M1031 genset head

[Garagefull]

Been doing a little refreshing on the old truck. A fresh Inj. pump, Filters etc. so I go to use the generator today, RPMs come up, air compressor kicked on and everything went dead. Got the meter out and open the distribution panel and measured directly off the leads coming from the gen head. I am only getting approximately 11.5 to 12 V. I only use the generator occasionally, but it will drive me nuts not having it working. I’ve dug through the The other generator posts on the M1031, but they relate mostly to the governor system failures. It appears to be going to the same RPM that it used to on the old injection pump, but the engine sounds so much different with the fresh pump I am not sure. Any help would be greatly appreciated.

 

[Garagefull]

Been doing a little refreshing on the old truck. A fresh Inj. pump, Filters etc. so I go to use the generator today, RPMs come up, air compressor kicked on and everything went dead. Got the meter out and open the distribution panel and measured directly off the leads coming from the gen head. I am only getting approximately 11.5 to 12 V. I only use the generator occasionally, but it will drive me nuts not having it working. I’ve dug through the The other generator posts on the M1031, but they relate mostly to the governor system failures. It appears to be going to the same RPM that it used to on the old injection pump, but the engine sounds so much different with the fresh pump I am not sure. Any help would be greatly appreciated.

I forgot to mention that I checked continuity through all the breakers.

 

[Guyfang]

The voltage you read, is excitation voltage. The main gen is not "Lighting off" when the excitation voltage is applied to the main gen.

 

[Garagefull]

Thank you for your reply, as I was thinking the same. If I am reading the print correctly, they’re basically using a wheat stone bridge as a shunt circuit. I think I’m going to open her up today and check the diode‘s.

 

[Garagefull]

The bearing cap is stuck on the race and I cannot remove it without getting radical. The disassembly image shows that bearing cap should come right off that race. If there is a bad diode, I’m going to have to pull the bearing. I do not own an induction heater to get the bearing back on if necessary. I think I’m going to start searching for a replacement head.

 

[Garagefull]

Ok fellow 1031 owners, Who has pulled off of one of these end cap/bearing retainers before? I am sure that it must be a tight fit for the race in the cap, otherwise the race would spin inside the cap. I am ashamed to ask this, as I replace electric motor bearings quite frequently on the job. But they are retained by a steel plate That is loosened from the outside of the motor to relieve tension on the race.The PDF does also not inform me if the bearing should be driven on or an induction heater used to replace it back on the shaft. I feel like I have a neutered 1031

 

[Garagefull]

An added twist ,I was walking past the truck and just had to try it again. Put my meter in a 120 V outlet and fired it up. Watch the voltage climb up to 120, plugged in a trouble light and it worked fine. After about 30 seconds I watch the voltage start falling off to the original exciter voltage. I think I have a bad diode. I wish I could get this bearing cap off so that I could get in there and Disconnect this bridge so that I can get a correct reading on these diode’s.

 

[Guyfang]

Why are you working on a 1031? Its a 400 hertz model. Do you need 400 hertz?

 

[Guyfang]

Now the last time I pulled an end bell off was a while ago, but its not much differance between a 006A and a 1031. After pulling all the bolts out, item 6 came out, yeah, maybe a bit hard, but they did come out without all that much trouble, then there you are. Thats all there is to it.

 

[Garagefull]

I apologize. This is an M1031 contact maintenance truck with the PTO driven genset. It is a 208/120 V set up. But thank you for your assistance as all is appreciated. I will snap some pictures, So others can get a better picture in their head about this end bell That appears to be stuck on the bearing race.

 

[Garagefull]

Top pic is the offending end bell. When the 4 bolts are removed, The Armature assembly will slide back approximately One and a half inches. But the bell does not want to come off of the bearing race that is attached to the Armature

 

[Garagefull]

I am using this file as a reference for disassembly and circuit configuration

 

[Guyfang]

As far as I can remember, Marathon made the main gen for the contact truck. I woked on it a few times back in 85-92. I had 2 of them in our maintenance company. Do you have the Army TM's? For the contact truck they should be TM 9-4940-562-13 and TM 9-4940-562-23P.

 

[Garagefull]

I do not have those and thank you for those TM numbers. I will start searching those out immediately, as with winter coming I want this generator working properly as an emergency back up.

 

[Guyfang]

I could not find them in liberated manuals. I will ask a pack rat friend, in a day or two. In the morning I am going on a beer tour in Bamberg. So I will be shot for Tuesday and Wednesday.

 

[dependable]

That manual in post 12 is the correct civilian manual for the M-1031 gen head.

 

[Garagefull]

Thanks for the heads up. I am going to space the pulley on the front of the GEN head so it can only travel approximately a half inch. Use some wood blocks on this end bell and force it off of the bearing race. My employer told me that I was welcome to use the company induction heater, so I may go ahead and put a new bearing in there while I’ve got it apart. I’m only going to replace the bad diode, leave the others alone. I had a generator tech tell me to look for a bad solder joint on the diode case, and to look for any white fuzz that may have accumulated on the solder joint Due to the nature of the solder that was used when it was assembled.

 

[dependable]

Good luck on the repair and let us know what you find, the solder joint info is interesting.

I never had any trouble with mine, and these are alleged to be pretty durable units.

 

[Guyfang]

Thanks for the heads up. I am going to space the pulley on the front of the GEN head so it can only travel approximately a half inch. Use some wood blocks on this end bell and force it off of the bearing race. My employer told me that I was welcome to use the company induction heater, so I may go ahead and put a new bearing in there while I’ve got it apart. I’m only going to replace the bad diode, leave the others alone. I had a generator tech tell me to look for a bad solder joint on the diode case, and to look for any white fuzz that may have accumulated on the solder joint Due to the nature of the solder that was used when it was assembled.

This is a good plan. But if you take the time to de solder the diodes when checking them, take the time to replace them all. Cheap insurance.
Oh, someone sent me a mail, he has the TM's. Its 23:00, just got back from the beer tour, so will try and get the TM's, in the morning if I can drag my butt out of bed. Didnt drink all that much, but walked a bunch of klicks!

 

[Garagefull]

Maybe a different plan of attack. The front drive pulley removed would allow aprox 3” more for the armature to travel back. That would give me enough access to the diode pack to lift the leads going to the armature to test the diodes without unsoldering them(preffered method in serv manual) and i can leave the bearing retainer plate attached without disturbing them. I am thinking about using all thread through the bearing retainer plate to keep the Armature from sliding back to far and falling out of the front bearing.Sorry to wesr you folks out on this,but Something not working on my vehicles tends to drive me nuts. And again thank you for your input.