'90 burb electrical, fusible link?

[b79holmes]

Hi all,
A couple weeks ago my alternator started making some bearing noise, so I sent it out for a rebuild yesterday. I got it back this afternoon, and as I went to install it, my hand slipped. The alternator fell onto the wires that normally bolt onto the back of it and I was suddenly reminded that I completely forgot to disconnect the battery! Man was that stupid...

There was a bright spark from where I dropped it, immediately followed by a big cloud of smoke coming from the area of the battery. Now it seems half my electrical system died. Wipers, blower motor, brake lights and hazards all still work, but the headlights, dash lights and interior lights don't. The engine will still turn over, but it seems I have no ignition.

After looking through a handful of forum posts both here and elsewhere, the symptoms most often seems to happen because of a blown fusible link. The ones I saw mentioned most frequently were near that electrical junction on the firewall up and inboard of the brake booster. I see two of those black useable links, and I tested both with the ohmmeter. Power seems to be getting through.

I know there must be more fusible links on this circuit, but I'm not sure where to look. I did pretty thoroughly check around and under the battery (where most of the smoke came from) and I don't see anything that stands out as melted or damaged.

I'm kinda at a loss at this point, so if anyone has suggestions for things to check out, that'd be greatly appreciated!

The truck is a '90 burb V1500, bone stock and mostly original.

Thanks in advance!

[kwmech]

There is nothing factory at the battery that would really cause what you describe. Fusible links at the starter are more likely the cause. That is unless one of the pig tails fried either at the neg or pos side post. The pos side post has an 8 ga wire that goes directly to the alt post and the neg cable pigtail goes to the core support.

[b79holmes]

Thanks! I'll take a look around the starter tomorrow. Tonight, I quickly checked with my multimeter and it seems I am getting 12 volts at the firewall junction. I know the connections between the battery, the alternator, and the grounds are all still functional. Does it make sense that my starter still turns over if a link is blown down there?

[kwmech]

Originally Posted by b79holmes

. Does it make sense that my starter still turns over if a link is blown down there?

Possibly, I think there are 2 links down there. I haven't been able to get to rewiring my burb yet and bring them up top

[b79holmes]

Well I checked the two links down there. One was at the end of the black wire, and the other in the middle of the red wire. Both seemed to have a solid connection from before the black link to the end of the wire.

Looking at my battery, I realize I forgot to mention that it looks to have been changed to a different style at some point and I think the wiring was changed (the wire from the alternator is ridiculously long.) I'll include pics of that.

Do you know which wire in the engine bay actually goes to the fuse box? If I could find that one, I may be able to follow it back until I find a bad connection.

[kwmech]

Check continuity on the orange wire or pull on it and see if it acts like a rubber band. The wire with the small eyelet should be purple, that is the wire that comes form the ign switch for cranking the starter motor over. what's with all the wires at the battery? Side post battery is correct

[b79holmes]

I checked the orange wire off the starter and it has continuity from the end to above the black link. I can't seem to trace it once it goes into that tube and up behind the engine. I'll take the air cleaner off tonight and see if I can follow it further. I don't think the 'rubber band' test would work on my truck, as the insulation on my wires feels pretty brittle. I'm not sure it would stretch.

As for the wires by the battery, I never noticed until recently that someone extended the wire from the alternator to the positive post. That's the wire you see in my hand. I'm not sure why this was done, but it seems two new segments of wire were added to it with crimp connectors. I did test that wire and it has continuity.

[b79holmes]

I pulled the air cleaner off and more or less guesstimated that the wire from the starter goes to the firewall junction. I checked and it does have continuity. I then put the wires back on the starter, and checked for fuel as I cranked the engine over. There wasn't any. I then pulled the plug on the #3 cylinder and it had a strong spark.

When I poured gas down the throttle body, the truck fired right up but ran really rough, so I only kept feeding it for about 15 seconds.


So knowing that, is there any single circuit which controls the fuel pump, ecm, radio, horn, and everything that runs off the headlight switch?

[Ryan Hubbard]

Have you checked the individual fuses?

[kwmech]

2 10amp fuses under the dash, I think they say ecm1 (or A) and ecm2 (or B) check those

[b79holmes]

I checked every fuse on the block. I had the truck taken to the shop a few days ago. It's my daily, so I can't afford to have it MIA for a whole three weeks. When I get it back, I'll post the cause of the problems.