Fuel pump fail on my 91 ?

[Vette73]

Was heading out to wildwood car cruise this past Friday....About 100 miles into trip the car would hesitate when I gave it more throttle.....I could cruise with it at 80-90 but when I would give it more gas I got no response....A few times I went to the floor and car did not respond....

Got off at rest area near Atlantic city...Turned car off and that was it...Car would not start again....Cranked but no start.....Even tried a push start with a few vette lovers ( I was at rest area for 5 hours)

Used AAA for the tow home...George Maz was a big help and came to my house with the jumper wire for the fuel pumps but that did not work...

I changed these pumps around 8 months ago...I used the airtek pumps.....You do hear pumps come on when I turn key....

I'm guessing I should pull out pumps...Another possibility I'm guessing would be the fuel pressure regulator ? How can you check that ?

When I took the screw off at the end of the fuel rail and pressed in pin, very little if any fuel came out......In guessing that should be under pressure even if car is off ?

[Paul Workman]

Putting a pressure gauge on the fuel rail and turning the key ON (not start) the pressure should come up to ~44± a couple psi.
Then turning the key OFF, pressure should hold to within a pound or two for as much as 30 minutes. Failure coming to or holding pressure could be the pressure regulator, a check valve (my experience with Airtek pumps).

Also, if the diaphragm in the regulator is bad, there will likely be fuel in the hose between the regulator and the plenum. (Do you smell gasoline near the rear of the plenum with the ignition switch in the ON position?)

Also on the checklist, especially since you used the bypass jumper already, is to measure the current draw of the pumps. Normal draw is between 4-5 amperes for each pump (8-10 Amps total, in other words). (With the ignition switch OFF, configure the VOM for AMPERES and put the VOM in series between the positive battery post and the little black diagnostic pump connector with a red wire [found jutting out of the big wire loom next to the windshield wiper motor].

And, of course, being able to scan the ALDL connector could provide significant clues as well.

So...after this, what have you found? Let us know.

[Perry Mitchell]

Since you hear the pumps run, my guess is that one of the rubber hoses that connect to the metal fuel pipe has deteriorated due to ethanol gas. This allows the pumps to run but only recycles the gas back into the tank. This has happened to me twice in my 84 Corvette. I have since changed to hoses to ethanol compliant ones.

[Vette73]

Originally Posted by Paul Workman

Putting a pressure gauge on the fuel rail and turning the key ON (not start) the pressure should come up to ~44± a couple psi.
Then turning the key OFF, pressure should hold to within a pound or two for as much as 30 minutes. Failure coming to or holding pressure could be the pressure regulator, a check valve (my experience with Airtek pumps).

Also, if the diaphragm in the regulator is bad, there will likely be fuel in the hose between the regulator and the plenum. (Do you smell gasoline near the rear of the plenum with the ignition switch in the ON position?)

Also on the checklist, especially since you used the bypass jumper already, is to measure the current draw of the pumps. Normal draw is between 4-5 amperes for each pump (8-10 Amps total, in other words). (With the ignition switch OFF, configure the VOM for AMPERES and put the VOM in series between the positive battery post and the little black diagnostic pump connector with a red wire [found jutting out of the big wire loom next to the windshield wiper motor].

And, of course, being able to scan the ALDL connector could provide significant clues as well.

So...after this, what have you found? Let us know.

Really don't have any testers...No gas smell near plenum w key on.....I guarantee if i put a gauge on the fuel rail it would not be close to what its supposed to be..

My next step was to remove pumps and visually inspect.....

[Vette73]

Well pulled the fuel pump assembly and one of the hoses was off the pump....What a bummer.....Should have made the repair at the rest area.....Pump is not back in car yet because it got to dark out and the car is on the street......I'm guessing that's the culprit..

[billschroeder5842]

Originally Posted by Vette73

Well pulled the fuel pump assembly and one of the hoses was off the pump......I'm guessing that's the culprit..

Well, that is a relatively easy fix. Good for you that you discovered the issue. BTW.... How many miles on your 91? I'm still on the original fuel pump with 80k and and wondering if I'm pushing fate?

[Vette73]

Originally Posted by billschroeder5842

Well, that is a relatively easy fix. Good for you that you discovered the issue. BTW.... How many miles on your 91? I'm still on the original fuel pump with 80k and and wondering if I'm pushing fate?

I replaced my pumps about 1,000 miles ago...Car has 51,000 miles.....Reason I replaced them in the first place was a mistake on my part.....Car ran great up until temp reached about 170 ..Car would hesitate until about 3,000 rpm than it would be fine.....

I thought it was the pumps....Wound up being a sensor on the passenger side near the header.....

[dredgeguy]

Originally Posted by Vette73

Well pulled the fuel pump assembly and one of the hoses was off the pump....What a bummer.....Should have made the repair at the rest area.....Pump is not back in car yet because it got to dark out and the car is on the street......I'm guessing that's the culprit..

Yup, I had the exact same issue this past spring. A hose had come loose so we replaced the hose clamps with new stainless steel ones.

[TX '90 ZR1]

Remember that there are 2 different size hoses.
Outlet from "Y" is 3/8". From "Y" to the pumps is 5/16".
Might also consider getting a new "Y" from Carter to replace the plastic one. My plastic one developed a crack and was the cause of pressure leak down.

[A26B]

Originally Posted by Vette73

I replaced my pumps about 1,000 miles ago...Car has 51,000 miles.....Reason I replaced them in the first place was a mistake on my part.....Car ran great up until temp reached about 170 ..Car would hesitate until about 3,000 rpm than it would be fine.....

I thought it was the pumps....Wound up being a sensor on the passenger side near the header.....

That would be the O2 Sensor shorted out. At temp below "about 170F" and above "about 3000rpm, engine management is in open loop and ignores O2 sensor signal.