No power to fuel pump
Thread Starter
Le Mans Master
Joined: Aug 2005
Posts: 5,130
Likes: 3
From: Winter Park FL
No power to fuel pump
I recently did a motor swap and installed a procharger. I have a dual external fuel pump setup. I got a Racetronix wiring harness for it. I have power at the relay from the battery but it is not switching over to the fuel pump. I believe the gray wire in the Racetronix harness from the stock FP harness to the relay is what switches the relay when the ignition comes on. I believe I am not getting power there. Checked fuse #13 and it is good.
Where does that stock FP wiring harness go? What can I check? It was working when I took the car apart so I assume I missed a connection or something like that.
Where does that stock FP wiring harness go? What can I check? It was working when I took the car apart so I assume I missed a connection or something like that.
Tech Contributor
Joined: Jan 2007
Posts: 19,470
Likes: 1,170
From: Dyer, IN
I recently did a motor swap and installed a procharger. I have a dual external fuel pump setup. I got a Racetronix wiring harness for it. I have power at the relay from the battery but it is not switching over to the fuel pump. I believe the gray wire in the Racetronix harness from the stock FP harness to the relay is what switches the relay when the ignition comes on. I believe I am not getting power there. Checked fuse #13 and it is good.
Where does that stock FP wiring harness go? What can I check? It was working when I took the car apart so I assume I missed a connection or something like that.
Where does that stock FP wiring harness go? What can I check? It was working when I took the car apart so I assume I missed a connection or something like that.
Thread Starter
Le Mans Master
Joined: Aug 2005
Posts: 5,130
Likes: 3
From: Winter Park FL
Drivetrain and motor out. The FP ground in the rear fender is connected. I am not sure where the wiring harness runs though. Looks like it runs up into the cabin. When the motor was in I jumped the stock pump to drain the tank to drill for the fuel system. No problems there.
Tech Contributor
Joined: Jan 2007
Posts: 19,470
Likes: 1,170
From: Dyer, IN
Drivetrain and motor out. The FP ground in the rear fender is connected. I am not sure where the wiring harness runs though. Looks like it runs up into the cabin. When the motor was in I jumped the stock pump to drain the tank to drill for the fuel system. No problems there.
http://forums.corvetteforum.com/c5-t...e-grounds.html
Tech Contributor
Joined: Jan 2007
Posts: 19,470
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From: Dyer, IN
Just trying to be clear here....G105 needs to have the appropriate number of terminals: one ground strap, and one black wire. Have you tried jumpering the fuel pump relay socket, to see if the pump runs....with the key on?
Thread Starter
Le Mans Master
Joined: Aug 2005
Posts: 5,130
Likes: 3
From: Winter Park FL
Second, I am getting power to the stock pump harness but only get a very slight reading at the relay when it was jumped.
Tech Contributor
Joined: Jan 2007
Posts: 19,470
Likes: 1,170
From: Dyer, IN
Yes, 2 connections. I just jumped the FP and got power to the relay/pump for a moment then it shut off. Now with the pump jumped I am getting power to the stock pump harness but am getting a lower reading at the relay and no power to the aftermarket pump. So I'm guessing I have 2 issues here. First, what is in the way of power getting to the stock pump harness. I jump it off the battery and get power. No power with the relay in.
Second, I am getting power to the stock pump harness but only get a very slight reading at the relay when it was jumped.
Second, I am getting power to the stock pump harness but only get a very slight reading at the relay when it was jumped.
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Thread Starter
Le Mans Master
Joined: Aug 2005
Posts: 5,130
Likes: 3
From: Winter Park FL
Instructor
Joined: Nov 2010
Posts: 100
Likes: 81
From: Katy TX
I've become very familiar with the fuel pump wiring over the last week....
Have you tried swapping out the fuel pump relay for another identical relay in the underhood fuse panel?
With the key in the "on" position (not running), the pcm signals the fuel pump relay to run for 2 seconds and then shuts off. Based on your testing above - it sounds like the relay is receiving the correct signal from the pcm and your relay might be bad.
Have you tried swapping out the fuel pump relay for another identical relay in the underhood fuse panel?
With the key in the "on" position (not running), the pcm signals the fuel pump relay to run for 2 seconds and then shuts off. Based on your testing above - it sounds like the relay is receiving the correct signal from the pcm and your relay might be bad.
Tech Contributor
Joined: Jan 2007
Posts: 19,470
Likes: 1,170
From: Dyer, IN
I've become very familiar with the fuel pump wiring over the last week....
Have you tried swapping out the fuel pump relay for another identical relay in the underhood fuse panel?
With the key in the "on" position (not running), the pcm signals the fuel pump relay to run for 2 seconds and then shuts off. Based on your testing above - it sounds like the relay is receiving the correct signal from the pcm and your relay might be bad.
Have you tried swapping out the fuel pump relay for another identical relay in the underhood fuse panel?
With the key in the "on" position (not running), the pcm signals the fuel pump relay to run for 2 seconds and then shuts off. Based on your testing above - it sounds like the relay is receiving the correct signal from the pcm and your relay might be bad.
Thread Starter
Le Mans Master
Joined: Aug 2005
Posts: 5,130
Likes: 3
From: Winter Park FL
Ooooooook. So, harness hooked up. The only way I get power to the stock FP harness is to jump it like Lucky said. With it jumped I can turn the key and get a pump. With the relay(I did try switching identical relays) I do not get the power. It has to be something in the stock wiring, either I have something not plugged in or I pinched a wire or blew a fuse.
At least I got the pump on so I could check the system for leaks.
At least I got the pump on so I could check the system for leaks.
Tech Contributor
Joined: Jan 2007
Posts: 19,470
Likes: 1,170
From: Dyer, IN
Ooooooook. So, harness hooked up. The only way I get power to the stock FP harness is to jump it like Lucky said. With it jumped I can turn the key and get a pump. With the relay(I did try switching identical relays) I do not get the power. It has to be something in the stock wiring, either I have something not plugged in or I pinched a wire or blew a fuse.
At least I got the pump on so I could check the system for leaks.
At least I got the pump on so I could check the system for leaks.
1) If you get a 12 volts signal at 86 when the key is on
2) What the resistance to ground is at 85.
Tech Contributor
Joined: Jan 2007
Posts: 19,470
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From: Dyer, IN
That's good. That tells us that the pcm is turning on the fuel pump relay. I'd have to see your meter, because they are all not the same. There should be a setting for "ohms". Do you have the manual for your meter. Post the type and model..sometimes they are available online.
Thread Starter
Le Mans Master
Joined: Aug 2005
Posts: 5,130
Likes: 3
From: Winter Park FL
That's good. That tells us that the pcm is turning on the fuel pump relay. I'd have to see your meter, because they are all not the same. There should be a setting for "ohms". Do you have the manual for your meter. Post the type and model..sometimes they are available online.
Tech Contributor
Joined: Jan 2007
Posts: 19,470
Likes: 1,170
From: Dyer, IN
Given all that, provided the relay is good, you will have 12 volts to the fuel pump. The only thing that will cause the fuel pump to drop during cranking, is if the pcm does not get an output from the crankshaft sensor.
Thread Starter
Le Mans Master
Joined: Aug 2005
Posts: 5,130
Likes: 3
From: Winter Park FL
I haven't turned the motor over. The pump isn't coming on when the ignition is turned on. Would that still be possibly caused by the sensor? Is there a way to verify the relay is good?
Tech Contributor
Joined: Jan 2007
Posts: 19,470
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From: Dyer, IN
1) If you jumper 30 to 87 on the relay socket, the pump runs.
2) Per the pic, 86 has 12 volts with ignition on
3) Per the pic, 85 has a good ground.
So you know the fuse is good, and all the conditions are there for the relay to work. If the relay does not energize, it's bad. You can test the relay, by providing 12 volts and ground to the 86 and 85 (numbers are on the bottom of the relay), and you should hear a click. While the relay is energized, you can measure the resistance across 87 and 30 of the relay.