[1985] Fuel Pump issues
Thread Starter
Melting Slicks
Joined: Jun 2004
Posts: 3,032
Likes: 4
[1985] Fuel Pump issues
I posted about a fuel pressure problem in my 1985 coupe over the weekend. And now I'm sitting here thinking of ideas of what could be the cause...
Here's the problem: The fuel pressure in my vette struggles to build to 30 psi when the pump is energized, and usually only makes it between 20 and 30 psi. On one occasion when I primed the pump, I saw the pressure start at 15 psi, then work its way up to ~25psi (?).
The pump sounds like its working harder then it should (going by the noise sitting in the drivers seat). Leakdown isn't bad at all, as whatever pressure it is able to build holds for a while. I was told that the pulse dampner above the pump in the tank could cause problems, but after some research that seems like it would only cause fast leakdown.
Any Ideas? Could bad wiring at the pump cause this? What should I look for?
BTW - new pump, inline filter, and strainer. 1985 pressures should be 34-39 psi. Oh and for those wondering, I re-ordered another FSM, and its should be here by the weekend *crosses fingers*. So if you just want to reference me towards something in there I'll gladly listen as well.
EDIT::: i feel as though I should add that while running pressure is always at ~30 - 32 psi, reguardless of RPM.
Here's the problem: The fuel pressure in my vette struggles to build to 30 psi when the pump is energized, and usually only makes it between 20 and 30 psi. On one occasion when I primed the pump, I saw the pressure start at 15 psi, then work its way up to ~25psi (?).
The pump sounds like its working harder then it should (going by the noise sitting in the drivers seat). Leakdown isn't bad at all, as whatever pressure it is able to build holds for a while. I was told that the pulse dampner above the pump in the tank could cause problems, but after some research that seems like it would only cause fast leakdown.
Any Ideas? Could bad wiring at the pump cause this? What should I look for?
BTW - new pump, inline filter, and strainer. 1985 pressures should be 34-39 psi. Oh and for those wondering, I re-ordered another FSM, and its should be here by the weekend *crosses fingers*. So if you just want to reference me towards something in there I'll gladly listen as well.
EDIT::: i feel as though I should add that while running pressure is always at ~30 - 32 psi, reguardless of RPM.
Last edited by mikey whipreck; Aug 21, 2006 at 09:39 AM.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Apparently it is receiving the 12v it needs or it wouldn't pressurize at all. You can check the connection and wiring above the tank, but doubt you will find anyting. If there was a leak, you would notice the pressure drop steady.
Start the engine and see what the pressure reads at idle and while giving throttle. Then pull the vaccum off the FPR while the engine is running and see what the fuel pressure does....I'm thinking you mentioned the FPR was original???
Start the engine and see what the pressure reads at idle and while giving throttle. Then pull the vaccum off the FPR while the engine is running and see what the fuel pressure does....I'm thinking you mentioned the FPR was original???
Thread Starter
Melting Slicks
Joined: Jun 2004
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Originally Posted by RRT vette
Start the engine and see what the pressure reads at idle and while giving throttle. Then pull the vaccum off the FPR while the engine is running and see what the fuel pressure does....I'm thinking you mentioned the FPR was original???
And I'm sure the FPR is a factory original. I guess I need to wait for my manual to run through the troubleshooting for the FPR.
Would a malfunctioning FPR make the fuel pump work harder, and cause it to not build up pressure?
And I know you've put a lot of time into helping me with this over the past couple of days, thanks
.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
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From: seattle WA
Well, since you're on your second fuel pump I doubt the pump is the
problem, and I believe you installed a new inline filter. I'd be looking at a restriction in the fuel lines, kinked or pinched, maybe the rubber line which is under the fuel door (how far it travels before attaching to a metal line I don't know). I'd also consider running some Seafoam in the fuel tank to help clean the lines etc. Bad wiring causing your problem is also doubtful. How is this puppy running? Is it possible your fuel pressure guage is not working correctly? Or the schrader valve is partially clogged?
problem, and I believe you installed a new inline filter. I'd be looking at a restriction in the fuel lines, kinked or pinched, maybe the rubber line which is under the fuel door (how far it travels before attaching to a metal line I don't know). I'd also consider running some Seafoam in the fuel tank to help clean the lines etc. Bad wiring causing your problem is also doubtful. How is this puppy running? Is it possible your fuel pressure guage is not working correctly? Or the schrader valve is partially clogged?
Thread Starter
Melting Slicks
Joined: Jun 2004
Posts: 3,032
Likes: 4
Originally Posted by rick lambert
Well, since you're on your second fuel pump I doubt the pump is the
problem, and I believe you installed a new inline filter. I'd be looking at a restriction in the fuel lines, kinked or pinched, maybe the rubber line which is under the fuel door (how far it travels before attaching to a metal line I don't know). I'd also consider running some Seafoam in the fuel tank to help clean the lines etc. Bad wiring causing your problem is also doubtful. How is this puppy running? Is it possible your fuel pressure guage is not working correctly? Or the schrader valve is partially clogged?
problem, and I believe you installed a new inline filter. I'd be looking at a restriction in the fuel lines, kinked or pinched, maybe the rubber line which is under the fuel door (how far it travels before attaching to a metal line I don't know). I'd also consider running some Seafoam in the fuel tank to help clean the lines etc. Bad wiring causing your problem is also doubtful. How is this puppy running? Is it possible your fuel pressure guage is not working correctly? Or the schrader valve is partially clogged?
It runs okay, though has a slightly rough warm idle (cold idle is solid) and maybe power seems to me missing on the topend, though that doesn't seem too bad. I ran a scan awhile back, and the BLM's seem to indicate that it was lean.
The fuel pressure gauge is new, though that being bad or the shraeder valve being clogged could be believable... however that would not explain why my pump sounds like its working so damn hard.... I should try a different gauge this weekend (I think I can borrow a friend's).
I checked for kinked lines before, but I can go over them again. That's free.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
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From: Louisiana
Originally Posted by rick lambert
Well, since you're on your second fuel pump I doubt the pump is the
problem, and I believe you installed a new inline filter. I'd be looking at a restriction in the fuel lines, kinked or pinched, maybe the rubber line which is under the fuel door (how far it travels before attaching to a metal line I don't know). I'd also consider running some Seafoam in the fuel tank to help clean the lines etc. Bad wiring causing your problem is also doubtful. How is this puppy running? Is it possible your fuel pressure guage is not working correctly? Or the schrader valve is partially clogged?
problem, and I believe you installed a new inline filter. I'd be looking at a restriction in the fuel lines, kinked or pinched, maybe the rubber line which is under the fuel door (how far it travels before attaching to a metal line I don't know). I'd also consider running some Seafoam in the fuel tank to help clean the lines etc. Bad wiring causing your problem is also doubtful. How is this puppy running? Is it possible your fuel pressure guage is not working correctly? Or the schrader valve is partially clogged?
As mentioned...how does the car run with the fuel pressure you have (lean?)?
EDIT: I see you have answered my questions..
Le Mans Master
Joined: Feb 2006
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From: Louisiana
Thread Starter
Melting Slicks
Joined: Jun 2004
Posts: 3,032
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Originally Posted by RRT vette
Other then the cutting out from 1000-1200 rpms, his situation is a copy of mine.
I'm not interested in an adjustable FPR- i just want to get to stock pressures - but this is really leaning me towards that as the culprit.
If I need to get one I see autozone has an edlebrock replacement FPR for $60. I think the magazines are all around $50... I don't have access to my car until friday, so hopefully I'll have my manual by them and will be able to test the FPR...
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From: The Top of Utah
Originally Posted by mikey whipreck
Would a malfunctioning FPR make the fuel pump work harder, and cause it to not build up pressure?
You should probably take it for a ride while you watch the fuel pressure gauge, to rule out the pump. You mentioned, "maybe power seems to me missing on the topend". If the pressure holds during a period of maximum demand, the pump is good. A simple test of the regulator, is to clamp off the fuel return line while the pump is running. The fuel pressure should jump up.
The fuel pressure should change as the manifold vacuum changes with the opening and closing of the throttle. Based on "Idle and throttle applied had no effect on Fuel Pressure (maintained 30-32 psi)", it may pay to check the vacuum source to the regulator to be sure it is active. If it is, this is another indication the regulator has problems. If if isn't, it needs correcting.
RACE ON!!!
Thread Starter
Melting Slicks
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Originally Posted by CFI-EFI
You should probably take it for a ride while you watch the fuel pressure gauge, to rule out the pump. You mentioned, "maybe power seems to me missing on the topend". If the pressure holds during a period of maximum demand, the pump is good. A simple test of the regulator, is to clamp off the fuel return line while the pump is running. The fuel pressure should jump up.
I checked the vacuum near the FPR (and it was ~22"), but I'll see if I can get right at the regulator to test it.
I need to figure out how to rig the FP gauge to the windshield so that I (or a passenger) can see it while driving... That hose on there is pretty short
Again... thanks all for the input. These problems seem the same as my last thread, I didn't mean to
it, sorry...
Last edited by mikey whipreck; Aug 21, 2006 at 12:53 PM.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
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From: Louisiana
Originally Posted by mikey whipreck
I clamped off the return line at the tank, and primed the pump, the pressure was at about 25 psi. Is that how I should have tested it?
I checked the vacuum near the FPR (and it was ~22"), but I'll see if I can get right at the regulator to test it.
I need to figure out how to rig the FP gauge to the windshield so that I (or a passenger) can see it while driving... That hose on there is pretty short
Again... thanks all for the input. These problems seem the same as my last thread, I didn't mean to it, sorry...
I checked the vacuum near the FPR (and it was ~22"), but I'll see if I can get right at the regulator to test it.
I need to figure out how to rig the FP gauge to the windshield so that I (or a passenger) can see it while driving... That hose on there is pretty short
Again... thanks all for the input. These problems seem the same as my last thread, I didn't mean to
it, sorry...
Instructor
Joined: May 2005
Posts: 132
Likes: 0
From: Torrington CT
When i did the pump on my 85 wiyhin a few days it was whining like hell. I got it from auotozone. I removed the valve core from the shrader valve and clamped a hose on. Had a friend turn the key and I had no volume. Went to chevy and paid the price but 3 years later no problem.
Race Director
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From: The Top of Utah
Originally Posted by mikey whipreck
I clamped off the return line at the tank, and primed the pump, the pressure was at about 25 psi. Is that how I should have tested it?
Originally Posted by mikey whipreck
I checked the vacuum near the FPR (and it was ~22"), but I'll see if I can get right at the regulator to test it.
Originally Posted by mikey whipreck
I need to figure out how to rig the FP gauge to the windshield so that I (or a passenger) can see it while driving... That hose on there is pretty short
Originally Posted by mikey whipreck
Again... thanks all for the input. These problems seem the same as my last thread, I didn't mean to it, sorry...
it, sorry...RACE ON!!!
Pro
Joined: Apr 2005
Posts: 590
Likes: 0
From: Boynton Beach, FL
[QUOTE=mikey whipreck]Here's the problem: The fuel pressure in my vette struggles to build to 30 psi when the pump is energized, and usually only makes it between 20 and 30 psi. On one occasion when I primed the pump, I saw the pressure start at 15 psi, then work its way up to ~25psi (?).
The pump sounds like its working harder then it should (going by the noise sitting in the drivers seat). Leakdown isn't bad at all, as whatever pressure it is able to build holds for a while. I was told that the pulse dampner above the pump in the tank could cause problems, but after some research that seems like it would only cause fast leakdown.
Any Ideas? Could bad wiring at the pump cause this? What should I look for?
Two things I'd do. 1) check the strainer inlet to the pump isn't clogged. 2) I'd replace the pulse damper with a piece of high pressure fuel injection hose. They all leak.
Larry
The pump sounds like its working harder then it should (going by the noise sitting in the drivers seat). Leakdown isn't bad at all, as whatever pressure it is able to build holds for a while. I was told that the pulse dampner above the pump in the tank could cause problems, but after some research that seems like it would only cause fast leakdown.
Any Ideas? Could bad wiring at the pump cause this? What should I look for?
Two things I'd do. 1) check the strainer inlet to the pump isn't clogged. 2) I'd replace the pulse damper with a piece of high pressure fuel injection hose. They all leak.
Larry
Thread Starter
Melting Slicks
Joined: Jun 2004
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First thing I'm going to do is run a line from the fuel feed line at the tank into a bucket. That will eliminate everything except the pump and the pulse dampner as suspect. If my pump still sounds like crap I know its one of two things.
If it sounds good, Then I'll check pressure at the various points that everyone has suggested, check the vacuum points and so on. By that time I should also have my fsm back, so I'll be able to troubleshoot using that as well...
I will post back with the results- but that could be a week or two away.
Thanks again for your help.
If it sounds good, Then I'll check pressure at the various points that everyone has suggested, check the vacuum points and so on. By that time I should also have my fsm back, so I'll be able to troubleshoot using that as well...
I will post back with the results- but that could be a week or two away.
Thanks again for your help.
Thread Starter
Melting Slicks
Joined: Jun 2004
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Ran a line into a bucket... not enough came out. Replaced pump with another Autozone unit, and it pumped out the requisit amount (1/2 pint in 2 second priming period). Hooked everything back up. Tested, fuel pressure shot up to 38 psi for approximately a second... then dropped down to 15 psi or so...
Following the flow chart my FSM leads me to: "Locate and correct leaking fuel injectors or cold start valve." The instructions for finding them lead me believe I have 3 bad injectors and 1 questionable one. I'll also probably replace the pulsator because its cheap.
I started a new thread in reguards to that problem.
Following the flow chart my FSM leads me to: "Locate and correct leaking fuel injectors or cold start valve." The instructions for finding them lead me believe I have 3 bad injectors and 1 questionable one. I'll also probably replace the pulsator because its cheap.
I started a new thread in reguards to that problem.
Last edited by mikey whipreck; Aug 27, 2006 at 11:27 PM.
