Ot:99 GMC Yukon

[rrman61]

How do I test a fuel pump on a 99 Tahoe with the 350 gas engine? Hot and ground to pump or is it more than that?

 

[Sprint 6]

99 should have a single wire taped back in the harness near the under hood fuse block. It will be a red wire with a female terminal in a black connector. Just hook that wire to positive and the pump will run if the pump is good. Pressure should be 60-66psi, much less and they are hard to start.

 

[Steve@Advance]

There are also fuel gauge wires in the same harness, don't want to put power to them!

If you're checking at the pump harness, I'm thinking gray is +, black is ground, but don't take my word for it! You could use them as test points to see if the pump gets power when the ignition is turned on, should run for a few seconds each time the ignition turned on.

If the pump is still in the truck and connected, you should be able to use a jumper wire across the pump relay, terminals 30 and 87. That should make the pump run and make pressure, about 65-70 PSI.

 

[rrman61]

It's my sons vehicle.he took it off already and I'd like to test it off the vehicle if possible

 

[Sprint 6]

You will have to match the pins on the pump with the wires on the harness to get the correct pins. Heavy gray wire is power and heavier of the two black wires is ground. You will be creating a massive fire hazard doing it this way as it will shoot fuel several feet, and no way to check pressure.

 

[Steve@Advance]

Just follow the wires that go to the pump, connect to battery voltage.

That will prove it will run, but would be difficult to test the performance. They also have a reputation for intermittent run/fail, so test running it won't prove much.

If it has a lot of miles on it (100,000+), best to just replace it. If this is a vehicle you plan to keep and make reliable, I would opt for a real Delco brand over an aftermarket.

 

[rrman61]

Tank is off the truck.want to make sure it's the pump before changing it.will take precautions,there shouldn't be alot of gas in pump.thanks guys

 

[MarkB_MI]

If the tank is already off the truck, why would you consider putting it back without replacing the pump? Either the pump is bad now or it will fail sometime in the future. And you can bet your bottom dollar it will fail when the tank is full of gas.

 

[Bryan inIowa]

if its out replace it. You can only test if its running. No way test pressure and volume. New pumps come with an updated harness connector also I believe . Why did he pull it out ?

 

[RobCons]

As suggested since tank is removed already replace the pump. I have 340k on a 2001 Silverado and I am on my third pump.

 

[BobReeves]

I had to replace the fuel pump on my 2000 Chevy pickup (probably the same as your Tahoe) not because the pump quit but because the pickup tube on the pump had a small hole it it. What it did was make it hard to start if it sat for any length of time. The fuel would drain out of the pump and it would loose it's prime.

I would replace it while you can. I pulled the bed off my pickup to keep from draining and dropping the tank but you are already there.