Cascade Crew

Dewey316 · Posted: Wed Aug 30, 2006 7:47 pm Post subject:

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.

aaron_sK · Posted: Wed Aug 30, 2006 8:18 pm Post subject:

So is the pump priming but not producing pressure, or is it just dead? Confused

Dewey316 · Posted: Wed Aug 30, 2006 8:37 pm Post subject:

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.

iansane · Posted: Wed Aug 30, 2006 9:37 pm Post subject:

It's getting proper voltage?

alloy · Posted: Wed Aug 30, 2006 10:31 pm Post subject:

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 Wink

Xophertony · Posted: Wed Aug 30, 2006 11:48 pm Post subject:

ALOY:
you are not going nuts (atleast not because of this . Very Happy

)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.

Twilightoptics · Posted: Thu Aug 31, 2006 7:19 am Post subject:

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)

iansane · Posted: Thu Aug 31, 2006 9:14 am Post subject:

85 T/A WS6 · Posted: Thu Aug 31, 2006 9:51 am Post subject:

Dewey316 · Posted: Thu Aug 31, 2006 9:53 am Post subject:

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. Wink

I took last night off, I'll be back to working on it tonight.

Xophertony · Posted: Thu Aug 31, 2006 11:18 am Post subject:

iansane: you are right, my bad

CheezX · Member Joined: 16 Jan 2004 Posts: 90

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.

Dewey316 · Posted: Thu Aug 31, 2006 4:55 pm Post subject:

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.

Twilightoptics · Posted: Thu Aug 31, 2006 5:48 pm Post subject:

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.

Dewey316 · Posted: Thu Aug 31, 2006 8:06 pm Post subject:

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.

aaron_sK · Posted: Thu Aug 31, 2006 8:55 pm Post subject:

Wild guess.... could it be a clogged return line?

Twilightoptics · Posted: Thu Aug 31, 2006 9:26 pm Post subject:

alloy · Posted: Thu Aug 31, 2006 9:39 pm Post subject:

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.

z28redline · Posted: Thu Aug 31, 2006 10:00 pm Post subject:

Dewey316 · Posted: Fri Sep 01, 2006 8:25 am Post subject:

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