2003 Chevy Suburban Fuel Pump

[jonage]

Ok I had a no start on this 2003 suburban 4x4 auto trans 5.3L vin "z" flexfuel. Easy diag........no noise from the pump, no fuel pressure, and a bump on the fuel tank while cranking started the truck.
I like using my new Verdict scope so here is what I got.




Now this is the bad fuel pump that was a no start, after it was running


And this is the replacment pump (from advanced auto, as per customer....cheap ***)


So whats going on here? why does this new pump look so bad. Let me add that the only way to hook up my low amp probe was at the pump, and not through the fuse.

[Chip Wright]

Thats normal, drive it around for a while and recheck it after the brushes have worn in.

[jonage]

thanks

[Joe Rappa]

I'm betting Chip is correct. Square brushes on a round armature. They will break in and the pattern will look better. It won't take too long on a GM pump...

Joe

[Orevin]

... Let me add that the only way to hook up my low amp probe was at the pump, and not through the fuse.

I think this truck has a dedicated fuel pump fuse, doesn't it? If not, pull the FP relay and use the jumper wire to connect pins 30 and 87.

[greasybob]

I think this truck has a dedicated fuel pump fuse, doesn't it? If not, pull the FP relay and use the jumper wire to connect pins 30 and 87.

There should be a fuel pump prime slot in the under hood fuse/relay box. Hook a probe into it and connect it to battery voltage. You can also set your scope to AC couple on a lower amp setting to get a better definition of the wave form. I would give you a quick screen shot of the settings I use but all my scope presets have mysteriously vanished since I put the update in.

[jonage]

There should be a fuel pump prime slot in the under hood fuse/relay box. Hook a probe into it and connect it to battery voltage. You can also set your scope to AC couple on a lower amp setting to get a better definition of the wave form. I would give you a quick screen shot of the settings I use but all my scope presets have mysteriously vanished since I put the update in.

Nice one Greasy.....i never thought about using the prime slot, and no there isnt a fuse for the fuelpump alone on this veh.

[greasybob]

Here's a video I made showing how to use a low amp probe to check a fuel pump amp draw and the wave form using AC couple. http://www.youtube.com/watch?v=BbK8Gt-rvBo I noticed that the scope with 10.4 now has a calibration tab for the pressure transducers.