling. Congrats!

 

Great fix, I always chuck the pulsator. Don’t really get much noise transfer through the line