New fuel system, won't stay running. (Page 1/2)
ketstang FEB 21, 09:28 PM
New to the Forum and Fiero's too.

I am helping my brother get his 87 Fiero GT 2.8L back on the road. It had sat in his garage for the last 10 years and the fuel tank started leaking.
Upon dropping the tank, I discovered that not only was the tank shot but so was the sending unit. I replaced the fuel tank with a brand new one, replaced the sending unit and everything attached to it inside the tank (all from The Fiero Store). I also replaced both the fuel and return lines from the tank to the fuel rail with new parts from TFS. All rubber lines have been replaced with EFI hoses and clamps. I put in a new fuel filter too. So, everything is new from the tank to the fuel rail.

When I went to start the car, I could hear the pump going and there is pressure at the fuel rail Shrader valve. So, I then tried starting the car and the engine started, but as soon as I release the key it dies. I can restart it right away and it does the same thing (over and over). I have connected a fuel pressure checker to the fuel rail and I have 43 psi at the rail and it doesn't drop when cranking or after it dies. I left the car sit with the pressure gauge on it and after about 30 minutes just sitting, the gauge pressure has dropped to 30 psi and stays there.

Any ideas what would cause the engine to run only when the key is turned in the start position and die once released?

Thanks in advance for any suggestions.

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Ketstang

82-T/A [At Work] FEB 22, 07:31 AM

quote
Originally posted by ketstang:

New to the Forum and Fiero's too.

I am helping my brother get his 87 Fiero GT 2.8L back on the road. It had sat in his garage for the last 10 years and the fuel tank started leaking.
Upon dropping the tank, I discovered that not only was the tank shot but so was the sending unit. I replaced the fuel tank with a brand new one, replaced the sending unit and everything attached to it inside the tank (all from The Fiero Store). I also replaced both the fuel and return lines from the tank to the fuel rail with new parts from TFS. All rubber lines have been replaced with EFI hoses and clamps. I put in a new fuel filter too. So, everything is new from the tank to the fuel rail.

When I went to start the car, I could hear the pump going and there is pressure at the fuel rail Shrader valve. So, I then tried starting the car and the engine started, but as soon as I release the key it dies. I can restart it right away and it does the same thing (over and over). I have connected a fuel pressure checker to the fuel rail and I have 43 psi at the rail and it doesn't drop when cranking or after it dies. I left the car sit with the pressure gauge on it and after about 30 minutes just sitting, the gauge pressure has dropped to 30 psi and stays there.

Any ideas what would cause the engine to run only when the key is turned in the start position and die once released?

Thanks in advance for any suggestions.





Shot in the dark here... but I seem to recall that the Fiero will not continue running if it's not getting oil pressure from the oil pressure sending unit. If it has A/C, it'll be sticking straight up from the block to the right (facing the car from teh back) of the intake plenum... sort of near where the MAP sensor is. There could be some other issues as well, but that's often one of the culprits. Have you checked to see if there's a check-engine light, and if it has any codes? You can check them by doing this:

https://www.pontiacperforma...icles/OSG/codes.html
ketstang FEB 22, 08:09 AM
Thanks for the help 82-T/A! I'll add this to my list of possible causes.
sanderson231 FEB 22, 10:24 AM
If the car sat for 10 years, I strongly recommend either getting the fuel injectors professionally cleaned or replaced. The car may be just starting on the cold start injector.

Mr. Injector in Idaho cleans and flow tests injectors for $18 each. Or Motor Man Fuel Injection Supply in Michigan has new injectors for $23 each.

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

ketstang FEB 22, 10:52 AM
I was considering replacing the injectors and fuel pressure regulator, just don't want to drop more $$ before getting opinions from some Fiero experts. Thanks!
82-T/A [At Work] FEB 22, 11:11 AM

quote
Originally posted by ketstang:

I was considering replacing the injectors and fuel pressure regulator, just don't want to drop more $$ before getting opinions from some Fiero experts. Thanks!




I kind of concur with him... my first thought was, if the fuel tank was leaking, and everything was trashed, the fuel injectors probably have so much gunk in them, if they're working at all. You can probably send them off to be cleaned. If your friend is planning on keeping the Fiero, then this is something you would want to do anyway.
theogre FEB 22, 12:46 PM
V6 F-pressure controlled by regulator that have vacuum port. Unplug and block the engine port/hose then read pressure.
If the regulator vac is not plumb to right engine/TB port then F-pressure will have problems.

Because Some TB/TBI/Carb ports are Ported Vac and gets Vacuum when GM says there "On" as throttle opens/shuts.

If still drops then may have other problems.

If not a problem w/ tank parts now...
⚠️ Warning: V6 F-pumps has a Pulsator between it and hard line.
Pulsators = to Hammer Stop methods for Plumbing for home etc.
V6 and others w/ high pressure F-systems often need this to prevent damage from "noise" from the pump and injectors. You may not hear sound but parts will get "Hammered" to death.

Note: Many new pumps are made different inside and Do Not use this so read any doc's came with or "call" TFS.

Pulsator can leak. Even new ones.
If Pulsator is deleted for any reason then the Hose to replace it must be J30R10 or will leak and very soon. You cannot use same hoses for external hoses to engine.

Wrong hose then Gas "eats" the outside and "E10" just "eats" faster.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

sanderson231 FEB 22, 02:41 PM

quote
Originally posted by ketstang:

I was considering replacing the injectors and fuel pressure regulator, just don't want to drop more $$ before getting opinions from some Fiero experts. Thanks!



I'm finishing up a 4.9 conversion for a friend and the car had been sitting for years. Just to be cautious I pulled the injectors. If have a test stand that can test the injectors but I can 't clean them . All 8 of the injectors were no flow not even a dribble. They were so bad (due to corrosion) that they had to be replaced. Mr. Injector did not charge me as he wasn't able to clean them. I have seen partial plugging on most other injectors that have sat for years.

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

ketstang FEB 22, 06:10 PM
Thanks everyone for your replies. I will suggest to him that we replace all the injectors and I think the pressure regulator while were in there.
Patrick FEB 22, 06:54 PM

quote
Originally posted by ketstang:

I then tried starting the car and the engine started, but as soon as I release the key it dies. I can restart it right away and it does the same thing (over and over).



Is there any chance that this might have something to do with the ignition assembly in the steering column? If it was somehow out of adjustment, could the mechanism that the key moves actually be in the OFF position when the key is still in the RUN position after being released from the START position? Just a thought!

[This message has been edited by Patrick (edited 03-03-2023).]