FRporscheman

I just finished prepping my dad's 928 for paint. I had also done a few repairs while I was prepping the car (rebuilt the PS rack myself, fixed the odo, replaced the coolant tank, bled the brakes, fixed a jammed sunroof, deleted a dumb PO horn that was added, replaced the oil pressure sender and fuel injection relay, and a bunch of PITA vacuum lines). Oh, I also took all the fuses out and put the right colors in the right spots. I went to start the car, so I could bleed the air out of the coolant, and get it ready to drive to the alignment shop, and it wouldn't start. It cranks, but the fuel pump wasn't turning on.

It would start 2 or 3 days ago when I last tried. The only things I did between then and now are bleeding the brakes, replacing the coolant tank, and removing and reinstalling the washer tank. I noticed that now the horn doesn't work (this may have broken when I deleted the extra horn), and the sunroof motor won't buzz at all. Before, the sunroof motor would work but the mechanism would get stuck, now the motor just won't do anything. And I cleaned the switch already.

I checked the voltages at the fuel pump relay socket and everything is good. I tried jumpering 30 and 87 and the pump still won't do anything. I tried giving the pump a few smacks with a hammer.

Here's the kicker: I had my brother jumper 30 and 87 while I was checking for voltage AT the pump with a voltmeter, and I read 0 volts. Is there something between the relay and the pump besides wires? What could cause this problem, and why did my sunroof (and maybe horn) go out with it?

Thanks much,

dr bob

Porsche thoughtfully puts the fuses in the circuits AFTER the relay contacts. Find the "before" picture that you took of the fuse panel, and then find the fuses for the 'missing' functions. My guess is that you have the wrong fuses in a few high-powered circuits, and accidentally replaced them with low-power fuses.

The reciprocol danger is that you now have high-power fuses protecting smaller wires. Or as Fig Newton so regularly reminds us, the small wires are protecting the bigger fuses. Check your diagrams again, and verify against that picture that you took.

HTH!

SharkSkin

Maybe something isn't right with the fuses. try twirling them around a bit, especially fuse 22.

SharkSkin

Bob, the '83 diagram shows the fuse between the 30 pin on the relay and the 30 bus....

FRporscheman

I really, really wish I took a "before" pic.

I found a fuse chart online and just went by that. Maybe it was bogus...? Can someone show me the correct fuse layout for an '83 S? Would '84 be any different, because the chart I found was for an 84.

My PET only showed the fuse layout for the later type of fuse panel, with the flat fuses.

SharkSkin

Should be the same: http://www.928gt.com/t-8384fuse.aspx

FRporscheman

Fuse 22 is "not used"... why should I check that one?

Hey, this IS different than the chart I had... quite different. Thanks! Let's see if I can set things right.

SharkSkin

Welcome to the world of wonky Porsche documentation... the wiring diagram shows fuse 22 between the relay & the 30 bus. Just for giggles, put an appropriate fuse in there and see if the fuel pump starts working.

FRporscheman

Dave, it was just a fuse issue. The table I had before was really off, and showed fuses 8 and 13 as not used. This explains why the FP and sunroof stopped working! Now I need to go through the whole fuse board over again with the new info.

Thanks for the good fuse table! Now we can get the car painted, and maybe put some miles on it!

SharkSkin

Cool, glad to hear you got it resolved!

Rufus Sanders

"unrelated Systems"... I have to tell this story. My 93 Jeep had an AC fan that would jsut come on an d go off when ever it wanted. But it seemed to do it more often when I steped on the brakes.

I took it into the Jeep place and the Serv. Mgr. tells me "The brakes and AC aren't connected, so we can't find the problem" This goes on for about 2 yrs, but sicne I only drive the car in winter and rarely in summer I could deal with it.

Finally, one day i'm sitting in a McDonald's drive thru, and I start hearing the familiear clicking sound that relays make as they engage. (haveing a 928, you get a good ear for that sound..). The sound is coming from behind the glove box, so I reach under the dash, and just wiggle some wires and Viola!

A loose wire, I don't even know which one. Stepping on the brakes just made enogh body motion to move this wire in and out of contact. But the morel of the story is that evertghing on a car is connected to everythign else, simply because they are all mounted to the same structure. - Ruf

FRporscheman

Good story - I'll remember the lesson.