Electrical short. Now no start, completely dead.

[Matt65]

The truck has been starting and running great since the problem in this thread was resolved: http://www.steelsoldiers.com/cucv/72149-sudden-no-start-tm-says-replace-starter.html

Today I slightly re routed the starter solenoid wire to gain more clearance to the exhaust. I then jumped it to the 24V starter feed to make sure the starter was still working, it was.

Later, while cleaning the rear most battery terminal post the battery connector found it's was to the firewall and produced sparks- Outstanding . All remaining battery terminals (3) were connected to the batteries when this took place.

I tried to start the truck and everything looked normal while waiting for the glow plugs to cycle. When the ignition was turned to the start position everything slowly went dead. No more dash lights, no start, completely dead. Batteries are charged and combine to about 25V.

I have been through the TMs but need more help. There are a few questions below. I am guessing a fuse and/or fuseable link.
- Am I guessing correctly that it is a fuse/fuse link?
- Based on the way that I shorted the system, which link(s) or fuses could have failed?
- How do you test a fuseable link?
- Does it completely lose continuity like a fuse when blown?

 

[Dave Kay]

I'm not a super-electrical fix-it guy but from your description it seems like you still have a big draw (short) on the starting system somewhere.

As far as fuse-able links go, I've had one burn on me and that is exactly what it looks like; a short section of wire with it's middle insulation burned away--- pretty obvious. Maybe even burned itself in half. Have you checked your starter solenoid UNDER the dash?

Hope that gives you some help

 

[mistaken1]

Too late but for the sake of others the front battery ground should be the first wire disconnected and the last wire reconnected when doing electrical work on the CUCV (or any other negative ground vehicle for that matter).

Was that terminal that made contact with the chassis the back battery positive or the back battery negative terminal?

 

[Matt65]

Too late but for the sake of others the front battery ground should be the first wire disconnected and the last wire reconnected when doing electrical work on the CUCV (or any other negative ground vehicle for that matter).

Was that terminal that made contact with the chassis the back battery positive or the back battery negative terminal?

I am going to check the starter relay tomorrow under the dash. I have a back up that I will swap.

Great advice mistaken1, I'm guessing I wont fail to practice this in the future!

The terminal that contacted the firewall was positive. (+)

 

[Matt65]

Starter Relay swapped, no change shes still dead.

 

[Warthog]

A fusable link is just a special wire. It is 4 gauges smaller the the regular wire it is protecting. The outer cover is a special plastic that doesn't burn as easily. Some times the cover will melt and open up but most of the time it will just get soft. You test the link just like any other wire. You can use an ohm meter, or if you don't have one handy, you can give the wire a gentle tug. It will stretch and be rubbery. The black barrel connector is just a cover for the connector.

More than likely it is the link connecting the front battery to the 12v diamond shape connector by the master cylinder. Check all of those. Also check the links at 24v terminal block, behind the rear battery

 

[Matt65]

I have confirmed that I have 12V on both sides of the diamond lug for the engine harness. I did not expect to see 12V here. I also have 24V at the adjacent glowplug relay.

So into the cab. At the fuse panel I have 12V. HOWEVER, when the ignition switch is turned on (not start) the voltage drops to almost 0, returning to 12 when turned to the off position. I know this means something, but I'm not sure what yet. Darkness is here, and truck work will have to wait another day.

Any thoughts on these latest findings?
Thanks for all the feedback. Electrical problems are tough for me, I have got to get better at them.

 

[Warthog]

Where are you checking the 12v at? Which part of the fuse panel?

Rereading you other post, have you tried loosening the starter again to see it the bendix is stuck? Just trying out ideas.

Have you load tested the batteries?

When you sparked the rear battery cable, that was a direct short from the front battery positive terminial to the front battery negative terminal (chassis ground). No fusable links of cab wiring involved. Only items involved where the front battery and the battery cables.

Remove the battery cable and clean/check them again.

 

[mistaken1]

I am still trying to figure out what shorted. I have not gone through the schematics yet. Just flying by the seat of my pants here but if you remove the back battery positive cable is there still voltage on that cable when measured to the chassis ground?

I need to change my back battery so I will measure that when I do do. Right now I am thinking 12V through passengers side alternator. Warthog, does that sound right?

 

[Terracoma]

Don't mean to threadjack, but I experienced a similar no-start today, so hopefully I can add to the discussion.

Like the OP, I was getting 12v at the diamond block at the firewall, but when I turn the key to the 'run' position, none of my warning lights came on and the voltmeter indicated nothing. However, upon jiggling the fusible link adjacent the 12v diamond block and turning the key again to 'run', everything came back to life, and the truck started per usual. I noticed that the insulation on my fusible link was very soft and spongy, and the insulation is broken in a few places.

I've read here on the forum that blown fusible links will very commonly pass voltage, but are unable to pass much current when prompted, which sounds similar to what we're both experiencing.

 

[Matt65]

Where are you checking the 12v at? Which part of the fuse panel?

Rereading you other post, have you tried loosening the starter again to see it the bendix is stuck? Just trying out ideas.

Have you load tested the batteries?


Remove the battery cable and clean/check them again.

I have now loosened the starter bolts agian. No improvement.
I still have 24V at main starter feed.
Solenoid does not recieve any voltage when attempting to start.
Solenoid will not engage or activate starter when fed 12V or 24V directly.

I am measuring the 12V on the fuse panel at the fuse on both sides of the small exposed portion of the fuses that is visible while the fuses are still installed.

Next step, remove the starter for testing, possibly tomorrow. It is possible that the bendix is still engaged to the flywheel, preventing the starter from attempting to start when voltage is applied straight to the solenoid.

I have not yet load tested the batteries.

I am still trying to figure out what shorted. I have not gone through the schematics yet. Just flying by the seat of my pants here but if you remove the back battery positive cable is there still voltage on that cable when measured to the chassis ground?

I need to change my back battery so I will measure that when I do do. Right now I am thinking 12V through passengers side alternator. Warthog, does that sound right?

I do not know what the voltage reading would have been before my direct short. I do know now that from the rear positve terminal back to chassis ground I get 0V. This does not seem correct to me. I will have to give this one some thought and look over the schematics a bit more and see what comes to me.

If you happen to take this same reading on your truck let me know what you get, and KEEP IT AWAY FROM THE FIREWALL!

Like the OP, I was getting 12v at the diamond block at the firewall, but when I turn the key to the 'run' position, none of my warning lights came on and the voltmeter indicated nothing. However, upon jiggling the fusible link adjacent the 12v diamond block and turning the key again to 'run', everything came back to life, and the truck started per usual. I noticed that the insulation on my fusible link was very soft and spongy, and the insulation is broken in a few places.

I've read here on the forum that blown fusible links will very commonly pass voltage, but are unable to pass much current when prompted, which sounds similar to what we're both experiencing.

I am certainly going to do this again. I have not been able to visually or by feel find a failed link. If it does not come back to life soon I will start jumping each fusible link.

 

[mistaken1]

Is this drawing an accurate representation of what happened when you were cleaning the battery wires?

 

[Matt65]

Is this drawing an accurate representation of what happened when you were cleaning the battery wires?

Yes, very good diagram.

So the sparks I made could have only been @ 12V? Measuring this voltage at 0 now can not be what it was before hand, or I would have got no sparks.

 

[mistaken1]

This came from warthog. Looking at the 24V bus there is the lead to the battery that you had disconnected and the there are two leads to the passenger alternator. The negative side of the passenger alternator is +12V above the vehicle chassis. I am thinking that this 12V is what sparked.

 

[Matt65]

This came from warthog. Looking at the 24V bus there is the lead to the battery that you had disconnected and the there are two leads to the passenger alternator. The negative side of the passenger alternator is +12V above the vehicle chassis. I am thinking that this 12V is what sparked.

Mistaken1 and Warthog: Thanks for the update - I really appriciate your time on this problem. I managed to get a few measurements taken before it got dark tonight, but can see that thinking the way you did in your last reply is what it will take to solve this problem. I would have probably never thought to look at the Alt links.

All voltage measurements will be relative to chassis ground:
Pass Alt Pos. = 24V
Pass Alt Neg. = 12V
Driver Alt Pos. = 12V
Driver Alt Neg. = 0V

The Pass Alt Pos. lug has the orange fusable link, along with a larger red wire. The Pass Alt Neg. lug has 1 wire.

I have continuity:
Through the orange fusible link to the Pass Pos. Alt Lug.
From Rear Batt Neg. Post to Pass Alt Neg. Lug
From Rear Batt Pos. Post to Pass Alt Pos. Lug

Granted it was getting dark on me, I did not see anything that indicated a blown link on the back of either Alt. I will review these again. With these fusible links I am starting to wonder if I need to start jumping them out individually.

I can't for the life of me figure out how I am getting 12V at the fuse panel with the key off in the cab, but no dash lights no nothing when on. I wished that whatever is consuming the 12V would start melting/smoking so I can find it! The way the dash lights intiitially died was slow, with the start buzzer going from normal to off in about 5 seconds. It makes me wonder of the spark that I created on the firewall was just a distraction, and not the root cause.

Path Forward:
- Remove the starter from the truck and test on the bench. - It will not work with voltage applied to the solenoid, and it's from China.
- If starter is NG, then swap it with a confirmed good starter.
- Check every single fuse in the cab panel.
- Possibly get another DogHead starter relay - the one I swapped earlier was old in unknown condition.

 

[Matt65]

An update for what appears to be slight progress.

I confirmed that I am getting the same drop at the Diamond terminal under the hood that I see at the fuse panel in the cab when the key is in the on/run position. Knowing that the glow plug system is also engaged for starting I wanted to remove it from the equation. I also wanted to make sure that I don't burn out the plugs from excessive burn time while troubleshooting. I removed two small wires (est. 12v?), mine were blue and pink, from their Glow Plug relay nuts. This is the relay adjacent to the diamond terminal on the firewall. After this the dash lights returned, the excessive voltage drop at the diamond terminal and cab fuse panel was gone, and the seatbelt buzzer working normal when the key was in the run position. The starter relay under the dash is now making the noise of correct function.
- So, either the GP relay or Card is no good. I will worry about that after I have the starter spinning again.

I have not had the chance to swap the starters yet. I am getting voltage drop from 25 to around 19V at the Batts when attempting to start. I have what was a known 24V direct drive starter that was rebuilt. However, it is not known if it was rebuilt at 12 or 24V.
- Does anyone know how to confirm the voltage of a direct drive starter, 12 or 24V? I will probably use my origional direct drive starter (known 24V) when I swap them for testing.

 

[antennaclimber]

I think your GP card and relay are good.
You eliminated approx 50-60 amps of current draw from the electrical system when you disconnected it.

It sounds as if you have a connection on the 12 volt side that fails with high current demand.
Possibly a cable, connection or the battery it self fails under load.
Karl

 

[mistaken1]

I went to start my M1009 last weekend. Turn the key on (I have 12V GP conversion) and everything was great. Turn the key to start and nothing. All lights go out, voltage drops to nothing on the gauge and the starter motor made maybe half a revolution.

Turn key off, wait, turn key on, all is good, turn key to start and same thing everything goes dead.

Voltage on the batteries was 12.6x volts.

Put a 12V civilian jumper in the front battery. Exact same response, nothing.

Move the civilian 12V jumper to the rear battery and it started right up.

The rear battery went bad from Wednesday when I started it to the following Saturday when it failed to start. It shows the proper voltage but fails under a load. Have your batteries load tested, I have had several instances where a battery has failed without warning. The vehicle will start without issue and then just minutes later fail when trying to restart the vehicle after a brief stop. Once it was so bad the vehicle could not be jumped until the bad battery was completely removed from the circuit.

 

[Matt65]

This morning I took the batteries in and had them load tested by 2 parts stores both times both ok.

I pulled the inspection plate on the transmission and could see that the starter bendix was not returning. Having had my fill with the China gear redux I replaced it with the factory piece.

Knowing that I had voltage when the key was off, I left it on to apply load. I jumped 12v to the engine diamond from my front battery positive (which was warm to touch) with ~10ga wire. Immediately the buzzer could be heard from the cab. I jumped over to my Rr batt. Neg, to the diamond, nothing dead. Hmmmm..... I jumped from the front batt pos. to Rr batt. Neg., buzzer is on. I found it! It was the battery cable from the front to rear batteries that was failing under load.
I used my jumper cables to jump the two batts together Fr + to Rr -, AND IT STARTS!

I replace the cable and terminals with 2ga and all is well. My no good cable was ~4ga.

Thanks for all the help here and through the PMs. I really appreciate it, and so glad to have this headache end!

 

[mistaken1]

Great news.

Glad you solved it and thanks for the after action report. This will help others with similar problems.

Just goes to show one can have all the proper voltages in all the proper places but the system fails under a load.

In the commercial electrical industry we use thermal cameras to look for hot connections. High resistance connections get hot when under a load, in an engine starting circuit the heat would not build until the starting load is put on the system. Tough to troubleshoot without a soldier B to engage the starter while one looks for things getting warm.