BluesFanGM

I knew old pump was going bad..stock steel lines where rusted, so I replaced them as well as a new filter. Got a new Delphi, worked well for about 20 days. Had a "dead crank" so I changed relay but it was good and the truck suddenly fired up. 4 days later, same problem, so I checked wiring plugs above the tank..unplugged, checked, plugged back in and it fired. Got the truck home and decided to change out the pump. Replaced sending unit and it was pumping fuel, no issues. Started again the next day and drove out but would not pump fuel after trying to depart my destination. I'm lost..all new SS fuel lines, new filter and tank cleaned to spec

chem_man

So, to clear things up, your fuel pump was going bad. You had a "dead crank" before you changed the fuel pump you changed the fuel pump relay and then the pump ran. Correct?

Then 4 days later same thing as above but this time you checked the wiring to the fuel pump and the truck started. Correct?

Now that you got the truck home you finally installed the new fuel pump and the next day it would not run. Correct?

If all of the above are correct, then I would say make sure you are getting 12 VDC at the fuel pump connector - back probe the connector with the positive test lead of a DMM, and ground the negative test lead to a frame or body ground NOT to the ground connection on the fuel pump connector. If you have battery voltage, good. Anything less than battery voltage (by more than 0.1 - 0.3 VDC) you have a bad connection between the fuel pump connector and the underhood electrical center. Now, we'll test the ground wire to the fuel pump. Put the DMM into ohms mode, and using the lowest resistance scale, connect the negative test lead from the DMM to a good frame or body ground, and the positive test lead to the ground wire at the fuel pump connector (back probe the connector). You should read 0.00 ohms. Now wiggle the wire a bit to make sure it is intact and if it is, the ohms reading should not bounce around. If you have more than 0.1 ohms of resistance between body/frame ground and the fuel pump connector, then you need to remove the fuel pump's ground wire where it connects to the frame and clean the terminal connector and the frame so it makes a good connection.

Another thing to do is to remove and reinstall the fuse in case the fuse terminals have corroded.

You can also perform a fuel pump current draw test by putting your DMM into current mode, select the 10 (or higher) amps range and use the DMM test leads in place of the fuel pump fuse. You should see somewhere between 5 and 9 amps being drawn by the fuel pump depending on the year of your truck.

Good Luck!

kevinkpk

What I read is intermittent fuel pump on\off. That points to me as a "flakey" electrical connection, go with that.

BluesFanGM

Appreciate the input.. it's was all correct. Checked all my electrical, but had to jumper the relay. And found my culprit. I was in a rush to put the initial pump on and did not wire the new connector in. This truck did have a new fuel pump installed almost 12 years ago and I remember putting that new harness on. My connector had definitely got that usual "heat up" issue and the pump was shorting intermittent where the wires were crimped! Still had a new harness in the shop, I soldered the connections this time and everything works great! Double checked the circuits and everything was good. Classic hurry up and get it done..but I didn't make any cash off THIS customer.

chem_man

Thanks for letting us know what you found!