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Ok, figured I would get some other opinions on this.
1997 Chevy pickup 5.7 Vortec 350 no start..
I could not hear the fuel pump when I turned the key. I checked the fuse and it was good. Can hear the fuel pump relay click when turning the key. Everything points to a bad fuel pump which is common in these trucks. I then tilted the bed and got underneath to the top of the fuel tank and put a test light on the harness coming from the front to the pump. I had power to the pump but the pump was not running so I pulled the pump out of the tank and installed a new one.
So, new fuel pump in the tank and it does not work. I have no fuel pressure, cant hear the pump run when I first turn the key and I again tested the power coming to the pump and my test light lights up when I turn the key on at the fuel pump. I wire brushed the bolt that holds the ground wire on the frame, and wire brushed the frame where that connects.
It again seems like my pump is bad but its brand new. What am I missing? I have power to the pump but it is not working.
I attached a picture to show the wires. The middle wire that is going to the pump is the one I get power from when I turn the key on.
I’m
stumped
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Replies
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It could be a out of the box bad pump or it could be voltage but no power. A high resistance circuit will light a test light but not run a motor.
Did you use the test light to test the ground or just the power? Ohmmeter is not enough of a test for a ground, some will show good continuity but cannot support reasonable current flow. I do voltage drop testing instead whenever possible. Could be a bad pump out of the box, I would connect 12v straight off the battery through an ammeter to the pump power feed with the key off for a few seconds and see if the pump is capable of running and to verify that there is enough current flow to rule out a bad ground.
Thanks for the replies.
I ran a wire directly from my battery to the fuel pump and touched the wire to the center pole going to the fuel pump and it does not power up. I’m assuming its the center wire that should be power as that is the one that lights up coming from the truck when I turn the key on. I really would like to make sure this new pump even works and I thought this should power it up.
I used a test light to check ground. I used the same wire coming off the battery, hooked the clip to the positive and touched the probe to the ground and it lights up showing me I have a good ground.
[quote=”barneyb” post=131715]It could be a out of the box bad pump or it could be voltage but no power. A high resistance circuit will light a test light but not run a motor.[/quote]
Agreed. A test light is perfect for checking fuses but useless in more advanced diagnostics. Always use a Multimeter.
I have a cheap Multi-meter and to be honest am learning how to use it.
Using a wire directly off the battery I am getting 11.5 volts on the gauge and that is using the positive probe on the wire and the negative prob on the ground. I then take the positive probe and put it in the connector and then turn the key on and I am getting 8.6. Going to my fuel pump website it says fuel pumps typically draw between 6-10 amps and the relay minimizes the current flowing through so the pump doesn’t get burned out. So I am not sure if the voltage difference is OK but it sounds like it will not read the same? I am trying to figure out the voltage drop test but everything I read online says the pump needs to be running and it does not power up.
I am still wondering why the pump would not run when I ran a power wire directly off the battery to the pump.
Hello 🙂
I just look at wiring diagram, and the Power feed to yor pump is not that middle Purple wire, that goes to fuel gauge.
Power feed to pump is nr C grey wire.
nr A black/withe wire is ground.Thats huge, Thanks!!
Now I know what the wires go to so I will have to start my way to the front and see where the power is lost. Knowing what color wires do what is a huge help.
Will have to give it a couple days as we are getting snow tomorrow and its sitting in the driveway.
And fuse is that ECM-B 20 amp..
Im sure you find the problem. Good Luck With the truck and the snow:)Thanks,
I checked the fuse earlier a couple times, and the relay was clicking when the key was turning. Going to start around that area with test light and multi meter and see where my power is lost.
Well now that the 6 inches of snow has melted I am back under this thing.
At this point I am thinking this new fuel pump is bad. Now that I know what wires does what I have been able to check it better. I have power at the plug going into the fuel pump (gray wire) for 3 to 4 seconds like its supposed to work. I checked he ground and that lights up the test light fine.
I took a meter to the gray wire when I turn the key on I get just under 12 volts. The pump does not run, I have 12 volts at the gray wire at the pump and the ground is good. I have to believe this new pump isn’t working? I find it hard to believe but if I have power there it should power up for those 3 to 4 seconds………
I am lost 🙁
Tried a different fuel pump and the same thing the pump is not running at all giving me no fuel pressure. Turn the key and I have 12 volts at the plug (gray wire) for the 3 seconds like its supposed to have but the pump does not fire up.
This is a long shot Don, but check out this video. Check the new pump by the VIN number. Saw this video a while back and it surprised me this was the case with the same year vehicle and two pumps.. Good luck.
My bad…it’s been a while since viewing this. The fuel pump was still operative it was the send unit…
Getting closer but still scratching my head.
Double checked all the terminals at the fuel relay and everything came out like its supposed to from what I have read online.
I then jumped pins 87 to 30 and turned the key on and the fuel pump runs. :ohmy:
I took my new fuel relay out and put my old one in. Turned the key and the fuel pump runs for 3 to 4 seconds like it supposed to !!
Now the truck starts but only runs for short bit then dies…….
Of course it starts raining out so I’m on hold to look further………..
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