Electrical problem solved (I hope)
#1
06-18-2007, 09:14 PM
Electrical problem solved (I hope)
Okay, for anyone who has been following my previous posts you know that I've been dealing with an electrical backfeed problem that has just about driven me crazy.
Well tonight I did some checking and seem to have found the problem....
What I did was start pulling fuses to try and make the problem go away. I figured that if I was to find where the backfeed was coming from I would have to figure out what circuit was feeding the EFI circuit from the backside.
Well when I got to fuse #4 (which is the fuel pump fuse) it killed the pump, which I fully expected it to do.
When I got to fuse #5 (which the owners manual lists as a SPARE) the problem immediately went away.
Now I do know that the previous owners have done some work on this circuit. First of all I found a spare fuel pump relay in the glove box which, when tested, was still good.
Secondly, I found a splice in the fuel pump relay wiring harness that went to a ground on the firewall. Now since this splice didn't even have a spade connector to connect it to the firewell I assume it was not a factory connection.
Well upon checking out the condition in the fuse box I found that the previous owners had put a jumper wire from fuse #4 (fuel pump) to fuse #5 (spare). I'm still not exactly sure why they did this but I figure it was while they were searching for a problem on the EFI circuit.
The way I figure it is the spare fuse holder is in case you want to add somethign to the system....say fog lights or something like that and it looks as if the previous owners decided to use that circuit....jumped to the fuel pump circuit to try and bypass some bad wiring.
Well with the fuse out of the spare holder, the system operates just as it should. The car starts, the car runs, the car shuts off with the ignition key. Also, I pulled the main spade type fuse under the hood and the entire system went dead which tells me that the circuit is now being protected by the fuse where it wasn't before.
The way I see it is that my whole electrical backfeed problem was on the spare circuit wiring and now that the fuse is out, it has taken that out of the way. Now the system is running on the fuel pump fuse which is exactly how it was designed to operate in the first place.
I guess the only worries that I have right now is that the previous owners problems will show up sometime in the future. I figure that what probably happened is that after throwing parts and trying fixes they finally came up with something that worked and decided not to change anything. I guess I won't really know anything until I try taking her down the road but until I get some other issues solved I won't be able to do that.
One thing that I'm thinking is that the fuel pump might be getting weak and this caused all of the problems that the previous owner had. As I said in my other posts, the fuel pump is really noisy...chattering and making almost sizzling type sounds. I have talked to several people (who are decent mechanics) that said on Chevys and Fords if the fuel pump starts sounding like that it is probably getting pretty weak. Well one thing that I saw is that the previous owner had a 25 amp fuse in the fuel pump holder instead of the 8 amp that the owners manual calls for. This tells me that they might have been having problems with fuses blowing and decided to fix the problem by leaving the circuit basically unprotected. If that is the case a weak pump would probably cause a blowing fuse situation simply by pulling high amps so if that is the problem it should show up the first long drive that I take.
So, that's where my deductive reasoning has taken me. Just in case anyone else has a similar problem they will now know to check for a backfeed situation and a way to trace the problem circuit. If anyone can shoot holes in my theory I'd love to hear from you because everything is just a guess to this point and I'm not going to feel comfortable until I have a chance to take it on an extended trip.
Dave
Well tonight I did some checking and seem to have found the problem....
What I did was start pulling fuses to try and make the problem go away. I figured that if I was to find where the backfeed was coming from I would have to figure out what circuit was feeding the EFI circuit from the backside.
Well when I got to fuse #4 (which is the fuel pump fuse) it killed the pump, which I fully expected it to do.
When I got to fuse #5 (which the owners manual lists as a SPARE) the problem immediately went away.
Now I do know that the previous owners have done some work on this circuit. First of all I found a spare fuel pump relay in the glove box which, when tested, was still good.
Secondly, I found a splice in the fuel pump relay wiring harness that went to a ground on the firewall. Now since this splice didn't even have a spade connector to connect it to the firewell I assume it was not a factory connection.
Well upon checking out the condition in the fuse box I found that the previous owners had put a jumper wire from fuse #4 (fuel pump) to fuse #5 (spare). I'm still not exactly sure why they did this but I figure it was while they were searching for a problem on the EFI circuit.
The way I figure it is the spare fuse holder is in case you want to add somethign to the system....say fog lights or something like that and it looks as if the previous owners decided to use that circuit....jumped to the fuel pump circuit to try and bypass some bad wiring.
Well with the fuse out of the spare holder, the system operates just as it should. The car starts, the car runs, the car shuts off with the ignition key. Also, I pulled the main spade type fuse under the hood and the entire system went dead which tells me that the circuit is now being protected by the fuse where it wasn't before.
The way I see it is that my whole electrical backfeed problem was on the spare circuit wiring and now that the fuse is out, it has taken that out of the way. Now the system is running on the fuel pump fuse which is exactly how it was designed to operate in the first place.
I guess the only worries that I have right now is that the previous owners problems will show up sometime in the future. I figure that what probably happened is that after throwing parts and trying fixes they finally came up with something that worked and decided not to change anything. I guess I won't really know anything until I try taking her down the road but until I get some other issues solved I won't be able to do that.
One thing that I'm thinking is that the fuel pump might be getting weak and this caused all of the problems that the previous owner had. As I said in my other posts, the fuel pump is really noisy...chattering and making almost sizzling type sounds. I have talked to several people (who are decent mechanics) that said on Chevys and Fords if the fuel pump starts sounding like that it is probably getting pretty weak. Well one thing that I saw is that the previous owner had a 25 amp fuse in the fuel pump holder instead of the 8 amp that the owners manual calls for. This tells me that they might have been having problems with fuses blowing and decided to fix the problem by leaving the circuit basically unprotected. If that is the case a weak pump would probably cause a blowing fuse situation simply by pulling high amps so if that is the problem it should show up the first long drive that I take.
So, that's where my deductive reasoning has taken me. Just in case anyone else has a similar problem they will now know to check for a backfeed situation and a way to trace the problem circuit. If anyone can shoot holes in my theory I'd love to hear from you because everything is just a guess to this point and I'm not going to feel comfortable until I have a chance to take it on an extended trip.
Dave
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