Help! Weird Starter/Genny Issue

[Mike'sHorseBarn 2,652]

I've got a weird problem that I couldn't get figured out this evening. So my starter generator on my 854. I have 12.5 volts at the battery, I hit the switch and I'm only getting 11.3 volts at the the starter/generator. I moved the ground to 3 different locations thinking that was the problem and had the same issue. Now, I took the battery out, and ran ground from the battery to the generator and positive to the A post to bypass the switch and it still won't turn over. 

 

Weirdest thing is if I take the generator out of the tractor and lay it on the floor and do the same procedure it will motor. 

 

What the heck is going on!!!!! 

[J854D 126]

First thing I thought of, is your engine locked up? Try to turn the engine over by hand to make sure it can spin over. Then best to have the battery load tested. -JD-

[Mike'sHorseBarn 2,652]

17 minutes ago, J854D said:

First thing I thought of, is your engine locked up? Try to turn the engine over by hand to make sure it can spin over. Then best to have the battery load tested. -JD-

 

Engine is good, I had it all apart. Battery works fine in another tractor.

[Achto 26,571]

10 minutes ago, Mike'sHorseBarn said:

Engine is good, I had it all apart. Battery works fine in another tractor.

 

Does it turn until compression stops rotation? Just wondering if the ACR is working properly?

 

S/G getting weak, need new brushes/rebuild?

Edited March 23 by Achto

[J854D 126]

55 minutes ago, Mike'sHorseBarn said:

 

 

Weirdest thing is if I take the generator out of the tractor and lay it on the floor and do the same procedure it will motor. 

 

 

When it motors freely on the floor with no load, does it spin over fast or slow? Maybe wrap an old belt part way around the pulley and pull on it to put it under a load while it is motoring. -JD-

Edited March 23 by J854D

[squonk 38,940]

Voltage drop. Bad switch, cables or the gen is so worn out it's drawing excessive amperage. It should draw about 60 amps just to get the engine spinning. 

[WHX?? 46,807]

Just went thru this on a 701. Spun fine free but no starting torque. 

Took it apart and diagnosed a bad armature. Took it to a starter shop to verify and they confirmed a bad armature as well as a open field winding. Also said armature coil has some resitance to ground.

Told them to just fix it. 

First mistake. Over three hundred bucks later got it back on and same problem. I get to town it's gonna get flopped on their counter again. 

 

Robbed another one off another tractor and works fine. 

Before you take it apart disconnect ALL electrical on it. With it on the motor and belt proper take a set of jumper cables. Ground on ground and pos on armature post. Hit it with a good charged battery and see if I wheels it over. Try it with plug ... no compression... and plug in. If it stalls for this test don't persist.

Second read Mike sounds like you did that.

 

Sounds like you should pull it apart and clean.

 New bearings & brushes. 

Once you have it apart I can walk ya thru checking the windings.  

Edited March 23 by WHX??

[Mike'sHorseBarn 2,652]

57 minutes ago, WHX?? said:

Just went thru this on a 701. Spun fine free but no starting torque. 

Took it apart and diagnosed a bad armature. Took it to a starter shop to verify and they confirmed a bad armature as well as a open field winding. Also said armature coil has some resitance to ground.

Told them to just fix it. 

First mistake. Over three hundred bucks later got it back on and same problem. I get to town it's gonna get flopped on their counter again. 

 

Robbed another one off another tractor and works fine. 

Before you take it apart disconnect ALL electrical on it. With it on the motor and belt proper take a set of jumper cables. Ground on ground and pos on armature post. Hit it with a good charged battery and see if I wheels it over. Try it with plug ... no compression... and plug in. If it stalls for this test don't persist.

Second read Mike sounds like you did that.

 

Sounds like you should pull it apart and clean.

 New bearings & brushes. 

Once you have it apart I can walk ya thru checking the windings.  

 

Will do.

[Mike'sHorseBarn 2,652]

I might try another switch too just in case.

[squonk 38,940]

Make sure all mounting points are clean and shiny. That goes for the generator ears, mount , block where mount attaches and where the negative cable attaches.

[953 nut 51,736]

9 hours ago, squonk said:

Bad switch, cables

 

9 hours ago, WHX?? said:

a set of jumper cables. Ground on ground and pos on armature post. Hit it with a good charged battery and see if I wheels it over

Mike, you had a voltage drop when attempting to start the engine, to me that indicates a battery cable problem. Battery cable would be the first thing to check. I have had a couple that looked great but didn't carry the current. Like Jim said, a good set of jumpers will help you find the problem.

[squonk 38,940]

Worn burnt , contacts in switch. Same issue

[WHX?? 46,807]

Didn't you get a new switch from @new to horses? 

Jumper right off the Ram... some serious CCA going on there...

I need to get off my duff and do that SG rebuild instructional since I play with them alot.

 I have all the pics just need to sit down a do the writing. 

Edited March 23 by WHX??

[Mike'sHorseBarn 2,652]

So I do have a brand new switch and brand new cables. It's one of the reason why I'm stumped. It's just floors me that on the floor it will motor, but in the tractor even with no belt attached it will so nothing even when I put power directly to the A terminal.

[pfrederi 17,147]

Try a heavy jumper from a bare spot on the genny body directly to Batt neg  sound like the genny isn't grounded well.

[953 nut 51,736]

12 minutes ago, Mike'sHorseBarn said:

brand new cables.

             New could be defective, use the jumpers to confirm as @WHX?? suggested.

[squonk 38,940]

Yep grounds. Like I said earlier, clean all attaching points including the engine block to gen mount area. If you painted it, get rid of the paint. I experimented on my engine stand with rusty / painted mounts vs. clean with a volt and ammeter. I was losing 2-3 volts and increasing amp draw by around 20 amps with dirty/  painted mount points

Edited March 23 by squonk

[J854D 126]

12 minutes ago, Mike'sHorseBarn said:

So I do have a brand new switch and brand new cables. It's one of the reason why I'm stumped. It's just floors me that on the floor it will motor, but in the tractor even with no belt attached it will so nothing even when I put power directly to the A terminal.

At this point it would be best to remove the rear end housing of the starter/generator to have a look at the brushes and to look for any problems with the terminals inside the S/G. It’s possible that with all the removal and installation and bumping around, it could free up a worn out or stuck brush to give you the inconsistent problem you are having. And with all the wrenching on the terminal connections, the A & F terminals could have broken insulators inside the S/G causing connection problems inside the S/G. -JD-

[WHX?? 46,807]

Yes the end bells can rust for a poor ground. Try connecting to the screw that holds the reg on. 

 

You may already have this one. 

Starter_Generator_Repair.pdf

Edited March 23 by WHX??

[squonk 38,940]

. Couple other thoughts. Is the engine original? Possibly someone put an older non compression release engine on it. Early spark advance engines are a " suffix A " on the I.D. Label. Compression release engines are "D". Or maybe the compression release is broken? 

Edited March 25 by squonk

[Mike'sHorseBarn 2,652]

So I got it turning over and running! It burned the wire on the bottom of regulator so not really sure what that means. It wasn't charging even with the NOS delco remy regulator. I tried adjusting it and nothing, I'm guessing that's why I almost caught the tractor on fire......I hope I didn't burn up the switch because the starter genny started to motor on its own and I had to disconnect the battery to stop the craziness!

[squonk 38,940]

11 hours ago, Mike'sHorseBarn said:

So I got it turning over and running! It burned the wire on the bottom of regulator so not really sure what that means. It wasn't charging even with the NOS delco remy regulator. I tried adjusting it and nothing, I'm guessing that's why I almost caught the tractor on fire......I hope I didn't burn up the switch because the starter genny started to motor on its own and I had to disconnect the battery to stop the craziness!

I've seen that wire burn many times. I had a 1075 that the charging light would work backwards. The more you revved it the brighter the light got. That wire was broke and I replaced the regulator

[Mike'sHorseBarn 2,652]

1 hour ago, squonk said:

I've seen that wire burn many times. I had a 1075 that the charging light would work backwards. The more you revved it the brighter the light got. That wire was broke and I replaced the regulator

 

That's exactly what happened! The amp gauge was running extreme discharge and it fried the amp gauge too! I'm gonna get a new regulator and go through the starter generator.

Edited March 28 by Mike'sHorseBarn

[WHX?? 46,807]

12 hours ago, Mike'sHorseBarn said:

starter genny started to motor on its own and I had to disconnect the battery to stop the craziness!

Contacts welded in the reg for this to happen. It tries to feed the starter through the bottom G terminal. Thus the way too small melted wire for start amps. Replace the reg. 

[Mike'sHorseBarn 2,652]

1 minute ago, WHX?? said:

Contacts welded in the reg for this to happen. It tries to feed the starter through the bottom G terminal. Thus the way too small melted wire for start amps. Replace the reg. 

 

That's the plan. Gonna go through the genny too. 

 

At this point though the engine ran really nice so I'm gonna start teardown to prep for paint and go through the transmission. Maybe I'll start a new thread on that.