High fuel pressure, bad idle, related?
11-04-2013, 10:50 AM
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High fuel pressure, bad idle, related? I have a brand new Delphi ls1 fuel pump assembly on my 5.3 swapped firebird. I use to blow the hoses off in the tank utill I installed a return line identical to the v8 return less system. It has ran without issues for a few months. It has stock rails and 36 lb injectors.
I have had the car dyno tuned. It ran like this before the tune, and has slowly gone back to it. Cold starts are usually fine, but by the time I get to the end of my neighborhood the car will not want to idle when I come to a stop. It tries to idle below 500 rpm, and will surge between 200-600 and die. Warm starts do the same thing.
I have a glowshift fuel pressure guage. I installed it a week ago. It goes to 58 priming, and holds it for a while before bleeding off (good). Running it would do 62-63psi. It has slowly been going up. One day to 64 the next day 65. Just yesterday it was reading nearly 76. Then it flipped ****. Flicking between 60-80 and moving up untill it maxed out at 100psi. Surely the car would not continue to run at 100+psi? I'd be blowing the hose again. I thought the sender lost its ground but its fine, and it still reads 60 when primed, but immediately maxed out when it starts.
Is it possible to run with that high of fuel pressure? Could the high fuel pressure be messing up my tune?
Edit: I have a racetronics Hotwire kit installed.
What does the fuel rail damper do?
I have had the car dyno tuned. It ran like this before the tune, and has slowly gone back to it. Cold starts are usually fine, but by the time I get to the end of my neighborhood the car will not want to idle when I come to a stop. It tries to idle below 500 rpm, and will surge between 200-600 and die. Warm starts do the same thing.
I have a glowshift fuel pressure guage. I installed it a week ago. It goes to 58 priming, and holds it for a while before bleeding off (good). Running it would do 62-63psi. It has slowly been going up. One day to 64 the next day 65. Just yesterday it was reading nearly 76. Then it flipped ****. Flicking between 60-80 and moving up untill it maxed out at 100psi. Surely the car would not continue to run at 100+psi? I'd be blowing the hose again. I thought the sender lost its ground but its fine, and it still reads 60 when primed, but immediately maxed out when it starts.
Is it possible to run with that high of fuel pressure? Could the high fuel pressure be messing up my tune?
Edit: I have a racetronics Hotwire kit installed.
What does the fuel rail damper do?
Last edited by Y87bird00; 11-04-2013 at 11:26 AM.
11-04-2013, 10:58 AM
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So I need to find why it's so high. Clogged return or faulty regulator are the only culprits? Shat about the fuel rail dampener? What is the purpose of that.
11-04-2013, 07:51 PM
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My gauge freaked out again and now reads 65. It idles when the pressure is normal. There were no codes untill a few minutes ago. In going to check it now
11-04-2013, 10:21 PM
#6
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That pump doesn't have enough oomph to make that kind of PSI... I have the glow shift fuel pressure gauge as well. I am about to call them up tomorrow because mine is doing the same thing bouncing all over occasionally. I have triple checked my wiring and I think its either a gauge or sending unit problem.
The gauge reads offscale high (100psi) with no signal from the sending unit. I think my problem is my gauge because sometimes it loses color memory on a start and sometimes it doesn't.
The gauge reads offscale high (100psi) with no signal from the sending unit. I think my problem is my gauge because sometimes it loses color memory on a start and sometimes it doesn't.
11-05-2013, 08:33 AM
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My trans temp gauge retains its color when I turn the key on. But it resets when I start the car. The color button is also screwed up. I guess you get what you pay for. I need to use a real fuel pressure gauge and double check then.
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11-06-2013, 06:08 PM
#9
check your regulator also. when you start it and it idles fine, pop the hood and pull the vacuum off of it. Best to have either a camera watching the gauge or a friend. If you use a camera, do some commentary. Or do like I did and put a mechanical gauge on the rail itself. I used a -4AN to 1/8th NPT adapter, then got a mechanical gauge and a T connector or 90 elbow will work. screw in the gauge, then screw it onto the fuel rail Schrader valve connection. Don't forget to remove the core so it will read the pressure.
You cant see it all that great, but you get the idea. Good part of using a T fitting is that you already have a place for the fuel side of a nitrous kit.
You cant see it all that great, but you get the idea. Good part of using a T fitting is that you already have a place for the fuel side of a nitrous kit.
11-06-2013, 06:58 PM
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With the throttle position sensor unhooked, the car starts an idles perfectly. Even drove down the street fine minus a ses light. It's a new oriellys sensor but hell it could be bad. I put the old one back on but it starts and revs high. I replaced the old I e because I thought it would help a trans problem I had.
11-06-2013, 08:08 PM
#13
you sure you have the right part in mind?? I could see it doing that with the IAC motor, or even the fuel evap solenoid, but the engine can not get info to know when to add gas to the cylinder without the TPS telling it when you are giving it gas...
Take a picture of the part you are talking about and post it up, cause I know I am not the only one going WTH???
Take a picture of the part you are talking about and post it up, cause I know I am not the only one going WTH???
11-10-2013, 05:41 PM
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Well I swapped my tps again. I thought I put the stock back on but I might have mixed them up a while back. I tried to return the new one that I thought was the problem but I wound up with the oem one in the oriellys store! It has been running great now, and rarely stumbles at all. I think the high readings are from the glowshift gauge, and are not accurate.