eddie jr

This is on an 85 2.8 firebird (fuel injected).

Very strange problem right now. Car ran perfectly fine today but after parking it for an hour while at an appointment, it started acting a little sluggish and then shortly after sputtered and choked and then stalled. If you leave it for a couple minutes it starts and runs perfect but it won't last long. I then left it for an hour and then i got quite a ways before acting up again....so it definitely can't be the fuel filter.

The real funny thing is, this is the EXACT same thing that happened to us last august down in ohio at the TA Nationals. Oddly enough, the next day it was perfect and has never doen it again until now, some 3500-4000km later.

My initial thoughts last year were either an ignition module acting up or the fuel pump acting up, but then why the heck never again until now and fine if you leave it for a while? Usually when both of those go they go quick. Fuel pump seems to prime fine too. But then you have to wait for it to happen again in order to test components like that to see the fault (electrical and pressure tests etc will be useless otherwise) so inever did find anything after the last time.

Is vapour lock possible on a fuel injected car? I didn't think so but i thought i'd ask as a couple old school guys have mentioned that.

Any opinions/experience would be appreciated.

project89

iTrader: (1)

i would not rule out the fuel filter.i have seen cars that one day would sputter and stall after say 5 miles,let it sit and then it might go 30 miles etc

does it have a check engine light on,even if not try to pull the codes out of the computer

use a paper clip or wire etc and jump the top right to pins on the aldl connector and the check engine light will flash any stored codes

eddie jr

True, anything can happen i guess, but 4000 more and never a propblem? Seems aweful unlikely. But you are right, i will definitely change it soon as it it a few years old anyway, can't hurt given that.

No codes.

One other thing is that it is quite hot today and it was that day last year too. However, there has been other hot days too ithink, although not yet this year.

project89

iTrader: (1)

other culprits could be a bad tps or maf sensor
though ive had 2 mafs go bad the car ran ruff and had no power cause it was running dead lean but it never stalled on me.

verify the voltage on the tps next time it acts up, just prob the center tps wire with a volt metter should be 0-.45 closed throttle and about 4.50-5v at wot
lemme refrase that im pretty sure its the middle wire. i belive its from the top down 5v ref line, signal wire, and ground

eddie jr

Yeah, its been so long i can't remember which one either and my book is at home. I will definitely check those though.

Unfortunately my resources are limited right now given i am out of town (and limped up to a relatives place), but i did try:

- bleeding fuel pressure a couple times (i thought vapour lock was only with carbed cars but it was worth a shot)
- changed the ignition module. I bought a spare last august coming home from the Nats since we were so far away and it was cheap. In case it happened again i figured it was a shot in the dark but at least it could be changed roadside.

Neither worked. If anything it is getting worse. Each time i go out i don't get as far. Last time i only made it half way around the block.

eddie jr

update:

the last thing i tried Saturday was putting on a new fuel filter. Didn't do anything. GOt towed home 100km on a flatbed (for free at least).

Yesterday i hooked up my fuel pressure guage and taped it to the windshield and drove around (of course after sitting it was fine again) and sure enough when it happened again the pressure dropped off. So it is a fuel problem.

So i am thinking since it is related to heat it should be the pump. The regulator is a vacuum diaphragm so it won't come and go and if wires were corroded it should be random you would think (although i will check the wires when i get under there.

So are there any other ideas out there or do you guys agree it is the pump? The tough thing is if i take the tank tank down and test the pump, it will work no problem. I suspect eventually it would finally die altogether though but it is peculiar that it keeps coming back to life!

project89

iTrader: (1)

try a fp relay and check over the wiring t the relay,also have u ever runt he tank just about dry,maybe the pump has a cloged up sock on it

eddie jr

Yeah, i often run it down into the orange but have never run out. But then again being related to heat, it wouldn't make sense with it being dirt....the longer you leave it the longer it works for, that is definitely heat related. But either way, when i pull the pump i want to look at that too and probably replace since i am in there.

For the relay, i did a test tonight. I looked at the wiring diagrams for the car (85) and it appears that there is a bypass for the fuel pump wired in parallel to the relay so that if the computer takes a crap (which triggers the relay) the fuel pump will still get power. This bypass goes through an oil pressure switch. one separate from the sending unit for the oil pressure gauge. So i unplugged the fuel pump relay and then tried to start the car....started right up! So that rules out the relay. So when i jack up the car i will look at the pump wiring and if that is ok then the pump itself is crapping out i guess.

thanks for the help. I will post what happens.

project89

iTrader: (1)

the more gas int he tank the cooler the pump runs,does it only happen when the tank is low?

eddie jr

No, that's the funny thing, both last august and again Saturday i had basically a full tank (at least 3/4).