LMTV '04 M1078A1 starting issues

[MatthewWBailey]

I hope this isn't a duplicate problem discussed on another thread. I've searched around and not found much on this particular problem.

Anyway, cold weather starting has been a big problem on my A1. The engine block heater helps but still that air inlet heater pulls 70amps and seems to drag down the voltage and causes the "chargeing system" light to come on after I've gotten the engine running. Usually I can turn off then restart and the system resets. That happens almost every time in cold weather.

Today however, the truck took 15secs to get running and then after about 60secs of running the voltage dropped below 10volts and the whole system went dead and engine stopped, but the starter motor kept spinning (and is still spinning) until I jumped out of the truck and operated the battery disconnect. Now I can't get the engine to crank and The starter motor is spinning and whining full speed whenever I turn the battery switch back on.
The K11 cutout relay is on (green light) when I turn on the ignition and all CBs are reset.
I've read thru the electrical schematics but those are hard to follow since they put a different part of the circuit on so many multiple pages. Not sure why I have a starter motor running on continuously but not the throw-out solenoid.
I'm wondering if I've welded a relay contact closed or something?
The amperage of the starting motor spinning free-wheel And the air inlet heater was 80 amps.

(I'm going to disable that air inlet heater since it pulls so many amps! Hell the Alternator is only rated 100.)

 

[Ronmar]

First off, K11 keeps the alternator offline untill 15 PSI of oil pressure is reached. The starter should be done cranking by then…

the starter solenoid does 2 things, it engages the bendix AND it has high current contacts to power the starter motor. if it is spinning without being engaged, I suspect those high current contacts welded themselves together. I have had this happen on a pickup, and with no battery cutout sw, the starter motor was pretty much done before I could get a battery terminal lifted. The contacts can fuse if they get old and pitted and start to present a higher resistant hot connection.

The bushings in the starter motor are not lubed for continuous high RPM and will not last long being spun at peak RPM(Loaded RPM is usually much lower). So you need to pull the starter, and overhaul or replace the solenoid and resolve that issue Before a complete starter replacement is needed. Also a great time to get in and clean any carbon out of the brushes and windings.

As to the no/halted start and voltage drop, look to weak batteries or loose/corroded connections. These are common at the LBCD as it is out in the weather. Hopefully browning out the ECU and TCU has not caused them any permanent issues.

A weak/high resistance connection resists CURRENT FLOW, not voltage, so will pass full voltage throughout the circuit until a load is applied. So voltage is only considered good when tested under load.

Once you get the starter fixed, you need to do loaded voltage tests at the battery. When you pull current, like when cranking, the battery voltage will drop. You need that loaded battery voltage number. If wired properly, and with good connections, the voltage thru the wiring at the power panel should only drop less than 3% more below that loaded battery voltage. This can help you determine if it is battery or wiring/connections…

 

[GeneralDisorder]

The air inlet heater should be pulling it's power from the batteries. The alternator only needs to replenish the batteries.

Have you tested the condition of your batteries? Disconnect each one and test it. Sounds to me like you have questionable batteries. or connections. Ground connections and LBCD connections are important not to overlook.

 

[MatthewWBailey]

First off, K11 keeps the alternator offline untill 15 PSI of oil pressure is reached. The starter should be done cranking by then…

the starter solenoid does 2 things, it engages the bendix AND it has high current contacts to power the starter motor. if it is spinning without being engaged, I suspect those high current contacts welded themselves together. I have had this happen on a pickup, and with no battery cutout sw, the starter motor was pretty much done before I could get a battery terminal lifted. The contacts can fuse if they get old and pitted and start to present a higher resistant hot connection.

The bushings in the starter motor are not lubed for continuous high RPM and will not last long being spun at peak RPM(Loaded RPM is usually much lower). So you need to pull the starter, and overhaul or replace the solenoid and resolve that issue Before a complete starter replacement is needed. Also a great time to get in and clean any carbon out of the brushes and windings.

As to the no/halted start and voltage drop, look to weak batteries or loose/corroded connections. These are common at the LBCD as it is out in the weather. Hopefully browning out the ECU and TCU has not caused them any permanent issues.

A weak/high resistance connection resists CURRENT FLOW, not voltage, so will pass full voltage throughout the circuit until a load is applied. So voltage is only considered good when tested under load.

Once you get the starter fixed, you need to do loaded voltage tests at the battery. When you pull current, like when cranking, the battery voltage will drop. You need that loaded battery voltage number. If wired properly, and with good connections, the voltage thru the wiring at the power panel should only drop less than 3% more below that loaded battery voltage. This can help you determine if it is battery or wiring/connections…

That all makes sense to me. Pulling the starter was the last thing I wanted to do but there it is. I see in the manual that there is an "auxiliary stater solenoid". Do I have to look at that as well?

These batteries were supposed to be new from Midwest Mil, but they've been acting funny in winter. They don't look like commercial truck batteries. I kept a trickle charger on them last winter and had fewer problems. This is the first cold start I've tried this season and now another issue.
Connections look pretty clean from battery to starter and this voltage never drops below 25 in summertime, even on cool mornings.

I appreciate the troubleshooting. I heard that motor whining and knew that was a bad sound.

 

[MatthewWBailey]

The air inlet heater should be pulling it's power from the batteries. The alternator only needs to replenish the batteries.

Have you tested the condition of your batteries? Disconnect each one and test it. Sounds to me like you have questionable batteries. or connections. Ground connections and LBCD connections are important not to overlook.

Only in cold do I have these problems. I'm wondering if the shop I bought this from put "new" batteries in there or just new looking.

 

[Ronmar]

The aux start solenoid provides the power to the starter solenoid. If it were stuck on, the solenoid would be powered and the starter would probably be engaged, cranking the engine.

what does it say on the batteries, and how many do you have? 4 is way more than the truck needs and the little alt has trouble keeping the 4 bank charged. I would reccomend you pull all of them, charge and load test them, then only re-install the best two. 2 is a much better match for the alt, and still way more than the truck needs…

 

[MatthewWBailey]

I'll check them tomorrow. There's 4.

even thou the starter motor is spinning, I still can't engage the start function via the start button so I'm wondering if something else is also broke.

 

[Ronmar]

Well if the transmission browned out, or is not receiving proper power, it would not give you a neutral start contact, so no crank(aux start and starter solenoid).

on the starter there is a short lead that runs from the solenoid to the side of the motor housing. that is what is powering the motor, and if you disconnect it, that will stop the motor, so you can troubleshoot the rest of the system until you get the starter fixed. I should mention, that you might be able to get the solenoid contacts to break free with a good wack with a hammer on the solenoid. Its already broke, so you cant hurt it much

When you turn on the ignition, you should get a display on the transmission and K11(alt excite) and K26(neutral start) should both energize. If they do, when you push the start button, you should hear the aux start and starter solenoid click Down below…

 

[Skyhawk13205]

The way you described the air inlet heater, it sounds like normal operation. On my truck the grid heater cycles on ignition on, once the grid heater finishes the cycle I run the starter, after start, the engine ECM will cycle the grid heater, when that happens my voltage will drop down to 20-22V. The ECM will continue to cycle the grid heater until a specific temp or run condition is achieved then the grid will will shut off.

 

[Ronmar]

The way you described the air inlet heater, it sounds like normal operation. On my truck the grid heater cycles on ignition on, once the grid heater finishes the cycle I run the starter, after start, the engine ECM will cycle the grid heater, when that happens my voltage will drop down to 20-22V. The ECM will continue to cycle the grid heater until a specific temp or run condition is achieved then the grid will will shut off.

That sounds normal. Remember the voltage you are seeing may be the result of a bad/high resistance connection or weak/bad batteries I mentioned earlier, which could be effecting how the controllers are operating…

this is a common failure on these trucks, and the first one I had on mine. Turn on the switch, things look good, push the start button and it goes clunk, clunk, clunk, 2-3 times per second, as the voltage falls under load, opens the ignition relay, voltage rises, closes the relay and tries to crank, then falls again under load to repeat the cycl….

 

[MatthewWBailey]

Well if the transmission browned out, or is not receiving proper power, it would not give you a neutral start contact, so no crank(aux start and starter solenoid).

on the starter there is a short lead that runs from the solenoid to the side of the motor housing. that is what is powering the motor, and if you disconnect it, that will stop the motor, so you can troubleshoot the rest of the system until you get the starter fixed. I should mention, that you might be able to get the solenoid contacts to break free with a good wack with a hammer on the solenoid. Its already broke, so you cant hurt it much

When you turn on the ignition, you should get a display on the transmission and K11(alt excite) and K26(neutral start) should both energize. If they do, when you push the start button, you should hear the aux start and starter solenoid click Down below…

Working on it today. I have 4 x 24-500D batteries that were new in 2021 but 1 could be bad who knows. I gotta get a battery load tester.

I had to pull it out into the middle of the barn with the tractor since I parked it in a bad spot for the cab lift. Luckily this forum has taught me how to air up with the gladhand to release the brakes. My 23 Hp kubota can pull this thing on a flat surface, good to know.

 

[MatthewWBailey]

Progress:

I removed the link as you suggested so the motor stopped spinning. The resistance across the power terminals of the solenoid is 0.7 when deenergized so those must be welded. I RE powered and the dash shows all the normal lights whenever the ignition turns on. "Check trans" is on. I hear the click of the Aux solenoid when I hit the start key (I put a key in place of the button for security), and the aux solenoid is putting out 24v when it clicks on. So far that all seems peachy.

I guess I could replace the solenoid in frame but I'm wondering if the starter is damaged bc it ran free wheel for at least a minute yesterday before I turned off the batt switch. Winding resistance reads 1.1 ohms but that's with a simple 9v DMM.

only odd thing now is that my amp meter on the battery + lead is showing a steady 4.5 amps even when the ignition is off. I wonder what that power is going to?

 

[GeneralDisorder]

These trucks have issues with not keeping the 12v and 24v battery pairs evenly charged. It's best to rotate them front to back every few months. Best is to drive them regularly or at least keep the batteries on a maintainer. I would recommend a proper tester to keep an eye on them. This kind of thing can quickly damage the transmission computer or the alternator, etc. This is the tester the Army uses:

Battery Analyzer - 390PT

Part #: 741X390 NSN: 6130-01-580-3882 Safe and Accurate Testing: Quickly, safely, and accurately test both 6V and 12V lead-acid batteries (VRLA, AGM, gel, and flooded cell) in or out of the vehicle. Also test 12V and 24V charging systems for proper operation. Combined single-load, dynamic...

pulsetech.com

The transmission controller will be the first to complain and possibly the first to be damaged by improper voltage. The Check Trans light may be due to low voltage or over-voltage, or other issues. If the voltage drops below about 10v the engine computer will drop offline and the engine will stall. I have seen transmission controllers mis-diagnosed as bad due to bad batteries.

 

[MatthewWBailey]

These trucks have issues with not keeping the 12v and 24v battery pairs evenly charged. It's best to rotate them front to back every few months. Best is to drive them regularly or at least keep the batteries on a maintainer. I would recommend a proper tester to keep an eye on them. This kind of thing can quickly damage the transmission computer or the alternator, etc. This is the tester the Army uses:

Battery Analyzer - 390PT

Part #: 741X390 NSN: 6130-01-580-3882 Safe and Accurate Testing: Quickly, safely, and accurately test both 6V and 12V lead-acid batteries (VRLA, AGM, gel, and flooded cell) in or out of the vehicle. Also test 12V and 24V charging systems for proper operation. Combined single-load, dynamic...

pulsetech.com

The transmission controller will be the first to complain and possibly the first to be damaged by improper voltage. The Check Trans light may be due to low voltage or over-voltage, or other issues. If the voltage drops below about 10v the engine computer will drop offline and the engine will stall. I have seen transmission controllers mis-diagnosed as bad due to bad batteries.

Thanks a bunch. Well I need one so might as well buy that. I thought of keeping two 12v trickle chargers on the bank when I'm not using it especially in winter. The NATO plug doesn't allow that connection of course so it'll be cover off.

 

[Ronmar]

Well thats good news, sounds like everything is still functional with proper voltage applied. Based on your symptoms I suspect you will find a voltage drop with load, so you will have to figure out which, and loaded voltage tests at battery and power panel bolt heads will tell that tale.

I have pulled solenoids apart and refaced the contacts. Some will have enough material and a design that supports it. Old tpyotas use a disk you can usually flip over, andpoints you can draw-file... the worst that can happen is it doesnt work...

 

[MatthewWBailey]

Well thats good news, sounds like everything is still functional with proper voltage applied. Based on your symptoms I suspect you will find a voltage drop with load, so you will have to figure out which, and loaded voltage tests at battery and power panel bolt heads will tell that tale.

I have pulled solenoids apart and refaced the contacts. Some will have enough material and a design that supports it. Old tpyotas use a disk you can usually flip over, andpoints you can draw-file... the worst that can happen is it doesnt work...

Fu with nuts:

I took the solenoid off and it sounded like stuff rattling around inside. Looks like the plunger nut is the culprit. The copper contact ring was weakly stuck to the stud, not welded. I guess the plunger slipped off the ring and did not pull the contacts apart as expected when the starter turns off. Seems like a 10/32 nut. It's not in the parts that were inside the solenoid but I may have dropped it lol. I'm on a mission to find it...

Solenoid interior is full of rust. It doesn't activate when I apply 24v so it's a goner. Another rite of passage continues..

 

[Ronmar]

Sure you were getting a complete circuit thru the coil? Getting them to energize when not fully installed is not always straightforward…

 

[MatthewWBailey]

Sure you were getting a complete circuit thru the coil? Getting them to energize when not fully installed is not always straightforward…

Good point. I had a rod in there but maybe not big enough to make magnetism happen. My Barn tech may be violating some laws of inductance.

I'll check it again once I get the starter out. That 3rd bolt is busting my balls. The solenoid wasn't activating before I pulled it, even with the plunger inserted, which is weird bc there was amperage flowing. Strange but I'll know tomorrow once I get the starter out and on the bench.

 

[MatthewWBailey]

These trucks have issues with not keeping the 12v and 24v battery pairs evenly charged. It's best to rotate them front to back every few months. Best is to drive them regularly or at least keep the batteries on a maintainer. I would recommend a proper tester to keep an eye on them. This kind of thing can quickly damage the transmission computer or the alternator, etc. This is the tester the Army uses:

Battery Analyzer - 390PT

Part #: 741X390 NSN: 6130-01-580-3882 Safe and Accurate Testing: Quickly, safely, and accurately test both 6V and 12V lead-acid batteries (VRLA, AGM, gel, and flooded cell) in or out of the vehicle. Also test 12V and 24V charging systems for proper operation. Combined single-load, dynamic...

pulsetech.com

The transmission controller will be the first to complain and possibly the first to be damaged by improper voltage. The Check Trans light may be due to low voltage or over-voltage, or other issues. If the voltage drops below about 10v the engine computer will drop offline and the engine will stall. I have seen transmission controllers mis-diagnosed as bad due to bad batteries.

With the sensitivity of the trans computer, I'm wondering why the designers stuck with the traditional vehicle power arrangement. We use isolated power sources all the time in industrial automation: battery backed/isolated dc power for solid state circuitry with separate power for large items motors etc. Seems that would be easy to achieve in this truck. The only big loads are the starter and air inlet heater. Separating them seems like common sense Enginerring and eminently feasible with the current state of power electronics. Or is this just "the army way" as my Dad used to say.

 

[MatthewWBailey]

Sure you were getting a complete circuit thru the coil? Getting them to energize when not fully installed is not always straightforward…

After getting the starter on the bench, it's clear how important that little 10/32 nut is. Without it on the plunger, the plunger sticks too far forward to engage the magnetism of the solenoid. I put power to the solenoid in the bench and it won't pull the plunger cylinder inward until I push the plunger in another 1/2" which is where it would be held if the dam nut was still on there with its washers. This why I couldnt get it to crank on the truck. Once the nut fell off, all hope was lost and trans-genders took to protest.

I'm going to see if I can put it back together and restore humanity.