Is there a slide switch on top of the column that hooks to the ignition switch?

 

[QUOTE=tempest411;14857740]There are only a couple sources of power into the truck from the positive battery post, and just a few grounds. I am not familiar with your specific year, but I bet there is a single connector that is causing all your grief. When you pull it apart it will be full of corrosion.

This /\ /\ /\ /\

Had the exact problem with my '84. No power anywhere, move things around a bit, then temporary power until a load is applied, then nothing again. My buddy used his meter to start checking from the battery positive out and when we got to the first major connector, the largest wire had no power on the other side of the connector. Pulled it apart and that one spade connector was all corrosion; wired around the connector and all worked again.

 

Okay did a few test/checks. There was NO power to anything so I decided to pull it over to the shop. The key was still in the on position (from when I towed it) and I went to turn it off and noticed that everything was on again. Started right up. Backed it out, turned it around, backed in, and shut it off. All systems are working.

Checked all connections, none are loose, no corrosion. The negative cable is grounded to the body up by the battery via a smaller wire, and then the main heavy cable runs down to the block. All connections were clean and tight.

All positive connections were tight and I didn't see any corrosion. The hot side runs from the battery to the starter relay and then down to the starter. All connections looked good.

I haven't followed the connections from the starter relay back to the ignition yet.

I think we are on the right track with trying to find a connection issue since we go from a normal state to NO power and back to a normal state.

Maybe I'm wrong but I don't see how it can be a bad battery or a short since it went back to a normal fully functioning state while it was not running. It seems to me that if it was a dead short that it would drain the battery and not self heal. It was dead on Friday, sat Saturday and was dead on Sunday when I went to move it. Then it was fully functional in seconds. That would seem to me to indicate a bad connection and not a dead short.

I wish it wouldn't have been so cold and windy outside, I could have / should have checked it when it was in the dead condition.

???????

 

The thing about bad connections, they start to get bad long before there is actually visible corrosion.

Once you can actually see corrosion, the connection has usually failed altogether, and the only reason people even notice, is because they are now troubleshooting at that point. One interesting quote from my 1950 Motors manual, said something like people check for bad grounds as a last resort when that should be the first thing checked. If yours is a 93 than some of those connections haven't been cracked open in 20 years. It won't hurt anything to clean them up, they need it. Every two years is best practice.

Even if a cable ground or connector, spade lug, whatever "looks" okay, put a wrench on it, disconnect it, wire brush, etc. Trust Me.

 

I pulled apart all of the easy connections. I didn't un-tape anything. I may try and run a separate additional ground to the block instead of undoing the existing one (the existing one is REALLY hard to get to because it's above the cross member by the motor mount).

I built and wrapped the entire harness from the firing wall forward when I did the mass air, engine, and MSD ignition conversion, SO it is possible that I have a loose connection somewhere. I also re-pinned a few things in the fuse block but I don't remember why it was necessary off the top of my head.

I'm a little stumped that the dome light came on on Saturday and then went off when she turned the key. (See post #7) Maybe it was just the additional draw when the key was turned to the on position that did it.

If the dome light doesn't work I would think that would indicate that it's pretty far upstream.

I just wish it was in the broken state for all this testing. It's like "everything was working, I unplugged the connection, cleaned it and plugged it back in and it was still working" D'OH!

 

Yes, they are hard to get to at times. Not saying this is your problem but after 20 years the main grounding point should be cleaned up. Edit: You have a "new" engine installed? I would check for LOOSE connections.

In recent years they even use dissimilar metals to make the connection. A simple voltage drop test between the negative battery terminal itself and the engine block would tell the tale.

 

Less than a 1/2 volt drop from Positive Battery post to Negative Battery post versus Positive Battery post to various places on the block.

 

If I am reading you right, your measuring 12.6 volts at the battery posts (12.6 is just a grabbed from the air number, yours may be different, but should be close.) and 12.1 volts when measured from the positive battery post to the engine block. If that is correct, and you are testing this with no load, 1/2 a volt is a serious voltage drop. Once you try and pass current through whatever connection(s) is introducing the resistance, your voltage will plummet.

Edit to add: Given the above test, your problem is with the ground cable which goes from the battery to the frame rail and on to the block.

 

Another test would be from negative post of battery to a clean metal portion of the engine block during a few seconds of engine crank (ignition disabled). Just a few tenths is all that is allowed.

Just an example, there are a bunch of drop tests. That particular one would tend to indicate whether the block ground is OK. Also remember each cable and connection voltage drop is cumulative, and like Island Time mentions, under load it makes a huge difference.

Did you paint the engine that you installed? Particularly, the engine block on any ground points, or alternator brackets or mounting pads, etc.

With all that, I think it sounds like something is loose or pinched too maybe as well? Try wriggling wires and connections at idle?

 

Okay, I added a new ground strap I had laying around the garage. 12.57 Volts everywhere, Post to block, post to post, post to frame.

I'll have to drive it for a while to see if it does it again.
It took several weeks last time.

I'll let you know.

Thanks for the help.

 

That's good, but that's not a voltage drop test. Because, there is no load applied at the time of measurement. Take the starting circuit as just an example.

Connect a voltmeter across the circuit or cable to be tested, here, from the negative battery post itself, to a clean spot on the engine block. Crank the engine over for ten seconds or so, (ignition disabled).

The total amount of voltage drop will be shown as a positive voltage. It won't be much, but it's important. Anything more than 2/10ths of a volt under load is too much. Same tests can be performed with the positive cable side of the circuit, the alternator itself and charging system, headlights, etc.

But have you tried the "wiggle test" at idle? It's gotta be something loose, fusible link, etc.

 

Something not mentioned yet, the main power cable from the starter relay to the under hood fuse box powers everything! Check the fuse box where this large yellow wire bolts on, could be broke or the metal conductor in the fuse box could be cracked causing all your problems.

 

That's a really good thought. As I mentioned before, I rebuilt a portion of that fuse block when I did the Mass Air and engine conversion. I really don't remember exactly why I had to do it but I had to re-pin a portion of it to accommodate the wiring harness needed for the mass air conversion, the E4OD transmission, and the HO motor.

Those plastic snap in safety clips are really easy to break. Maybe the one on the yellow "Hot" wire is cracked or broken and is loose in the fuse box.

I may try wiggling it to see if it cuts the power.

I'll let you know what I find.
Thanks for the idea.

 

I really hate it when someone doesn't complete a thread with the answer to the problem, SO after many months of trying to find the problem here is the update / resolution.

Based on the fact that at times the truck would be COMPLETELY dead and then the next second it would start fine I decided it must be a bad connection somewhere. So the next time the truck started running like someone was turning the key on and off I quickly pulled over. When I got to the side of the road it quit completely, AGAIN. I had no dome light, no radio, nothing. I turned the radio all the way up, turned the dome light on, and left the key on. Got out and started wiggling wires. Since I had rebuilt the entire wiring harness when I did the MAS air conversion I figured it must be a loose connection. I tried the power / fuse box on the drivers side fender first. Nothing! Then I tried the wires by the starter solenoid next to the battery on the passengers side fender. Wahoo! The radio and the dome light came on. The truck started fine and I drove home.

I now knew it was the hot side of the battery cable somewhere. I took apart the connection on the short little battery cable at the top and sure enough it was bad. Cleaned it up and put it back together and I've had no problems since. Now that's my kind of repair. . . FREE!

Thanks for all the help.

Here is a picture of the connection that was bad.




It was the connection by the red wire. Untapped both of them, cleaned them and put them back together again. Oh and put a cap on the hot connection of the battery terminal

 

Sounds like a loose cable or ground to me...
Scott