97 Blazer 4.3L - Ground Wire for Fuel Pump

[Rod Man]

I have been having a hard time diagnosing a non-working fuel pump. Here's what I do know:
1. Fuel Pump Relay works and power to relay was tested and works.
2. ECM fuses are good
3. Tested for power to fuel pump and power works.
4. Replaced oil pressure switch
5. Took fuel pump out of tank and put power to pump - fuel pump works.
Here's what I don't know:
1. Didn't test ground wire to fuel pump individually.
2. Don't have a ground wire for the fuel tank. Have heard before that there should be one, but never saw one since I bought the truck(3 years ago).

So, my question is what's the best way to test the ground wire on the connector for the fuel pump? And, if the wire is bad, should I run a new wire from the connector all the way up to the negative side of the battery, or can I just connect it to the frame. Also, should I buy a ground strap for the tank? Any help that I can get is well appreciated. Thanks in advance!

[sleslie17]

I would think you would be best grounding the fuel pump on the frame - as long as the frame is ground. That frame is a much bigger wire than one you could run to the battery. Make sure the frame is ground by measuring battery voltage(+ on battery post) with respect to the frame somewhere up by the battery - if you get 12V, the frame is gnd obviously. You could check continuity of the wire though 1st with a ohmeter. I don't have a good idea of the cable or the working of the fuel pump though - that's the best advice I could offer, electrically speaking.
-Shawn

[Rod Man]

Originally Posted by sleslie17

I would think you would be best grounding the fuel pump on the frame - as long as the frame is ground. That frame is a much bigger wire than one you could run to the battery. Make sure the frame is ground by measuring battery voltage(+ on battery post) with respect to the frame somewhere up by the battery - if you get 12V, the frame is gnd obviously. You could check continuity of the wire though 1st with a ohmeter. I don't have a good idea of the cable or the working of the fuel pump though - that's the best advice I could offer, electrically speaking.
-Shawn

Thanks for replying Shawn. I am a little confused, though. I did put a multimeter on the battery, and I did get 12 volts. I was thinking of splicing the ground wire on the wiring harness that leads to the plug for the fuel pump and directing that wire to the frame to see if that gives me a good ground. I think that there is a break somewhere, and I don't know how much work would be involved to pull that ground wire out of the harness to see where it goes. Your thoughts?

[GMMerlin]

Originally Posted by Rod Man

I have been having a hard time diagnosing a non-working fuel pump. Here's what I do know:
1. Fuel Pump Relay works and power to relay was tested and works.
2. ECM fuses are good
3. Tested for power to fuel pump and power works.
4. Replaced oil pressure switch
5. Took fuel pump out of tank and put power to pump - fuel pump works.
Here's what I don't know:
1. Didn't test ground wire to fuel pump individually.
2. Don't have a ground wire for the fuel tank. Have heard before that there should be one, but never saw one since I bought the truck(3 years ago).

So, my question is what's the best way to test the ground wire on the connector for the fuel pump? And, if the wire is bad, should I run a new wire from the connector all the way up to the negative side of the battery, or can I just connect it to the frame. Also, should I buy a ground strap for the tank? Any help that I can get is well appreciated. Thanks in advance!

When you look at the connector for the fuel pump there should be 4 wires.
Gray wire is the Fuel pump 12volt feed wire
Purple wire is the sender wire
there are 2 black wires..they are the ground wires for the pump and sender
Since you have a multimeter, put the dial on ohms and check the continuty between the connector and ground..if you have good resistance..less than 1 ohm, then you have the ground necessary to operate the fuel pump

[GMMerlin]

Next question is..does the fuel pump put out enough pressure for the vehicle to run..should be around 65 psi...

[Rod Man]

Originally Posted by GMMerlin

When you look at the connector for the fuel pump there should be 4 wires.
Gray wire is the Fuel pump 12volt feed wire
Purple wire is the sender wire
there are 2 black wires..they are the ground wires for the pump and sender
Since you have a multimeter, put the dial on ohms and check the continuty between the connector and ground..if you have good resistance..less than 1 ohm, then you have the ground necessary to operate the fuel pump

Hey GMMerlin,

Will I have to have the key to the "ON" position when I do this? If so, I will probably have to drop the tank about 6 inches to be able to reach the wires while they are still plugged in to the pump.

[Rod Man]

Originally Posted by GMMerlin

Next question is..does the fuel pump put out enough pressure for the vehicle to run..should be around 65 psi...

The pump was never an issue. I dropped the tank and pulled the pump out and was able to hook up power to it and it works. Never had a pressure issue.....It just stopped running one day after it was sitting for a few hours. I would turn the key and you couldn't hear the fuel pump prime. Had it towed home, and while the tow truck still had it up(towed from the rear wheels), we got under it and jiggled the fuel lines and the pump wires, and it started, which led me to believe that there may be a short.

[GMMerlin]

Originally Posted by Rod Man

Hey GMMerlin,

Will I have to have the key to the "ON" position when I do this? If so, I will probably have to drop the tank about 6 inches to be able to reach the wires while they are still plugged in to the pump.

No..do not do resistance checks with the key on.

[Rod Man]

Originally Posted by GMMerlin

No..do not do resistance checks with the key on.

Hey GMMerlin,

Is it possible to blow the pump out if you put power directly to it? It seems now that the pump is not running when you put power directly to it. I hooked it up directly to the car battery, and the battery was giving out about 13.6 volts. If that's the case, I will have to buy another pump. Good thing there's a company in California that sells the pump only for $50.00!

Rod Man

[mjohn]

whats the name of the Company in Calif...?

[Rod Man]

Originally Posted by mjohn

whats the name of the Company in Calif...?

Direct Auto.com

Keep in mind that what they sell is the pump only, not the whole assembly. You would have to take the assembly apart and take the pump out and return the core. It's not that hard to do. My sending unit works just fine, which is why I opted for this way.