Always Something, But I am learning.

[Smitch320]

Ok, So not to long ago I had a blown fusible link, from the starter to the junction block. Did my best to trace back to what caused it to blow, no grounded out wires, nothing obvious. The 50amp resettable fuse I put in line would hold for about 3 days, then "pop", then no juice to the ignition switch, had horn and lights.

Now, I have done my homework and studied a chassis wiring diagram from a Chilton's manual and everything seems to be plugged up correctly.

Now, with that said, I was fooling with my square today, and I have the symptoms of a wrongly connected battery. As I went to plug the negative up, (positive was already plugged) "SPARK" and I heard the resettable fuse pop...

Hard ground somewhere? as in live wire touching the frame somewhere? Starter connected wrongly? Altenator shorted out?

I need help...., I will try and photocopy the wiring diagram from my Chilton manual and post it up here.



As always, thanks. Bare with me as I am learning

 

[chengny]

As I went to plug the negative up, (positive was already plugged) "SPARK" and I heard the resettable fuse pop...

The spark you noticed when attaching the negative cable would be considered normal if the battery is connected with a good sized load waiting to be hooked up.

And, it makes sense that, if you have a dead short to ground in a hot wire (like the one that keeps blowing your fuse) - you would notice a heavy spark as the cable gets near the post. A short circuit to ground is about the heaviest load you can get.

Hard ground somewhere? as in live wire touching the frame somewhere?

That would be my guess.


Altenator shorted out?

I don't think that is it. The alternator has been working and keeping the battery charged correct?


You could try disconnecting the large red lead at the alternator (tape it up so it can't short out) and drive around for awhile. If the fuse stops blowing, the short is either in the wire from the splice near the fusible link to the alternator or in the alternator itself.

You will be running only off the battery with that wire disco'd so you can't run this test for very long. Especially if you use your headlights, wipers, radio, etc. It should run for a couple of days if you keep power usage to a minimum. Put the battery on a charger at night to get a longer test.

Starter connected wrongly?

I can't see this as the cause. The fusible link (in-line fuse) is "downstream" from the starter connections so a short in the starter area would not cause a high current condition in the wiring that the fusible link is designed to protect.

Unfortunately the other branch off of the fusible link goes through the firewall and into the cab. It splits off again inside the cab and it feeds both the far right bank of the fuse block and the ignition switch. It is going to be a struggle to hunt down your grounded wire.

Try to detect a pattern of what happens (what you are doing) just before the fuse blows.

Another option:

Rig up a test lamp connected to the problem wire. One lead of the lamp to the inline fuse outlet and the other to a good ground. Use nice long wires for the leads - 10 feet or so. When you have it connected and it is lit up, start going around and shaking different areas of the wiring harness. Keep an eye on the test lamp. If you jiggle a certain area of the harness and the light goes out that means the fuse blew. If it consistently blows when you shake that section of wiring... you are getting close to where the ground is.

Sorry for the weak response but a wire that intermitently shorts to ground (in an unfused circuit) is a real challenge to locate.

 

[Smitch320]

No, that response is awesome. I needed some tips as to wear to start to work again.

All this wiring **** just is confusing to me. I am almost positive it is a hard ground somewhere in the line(s).

I'll try and rig up a test lamp sometime soon

 

[Smitch320]

As for what I am doing before the fuse pops


1) replace resettable fuse (50amp)
2)go to connect negative battery cable to side post. (heavy sparks)
3)fuse pops and no juice to the ignition switch.

 

[chengny]

Just to be sure we are both talking about the same things:

I now understand you to mean that this is not an intermittent type problem.

You saying that, every time you connect the battery to the trucks electrical system the fuse blows (and it blows almost immediately) - correct?

And this is the fusible link that you have replaced with an in-line fuse?

You must be registered for see images attach

 

[Camar068]

I would start with whatever you were working on before the issue came up and also check all wires near the exhaust.

It's good you have a resettable fuse. You won't be wasting money on fuses. Also you can do a hearing test at each corner of the vehicle while someone else hooks it up. Do it under, outside, and inside the vehicle. Maybe even do it with low light so you can see a spark.

Those are the quickest tests that could point you in the right direction. Also, if you've ran any wire through the firewall and didnt protect the wiring from the sharp hole.....check those. All the above can be done in less than 20 minutes with the exception of what you worked on before.

Hope this helps, good luck. It might be obvious stuff, no offense intended.

 

[Camar068]

Also, if you've hooked up an stereo amp directly to the battery (fused or not) check that cable all the way back to the amp or disconnect it.

 

[Smitch320]

Chengny- Correct. I hook it up and before I even tighten the cable I hear the fuse blow. Sorry my terminology is messed up, it is not intermittent.

 

[Smitch320]

I would start with whatever you were working on before the issue came up and also check all wires near the exhaust.

It's good you have a resettable fuse. You won't be wasting money on fuses. Also you can do a hearing test at each corner of the vehicle while someone else hooks it up. Do it under, outside, and inside the vehicle. Maybe even do it with low light so you can see a spark.

Those are the quickest tests that could point you in the right direction. Also, if you've ran any wire through the firewall and didnt protect the wiring from the sharp hole.....check those. All the above can be done in less than 20 minutes with the exception of what you worked on before.

Hope this helps, good luck. It might be obvious stuff, no offense intended.

None taken. I always find myself battling issues that If they were a snake would have bitten me. thanks for the response

 

[MrMarty51]

Be sure too that the battery + has the positive battery cable hooked to it.
Sometimes people replace a neg. battery cable with a red cable, bad things can then happen.

 

[chengny]

First eliminate the lead that goes to and from the alternator (and the alternator itself) as the source of the dead ground.

In the image above, you'll notice that right after the fusible link (fuse in your case) the single wire splits into two wires. One wire dives down into the section of the harness that goes around the back of the distributor. That is the feed coming out of the alternator.

Before you start up - and while cranking the starter - the battery is the sole source of power for the electrical system. After the engine is started, the battery's job is done and the alternator takes over.

From then on, until the engine is stopped, the alternator supplies all the power to the trucks electrical system. Power flows from the terminal with the nut, through the big red wire, to the splice (under the F/L). From there, the flow is down the other wire, through the firewall and into the cab. Once through the firewall, it splits and feeds the fuse block and ignition switch.

When the alternator powers up it also recharges the battery. It does this by back feeding down the wire that comes off the solenoid and then back to the battery.

Anyway - that was just an overview of what that wire does. To find out if the ground is in it - or the alternator - you need to cut it, or disconnect it from where it splices in.

If you don't blow your fuse with that wire removed from the circuit, you have a direction to start looking in. Don't get your hopes up. This is the easiest branch to check so you might as well do it first, but the problem is more likely in the cab interior.

You'll probably be checking the wiring behind the fuse block, the bundle that runs up the steering column and the ignition switch itself.

I hope you have a decent multimeter (and know how to use it) - you're going to need it.

 

[chengny]

Ok, So not to long ago I had a blown fusible link, from the starter to the junction block.

That is the first sentence in your OP. I have to ask - what was the last thing you did to the truck immediately prior to the initial failure of the fusible link?

It doesn't have to even be electrical. Fill us in on anything that you might have been working on when this whole thing started.

 

[Smitch320]

Fixed. Hard wire running to the amp that the previous owner had run under through the fire wall from the junction block had shorted out and fried real good, causing a hard ground. Removed the wire and replace the resettable fuse with a factory fusible link, and BAM. 5.7l was breathing again.


Thanks for all the patience and help. It is much appreciated