Fuel pump fuse

garrett

Member
The other night I had my GN out and it died just after leaving a burger joint. I checked the fuses and the fuel pump/injector fuse was blown. Also the AC fuse was blown. The AC fuse may be totally unrelated. I have searched the car up and down for a rubbed wire. I searched the injector harness, the rear tank wires, where the grommet goes through the trunk, etc . I have a hotwire kit. It looks perfect. When I hook the fuel pump wires up in a stock fashion, the fuse blows immediately. With the hotwire kit, the car will start, but blows the fuse after two seconds. The tank was cleaned and a new XP fuel pump was installed in 2006. To make matters worse, I had just filled the tank that night. Anyone have any ideas I could try before I drain the tanks and mess with the pump?
 

Ttype6

Well-Known Member
The other night I had my GN out and it died just after leaving a burger joint. I checked the fuses and the fuel pump/injector fuse was blown. Also the AC fuse was blown. The AC fuse may be totally unrelated. I have searched the car up and down for a rubbed wire. I searched the injector harness, the rear tank wires, where the grommet goes through the trunk, etc . I have a hotwire kit. It looks perfect. When I hook the fuel pump wires up in a stock fashion, the fuse blows immediately. With the hotwire kit, the car will start, but blows the fuse after two seconds. The tank was cleaned and a new XP fuel pump was installed in 2006. To make matters worse, I had just filled the tank that night. Anyone have any ideas I could try before I drain the tanks and mess with the pump?
Oil pressure switch. Disconnect it and see what happens.
 

GNVenom

Well-Known Member
The biggest cause of fuel pump fuse burnout is the oil pressure switch connector - which most people have disconnected in favor of an aftermarket sender in that switch location. The connector hangs down low enough to hit the header which burns the connector and ultimate shorts the pink/black wire to the header.

The second biggest cause of failure is the No. 3 injector wiring contacting the EGR valve, burning through, and shorting to the ground.

The third biggest cause would be a shorted fuel pump.

Look in that order, and you'll find the problem.
 

garrett

Member
short

With help from John Spina at Casper's electronics, I narrowed down my problem today. I unplugged the injector harness- the fuse still blew. I unplugged the oil pressure sending switch- the fuse still blew. I unplugged the fuel pump relay- the fuse did not blow. I then tried a new fuel pump relay- the fuse blew. I then completely unplugged the wiring harness from the fuel tank-fuse still blew. This tells me that int is not the fuel pump. It is not the injector harness or the oil pressure switch. Now I have to figure out where the short is in the wiring. If it doesn't blow with the relay out, am I to assume that the engine wiring harness is ok and the problem is somewhere from the relay to the trunk?:confused:
 

salvageV6

Daily Driver
It's most likely in the wire from the fuel pump relay output to the hotwire kit.

Just remember the output of the relay which provides power when the relay in there also feeds the prime circuit wiring and the oil pressure switch wiring.

Where is the hot wire relay located?

I'd check the fuel pump prime connector down near the drivers header first it could be shorted out.

You could also unplug C100 connector into the firewall under the wiper motor if you can get at it and try the relay in there with a new fuse.

That eliminates the fp. relay output wiring to the back of the car if your relay is located back there.

Lots to check still. Do the easy ones first check the wiring at the oil pressure switch it could be touching ground somehow if squishy and double check the prime connector as mentioned it's a gray wire behind the alternator near the tach. output wire should be free and not plugged into anything and certainly not grounded.
 

garrett

Member
wires

Just remember the output of the relay which provides power when the relay in there also feeds the prime circuit wiring and the oil pressure switch wiring.

Where is the hot wire relay located?

I'd check the fuel pump prime connector down near the drivers header first it could be shorted out.


I'll have to look at this. I'm not familiar with this wiring. As far as the oil pump switch, it is out of the mix. Also, the hot wire kit is also not the problem, because it blows the fuse quicker when I hook the fuel pump wiring up in a stock fashion and don't use the hotwire kit.
 

salvageV6

Daily Driver
I know the oil pump switch is out of the mix I got that from your first post, it's the wiring that is the problem.

The location of the hot wire relay can determine where the problem is also, I will assume it's at the back of the car since you never answered the question.

Obviously the problem is with the factory wiring, we need to find where it's shorted, answering the questions asked just might do that. :smile:

If you can get at the C100 connector and plug in the relay and new fuse it would eliminate the factory wiring to the back of the car which is used as a trigger to the hot wire kit.

It's simple stuff to check the factory wiring and it goes in many places in the engine bay as well as the long run through some connectors out back.

We need to find the short. Check the prime connector in the location I mentioned if you feel the wiring itself is okay at the oil pressure switch and immediate area back into the harness.
 

garrett

Member
pump fuse

The wiring to the oil presure switch is fine. The relay for the hotwire kit is in the back, I'm not sure why that matters, since the hotwire kit is not hooked up at the moment. I don't know what the C100 pin is or where to find it. I guess I will have to get more professional help.:confused:
 

UNGN

Can't Re- Member
Oil pressure switch. Disconnect it and see what happens.

Happened to my old car last month. After swapping out the sending unit, my dad had the car half disassembled to figure out it was the fuse.
 

salvageV6

Daily Driver
The stock fuel pump wire feeds the hotwire kit, it's the trigger for it.

If the relay is up front like I made one of my kits you have less wiring to trace, the short would have to be up front it's not in your case now we know where it is.

Your short can be anywhere the relay output feeds the stock wiring, which is up front including the following areas:

Oil pressure switch wiring gray wire, fuel pump prime wiring over behind the A/C and alternator area also a gray wire with a single cavity connector on the end of it, a splice S115 for those two wires just mentioned and the long run to the back of the car.

The splice S115 is located behind the L/H valve cover inside the harness it probably isn't your problem but it has in rare instances been poked by a grounded bolt or become exposed. I wouldn't start at this splice but you may end up there. :(

From there the stock feed goes out the C100 connector which is the huge main harness connector into the car, it's under the wiper motor and is kinda hard to get at but finding it and unplugging it would separate the wiring in half, just like you did with the fuel injector harness to rule that out as a problem.

From that connector it heads to the back of the car towards the fuel pump, and of course to your hot wire relay where it acts as the trigger, it's the tan/wht. stripe wire at pin K of the C209 connector to the left of the fuse panel an 11 pin connector that runs wires to the trunk area and it becomes the tan wire headed to the back out of that junction.

It next goes into a connector C320 which is in the trunk area, L/H corner 6 cavity connector, right near the rear tail lamp under some cardboard and the foam trunk liner. It's this tan wire that can cause problems occasionally but it usually breaks not shorts. It's easy enough to check the wiring there.

So if you can separate the wire that feeds back to the trunk at one of the connectors it will separate the task at hand in half. I would look to the left of the fuse panel and find that 11 pin connector, separate it and plug the relay back in with a good fuse if it holds it's a problem from that point to the rear of the car, if it blows it's most likely still under the hood.

Or you can trace the wire by inspection along it's path from the hotwire relay area into the trunk and of course at the prime connector which was explained as a likely source of a short since the wire is exposed and free there and can short on the header.

So now you know why the location of the hot wire relay is important and where all the splices and connectors are located, and should you decide to actually do any of these tests, just maybe you will find the problem. ;)

I think you should search for a more professional troubleshooting helper myself. :p
 

salvageV6

Daily Driver
Hopefully this wiring diagram picture will work from Steve Wood's vortex Buicks site. :cool:

 

garrett

Member
thanks

I will try this idea of disconnecting the 11 pin connector that goes to the rear of the car under the door sill plate. This would help identify which half of the car to look at. This will save me some time and I won't have to tear as much of the car apart, thanks... I will post back with the results.:)
 

salvageV6

Daily Driver
The fuel pump prime connector is easily accessible, (which is why it can be a problem), and is probably the easiest thing to check, even easier than the oil pump switch wiring. :cool:

Separating that connector under the dash could take a bit of work.

Inspect the gray fuel pump prime wire behind and down a bit from the alternator and trace it the few inches until it goes safely up into the harness. :)
 

garrett

Member
gray wire

It ws the gray wire behind the alternator. I had another wire tapped into this wire which ran into the cabin for a tach. It was hitting a ground and shorting out the system. Thanks to everyone for the help. Hopefully this helps someone else in the future.:D :D
 

1chance

Active Member
Thank's guy's and girl's. I found the oil psi wire ground against the front of the engine! Car is running again, at least it's got a new harness in the tank, this was a great help, i had forgot about that oil psi wire, thinking it was out of the way. I got it tied up this time, thx again!
 
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