1988 7.3 Electrical Challenge - Died while driving; non-start condition.

[SE_Alaska]

1988 7.3 IDI, 124,000 miles

Has set 10 years.

Restored to running condition recently.

While driving, engine quit, pulled over, found negative battery post too hot to touch, disconnected it.

Now, currently with:
positive battery cables attached to battery and starter, and
negative battery cables disconnected from batteries but still grounded to engine block, and
fender-mounted booster solenoid disconnected from battery power, and
12 Volts in both batteries, and
all wires disconnected from booster solenoid, I show:

The negative battery cable (disconnected from battery) terminal is energized, and
The wire to the actual engine starter solenoid (disconnected from booster solenoid) is energized, and
Of course the positive battery cable is energized.

When I touch the negative battery cable to the negative battery terminal, sparks (as the Good Book says) fly upward.

My friend thinks the starter may have been stuck and shorted out.

Any other thoughts out there?

From SE Alaska

 

[Big Bart]

This has been a somewhat common issue. These trucks are getting old. I have seen several members have a similar story. Lock cylinder is broken, ignition switch broken, solenoid sticks on, but end result the starter stays on, acts like a generator and causes issues. My guess is something in the starter is broken and it’s grounding out.

I would unhook positive power to battery. Unhook positive power cable on the starter.(Down by exhaust.). Tape up with electrical tape the end by the starter so it can’t touch a ground. Hook up battery positive and grounds and retest. I would imagine no more sparks and no voltage on the ground.

If you still have an issue check your battery cables, the plastic cover starts to crack open over time.

Let us know how it goes. Send a pic or two.

 

[IDIBRONCO]

This has been a somewhat common issue. These trucks are getting old. I have seen several members have a similar story. Lock cylinder is broken, ignition switch broken, solenoid sticks on, but end result the starter stays on, acts like a generator and causes issues. My guess is something in the starter is broken and it’s grounding out.

I would unhook positive power to battery. Unhook positive power cable on the starter.(Down by exhaust.). Tape up with electrical tape the end by the starter so it can’t touch a ground. Hook up battery positive and grounds and retest. I would imagine no more sparks and no voltage on the ground.

If you still have an issue check your battery cables, the plastic cover starts to crack open over time.

Let us know how it goes. Send a pic or two.

This is the only way that I can imagine all of the symptoms happening.

 

[SE_Alaska]

You are right abut the ignition key switch, has not been working. I have been bypassing it it by manually engaging the starter relay on the fender. I will follow your instructions and reply.

I have also been bypassing the GP solenoid with a on/off switch to ground.

 

[SE_Alaska]

But I have left the ignition switch start wire off of the starter relay all this time. Have just jumped the small relay bolt to the positive side of relay. Tests are pending.

 

[Big Bart]

I believe your train of thought is I did not leave power on the ignite post, how did the starter stay on.

When you energized the solenoid on the fender well it could have welded into start mode or gotten stuck in the start mode. Thus delivering constant power to the starter solenoid on the starter. You perhaps did not noticed over the loud engine noise these diesels produce.

As I mentioned earlier keep in mind the starter also has a second solenoid. (Its odd but it’s how they did it.) It pushes the starter gear out to the starter ring gear and about the time it’s ready the solenoid makes the connection and sends power to the starter wiring and it turns the ring gear. So that solenoid or it’s moving parts could of melted into start mode or something like rusted parts or a piece of metal lodged in and prevented the solenoid from retracting.

Either way once you gave it some gas the stuck starter become a generator of power not a starter using power. The the fun starts depending on how long, what rpm, how hot it is outside, etc. But usually a new starter and fender starter soleniod will fix it. But don’t stop there fix your ignition switch too.

 

[SE_Alaska]

I disconnected the positive battery lead from starter and batteries and removed it from truck..

I found a burnt-through cable resting against the frame - see pictures. Does this jibe with starter becoming a generator?

 

[IDIBRONCO]

Not for certain, but it does create a short to ground if it's constant hot and may cause strange issues. If it's only hot in the start position of the key (where the starter is supposed to turn the engine over ) then it may have caused the starter/generator issue. Either way, you know that it needs to be taken care of and remedied so that it doesn't happen again.

 

[Big Bart]

Hard to know but that is not factory wiring and seems like someone wanted to tap into that wire. It also looks like a small gauge. My advice is replace that wire with at least a 10 guage wire with good connectors. Take out the starter and have it tested (Electrical rebuild shop or auto parts store.) to see if it was cooked because it perhaps stayed on or due to the short in the wiring. If the starter works, put it in with your new wire and see if she starts. I would replace the solenoid on the fender well, likely the short damaged it.

 

[SE_Alaska]

The wiring shows thus on RockAuto 2/0 gauge DEKA 04357 - very heavy (see picture).

I am having the wiring repaired with heavy duty parts (new one is $250+) and will then fix ignition, check starter, and starter relay.

Give a week, likely.

Thanks, folks.

SE

 

[Big Bart]

How is the wire from the starter solenoid on the fender well to the starter solenoid on the starter?

My bad I did not realize the picture above was your battery cables. I thought that wire was the one between the two starter solenoids.

Folks have used the Rock Auto set up. Even though it is not as heavy duty as the original, it seems to work good.

 

[SE_Alaska]

Thank you.

The wire between the starter relay solenoid and the actual starter solenoid seems sound.

I got the positive battery cable repaired ($56), installed it, tested the starter relay - worked. Starter also worked.

It may be, after reinstalling the repaired cable, that I had the original cable lying against the exhaust manifold; melted insulation, then shorted?

Will work on ignition switch next day.

 

[Big Bart]

I agree, if the + battery cable was grounding out it would have made the battery ground wire hot. If it starts and runs go with it it.

 

[SE_Alaska]

Have low charge from alternator (12.2 V), am installing reman motorcraft, 70 amps, today. Then new external regulator.

Un successful, so far, with ignition switch.

SE

 

[Big Bart]

Likely when your battery cable grounded out it took the alternator with it. It’s smart you are doing the regulator too. I always suggest doing the regulator too, seems like if you don’t it goes shortly after or was the cause of the alt failure in the first place. Might find a couple other electrical issues but hopefully not.