Can too much fuel pressure cause idling/running issues?
08-24-05 | 05:00 PM
#1
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Joined: Jan 2004
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From: Utah (land of mountains)
Can too much fuel pressure cause idling/running issues?
So I'm still in the process of trying to get my new rebuild running. It will fire up pretty fast, I can rev it a bit, then it dies.
I stuck a pressure gauge inline between the fuel filter and the primary fuel rail. With the car off and just the pump running, the system shows about 90PSI. When I disconnect the pump, it drops to ~40psi.
When I try and start the car, pressure shows at ~50psi, at initial start, but when I rev the engine it shoots up to 70PSI before the car dies, then once it dies it builds up to about 90 again.
I thought maybe my FPR was bad, so I switched it out with another one I had here and it still does the same thing.
Can the Pulsation dampener affect fuel pressure? I'm getting hardly any fuel out of the return line with the car off and the pump running.
Also, someone said a bad water temp sensor can cause the car to run really really rich, is it possible it could be causing the problem? Any help would be greatly appreciated!
I stuck a pressure gauge inline between the fuel filter and the primary fuel rail. With the car off and just the pump running, the system shows about 90PSI. When I disconnect the pump, it drops to ~40psi.
When I try and start the car, pressure shows at ~50psi, at initial start, but when I rev the engine it shoots up to 70PSI before the car dies, then once it dies it builds up to about 90 again.
I thought maybe my FPR was bad, so I switched it out with another one I had here and it still does the same thing.
Can the Pulsation dampener affect fuel pressure? I'm getting hardly any fuel out of the return line with the car off and the pump running.
Also, someone said a bad water temp sensor can cause the car to run really really rich, is it possible it could be causing the problem? Any help would be greatly appreciated!
08-24-05 | 06:17 PM
#2
HAILERS
Joined: May 2001
Posts: 20,563
Likes: 23
From: FORT WORTH, TEXAS,USA
You should read only about 28-31 psi at idle on the fuel rail.
I'd say you have a bad FPR but then again you said you swapped in another with the same results. Sooooo???
Rule out the water thermo sensor altogether.
Pulsation damper.....not likely.
I'd say *something* is plumbed wrong. What? Got me.
Some of the characteristics of what it's doing are like a normal car in one sense. Say you idle a NORMAL car. Looking at the fuel pressure you would see approx 30psi fuel rail pressure. Turn the key to OFF. Sit and look at the gauge and you'll see the pressure rise to approx 37 psi. That is normal. Your engine seems to ape this but the pressure is waaaay too high.
When at idle, can you pull the vacuum hose off the FPR and see if it has vacuum on it. It should. That won't solve the high pressures your seeing but I think you should do that as a starter. Only do that after a full minute has passed since the car has been started. There's a reason for the full minute passing.
If you were just looking at the fuel pump pressure with the gauge in the end of the outlet line of the filter, then your 90 psi would be pretty much right for pump outlet pressure. This is with nothing else in the circuit, just the fuel pump.
Have you looked in the fsm's and looked at how the fuel lines run under the intake? Yours are similar?
Was this engine ever in a fire? I had one of those and the guts of the fpr blocked the passage of fuel.
No answer for you here, just some thoughts. There is BLOCKAGE somewhere in the run of lines or they are arranged wrong.
I'd say you have a bad FPR but then again you said you swapped in another with the same results. Sooooo???
Rule out the water thermo sensor altogether.
Pulsation damper.....not likely.
I'd say *something* is plumbed wrong. What? Got me.
Some of the characteristics of what it's doing are like a normal car in one sense. Say you idle a NORMAL car. Looking at the fuel pressure you would see approx 30psi fuel rail pressure. Turn the key to OFF. Sit and look at the gauge and you'll see the pressure rise to approx 37 psi. That is normal. Your engine seems to ape this but the pressure is waaaay too high.
When at idle, can you pull the vacuum hose off the FPR and see if it has vacuum on it. It should. That won't solve the high pressures your seeing but I think you should do that as a starter. Only do that after a full minute has passed since the car has been started. There's a reason for the full minute passing.
If you were just looking at the fuel pump pressure with the gauge in the end of the outlet line of the filter, then your 90 psi would be pretty much right for pump outlet pressure. This is with nothing else in the circuit, just the fuel pump.
Have you looked in the fsm's and looked at how the fuel lines run under the intake? Yours are similar?
Was this engine ever in a fire? I had one of those and the guts of the fpr blocked the passage of fuel.
No answer for you here, just some thoughts. There is BLOCKAGE somewhere in the run of lines or they are arranged wrong.
08-25-05 | 12:55 AM
#3
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Joined: Jan 2004
Posts: 515
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From: Utah (land of mountains)
Originally Posted by HAILERS
You should read only about 28-31 psi at idle on the fuel rail.
I'd say you have a bad FPR but then again you said you swapped in another with the same results. Sooooo???
Rule out the water thermo sensor altogether.
Pulsation damper.....not likely.
I'd say *something* is plumbed wrong. What? Got me.
Some of the characteristics of what it's doing are like a normal car in one sense. Say you idle a NORMAL car. Looking at the fuel pressure you would see approx 30psi fuel rail pressure. Turn the key to OFF. Sit and look at the gauge and you'll see the pressure rise to approx 37 psi. That is normal. Your engine seems to ape this but the pressure is waaaay too high.
When at idle, can you pull the vacuum hose off the FPR and see if it has vacuum on it. It should. That won't solve the high pressures your seeing but I think you should do that as a starter. Only do that after a full minute has passed since the car has been started. There's a reason for the full minute passing.
If you were just looking at the fuel pump pressure with the gauge in the end of the outlet line of the filter, then your 90 psi would be pretty much right for pump outlet pressure. This is with nothing else in the circuit, just the fuel pump.
Have you looked in the fsm's and looked at how the fuel lines run under the intake? Yours are similar?
Was this engine ever in a fire? I had one of those and the guts of the fpr blocked the passage of fuel.
No answer for you here, just some thoughts. There is BLOCKAGE somewhere in the run of lines or they are arranged wrong.
I'd say you have a bad FPR but then again you said you swapped in another with the same results. Sooooo???
Rule out the water thermo sensor altogether.
Pulsation damper.....not likely.
I'd say *something* is plumbed wrong. What? Got me.
Some of the characteristics of what it's doing are like a normal car in one sense. Say you idle a NORMAL car. Looking at the fuel pressure you would see approx 30psi fuel rail pressure. Turn the key to OFF. Sit and look at the gauge and you'll see the pressure rise to approx 37 psi. That is normal. Your engine seems to ape this but the pressure is waaaay too high.
When at idle, can you pull the vacuum hose off the FPR and see if it has vacuum on it. It should. That won't solve the high pressures your seeing but I think you should do that as a starter. Only do that after a full minute has passed since the car has been started. There's a reason for the full minute passing.
If you were just looking at the fuel pump pressure with the gauge in the end of the outlet line of the filter, then your 90 psi would be pretty much right for pump outlet pressure. This is with nothing else in the circuit, just the fuel pump.
Have you looked in the fsm's and looked at how the fuel lines run under the intake? Yours are similar?
Was this engine ever in a fire? I had one of those and the guts of the fpr blocked the passage of fuel.
No answer for you here, just some thoughts. There is BLOCKAGE somewhere in the run of lines or they are arranged wrong.
Can the charcoal canistor affect fuel pressure at all? I know it goes to the gas tank, and since I did the emissions removal the diagram showed one of the lines being cut, could that affect it?
No fire, so I don't think that's the issue. I guess I could have 2 bad FPRs, though it seems highly unlikely...
08-25-05 | 01:02 AM
#4
HAILERS
Joined: May 2001
Posts: 20,563
Likes: 23
From: FORT WORTH, TEXAS,USA
Nope. Charcoal canister has NO effect
JSPEC engine?
The very last thing in the fuel run should be the FPR. From the fpr the fuel goes back to the fuel tank.
JSPEC engine?
The very last thing in the fuel run should be the FPR. From the fpr the fuel goes back to the fuel tank.
Last edited by HAILERS; 08-25-05 at 01:05 AM.
08-25-05 | 01:14 AM
#5
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Joined: Jan 2004
Posts: 515
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From: Utah (land of mountains)
No Jspec, stock engine, ported, w/FD housings and NA rotors.
Fuel path is pump, filter, lower (primary) fuel rail firewall side, then from the front of the primary rail up to the front of the secondary rail, then through the FPR on the firewall side of the secondary rail back to the tank.
The engine sounds really good when it revs, then it will hold for an instant, then you can hear it start to sputter, then it dies. Once it starts sputtering and begins to die, gas pedal input has no effect on the engine.
Fuel path is pump, filter, lower (primary) fuel rail firewall side, then from the front of the primary rail up to the front of the secondary rail, then through the FPR on the firewall side of the secondary rail back to the tank.
The engine sounds really good when it revs, then it will hold for an instant, then you can hear it start to sputter, then it dies. Once it starts sputtering and begins to die, gas pedal input has no effect on the engine.
08-25-05 | 01:22 AM
#6
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Joined: Aug 2005
Posts: 555
Likes: 0
From: Midwest
Did you check to make sure your return line isnt clogged? How long did the car sit unused when you rebuilt the motor?
could be gelled gas in the line. Or maybe you kinked the return line somewhere...
Just some ideas
could be gelled gas in the line. Or maybe you kinked the return line somewhere...
Just some ideas
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