Hey guys I have a 94GXE and the error codes for the computer pointed to "Fuel Pump Circuit".

It kept blowing fuses when trying to start. Then on my last trip it was running then another fuse blew while I was driving and the car died.

So I removed the fuel pump from the tank to check if it was OK and the wires look rotten and bad, so I fixed them up, stripped them back and replaced two of the ground connectons, and resoldered the one ground terminal (black wire) back onto the top of the sending unit.

When I went to go start it, the pump started running, and that soldered joint started smoking and the black wire (Ground I think ) basically just un-soldered itself from the heat.

Anyone have an idea what to check next?

 

Are you sure you soldered it to the correct spot? If so then I'd take a wild guess and say the obvious; an electrical short but I'm sure you figured that last part out already. Hopefully someone else can be of more help.

 

I'm certain it's soldered to the right spot.

 

Not sure if this is relevant but have you checked both relays?

 

No other joint/wire smoking at the same time while the pump is running ? - just this one solder joint? ................ if so, then its basically a bad solder joint or bad mechanical connection - really as simple as that - check your handiwork again and make sure the wires you soldered have been properly cleaned and fluxed and is properly tightened down on clean tags/faces

 

Thanks. I'll check the relays in the trunk. The terminal that the wire de-soldered itself and smoked, was the Red wire inside the sending unit connecting to the fuel pump, but ultimately appears on top of the sending unit out those terminals to a white wire. So the part that smoked is the white wire soldered to the terminal of the Red pump wire.

LVR: When the pump was running immediately upon turnning key in ON position (not start) is when it immediately started smoking. And the smoke came from just that one solder joint. It wasn't a cold solder either, it was done correctly.

Maybe i'll remove the sending unit from the tank again and check the connection of that red wire to the pump terminal on the actual pump itself.

By the way, I used my ohm meter per the FSM instructions to test the Red & Black wire to the pump itself and it read ZERO ohms. FSM states 1.0 Ohms should be the reading. Not sure if this means anything.

This pump is fairly new (bought new) and has low KM on it.

 

You seem to understand the electrical stuff so let me suggest you break a pump feed wire and stick a current meter in series with the pump and run it under load (engine running) to measure the pump's current consumption (just so no magic blue smoke come out of the vehicle - connect everything properly before you apply power to the pump circuitry ............. lots of fumes and high current sparks makes for funky environment)

 

Sure I can try that. What should the pumps current consumption be in a normal range, and what is the maximum current that it may pass through so I know to get the right meter for it. My meter is just milli amps.

Also I'll only be able to do it when I immediately turn the pump to the ON position (not start), if the car does run for 10 seconds, it will blow the fuses like it's been doing.

 

My guess would be around <50% of the fuel-pump fuse rating for a nominal consumption - if you get close to fuse rating there is something wrong, and 5 seconds worth of measuring should be good enough.

Been a long time since I last had to measure current on a running pump so cannot be more specific - perhaps there is another unlucky soul here that had to do the same recently with better memory than mine.

The fact that it blows the fuse after about 10 seconds already confirms there is something wrong there and if you really have no funky wiring then the pump itself is the culprit (irrespective of age/condition)

 

To my surprise it looks like the pump's motor is of brush-commutator type with all the arcing, sparking, etc. They state it is safe as there's no oxygen there. I wonder what would happen when I run out of gas? Anyway, to OP question - if my assumption about type of the motor is correct it sounds like it's about to go and I'd estimate its consumption to be less than .5 of the fuse value - during startup these motors consume much higher current so fuse must have some room to survive.

 

Thanks for the assistance everyone. I went to a local garage and gave the symptom to one of the seasoned mechanics. I told him where the smoke came ie. at the terminal. He sugested that the terminal itself is where the short is.

Sure enough last night I investigated further. First I unhooked the pump inside the sender unit, and tested it's two prongs, Resistance came to 1 Ohm per FSM.

Then I put one probe on the suspect terminal on the top of the sender unit and 1 probe on the body of the top of the sender unit (ie ground), sure enough, I got a few ohms. This pointed to the fact that the terminal had worn somehow and was touching the surrounding metal of the sender unit.

I then proceeded to knock out the terminal from the top by hammering it, and sure enough it was already loose. It knocked out, and there was an old piece of rubber grommet thing surrounding the solder terminal. One side of the rubber grommet was burnt open.

Anyhow, hopefully this is the source of the problem. I'm going to try and replace that terminal and all the others ones (before they do the same). Does anyone know where to get the replacements for those terminals? Obviously it doesn't have to be the exact same ones, but something that would allow a new wire to feed through but gas not to escape, some sort of rubber thing?

Hopefully this is it, I'll keep you posted. This will explain the random fuse blowing that it's been doing over 1 yrs time, very intermittently.

 

If this is the case forget what I said about the motor, it would be gone by now. If it was doing it intermittently then it must be a short and it seems you already found it by yourself.

 

Correctamundo Max 5gen. That was the source of the intermittent fuse blowing for over a yr or 2. It was a short on the cap of the fuel sender unit, the RED wire going to the pump. I'll try to post some photos.

Little did I know I could have been driving around with a ticking time bomb.

I've heard extremely rare stories of cars exploding for no reason, going up in flames, now I'm beginning to wonder if it purely would be fuel pump related, some sort of malfunction in the circuit or wiring.

Anyhow, thank god I found it. I'm sure I am over dramatizing it, but these 3rd gens are damn old and these types of things can be found on old cars. I talked to a mechanic and he says he's seen it many times, on many cars.

 

I bought a pump with sending unit off the .org and the thing looks absolutely amazing. Anyway I go around my car looking for crappy looking stuff that needs replacing and I don't wait for **** to start fuuckin up before I gets on it...know what I mean?

 

That's the way to do things my dude, in my trade we call that PM's or preventive maintenance, excellent post.