View Full Version : Shorted Fuel Pump (Reply to bbobynski)

96 STS
12-04-04, 01:20 AM
bbob, I didn't want to hijack the "No problems with my N*, how bout you?" thread so I opened this new one.

I appreciate the advise about replacing the fuel pump. Overall, I felt the same as you the more I thought about it. Your right, wires don't just melt & short out for no reason. At the time I figured that maybe one or two of them had somehow gotten pinched by the springs & this exposed bare wire allowing them to arc off of each other.

But then I began to think of what you described. That the pump itself was drawing heavy current in order to operate. Hence the wires get hot & melt into each other.

So far the car has been running fine since I repaired the wires & the fuel gauge seems to be reading accurately vs. going back & forth like it was before.

I did notice that when I filled the tank after the repair that it took a long time for the gauge to finally register full. I've only used 1/2 a tank since then, so I don't know yet if it has a problem reading TOTALLY full or not. Seems like it needed to use up some of the fuel before it could register as full. This was on my Thanksgiving trip & seemed to take about 20 miles before the gauge registered all the way. Could this be a sign of something? I did top the tank off a couple of times. Is this a no-no with Cadillacs?

This WAS my 1st experience with a tank mounted pump (and sender as the same unit). Are there any drivability signs that warns you in advance that a pump is going out? Or does it just die suddenly like mine did?

I can't remember if I posted this, but my car seemed to run fine. I did have the gauge issue (back & forth). I took my car in to the dealership one Saturday for the fuel rail recall, drove it back home with no problems. Then later in the day I went out to run some errands, started the car, backed out of the garage & it just died. Wouldn't start & after some testing I figured out that no fuel was coming out of the pump. It then bacame the weekend project to drop the tank, pull the pump, & see what's up. That's when I found the wires & repaired them.

Again, it's been running fine ever since. Just wondering if there's anything to look out for as warning signs before it goes.

96 STS

BTW...The humming sound is definitely in the front of the car. I've got a decent sized post about that called "Transmission "Whine"", i think. Please check it out if your interested. I'd be happy to hear your thoughts on that as well.

12-04-04, 06:04 PM
Are there any drivability signs that warns you in advance that a pump is going out? Or does it just die suddenly like mine did?

FTIW, I have seen pumps die all sorts of ways from slow and lingering to sudden and fatal (sometimes in their sleep). My '92 would run fine til I went WOT. It would fall flat on it's face, somewhat like a carburated engine with a bad accelerator pump. My wife had an S10 Blazer years ago that would just quit, but always restarted and continued down the road like nothing happened. A friend drove to work just fine. Eight hours later the car would not start. The pump had died in it's sleep.

12-05-04, 06:11 PM
Hey STS, I got an eldorado, same year, so I'm sure the fuel tank and pump are the same. Your problems sound identical to mine. I've changed the fuel pressure regulator, and now the car won't start at all, it just cranks. I'm going to drop the gas tank sometime this week and see if I have the same problem as you. What did the wires look like, was the rubber lining melted through exposing the wires, or what. I'd like to hear your experience with that if you get a chance, thanks

96 STS
12-06-04, 12:11 AM
No problem soccer_eldorado!! This is what makes this forum such a beautiful thing. All of us helping each other out when we can.

Unfortunately, I can't remember exactly which wires were fused together, but I did take some notes while repairing & can give you this.

There were five [5] wires total. Three [3] to the sending unit & two [2] to the pump. The sending unit colors were Black/White stripe, Purple, & Red/Black stripe. The pump wiring colors were Gray & Black.

I think one of my pump wires was fused to one of the sending unit wires. This made since because before I had the starting problem my fuel gauge was really acting crazy. One minute it read 1/4 to 3/8 tank & the next minute it would read empty & the DIC would give the "Very Low Range" message. Back & forth all the time. So I now figure that when this started it was just enough current transfer to affect the sending unit but not yet enough to kill the pump. Then it finally fused together enough to completely ground the pump current & not leave any remaining power for the pump. Weird thing is it never blew the pump fuse.

When you get the pump out you'll see how this can happen. The pump is spring loaded to the bottom of the tank and the location of the wires makes it very possible for these wires to be touching each other at any time. As bbob mentioned, this in itself isn't really a problem until something causes the wires to heat up (like too much current draw because of a struggling pump). Then the insulation begins to melt & they fuse together causing a short.

BTW, I can't remember the name of the thread, but just look at all of my posts & you'll find a "helpfull hint" about dropping the tank. This is assuming that the Eldo tank is mounted the same as a Seville. Basically, you won't have to remove the filler pipes if you follow my tips. And trust me, if at all possible you don't want to. I had to once & hope to never have to go thru that again.

Good luck & write back if you need any more info. We're all here to help our fellow brothers (& sisters :))

96 STS