Starter test question

[Crazyls2]

Before I get web attacked from 100 different people, I attempted to find the information in old posts and the TM.....
My LMTV had the starter rebuilt the week I brought it home. It has given me fits since I got it. I chased an electrical issue a few months ago only to figure out if I smacked the starter with a hammer it would start. I would need to do that from time to time especially if I let it sit for a month or more. My alternator craped out on me 6 months ago so it's been sitting. I finally got around to having the alternator rebuilt and when I put everything back on the truck just makes a clicking sound when I try and turn it over. I beat the hell out of the starter thinking that was my problem but it never made any difference. Yesterday I pulled the starter and brought it home with the intention of finding someone to rebuild it. After going through the TM i am wondering if I gave a secondary solenoid problem.

Is there a way to hook the starter up to batteries while it's off the truck and try testing it? I put 24v to it this afternoon thinking if I jumped the two smaller lugs it would spin over but it didn't. Must I have the other solenoid to get it to spin over? If not, can someone tell me how to test it?

 

[MatthewWBailey]

Before I get web attacked from 100 different people, I attempted to find the information in old posts and the TM.....
My LMTV had the starter rebuilt the week I brought it home. It has given me fits since I got it. I chased an electrical issue a few months ago only to figure out if I smacked the starter with a hammer it would start. I would need to do that from time to time especially if I let it sit for a month or more. My alternator craped out on me 6 months ago so it's been sitting. I finally got around to having the alternator rebuilt and when I put everything back on the truck just makes a clicking sound when I try and turn it over. I beat the hell out of the starter thinking that was my problem but it never made any difference. Yesterday I pulled the starter and brought it home with the intention of finding someone to rebuild it. After going through the TM i am wondering if I gave a secondary solenoid problem.

Is there a way to hook the starter up to batteries while it's off the truck and try testing it? I put 24v to it this afternoon thinking if I jumped the two smaller lugs it would spin over but it didn't. Must I have the other solenoid to get it to spin over? If not, can someone tell me how to test it?

To test while out of the truck, you need the always-hot battery lead connected to the big Sol+ terminal, then jump that + to the small control terminal. The solenoid activates the pull and hold coils, those coils pull the Bendix which pushes a big copper disc across the big terminals, which makes the motor spin.

 

[Crazyls2]

To test while out of the truck, you need the always-hot battery lead connected to the big Sol+ terminal, then jump that + to the small control terminal. The solenoid activates the pull and hold coils, those coils pull the Bendix which pushes a big copper disc across the big terminals, which makes the motor spin.



View attachment 929059View attachment 929060

Thank you, I kinda tried that but tried using a wire from the positive terminal on the battery. Will try jumping that when I get home!

 

[Crazyls2]

Should I have continuity from the ground to the control terminal?

 

[MatthewWBailey]

Should I have continuity from the ground to the control terminal?

Yes. It should read some ohms, not open circuit. Mine reads 3.3 ohms but each starter may show different. There's 2 relay coils across those 2 small leads

 

[MatthewWBailey]

Thank you, I kinda tried that but tried using a wire from the positive terminal on the battery. Will try jumping that when I get home!

That should still work since it's the same voltage.

 

[GeneralDisorder]

Pull your batteries and full charge them out of the truck.

While that is happening in the background. Clean EVERY ground on the truck. Especially the ones from the battery box to the frame, the frame to the alternator, the frame to the cab (just replace it), and the frame to the engine block near the starter. Check every connection to the starter and the aux solenoid.

And probably re-rebuild that starter since it could have been a poor rebuild that was done. But it also sounds like it might not be throwing the Bendix/solenoid contacts hard enough.

Or the batteries are dead. That's usually the issue along with bad connections 99% of the time that people make this thread.

 

[Crazyls2]

Pull your batteries and full charge them out of the truck.

While that is happening in the background. Clean EVERY ground on the truck. Especially the ones from the battery box to the frame, the frame to the alternator, the frame to the cab (just replace it), and the frame to the engine block near the starter. Check every connection to the starter and the aux solenoid.

And probably re-rebuild that starter since it could have been a poor rebuild that was done. But it also sounds like it might not be throwing the Bendix/solenoid contacts hard enough.

Or the batteries are dead. That's usually the issue along with bad connections 99% of the time that people make this thread.

The first thing I did was pull the batteries and charge them. I did clean the battery to alternator connection. Something I did notice on the starter ground strap, it seemed to have been full of water. The truck has a nasty oil leak on the timing chain cover near the hydroloc and air pumps from when the bolts worked their way loose. That was intended to be a summer fix but I haven't had time yet. The strap to the starter had milky water (oil water mixed).

I don't doubt the rebuild wasn't great, the starter fell out of the truck on the way home from them rebuilding it, that didn't instill great confidence.

Back to chasing a ghost.....

 

[Crazyls2]

Problem one, I'm an idiot, the ground from the ground lug to the solenoid was wired to the wrong lug. I corrected that and now the teeth move forward but the starter doesn't turn. I am going to take it in to be rebuilt. I have a strong suspicion the oil and crap have worked their way into the starter and left me a gift

 

[GeneralDisorder]

Could be the starter. Have you *tested* the batteries that you charged? What is their voltage and have you done an actual load test? 12v is dead. 12.6v is fully charged. Many people have trouble with this. I've been bitten myself by this. Even a battery that reads 12.6v can still be bad. Only an actual load test will tell for sure.

 

[MatthewWBailey]

the starter fell out of the truck on the way home from them rebuilding it, that didn't instill great confidence

Maybe use a different shop

 

[GeneralDisorder]

Maybe use a different shop

NEVER take an FMTV to a shop. YOU ARE THE SHOP. Or forget it - buy a Land Cruiser and accept that It's All Over But The Crying.

 

[MatthewWBailey]

NEVER take an FMTV to a shop. YOU ARE THE SHOP. Or forget it - buy a Land Cruiser and accept that It's All Over But The Crying.

Lol I take individual parts in like driveshafts and hoses but I'm doing the exhaust myself for that very reason. A starter shouldn't fall out of a truck post install unless it was a Dive shop.

 

[Crazyls2]

That wasn't the worst part, I paid about $900 for a rebuild only to find I could have bought one for that.

This LMTV is turning into a boat, best two days.... bought.....sold

 

[Crazyls2]

Could be the starter. Have you *tested* the batteries that you charged? What is their voltage and have you done an actual load test? 12v is dead. 12.6v is fully charged. Many people have trouble with this. I've been bitten myself by this. Even a battery that reads 12.6v can still be bad. Only an actual load test will tell for sure.

Not yet, I am out of time for the week. It is now a next weekend problem. Indid pull the starter apart because I wanted to make sure there wasn't any sludge or crap inside it. The brushes were a bit nasty as was the copper base on the shaft. I cleaned them both really well then put everything back together but my luck isn't good enough for that to have worked. I do plan to verify the batteries next weekend. If they test good I am likely still going to get the starter into a rebuild shop while it's off.

 

[MatthewWBailey]

Problem one, I'm an idiot, the ground from the ground lug to the solenoid was wired to the wrong lug. I corrected that and now the teeth move forward but the starter doesn't turn. I am going to take it in to be rebuilt. I have a strong suspicion the oil and crap have worked their way into the starter and left me a gift

I feel like one too! I just looked at mine and realized my "sketch" was incorrect. The "switch" label (terminal 1) IS the + control lead. That black wire from the neg post should loop under the bus bar and land on terminal 4. I didn't catch that first time sorry. I've taken mine apart twice during a new starter install and that neg control lead can be confusing if it's removed. That was bugging me last night lol. The dc solenoid is polarity sensitive. (Correction, not polarity sensitive)

 

[Ronmar]

I have never seen a fly-back diode internal to a solenoid coil, and unless they already grounded one side of it, the solenoid coil is not polarity sensitive. many starters already have one coil lead tied to ground on the starter case and no second terminal to connect to. The second terminal simply allows for more possible control, like a thermal switch or some other interlock in the ground leg.

Now a fly back diode/diodes across that coil might allow us to remove the 100A aux start solenoid on the frame rail and control the starter solenoid directly with K1 as it does not pull all that much current. the large aux start contactor is just the old school way of dealing with the fly-back energy created by the solenoid when you de-energize it and its field collapses...

But where you show to move the ground connection to is how it is shown in the 20-3 manual, starter replacement diagrams...

 

[MatthewWBailey]

I have never seen a fly-back diode internal to a solenoid coil, and unless they already grounded one side of it, the solenoid coil is not polarity sensitive. many starters already have one coil lead tied to ground on the starter case and no second terminal to connect to. The second terminal simply allows for more possible control, like a thermal switch or some other interlock in the ground leg.

Now a fly back diode/diodes across that coil might allow us to remove the 100A aux start solenoid on the frame rail and control the starter solenoid directly with K1 as it does not pull all that much current. the large aux start contactor is just the old school way of dealing with the fly-back energy created by the solenoid when you de-energize it and its field collapses...

But where you show to move the ground connection to is how it is shown in the 20-3 manual, starter replacement diagrams...

That's nice to know, I'd have never found that in the TM series. I had to look at pictures to confirm mine when I had it removed bc the schematic doesn't reference those terminals.

I was expecting to see a fb diode on the Aux relay coil itself when I had it out. Shouldn't there be one there? Always thought that was a commandment for dc relays.

I was thinking of the actual operation of the solenoid coil magnetics being polarity sensitive. Won't that go backwards if it's polarity is reversed?

 

[Ronmar]

Yep, that's the diagram...

Fly-back diodes are good practice to lessen arcing on the controlling sw and resultant noise, but are not typically necessary. they also help the field collapse a little faster, and of course the larger the coil the larger the fly-back, which is where the large aux start contactors came from to keep the large coil from damaging the little control relay or starter sw up in the panel. predates diodes and other forms of reactance suppressors.

coil polarity might make a difference in the field it builds if you were working with another magnet, but you are simply pulling in a ferrous/steel solenoid core. a magnet doesn't care which way it approaches and attracts a piece of steel, only another magnet...

 

[MatthewWBailey]

Won't that go backwards if it's polarity is reversed?

I guess that can't happen if the plunger is simple iron