Fuel Pressure question
Thread Starter
Melting Slicks
Joined: Jan 2001
Posts: 2,940
Likes: 5
From: Chesapeake VA
Fuel Pressure question
Hi all!
I have an 86' and I am trying to figure out a significant loss of power and stumble under acceleration.
I replaced the injectors because one was 4 ohms lower than the rest and they were original. I still have the loss of power under load issue. I noticed when I pressure tested the injectors that I could not get more than 32PSI of fuel pressure with the motor off. It takes a good bit of cranking to start the car, but it will rise to 42PSI with the vacuum line removed.
My question is, should the car produce 42PSI without the engine running?
I am planning on replacing the fuel filter next and I will replace the fuel pump if the pressure is not right, but it would help to know how much pressure I should be seeing with just the battery before I start the engine.
Thanks!
I have an 86' and I am trying to figure out a significant loss of power and stumble under acceleration.
I replaced the injectors because one was 4 ohms lower than the rest and they were original. I still have the loss of power under load issue. I noticed when I pressure tested the injectors that I could not get more than 32PSI of fuel pressure with the motor off. It takes a good bit of cranking to start the car, but it will rise to 42PSI with the vacuum line removed.
My question is, should the car produce 42PSI without the engine running?
I am planning on replacing the fuel filter next and I will replace the fuel pump if the pressure is not right, but it would help to know how much pressure I should be seeing with just the battery before I start the engine.
Thanks!
Burning Brakes
Joined: Aug 2010
Posts: 833
Likes: 1
Right after I replaced my injectors it would only build up 22 psi without cranking. Then when I did it would go to 42. A while ago I had the same problems. Go for a ride with the pressure gauge taped to the windshield and see if the pressure drops when you put a load on the engine. My problems only showed up then.
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
Drifting
Joined: Feb 2009
Posts: 1,302
Likes: 2
From: colchester CT
I had the same issue with my 86. I replaced the fuel pump and it solved the problem. I could start it but when I gave it some gas it would stumble. I would also change the fuel filter if you have not done that. The pump was easy to change, just be careful when you torque the bolts back on.
Thread Starter
Melting Slicks
Joined: Jan 2001
Posts: 2,940
Likes: 5
From: Chesapeake VA
Thanks guys!
I changed the fuel filter last night and I drove ot to work and back today (it's my daily driver). The car has improved noticably, but the main issue still persists. I will need to drive around with thepressure gauge taped to the windshield (do I need to provide a support to the hood so it dosen't pinch the hose?).
Also, I was thinking, would a faulty IAC valve cause my issue. When I start the car cold, I have to feather the gas to keep it from dying for the first minute or so. Once it is warm it is better, but in neutral it wants to idle around 900RPM, and I know I set the base idle not too long ago.
Thanks!
I changed the fuel filter last night and I drove ot to work and back today (it's my daily driver). The car has improved noticably, but the main issue still persists. I will need to drive around with thepressure gauge taped to the windshield (do I need to provide a support to the hood so it dosen't pinch the hose?).
Also, I was thinking, would a faulty IAC valve cause my issue. When I start the car cold, I have to feather the gas to keep it from dying for the first minute or so. Once it is warm it is better, but in neutral it wants to idle around 900RPM, and I know I set the base idle not too long ago.
Thanks!
Last edited by Square; Feb 24, 2011 at 09:57 PM.
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
I don't know how old your plugs and wires are, but quite often a stumble and loss of power can be cured with a tune up including plugs, wires, cap, rotor, and maybe ignition module. Just a thought.
