86 starts then dies immediately

[tcolyer]

Hopefully some one can help me with this problem: 86 mostly stock L-98 will start then die immediately. Usually happens when front end pointing down hill. I will push car to level ground and either remove gas cap (1st time) or bleed the fuel rail shrader valve (2nd time) and the car will start fine.
Things i have done in last six months: injectors removed, cleaned & new o-rings & filters, new fuel filter, new pump (AC) and strainer. I have set the fuel pressure to 35psi, 40psi & 45psi with no change. Any ideas would be appreciated.

Terry Colyer
82 Silver / Blue Crossfire
86 Bright Red Z-51

 

[tdr1919]

Hopefully some one can help me with this problem: 86 mostly stock L-98 will start then die immediately. Usually happens when front end pointing down hill. I will push car to level ground and either remove gas cap (1st time) or bleed the fuel rail shrader valve (2nd time) and the car will start fine.
Things i have done in last six months: injectors removed, cleaned & new o-rings & filters, new fuel filter, new pump (AC) and strainer. I have set the fuel pressure to 35psi, 40psi & 45psi with no change. Any ideas would be appreciated.

Terry Colyer
82 Silver / Blue Crossfire
86 Bright Red Z-51

have you put the fuel pressure guage on while you are starting it? maybe your
fuel pump shuts down after you release the key when it starts.
Tom

 

[vetteboy86]

I doubt this would correct your problem, but the fuel pressure on your car should be set between 40 and 47 psi with the vacuum line disconnected from your adjustable fuel pressure regulator. I would also watch the fuel pressure. The next time you start the car, turn the key to on, and listen for the fuel pump to run then shut off. Watch the fuel pressure and see how quick the pressure bleeds off. You get fuel out of the schrader valve when you bleed the pressure do you not??

 

[jester]

Monitor the fuel pressure like Tom said. It sounds like the fuel pump relay may not be closing.

When the key is turned on the fuel pump will run for two seconds to fill and pressurize the fuel system. After the car starts the fuel pump relay will close to turn the fuel pump on. The relay is relatively cheap and easy to change. It's on the firewall by the battery. There are two relays there. If you need to change one, you might as well do both of them while you're at it. They're both the same part number.

Good luck and let us know how you make out.

John

 

[tcolyer]

Monitor the fuel pressure like Tom said. It sounds like the fuel pump relay may not be closing.

When the key is turned on the fuel pump will run for two seconds to fill and pressurize the fuel system. After the car starts the fuel pump relay will close to turn the fuel pump on. The relay is relatively cheap and easy to change. It's on the firewall by the battery. There are two relays there. If you need to change one, you might as well do both of them while you're at it. They're both the same part number.

Good luck and let us know how you make out.

John

I have change both relays in the last year (dosn't mean it is not bad) Also put new ends on both relays & soldered the ends. What is really weird about the problem is it has only done it three times and only when nose of car is pointed down hill. Hopefully next time I will have Pressure gauge with me.

 

[jester]

I have change both relays in the last year (dosn't mean it is not bad) Also put new ends on both relays & soldered the ends. What is really weird about the problem is it has only done it three times and only when nose of car is pointed down hill. Hopefully next time I will have Pressure gauge with me.

An interesting problem. I don't have any more ideas right now. What's happening with the fuel pressure will be a key piece of information. You might also monitor the voltage to the fuel pump to make sure it's getting power when it's supposed to. I'm assuming you have plenty of fuel in the tank.

 

[tdr1919]

I have change both relays in the last year (dosn't mean it is not bad) Also put new ends on both relays & soldered the ends. What is really weird about the problem is it has only done it three times and only when nose of car is pointed down hill. Hopefully next time I will have Pressure gauge with me.

Odd problem, almost like a vapor lock, air trapped in the system -

if you put the guage on do you have pressure? I didnt see you answer that question?

- Tom

 

[tcolyer]

The three times this has happened, I have not been near a pressure guage. I now carry one with me to check. The first time it did it was during a fill up. I had run the tank very low & filled up with the car on a slant. I push the car on level ground & removed the gas cap & then it started. I replace the pump, stainer & filter, then it did it again. The last time this did not work and I pushed in the shrader valve on the fuel rail and it spit just a little gas then car fired right up.

 

[tdr1919]

The three times this has happened, I have not been near a pressure guage. I now carry one with me to check. The first time it did it was during a fill up. I had run the tank very low & filled up with the car on a slant. I push the car on level ground & removed the gas cap & then it started. I replace the pump, stainer & filter, then it did it again. The last time this did not work and I pushed in the shrader valve on the fuel rail and it spit just a little gas then car fired right up.

Terry,
It just sounds like there is air in your system, when you bleed it off (shrader) the pump starts up and you have fuel to the injectors. Is the fuel return working properly? sure nothing got blocked or is restricted?

- Tom

 

[tcolyer]

Regulator

Problem happened again on Friday night. No fuel pressure - new pump would run for the two minutes for start pressurization but would not build pressure. I tapped on the side of the pressure regulator and pressure went up & car started fine & ran. I replaced the regulator and had to turn the pressure adj. screw way out from where it was.

I hope this is the fix.

Thanks for all you help.

 

[tdr1919]

Problem happened again on Friday night. No fuel pressure - new pump would run for the two minutes for start pressurization but would not build pressure. I tapped on the side of the pressure regulator and pressure went up & car started fine & ran. I replaced the regulator and had to turn the pressure adj. screw way out from where it was.

I hope this is the fix.

Thanks for all you help.

Got my fingers X'd for ya! thanks for getting back and letting us know.
-Tom

 

[jester]

Thanks for the update. It sounds like you found the problem.

 

[mancubpiggyfire]

87 C4 starts and immediately dies

i Brought my car into our family mechanic to have him swap my bad heads for some good ones, the car ran and drove great when i brought it in (besides the fact that my heads were bad) i had it towed in to the mechanic and they got the new heads on.. now it will fire up and immediately die, we hooked the guage up to the fuel rail and were getting a steady read at 45psi we replaced the fuel pump relay, iac, and tps, after we replaced the iac it will now idle but its rough and wont idle much longer than a couple minutes. im not sure where to go with this and neither does our mechanic. Any ideas???:W