EFI fuel pump voltage issues

[kbronco]

I'm having problems with getting adequate voltage to my in-tank pump. Was running great but dropped the tank to test the sender and now I have issues. I'm using Ryan harness and have 12v at the fuse block but past that in the harness the voltage drops to about 6.6v. Swapped the relays around and no change. Also tested the pump with 12v and ground direct from the battery and pumps like it should. Would appreciate any suggestions on what to try.

Thanks

 

[needabronco]

You need a better/thicker ground! Quickly before you burn out your pump...

 

[kbronco]

You need a better/thicker ground! Quickly before you burn out your pump...

Well, problem is it was working fine before I dropped the tank. Plus I'm checking the voltage with my multimeter without the pump hooked up. Checked from the dash all the way back to the pump hookup. Only place I have 12v is at the fuse block. Also I might mention that when testing I've hooked the meter all up and had my wife switch the key and the meter will show 11.? v for about 1/2 a second before going down to 6.6 or 6.5 v.

 

[beaux312]

check the fuel shut off switch if its tripped the voltage drops to 6v just reset it

 

[Viperwolf1]

You need a better/thicker ground! Quickly before you burn out your pump...

A bad ground will show 12V on the meter. The problem is in the supply side, possibly a tripped inertia switch.

 

[broncnaz]

I'd check the feed wire for breaks and the connectors as well might have stressed the wiring or connector while dropping the tank. broken wires or connectors may not be able to carry the full voltage required for the pump

 

[Broncobowsher]

A bad ground will show 12V on the meter. The problem is in the supply side, possibly a tripped inertia switch.

Correct.

take the meter and put a really long ground wire on it all the way to the - battery post.
Get the pump into the 6V problem. Check the pump at both + and - legs.
If the - is up around 6V, it is a round issue.
More then likely a feed issue from what you describe so when the + at the pump is 6V start checking everything upstream. Inirtia sensor (both legs), Relay (both legs), fuse... Somewhere it has to get back to 12V. You just found your problem.

 

[kbronco]

Thanks for the input. I'll do some more checking maybe this evening. This thing is wearing me out so I hope I can get it fixed soon.

 

[Steve83]

Where exactly are you putting the meter probes when you take each reading? Which tank are you working on: the rear one mounted to the frame, or the side one mounted to the body? Do you have a dedicated frame ground, or body ground, coming straight off the battery clamp?