Captain Hook,
I have 12.8 volts at the battery and 12.4 volts at the connector. Is that about the right voltage drop?
Also could I be getting 12.4 volts at the connector through the meter but not getting that much when a load is put on it?

 

That's a possibility and it might be worth checking. There are also connections at the pump motor, checking those will require removing the fuel pump module.
You'll need to check power and ground both. This link explains how to check for voltage drop. http://www.aa1car.com/library/voltage_drop_testing.htm

 

Captain Hook,
I dragged an extra battery out to the blazer and ran direct wires to the pump and it came on.
So now I need to trace the grey wire and the 2 blacks to see if I can find any corrosion or loose connections.


Can I just cut the ground wires and run 2 new ground wires to the frame? Or will this cause a problem?


Do you know the routing of the grey wire?

 

The two black wires at the module connector are the grounds for the fuel pump motor, and the fuel level sensor. Yes, you can run them to a good clean chassis ground. Originally, the fuel pump ground is at the top left rear corner of the frame, behind the bumper. The level sensor grounds to the rear of the right cylinder head. If you solder the 2 black wires together, (where they come out of the module connector), along with a 14 ga wire and run it to ground, that will work fine. I do that whenever I replace pumps on these things. The grey wire runs directly to the underside of the underhood fuse panel, with no connections in between. Really wouldn't be that difficult to run another wire if you suspect a problem with the original wire. I'd use 14ga instead of the OEM 18ga wire though. 18ga is borderline cheezy on a run that long

 

Captain Hook,


I already bought 30 feet of 16 gauge.


While tracing the ground I found where someone had connected a piece of wire to the pump ground and ran it to the frame. It seems they had a problem before I bought it. I took it loose and wire brushed it, put some dielectric grease on it an reconnected. But alas no soup for me.


I will be checking the fuse/relay box later for corrosion and may just run a new wire from there to the pump.


If it wont come on then I will be buying some dynamite...


Thanks so far for your help. I will post back my results.

 

Really ought to consider using 14 ga wire if you're going to the trouble of running a new one Bigger wire equals more available amperage to the pump motor. More amperage equals cooler motor operation, higher pressure output, and better longevity. Ground wire needs to be same gauge, (or bigger) to get the benefit of a bigger feed wire, that's why I recommended it in post #14.

 

Captain Hook,


I took apart the fuse block and checked ohms on the grey wire from the box to the pump. 68 ohms. Ran a new wire from box to pump. While running the new wire along the frame I noticed the factory conduit was smashed right in front of the rear axle. I opened the conduit and the grey wire was damaged and hard a brittle. Crumbled when I touched it. Went ahead and soldered in the new wire. Turned on the key and the pump primed. YAY!




So an expensive lesson was learned.


Just because you have proper voltage and good grounds to the pump but the pump does not run it does not always mean the pump is bad. If possible always run a direct wire to the pump to see if it runs.


I had to buy a new one anyway because when I was lowering the tank to get to the wire connector it slipped off the jack and came down enough to break the pump at the fuel quick disconnects.


Thanks again for all you help.
Rick

 

A good visual inspection is the first thing that is taught in automotive classes. Tough to do online though Good job! You found it.

 

A good visual inspection is what I would normally do, but there was about 14 inches of snow on/under it at the time. I knew the pump wasn't coming on so I started with the obvious fuses/relays. Then getting to the connector to check voltage, which it had, so I just figured bad pump and stopped looking.

 

That's a perfectly logical conclussion under any circumstance, much less working in a snow bank!