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Dewey316 The Lama
Joined: 08 Jan 2004 Posts: 7295 Location: Bringing the tech
1990 Chevrolet Camaro RS
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Posted: Wed Aug 30, 2006 7:47 pm Post subject: |
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Still nothingt. Tried a diffrent fuel pressure gauge tonight, I have no fuel pressure.
So, I get to start troubling shooting, checking things, checking lines, checking voltage, etc. |
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aaron_sK Member
Joined: 23 Jan 2006 Posts: 8834 Location: Back in beautiful Tacompton
1987 Chevrolet Camaro IROC-Z
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Posted: Wed Aug 30, 2006 8:18 pm Post subject: |
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So is the pump priming but not producing pressure, or is it just dead? |
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Dewey316 The Lama
Joined: 08 Jan 2004 Posts: 7295 Location: Bringing the tech
1990 Chevrolet Camaro RS
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Posted: Wed Aug 30, 2006 8:37 pm Post subject: |
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it primes. Sounds normal, as soon as I key on, and pump start, the guage flickers up to about 10psi, then drops right back down to zero, and never build pressure again. until I turn it off for 10-15 seconds, then key on, pump cycles, pressure flips up for a second, then back to zero. |
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iansane Member
Joined: 16 Jan 2004 Posts: 5740 Location: Bothell
1991 Pontiac Trans Am
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Posted: Wed Aug 30, 2006 9:37 pm Post subject: |
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It's getting proper voltage? |
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alloy T56 Elitist
Joined: 25 Jan 2004 Posts: 1716 Location: Vancouver, WA
1987 Chevrolet Camaro IROC-Z
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Posted: Wed Aug 30, 2006 10:31 pm Post subject: |
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I had a fuel pump relay go bad on me. It would start the pump........and the pump immediately quit. Turns out the relay was badly rusted inside and if you checked the voltage, I had full battery volts there, but when a load was put on it, the load overcame the bad connections ability to carry amperage and wouldn't pass enough current to run the pump. Drove me nuts. This was probably 10 years ago this happened to me. Just something to check and eliminate.
Also..............I seem to remember something about a second oil pressure switch controlling the fuel pump or something like that. I've not had that problem yet......but I seem to remember something about the extra switch. I hope I'm not having delusions about this......I am getting old ya know |
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Xophertony Rodeo Queen
Joined: 13 Oct 2005 Posts: 5304 Location: Portland, Oregon.
1988 Pontiac GTA
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Posted: Wed Aug 30, 2006 11:48 pm Post subject: |
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ALOY:
you are not going nuts (atleast not because of this . )there is an oil pressure switch that tells the car not to give fuel until oil pressure has built to a reasonable level. this switch is down low near the oil filter. on 1982-88 cars this is JUST for the fuel pump, with a seperate "bell" shaped sending unit under the dizzy for your PSI guage. then in 1989 they intergrated the PSI sender with the fuel pump switch (or so i have been told).
when this goes out it usualy just causes the car to not crank. this actualy sounds ALOT like a bad realy. there was a thread about this on TGO about two weeks ago, i was looking for it early today and cannot find it. _________________ 86' firebird (Junked in 2015). 88' GTA (sold in 2020).
aaron_sK wrote: | Hell, Tony drove his GTA to Cows a few years back with the pickup coil that came out in pieces. |
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Twilightoptics Hardcore (12sec Club)
Joined: 13 Jan 2004 Posts: 9191 Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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Posted: Thu Aug 31, 2006 7:19 am Post subject: |
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Oh John.... with TBI you might have rubber line for the return at the tank. Might be able to clamp it off there. My '85 Iroc had 3 rubber lines (vent/evap/return) |
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iansane Member
Joined: 16 Jan 2004 Posts: 5740 Location: Bothell
1991 Pontiac Trans Am
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Posted: Thu Aug 31, 2006 9:14 am Post subject: |
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Xophertony wrote: | ALOY:
you are not going nuts (atleast not because of this . )there is an oil pressure switch that tells the car not to give fuel until oil pressure has built to a reasonable level. this switch is down low near the oil filter. on 1982-88 cars this is JUST for the fuel pump, with a seperate "bell" shaped sending unit under the dizzy for your PSI guage. then in 1989 they intergrated the PSI sender with the fuel pump switch (or so i have been told).
when this goes out it usualy just causes the car to not crank. this actualy sounds ALOT like a bad realy. there was a thread about this on TGO about two weeks ago, i was looking for it early today and cannot find it. |
It's actually a missconception to think that it prevents the car from starting. It's purpose is to allow the car to start when the FP relay goes out. It's another one of those limp home features our cars have. It will automagically give power to the pump when a certain oil pressure is reached.
At least, that's how my 91 is.
When I bought the car it would crank and crank and crank and then fire. Took a good 10-15 seconds when it had sat for awhile. When I pulled the pressure sender out and put in autometer one the car wouldn't start. Checked voltage at the pump and there was nothing. I put that old pressure sender back in and just started testing wires and when I applied 12 volts to one side of the sender unit harness the pump would come on no matter what. Even if the key was off. _________________
Quote: | Sometimes I actually think I'm slightly retarded in the mouth. |
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85 T/A WS6 Member
Joined: 18 Feb 2004 Posts: 539 Location: Buckley
1985 Pontiac Trans Am
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Posted: Thu Aug 31, 2006 9:51 am Post subject: |
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alloy wrote: | I had a fuel pump relay go bad on me. It would start the pump........and the pump immediately quit. Turns out the relay was badly rusted inside ......... |
Same thing happened to me, car went from really crappy operation to none at all. Wife cleaned it up, called me at work and said "listen to this" She then held the phone up to the car and it started right up music to my ears.
It seems this may be a common problem, so much that somebody had siliconed around the relay to prevent corosion. |
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Dewey316 The Lama
Joined: 08 Jan 2004 Posts: 7295 Location: Bringing the tech
1990 Chevrolet Camaro RS
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Posted: Thu Aug 31, 2006 9:53 am Post subject: |
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Its easy enough to test that, I can just toss one of the other relay's in its place to test. I don't really need my cooling fan right now.
I took last night off, I'll be back to working on it tonight. |
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Xophertony Rodeo Queen
Joined: 13 Oct 2005 Posts: 5304 Location: Portland, Oregon.
1988 Pontiac GTA
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Posted: Thu Aug 31, 2006 11:18 am Post subject: |
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iansane: you are right, my bad
Dewey316 wrote: | Its easy enough to test that, I can just toss one of the other relay's in its place to test. I don't really need my cooling fan right now.
I took last night off, I'll be back to working on it tonight. |
i finally found that post on TGO i was thinking of. here is the quote on how to test your relay:
BigBabyLou on TGO wrote: | For future reference, you can find a lot of diagrams (including many special ones) on our ATGO page (AustinThirdGen.Org) in the Tech Article section HERE.
Now for some basic troubleshooting.
1) Take a test light and put the alligator clip on a good ground. Then pull off the fuel pump relay connector and test the big orange wire terminal with the test light. Does it light up? Good. If it doesn't, check the fuse by the battery.
2) Now stab the light into the terminal for the green/white wire. Go turn the key on. Does the light come on for 2 seconds? Good. If not, you have a problem in the wire going to the ECM (that controls the fuel pump relay).
3) Plug relay connector back in. Put your hand on the relay and yuor ear close to it. Have someone turn the key on. Does the relay click once and then again 2 seconds later? No, pull the relay out of the car, grab a hammer and have at it! Then go buy a new one for $10. (link here)
4) Put the test light on the tan/white wire (with the relay plugged in). Turn the key on. Does the test light come on? No? See solution to #3.
However, if the test light did come on in the last test but the fuel pump didn't prime, there's a wiring problem on the tan/white wire going down the harness to the oil pressure switch.
Let us know what you find out. But my guess would be that the relay is burned out. I'm curious how wrong I am.
Lou |
http://www.thirdgen.org/techboard/electronics/383820-wire-cut.html?
hope this helps |
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CheezX Member
Joined: 16 Jan 2004 Posts: 90
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Posted: Thu Aug 31, 2006 4:41 pm Post subject: |
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Sounds like blockage and/or leakage. System should be able to hold that 10psi for some time. Sounds like the relay works fine, even then the oil pressure switch would act as a backup power circuit once you get it cranking (just won't prime for 2 seconds with key on).
Do you have an adjustable regulator? Did you replace the in-tank filter or if not, how did it look?
BTW, if you were ever going to upgrade the pump, I'd do a Walbro 255 L/h, drops right in like stock and works great. Only $100-ish. |
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Dewey316 The Lama
Joined: 08 Jan 2004 Posts: 7295 Location: Bringing the tech
1990 Chevrolet Camaro RS
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Posted: Thu Aug 31, 2006 4:55 pm Post subject: |
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Mike,
Yes, I replaced the sock filter when I did the new pump. No visual leaks in the fuel system, with TBI luckily enough I can even see the injectors, I do not see any leaks there. I am going to run a few more test tonight, and see what I can find. |
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Twilightoptics Hardcore (12sec Club)
Joined: 13 Jan 2004 Posts: 9191 Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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Posted: Thu Aug 31, 2006 5:48 pm Post subject: |
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Oil pressure switch is supposed to shut the fueling OFF when there is no oil pressure in the event of an accident.
IIRC under wiring diagrams, when the key is at "start" it runs through a different piece of the circuit that allows fuel when the oil pressure isn't there. |
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Dewey316 The Lama
Joined: 08 Jan 2004 Posts: 7295 Location: Bringing the tech
1990 Chevrolet Camaro RS
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Posted: Thu Aug 31, 2006 8:06 pm Post subject: |
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Well, checked again tonight, capped the fuel off and still not holding pressure. I also tried a diffrent relay (borrowed the fan relay), same deal.
Fuel pump is pumping, i left the line unhooked and it does pump fuel into a bucket.
Looks like the tank is coming back out, and I am going to have to check the rubber connector inside the tank again. Not a lot of other places for my pressure to be going.
This whole issue just makes me scratch my head. |
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aaron_sK Member
Joined: 23 Jan 2006 Posts: 8834 Location: Back in beautiful Tacompton
1987 Chevrolet Camaro IROC-Z
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Posted: Thu Aug 31, 2006 8:55 pm Post subject: |
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Wild guess.... could it be a clogged return line? |
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Twilightoptics Hardcore (12sec Club)
Joined: 13 Jan 2004 Posts: 9191 Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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Posted: Thu Aug 31, 2006 9:26 pm Post subject: |
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Asdfga3 wrote: | Wild guess.... could it be a clogged return line? |
That would increase pressure. |
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alloy T56 Elitist
Joined: 25 Jan 2004 Posts: 1716 Location: Vancouver, WA
1987 Chevrolet Camaro IROC-Z
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Posted: Thu Aug 31, 2006 9:39 pm Post subject: |
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I hope you are not using the stock fuel pulsator between the pump and line. They are crap and leak like a sive. Replace it with a short length of high pressure line and fuel injection hose clamps. |
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z28redline Member
Joined: 21 Jan 2004 Posts: 83 Location: Vancouver, B.C
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Posted: Thu Aug 31, 2006 10:00 pm Post subject: |
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alloy wrote: | I hope you are not using the stock fuel pulsator between the pump and line. They are crap and leak like a sive. |
I have heard this comment made by lots of people. They seem to have a habit of failing. Once it leaks it will just pump fuel right back into the tank and doesn't presurize the lines. Worth taking it out if your dropping the tank anyway.
As a side note, it does serve a purpose. It is suspose to dampen the pumping action of the pump so you get a more even pressure without spikes.
z28redline |
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Dewey316 The Lama
Joined: 08 Jan 2004 Posts: 7295 Location: Bringing the tech
1990 Chevrolet Camaro RS
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Posted: Fri Sep 01, 2006 8:25 am Post subject: |
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The Dan's...
All signs are pointing to the pulsator. Looks like the tank is coming back out this weekend, and I will be replacing the pulsator. I will probably just go with high-pressure rubber fuel line, and real hose clamps.
I sure hope that fixes it. I really don't want to be taking the fuel tank out of the car for a third time!!!
--john |
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