I follow you re: all the reasons why testing for voltage at the pump prime terminal is a good diagnostic tool.

What I don't understand, though, is why the fuel pump is not getting voltage without bypassing the relay? It leads me to believe that I may replace the fuel pump and it still won't work because the circuit is not supplying voltage the way it should under normal circumstances (i.e. not bypassing the relay).

 

This confirms there is continuity from the relay output terminal to the pump prime terminal.


This confirms there is continuity from the pump prime terminal to the fuel pump module connector.

Recheck it and make sure. If that's the case, we already know the ground at the module connector is good, and the pump must be faulty.

 

Sorry, perhaps I'm not phrasing my question the right way.

Why does the fuel pump only receive voltage when I run the jumper wire from the positive terminal of the battery to the pump prime terminal (vacant female connection next to the fuel pump relay)?

I have the factory repair manual for the truck and in the diagnostic routine it says if the pump only receives power when using a fused jumper wire, to check for a bad connection at the relay.

 

Exactly right, BUT, you have voltage from the relay at the prime terminal during pump prime, which also means you have voltage at the pump module.


Connect your positive voltmeter probe to the grey wire in the fuel pump module connector, and connect the black probe to ground. Have an assistant turn the ignition to the RUN position, you should show battery voltage for 2 to 3 seconds according to the data you've posted.

 

Ok, that worked, yes, I had voltage at the pump connector now. Neither the factory repair manual or the aftermarket repair manual mention that voltage is only supplied at the connector for 2-3 seconds. I just wasted hours of time on diagnostics when I could have had the pump replaced by now. I was working alone, turning the key to run, then going under the truck and checking voltage and by the time I got there, the signal had run it's course.

Thanks for your patience and this helpful information; i appreciate it.

 

My first post explained the 2 to 3 second pump prime

No problem bud, stick an AC Delco or Delphi pump in it, (don't use aftermarket cheapie stuff) and call it a day
Amazon and eBay both have pumps, make absolutely sure that it states "AC Delco" or Delphi" as the manufacturer. The way they word their ads is very misleading, be careful.

 

One additional question...I was looking at fuel pumps online and it looks like even the AC Delco and the Delphi pumps require splicing in a different style connector...is that right?

 

Most pumps come with the new style connector. It must be soldered on to the vehicle harness using rosin core solder, and the connections insulated with heat shrink tubing or other suitable material. DO NOT use the crimp style connectors that come with the pump.

 

This thread just saved my bacon...

I am not an electrical person, but now knowing that the fuel pump fuse is actually labeled ECM B helps as well as the information regarding the new GT280 connector...thanks to you both!