Fuel Pump Issue

[Corvette Emma]

(1989 Corvette Coupe) The other day I had my car warming up in the driveway and it just died. I could crank the motor but it wouldn't turn over. I hooked up a fuel gage to the schrader valve and I didn't have any fuel pressure. I listened for the fuel pump when I turned the key but I didn't hear anything. I got out my factory book and it said to put 12 volts to the fuel pump to see if the fuel pump is OK. I am just a back yard mechanic, how do I put 12 volts to the fuel pump? What else could the problem be? Is it possible that the fuel pump relay is bad? How do I check the relay? Sometimes having the book to trouble shoot is good but having you guys with experience and tricks is more helpful.
Please help me again.
Thanks,
Lee

 

[vette079]

On my ´91 there is a small connector hanging loose from the main harness right under the master brake cylinder.

That wire can be connected to the POS. batt. post to drive the fuel pump.

See if you have it there, otherwise you could short two connectors at the aldl (a+g?).

I´m not shure wich it was, you should get the same result.

But wait for someone here with the right pins to connect.

 

[vetteoz]

Relay check ; swap with radiator fan relay ( assume that works ?)

 

[Corvette Emma]

I went out and looked at my car and I do have a wire with a connector by the brake booster. I will run a jumper from the battery to the connector to check if the fuel pump is ok. If that checks out I will try the fan relay swap. Thanks for the input.

 

[doublefoxed]

Here is another simple trick.. take a rubber hammer and smack the
fuel tank. Crank car.... it should crank right up and if it does do not
drive it cause it will not last long. This trick works every single time to
find a bad fuel pump. I have never seen one to date that didn't start.
If it doesn't usually it's a relay problem.

 

[Corvette Emma]

I tried the rubber mallet trick but it didn't work. I swapped the fan relay but it still didn't work. Does anybody know which two connectors on the aldl can be shorted to run the fuel pump? I looked at my wiring harness for the loose wire by the brake booster, I have a wire that comes out of the harness that is connected then runs back into the harness. Is this the wire I can disconnect then connect it to the battery to run the fuel pump? I read something somewhere about a low oil pressure sensor that will shut down the fuel pump. Has anybody heard about this?

 

[jmccloud]

Fuel pump

Have you checked the fuel pump fuse?

 

[Corvette Emma]

I didn't see anything in my book about a fuel pump fuse. Where is the fuse located? Is it in the fuse panel or is it a in-line fuse?

 

[JAKE]

Should be in the fuse panel marked FP.

Guys, correct me if I'm wrong, but there's a back-up for the fuel pump that'll allow the pump to continue to run even if the relay fails as long as there is at least 4 psi (give or take) of oil pressure.

In fact, the engine will start with a failed relay after the sensor detects 4 psi of oil pressure. The sensor is screwed into the block at the extreme rear of the intake manifold, just to the driver's side of the distributor on L98s.

I know my previous 86 was setup that way. On my 96, the relay is located under and behind the driver's side dash and the fuse is under the hood.

Jake

 

[JAKE]

Also, on the TPI engines you can apply battery voltage to terminal "G" on the ALDL (Assembly Line Diagnostic Link), also referred to as ALCL, which is mounted under the dash, near where your right knee would be when sitting in the driver's seat.

Terminal 'G' is the opening in the lower row, extreme left hand side of the ALDL/ALCL.

You can also jump terminals "D" AND "E" of the fuel pump relay using alligator clips. To do this, the relay has to be unbolted from the firewall for access.

If the pumps runs, you'll need a fuel pressure gauge to see that it creates around 39 psi with the engine idling. One book I have says 34-39 psi. If no pressure or pressure below 34 psi, the fuel filter may be blocked. If after checking the filter and the fuel lines and nothing is leaking but pressure is still below 34 psi, replace the fuel pump.

Hope this helps.

Jake

 

[Corvette Emma]

Hi Jake,
I jumped power to the "G" terminal on the ALDL, I could hear the pump running but the fuel pressure didn't budge from the 10 psi on the gauge. Although the pump is making a whining sound, could the pump still be bad. The fuel filter had been previously changed so now it has about 1,000 miles on it. I think the filter is OK.
Reading some forums on the fuel pump removal seems like a doable task for a backyard mechanic like myself. If I was reading right, the fuel pump can be removed from the fill pipe and not by dropping the the tank. Do you or anybody else out there think it is the fuel pump?
Thanks for all your help.
Although I haven't found the problem yet, at least you guys are giving me things to check before I throw the towel in and have it towed to a shop.
Thanks again,
Lee

 

[JAKE]

Some fuel pressure gauges don't work well unless the Schrader valve is removed. My Accel gauge is that way, maybe yours needs to have the valve unscrewed.

You should check the fuel pressure regulator for any sign of leakage. If fuel flows from the regulator or hose, it's bad. I'd check that before buying a new pump.

Yes, the pump's easy to change, but I'd first check the sock located on the very end of the fuel pump assembly to see if it's partially blocked with trash. Pulling the pump only involves removing the hoses (I believe there are three), and electrical connector and a few screws. All done from working under the fuel filler door; no need to drop the tank.

Even though you say the filter is relativel new, it could still be the cause of the problem if it's become clogged with sediment/trash. If all else checks okay, check the filter to be sure it's not installed backwards (there's an arrow showing the direction of fuel flow and should be pointed forward). You can also pour out any fuel in the filter to see if any trash comes along with the gas.

Be sure to use a back-up wrench when unscrewing the filter to prevent tweaking/twisting/bending the fuel line.

Of course I'm sure you know you'll need sturdy jackstands in place before crawling under the car.

Keep us posted.

Jake

 

[Corvette Emma]

Hi Jake,
My schrader valve a fuel pressure gage are both Ok, the gage is new and I used both to adjust my fuel pressure just a couple of weeks ago. If I get a break in the weather, I was going to replace the fuel pump sock. It is about an 8 dollar part. I think since I hear the fuel pump whining, it must be starved for fuel. Like you said, maybe the sock is blocked. My question is this, if I am going thru the trouble of replacing the sock, should I just replace the fuel pump while I am in there?
Thnaks for the comments,
Lee

 

[LT4man]

If you think your fuel pump is the one which was installed in Bowling Green, I would definitely replace the whole unit.

SAVE THE !

 

[Corvette Emma]

Hi LT4man,
I believe the fuel pump is original, the car has 20k miles and I am the second owner. I am going to go with your recommendation and replace the pump. I saw one in Ecklers, it is a high volume pump with the sock and install hardware for $125. It didn't say what brand it was. Do you have any pump recommendations or do you think the one from Ecklers is OK. Ecklers also carries the AC Delco replacement but I figured it wouldn't hurt to upgrade to a high volume since I had made some intake modifications.
What is you opinion?
Thanks for the comments,
Lee

 

[minifridge1138]

If you're already in the tank, then i would replace the fuel pump.

19 years is a long time to sit and soak in gasoline without going bad, even if it is low mileage.

Good Luck!!!

 

[Corvette Emma]

Hi Mini,
I just purchased a fuel pump (AC Delco Stock Replacement) and sock from Ecklers, I'll let all of you know how it goes.
Hopefully it is an easy install.
I would like to thank everybody for your comments.
I know everybody says to get a factory manual or a haynes manuel but I have both and I still rely on everybody at CAC for input. The manual doesn't always give the easiest way so I rely on CAC to give my the best way based on experience.
Thanks again and stay tuned for the outcome of the fuel pump replacement.
(Same channel, same Bat time)
Thanks,
Lee

 

[JAKE]

The reason I mentioned the Schrader valve is that some fuel pressure gauges are designed to depress the Schrader valve when the gauge is screwed on, but other types of pressure gauges aren't designed that way.

When using the second type, the Schrader valve has to be unscrewed and removed before the gauge will show the correct pressure. I have the kind that requires me to unscrew the valve.

Jake

 

[LT4man]

Hi LT4man, I saw one in Ecklers, it is a high volume pump with the sock and install hardware for $125. It didn't say what brand it was. Do you have any pump recommendations or do you think the one from Ecklers is OK. Ecklers also carries the AC Delco replacement but I figured it wouldn't hurt to upgrade to a high volume since I had made some intake modifications.
What is you opinion?
Thanks for the comments,
Lee

The OEM pump is good for over 400hp. Just your personal preference. The price from Ecklers is certainly very reasonable.

SAVE THE !

 

[tonylong]

I want to follow this too. I may also have pump issues.