Alright yall. Here’s the problem. Buddy of mine has a 2000 GMC 1500 with the 4.3 L V6 (I think, I know it’s a V6) pickup. Whenever he puts the key in the on position, but doesn’t start it, everything is working fine. Gauges, lights, radio, AC, everything. As soon as he turns the key to start, the fuse marked “IGN C” (ignition C) blows. The truck doesn’t even try to crank. The fuse instantly blows. You can hear the fuel pump running just fine. When the fuse blows, everything except the gauge cluster works. We’ve checked all the wires going from the starter to the battery and alternator. Don’t know if this helps, but last night while working on it, we shorted the courtesy lamp fuse out. That fuse is located directly below the IGN C fuse. We took apart his fuse block to see if maybe we screwed something up internally and that was causing it to short. Everything is fine. We called Napa and O’reiley’s and they both said it has to be somewhere in the fuel injector wiring or the crank wiring that is shorting. I’ve looked at the fuel injector set up and it is one single nozzle mounted vertically in the intake manifold. We don’t know what to do. We’ve checked everything. His battery terminal was very corroded a while ago, but we replaced that with a new terminal and battery and sprayed anti corrosion stuff on there. The positive wire however is very stiff going into the auxiliary battery cable hook up (yall that know Chevy’s, I’m talking about the little red box connected to the power wire on the battery). Please help us. We are out of options. Thanks yall.

 

Alright. Here’s what I’ve done so far. I’ve taken the power wire off the starter and turned the key to the start position. Fuse blew. So there goes the starter as a possible source of the problem. What else is there? I’m going to unplug the alternator next and try it then and see if that doesn’t help. I’ve re-run all new wire (4 gauge) thinking maybe the wire was bad (it was corroded pretty bad). I’m going to hook up a piece of 4 gauge wire from the positive post of the battery to the positive on the starter and see if that helps. If yall have any more ideas, let me know. This is really starting to get annoying. I’ve been working on this since 3:00 this afternoon.

 

I don't know that particular model but am willing to take a stab at possible problems.
You said that you removed the power from the starter. Did you remove BOTH wires? The large wire from the battery and the smaller wire from the switch. Does this model have the starter solenoid incorporated into the starter or is it separate? It seperate, you need to find it and disconnect the wire going to it.
How about the possibility of a bad ignition switch?
How about a bad ignition coil? Try disconnecting the wire going to the coil.
Sorry, that's all I can think of for now. Let us know wha the problem was.

 

The wire I disconnected was the small purple wire to the solenoid. The solenoid is incorporated into the starter. When I hooked a wire to the power wire on the solenoid to the positive on the battery, the truck fired. When I removed the wire, the truck died. I'm starting to look at the switch now and trace wires back from there. I'll try disonnecting both wires and see if that helps. Oh, when the truck fired, the fuse did not blow.

 

From what you have just told me, I don't think that you need to disconnect the battery wire from the starter. It is sounding more like a either a bad igniton switch or maybe that purple wire you disconnected is shorting out somewhere, like at the firewall. It is not the ignition coil if it fired up after what you did. Almost sounds like it is time to pull the steering wheel off.

 

GOOD NEWS!!! I disconnected the big wire from the starter motor (the one that runs into the auxiliary jumping point, AKA the little red box next to the upper radiator hose) and left the purple smaller wire connected. I turned the key to start and I heard a single CLICK. And it wasn’t the fuse!!!!!! So now that I’ve gotten it down to that, do yall think it’s the solenoid or the starter itself? Thanks so much for yall’s help.

 

If you heard a click it possibly indicates that the solenoid is working. But in an earlier post didn't you say that with the purple wire disconnected and bypassed that the starter worked and the motor fired up? If so, how can it be the starter motor? Also, unless I am mistaken, that heavy wire you disconnected is not fused, or if it is, is not connected to the fuse that blows.
Is it possible that with all the moving of wires that the short was temporarily removed? Now try reconnecting all the wires and try it.
On rereading your post I now suspect that on your model that there are three wires going to the starter motor. One really heavy one going to the battery. This is not fused. One light one going to the starter switch, maybe that purple one. Then maybe a medium sized wired connected to the same post that the heavy battery wire is connected to. If it is this medium sized wire that you disconnected and the solenoid clicked, then the problem probably has nothing to do with the starter motor.
If what I have just surmised about there being three wires, then reconnect the purple wire and the really heavy wire going directly to the battery. Turn the ignition switch. The motor should turn over but not fire. That then isolates something in the auxiliary circuit, like the ignition coil or again, back to the ignition switch.

 

The way it works is this. There's a big wire on the solenoid that goes straight to the battery. It is not fused. There is a smaller, purple wire that leads into another wire loom and there is a small, little wire that connects both the big wire and the purple wire. When I disconnected the purple wire, and left the big wire on, nothing clicked and the fuse blew. When I connected the purple wire back up and disconnected the big wire, the thing clicked, didn't start, and the fuse didn't blow. When I ran a wire from the battery post to the purple wire on the solenoid, the truck fired, but wouldn't keep running once the wire was removed. Both the big wire and purple wire were connected during that step. That tells me that the solenoid is working, but the starter might be bad. Cause if the solenoid is clicking, and the fuse isn't blowing, but the engine isn't turning over, that means the problem is with the starter.

 

Please explain what you mean when you say the truck fired. There may be some confusion here which changes my diagnoses. I took that to mean that it cranked over and started or tried to start. Now I am wondering if you mean you took a HT lead off and made a spark jump without the engine cranking over.
Here is something else you can try. Take a look at the solenoid. It will have two connections. One wire goes to the starter and the other goes into a wire loom. Take a wire from the positive side of the battery or where that really heavy battery wire connects to the starter. Touch the end of the wire to the solenoid contact that goes into the loom. Do this with the switch off. If the solenoid and the starter are working OK the engine will crank over. If it does not crank over and funny things happen or nothing happens then you could have a bad starter. If it cranks OK, then connect all the wires back up, change any blown fuses, turn the ignition switch ON but not to the START position. Repeat the above. Bet the engine starts and runs.
If it starts and runs then I come back to either a bad igniton switch or a short in a wire between the igniton switch and the solenoid.

 

Sounds like you are getting excellent help from mexstan, but just a thought. Gm's are famous for the battery conections actually pulling out of the battery (as you tighten the battery bolt it pulls the connection point out of the battery). Plus the little lead spacer between the battery wire and the battery connection point can compress.

So, for giggles, switch the battery from another vehicle that is know to be good and give it a shot. Good thing on replacing the battery cables also.

BTW what brand fuse are you using so I can buy stock in the company ;D. Good luck, Kevin

 

[quote author=Mexstan link=board=13;threadid=22306;start=0#msg208782 date=1068625881]
Please explain what you mean when you say the truck fired. There may be some confusion here which changes my diagnoses. I took that to mean that it cranked over and started or tried to start. Now I am wondering if you mean you took a HT lead off and made a spark jump without the engine cranking over.
Here is something else you can try. Take a look at the solenoid. It will have two connections. One wire goes to the starter and the other goes into a wire loom. Take a wire from the positive side of the battery or where that really heavy battery wire connects to the starter. Touch the end of the wire to the solenoid contact that goes into the loom. Do this with the switch off. If the solenoid and the starter are working OK the engine will crank over. If it does not crank over and funny things happen or nothing happens then you could have a bad starter. If it cranks OK, then connect all the wires back up, change any blown fuses, turn the ignition switch ON but not to the START position. Repeat the above. Bet the engine starts and runs.
If it starts and runs then I come back to either a bad igniton switch or a short in a wire between the igniton switch and the solenoid.

[/quote]

When I say fired, I mean it started and ran as long as I kept the wire on the contact. You actually described what I did. I took a wire from the positive lead on the battery and hooked it up to the wire on the solenoid that goes into the wire loom. That's when the truck fired and ran. They was in the on position.

Kevin, this isn't the factory battery we are working on. We are working with a DuraStart. The fuse company is AMC or something like that. It comes in a little yellow tin can from Wal-Mart.

 

Well???? Have you done some more testing? Waht have you discovered? Is the problem resolved? Let us know when you find the cause of the problem and the fix.

 

Sorry it's taken so long. We found out it was the starter relay in the underhood fuse box. Apparently it was just bad enough to not allow it to start. We switch it out with the headlamp relay and the truck runs great. We then put the bad relay in the headlamp relay spot and the headlamps work great to. Oh well. Thanks for the help everyone.

 

Glad you got it fixed. However, I would be a little nervous leaving a suspect part in the headlamp circuit. Unless all night driving is in the city.
Years ago had my headlamps fail on a dark country road, on a curve, just about to cross a single lane bridge. That got my attention fast!!! Fortunately I knew the road well enough to steer round the curve until I got my car stopped.

 

He's got another relay on order. It made me pretty mad when I realized that it was such a simple fix. Oh well. And the fact that we completely tore apart the fuse box, and even MARKED THE RELAY, we didn't even think about it. Oh well. Such as life. Thanks for the help everyone.