89 iroc 350n tpi...ok so after the car is warmed up if you cut it off and try to start it again the fuel pump wont engage...the pump should be fine i mean it runs ok any other time just wont engage after you cut it off and it cools...so i hooked a fuel pressure gauge up and engauged the pump by running 12 volts through the diagnostic terminal...first reading was 48 psi...the book says the most it should be is 39 but the car does have an adjustable regualtor but the lowest i can get it is 44 screwed out almost all the way out...is something wrong with the regulator? i didnt install it myself i just bought the car from my friend and nobody can figure it out...i dont see why it would cause the pump not to engauge though...anyways sorry for taking so long...thanks!

 

The psi that is in the manual is the running pressure, not the dead head pressure. There is a difference. Your dead head pressure should be about 48 psi as it was.

Is this the same car that has a thread on the 3rdgen.org forum. I have been trying to help on the same problem over there.

 

i didnt post anywhere else but its possible my friend(the previous owner) did...

 

just fyi all of these cars have hot start issues. The starter motor gets heat soaked and it just doesnt crank very well, even if you have a good heat shield in place. Your only real option with that problem is to buy one of the aftermarket hi power mini-starters. You may already be well aware of that you just seemed awful quick to blame your hot start problem on fuel which i doubt is your problem.

 

The relay is locatied under the hood with the engine..."SOMETIMES" the relay (if going bad) will stop working when it gets hot, then will work after it cools. It's is rare but does happen... Goodluck

 

its not the starter...or the relay

 

so what exactly is the car doing? you said when starting it from hot it doesnt have fuel pressure, but that you checked it and it does and someone confirmed it was the correct pressure.

Is it cranking and just sounding dry? need more info

 

ok i know whats going on now but i dont know exactly what the problem is...it something with the regualtor...i was messing with it yesterday and decided to crank the pressure up to 50 psi car was running fine for the moment...i cut it off and couldnt get it started back up...so tonight i start it and i noticed it wasnt running right so i pulled the vaccum line to see what the pressure was and the car cut off...and of course wouldnt start back up...so i decided to see how low i could get the psi...i removed the screw completely and put a piece of duct tape over the hole...44 psi is the lowest with the vaccum off with the vaccum on its around 37...but the car starts up everytime now...whats going on??? is the regulator screwed up? it should go lower then that and i cant adjust the pressure up with out starting problems

 

The only aftermarket AFPR I have used it the Crane version. I the kit there is a small metal disk. When I assembled the regulator, I put that disc in between the diaphram and the screw. I thougtht that was what you were supposed to do. I wasn't able to get the pressure down with it set up like that, so I pulled it back apart and took the disc out. Now the regulator works just fine.

Maybe, whomever put yours in, used that disc or something like it. I would pull the AFPR apart and make sure there isn't anything between the diaphram and the screw.

 

cool...yeah its a crane kit...i will try that tonight...why do you think it wont start when the pressure is raised?

 

I have the same problem on a 89 IROC and have a theory I am going to work with and see when I find the time. My car seems at 50lbs of pressure to not start. Drop it down a little and it works--so I have it set to 48lbs. The injectors are triggered with magnetic windings which loose power under heat soak and are unable to open the injectors at the 48lbs when hot. I believe this gets worse with injector age. Now with higher summer temps the problem is consistant where in spring or fall all seems fine. I think dropping the pressure to mid 40's will cure this--but I need the fuel so new larger injectors will follow.
Any of this seem like a possibility? Jack

 

i just put my lt1 injectors in...car still does the same thing when you crank the pressure up...and it has a rough idle now almost like a miss but seems to run fine when you take off

 

i have this same problem guys, my guess is heat soak, atleast in my case. It ran fine up until i turned it off, once i tried to start it again, it fired but would stumble, cut out and repeat about 3 cycles of this then die. Im not sure exactly what causes it but i smell gas so i know its not firing right, perhaps too much fuel pressure or heat soak on the starter, i really would like to figure this problkem out. If i find any clues ill let you guys know.

 

ok new info, my problem is not fuel pressure, i checked relays and they are good as far as i can tell, dissconecting them will not let the car start, aparently not even in limp mode. when i turn the key the SES light comes on and goes off as i turn the key, then it starts, dies, starts, dies and then finally give up, and the SES light comes back on, which i assume is normal when the key is in on position anyway. I checked the MAF as that would seem to be my culprit but i see no visual damage to the wires or anything of that nature, so it could possibly be my IAC valve?