Troubleshoot / Diagnostic help?

[RckyMntnKng]

Gents, wondering if you could provide some ideas or hints.
Here are the events in chronological order

1. Start Jimmy, drive 30 miles. No Probs
2. 1 hr later get in, turns over slowly and wont start
3. Take battery, have it checked (its bad) and get new battery
4. Jimmy starts great, but sits for about a month
5. Start Jimmy (no prob) , drive about 20 mins, park...wont start or even click over
6. Get a Jump, drive it all the way home on dead battery (Alternator must be fine?)
7. Find that the red wire on the back of the Alt has corroded Off completely (Ahah!). Replace connection...This should charge the new Battery now.
8. Jump start Jimmy, drive all around and let it idle so the battery can charge.
Turn off....and then nothing, not even a click.
9. Jump it again, drive a long ways, let it idle etc etc....no starty.

My thoughts at this point:
1. Alt seems good because I can drive it as long as I want, once it is jumped.
2. Possibly got a defective new battery that wont charge?
3. Alt isnt charging battery but is sending power to the spark
4. Voltage regulator or ignition switch? doesnt seem likely if I can run it after a jump.

Im stumped guys, what am I over looking?

Here is another question:
2 red wires come off the battery-one goes to starter, one heads back toward Alternator etc. That second wire hits a terminal and splits off into 2 more hot wires....one is fused and the other is not. I assume the inline fused wire is for the radio or lights or what? That red larger gauge wire hits the Alt.

[Mark Mazzanti]

Make sure you have a ground cable from the engine block to the frame.

[RckyMntnKng]

I will do that next!

I did notice after disconnecting the battery a few times to work on wiring, that the negative terminal of the Batt became a little loose and wouldnt tighten up/stripped.

[vtblazer]

Internal or external alt?

If factory external regulator is still being used, I'd check that next.

[Chris27]

Bad starter solenoid? Will it start after the truck is cooled right down? Could be starter heat soak.

[RckyMntnKng]

Internal or External Alternator?
I guess i didnt know there was Internal ones....
This one is a standard looking Alt mounted on the Front top right of motor and turned by belt etc....Assume its a normal 63 or 100 amp.

And no it wont start period anymore w/o a jump...hot, cold or in the middle.

[RckyMntnKng]

-Battery is new

-Alternator works because I can drive around w/o a battery and it wont die

- Starter Solenoid and Voltage Reg seem to work because it fires right up with a Jump

Battery wont charge up when running.

Must be a bad battery? Bad in that it only lasted about 2 months and it was brand new? All I can think of

[EFI70Blazer]

To test your alternator, remove the negative cable while it is running. If it continues to run your alternator is good, if not it is bad or you have a wiring problem somewhere. Try pulling it off and having it tested. Also have you ever completely charged your battery? Might want to put it on a charger for a day. Another thing you might check is the fusable link that comes off of the distribution block next to your battery. On your positive battery cable there should be another wire that goes to the distribution block. If this is not there your battery won't charge either. There should also be another wire going from your negative cable to the core support for ground. Might check that too.

[Chris27]

Don't rule out the starter solenoid. Most will start with a boost with a bad solenoid, but not on their own. Check the voltage on your battery after a drive, if it's still got 12v, I'd look at the starter. Very common problem on Chevys.

[RckyMntnKng]

Sounds good, thanks guys, I will check these things tonight.

So if I take the Neg battery cable off and it continues to run then the Alternator is good....

I also need to buy a volt meter and Battery charger so I can see if the Battery is at 12v and can charge the dang thing up all the way.

Also I need to check to the starter Solenoid if those dont work....

GOOD DEAL thanks!

I do have 2 hot wires from the battery....I know one goes to starter, other goes to a little block like you describe (Basically a bolt/nut), and then splits into 2 wires....one has an inline fuse and is black, the other is red. I know one of those goes to the Alt.....other not sure

I only have 1 black ground from the battery to the block....no other to the core support. Better check all that too

[EFI70Blazer]

Originally Posted by Chris27

Don't rule out the starter solenoid. Most will start with a boost with a bad solenoid, but not on their own. Check the voltage on your battery after a drive, if it's still got 12v, I'd look at the starter. Very common problem on Chevys.

Just had that problem on mine. New starter and all is good now. Mine would only do it when it was hot. Had to wait an hour to start it or jump the solenoid to get it started.

[RckyMntnKng]

Is the starter solenoid inside the starter?....ie i have to get a new starter to get a new Solenoid?

[Chris27]

solenoid is external to the starter, but to replace it you have to remove the starter and dissassemble it. Usually easier to just replace the whole thing.

[RckyMntnKng]

Learn something new everyday....sometimes a solenoid going bad can start with 2 batterys, when 1 wont get it done.....

[hgs_notes]

When mine did this last year, it was the voltage regulator. It is mounted on the driver side of the radiator support.

[chiggly626]

If your Jimmy is all stock, the points type ignition is designed to run on 6 volts after start-up so even if your battery not charged enough to turn over your starter it will still run your ignition. Be carefull when disconnecting your battery while your motor is running. The alternator is not designed to do that and it can cause more problems.(Not saying it wont work or that I haven't done it in a pinch) Test your alt. with a volt meter, it should be around 13 to 14 volts when running. If you do need to replace your alt. convert to an internal regulated type. Have you tried to run your Jimmy at night to see if your lights are working like normal? Not very scientific but you can usually tell if your alt. is working or not. Good luck!!!

[Elwayno]

Not all trucks idle high enough to charge the batt. at idle. If it is not charging at idle you are just running it down farther. Could be the solenoid on the started and could be the regulator as was said. Fire it up. Put a volt meter across it and see what you are reading. Raise the rpm a little and see waht you are reading.

[florida4x4]

It may be very obvious but check that the battery terminals and cables have a clean connection. everything else can be in perfect working order but a bad connection / corrosion can prevent charging all the while allowing jump starting.

[RckyMntnKng]

Here is what Ive done so far:

Bought a new battery charger, Voltage / Alternator tester, and Voltage regulator.

I replaced the voltage regulator just for the hell of it ($25). Simple 3 bolts and 4 prong wire harness hook up.

I used the 50 amp jump setting on the charger to fire the jimmy up.

While she was running I got 12-12.5 v off the alternator, and less off the battery.

I concluded the Alt was making juice....and then let the jimmy's battery charge overnight on the 2 amp setting. This morning the green light was on saying she was full charged.

My next steps will be this evening to see if the alt is charging the battery, and if the starter will fire w/o a jump.

With the truck running on a good battery and Alternator...what voltage should i get off the battery terminals? Im not an expert but it should be more than 12v if its accepting juice from the Alt, right?

[Musclerodz]

You still have not addressed what type distributor you have. If it is the original points distributor, it will run on a dead battery where HEI won't. Somewhere you have a closed circuit draining the battery all the time.

mike

[RckyMntnKng]

Ok....What do I look for to know if it is original pts type or HEI

Im not much of a mechanic as you can tell. Maybe after all this I will know a little something....

[Musclerodz]

Originally Posted by RckyMntnKng

Ok....What do I look for to know if it is original pts type or HEI

Im not much of a mechanic as you can tell. Maybe after all this I will know a little something....

HEI distributor will have a couple wires coming off it to plug in the spark module, where a points distributor will have 2 wires going to an external coil.

[RckyMntnKng]

It appears as if I have the original Points Type w/External ignition coil.
Looks exactly like the one in LMC. (page 150 GMC). So as i experienced, it will run off a dead or almost dead battery.

Also I think I must have an External Regulator(Alt). Looking at the parts in LMC (pg 148), I dont really see a visual difference between External and Internal Regulators...except the internal model has a different Wiring harness? Am I right in saying the Alternator is an external, if the Voltage regulator is External? This is what I have.

The starter/solenoid and Voltage regulator are tested and working.

The Alt is testing at 12.5+ volts at back when motor runs....
The battery is at 12.5+ volts after a charge
The battery voltage does not surge higher with revving the motor etc

So I must have a wiring problem between the battery and Alt.....Somewhere over the rainbow

[Chris27]

Am I right in saying the Alternator is an external, if the Voltage regulator is External?

You are correct.

The Alt is testing at 12.5+ volts at back when motor runs....
The battery is at 12.5+ volts after a charge
The battery voltage does not surge higher with revving the motor etc

You should have around 12.5V at the battery (engine off), with the engine running (alternator charging) you should have around 14.5V. Sounds to me like you alternator isn't "alternating". Good luck.

[RckyMntnKng]

Does anyone have a pic or wiring diagram for the Alternator to Voltage Regulator-Battery?

I had my Alt tested on Saturday...she is fine at 14.5 volts, 3 test runs

My problem has got to be in the wiring somewhere....

The PO has the Red wire from the Voltage Regulator connected to 4 wires in a butt splice....the Battery, Alternator, a black and a red wire running back into the cab......

I suppose I will seek proffesional help soon