Mike LaBranche

My 78 has been giving me some trouble lately. It waited til I had the 84 down for maintenance. Nice touch, huh? Anyway, I've been eating fuel pump fuses last few months until finally it just wouldn't run. The fender pump was squealing like a pig so I figured it for the culprit. Bolted in a new Bosch, and it got better, but not well. Turns out the primary pump under the tank was doing nothing. Called around and nobody had one for less than $400, so figured I'd try the reverse polarity trick on the pump. Worked like a charm. Pump fired up so I pulled the relay jumper, put the wires on correctly, and it runs fine again. Question is, for how long? And it still manages to burn the fuel pump fuse. I must have a short or poor connection somewhere. Anybody had any luck with these symptoms?

TIA

Mike LaBranche
78 ob, silver/tan, 5spd
85 S, blk/blk, AT

Jack Riffle

Mike, check very carefully, the positive wire on the pump mounted on the tank. My 87 S4 was blowing the fuel pump fuse, and it turned out that the positive wire to the pump had rubbed against one of the mounting bolts, creating a short. Repaired the wire, and life is good!

Dennis Wilson

Mike,

Since it was plugged instead of worn out, it should lead a long and happy life. The big question is how long has it been in there. The same one on my 78 US 5 speed looks original. I've decided that if mine ever goes, I'll set it up like my 78 euro (one external pump only) and not worry about another possible restriction. If the big one in the fender goes, I'm replacing it with a 6.5 bar Pierberg.

Dennis

Mike LaBranche

Thanks for the info, gents. I'll take a long hard look at those wires.

Dennis, I replaced _both_ pumps 2 years ago, so they're pretty fresh. I'm thinking I should probably drain the tank, clean the screen, get rid of any gunk that may still be in there. I assume reversing the polarity reverses the pump direction and it spit out something that kept it from working. That means it could still be in there, waiting for the right moment to strand me. Sure seems like the filter should come before the pumps instead of after them. Sure glad this went down in my driveway instead of halfway to Detroit.

Dennis Wilson

Mike,

It's possible the strainer itself as started coming apart. That plastic mesh could freeze up a pump. You should be able to remove the hose at the pump to drain the tank and watch for any debris. BTW a lot of the 924 guys have installed a low pressure filter on the suction side of the pump without any ill effects. The problem with mounting one on the 928 is space.

Dennis

TAREK

you're due for tank cleaning. Do a search here anf on Nichols site

Steve J.

Don't forget to change the fuel filter. The pump works hard against a clogged filter, pulls more current and blows fuses. One way to diagnose a clogged filter is by how much current the pump draws.

Mike LaBranche

Yep, changed the filter when I put the new secondary pump in.

Can't find any shorts or bad connections in the fuel pump wiring. The fuse turns black pretty quick so I'm definitely pulling too much current. Will run this tank down so I don't have so much fuel to deal with and pull the strainer/hose assembly. Somethings not right and I'm tired of going thru fuses.

Brett Matthews

Mike,
Have you checked the swarf in the tank, or the strainer screen's condition, through the sender's access hole? When my problem started manifesting itself, someone piped up about that access hole, I promptly got about looking through it, saw some green muck and "bits" down in the bottom, and dropped the tank immediately, and took it to a place to have it thoroughly flushed out!

That didn't fix my problem though....