fuel pressure problem
Thread Starter
Melting Slicks
Joined: Feb 2005
Posts: 2,135
Likes: 0
From: Sebastian Florida
St. Jude Donor '06
fuel pressure problem
I have an AFPR and FMS 24# injectors on my car and when I turn the car off, the fuel pressure drops to 0 in about 2 seconds.
Any ideas on what could cause this?
The car runs good, after I put new plugs in today.
Also, what should I set my fuel pressure to?
Currently have it set at 39psi.
Thanks!!
Any ideas on what could cause this?
The car runs good, after I put new plugs in today.
Also, what should I set my fuel pressure to?
Currently have it set at 39psi.
Thanks!!
Last edited by Randy93; Apr 13, 2008 at 11:46 AM.
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
My guess would be the check valve on the fuel pump. If FP drops to 0 in 2 seconds, that is faster than the injectors would bleed off pressure. If the check valve was bad, then it would allow unrestricted backflow to the tank.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Fuel pressure can drop due to three possible internal leaks. Leaky injectors, a leaky fuel pressure regulator, or a bad check valve in the fuel pump. You can isolate the culprit by alternately pinching off the supply and return fuel lines and checking for pressure drop. The only harm the check valve can cause is slightly extended cranking times. I wouldn't replace a fuel pump for that reason. The other two can cause serious engine damage of left uncorrected. Diagnose the cause before you throw parts at the problem.
RACE ON!!!
RACE ON!!!
Thread Starter
Melting Slicks
Joined: Feb 2005
Posts: 2,135
Likes: 0
From: Sebastian Florida
St. Jude Donor '06
I always try and diagnose the problem first, just replaced the fuel pump about a year ago. They AFPR is almost brand new and I had the problem, before I put it on. So, I probably have leaky injectors.
So, to test this theory; all I need to do is take the injectors out of the intake and leave on the rail, then turn the key to the 'on' position, right?
Thanks guys!!
So, to test this theory; all I need to do is take the injectors out of the intake and leave on the rail, then turn the key to the 'on' position, right?
Thanks guys!!
Thread Starter
Melting Slicks
Joined: Feb 2005
Posts: 2,135
Likes: 0
From: Sebastian Florida
St. Jude Donor '06
Nope, I was wrong, just checked the injectors and they are fine. Want to check the check valve, can someone tell me which line is the return line?
Is it the one of the 2 coming from the right or the 1 from the left???
Is it the one of the 2 coming from the right or the 1 from the left???
Instructor
Joined: Feb 2008
Posts: 201
Likes: 0
From: The Ham AL
With my limited knowledge of these engines, I can't tell you exactly which line it is. I know there is two lines going to the fuel rail and they are right next to each other on the passenger side of the engine.
I have fuel pressure issues as well. I think my problem is the injectors. To check mine, Siveck (a senior dude here) took a soft towel and clamped down the return hose that goes back to the fuel pump. The check valve is inside the pump to the best of my knowledge. The understanding is the if you loose pressure with the return line blocked off then its an injector issue.
I guess you could try this and if you hold pressure better then its probably your check valve and I am not sure, but I think you have to replace the pump. Perhaps someone else here can give you more information or correct me if I am wrong with my response.
Good luck.
I have fuel pressure issues as well. I think my problem is the injectors. To check mine, Siveck (a senior dude here) took a soft towel and clamped down the return hose that goes back to the fuel pump. The check valve is inside the pump to the best of my knowledge. The understanding is the if you loose pressure with the return line blocked off then its an injector issue.
I guess you could try this and if you hold pressure better then its probably your check valve and I am not sure, but I think you have to replace the pump. Perhaps someone else here can give you more information or correct me if I am wrong with my response.
Good luck.
