confirming that a bad starter is my problem...

[gbonawitz]

Hi. I have a Super LT1500 that won't start.

For the longest time sometimes when I'd try to start it I'd hear a ~ thunk but nothing more; then I'd have to turn the key off and then try again and it'd start. (I'm wondering if that sound was the starter pinion engaging the flywheel but not turning it.)

Now I'm at the point where when I turn the key I don't even hear the "thunk".

I did try a benchtop test of the solenoid after removing it, and it seems to work correctly.

I also removed the starter and did a benchtop test, and it seems to work fine by itself.

One odd thing I noticed: with everything hooked up in the tractor I took a voltmeter to the post on the starter + chassis ground, and when I turn the key I see only 4-5 volts. If I disconnect the red wire going to the starter post and measure it's voltage I see 12 volts when I turn the key.

I did bypass my tractor batter and hooked up my car's battery and see the same behavior 4-5 V and 12 V behavior... so I think that eliminates the tractor battery as the culprot (and my battery charger states the tractor battery is at 90%).


- Benchtop-wise both the solenoid and starter seem to work by themselves.
- Regardless of tractor or car battery I see that weird 4-5 V versus 12 V behavior

I'm guessing maybe its still something with the starter, i.e. a short... but that doesn't seem to match up with the fact that on the benchtop the starter works/spins.

Last clue (maybe): I took the starter apart and measured the continuity on the commutator. I get continuity from any one terminal around the circumference to every other terminal on the circumference - shouldn't that continuity only be in pairs?

Thanks for any suggestions.

[Oak]

So it sounds like you're only getting 4-5 VDC to the solenoid when you turn the key. You're loosing voltage somewhere in the start circuit. This is a common issue on some of the GT's and here is a good fix for that problem. Add in a relay like Sam shows here in reply #19.

https://onlycubcadets.net/forum/showthread.php?p=397178

[ironman]

Originally Posted by gbonawitz

Hi. I have a Super LT1500 that won't start.

Can't find that model number.
What is the model and serial number on the sticker under your seat?

[gbonawitz]

Model #13AQ11BP756
S/N 1E046H30199

[gbonawitz]

@Oak... The odd thing is that I get 12V at the red lead to the starter if I disconnect that wire from the starter.

If it were an electrical problem with the starter circuit wouldn't it stay at 4V regardless of whether or not that red lead was connected to the starter?

[ironman]

Originally Posted by gbonawitz

Model #13AQ11BP756
S/N 1E046H30199

That helps!
Here is as link to the parts manual for your tractor.
Put in the model and serial numbers as you have shown.
http://manuals.mtdproducts.com/mtd/Public.do
Scroll down to 5 lines up from bottom (769-01652E)
Page 39 has your wire diagram.

The relay mod that Oak suggested will not help you because your solenoid is not incorporated into the starter motor, it is external.

So two possibilities are your problem:

1. You tested the solenoid and probably assumed it is good because you heard it clicking. But if the contacts inside are burnt/corroded, it can operate but not deliver full current flow to the starter (i.e. low voltage).

2. Your starter has a problem as you suspect (i.e. shorts, burnt brushes, etc.) You can't read correct voltage across a short.

So unless you have spare parts laying around to swap, you gotta make a decision on where to start spending money. Solenoid $10-$15, starter $50-$80.

Or you can open the solenoid up and have a look at the contacts and decide from there.

[Oak]

Originally Posted by gbonawitz

@Oak... The odd thing is that I get 12V at the red lead to the starter if I disconnect that wire from the starter.

If it were an electrical problem with the starter circuit wouldn't it stay at 4V regardless of whether or not that red lead was connected to the starter?

Not with a load on it. Are you talking about the large cable from the battery or the small red wire from the start circuit?

[gbonawitz]

@oak - I was referring to the red cable downstream of the solenoid, i.e. the one connecting the solenoid to the starter.

I actually did another test after I got my starter re-assembled (what fun it was trying to hold the brushes back so that I could insert the commutator back into place!)...

- I first bench tested the starter again to make sure it spins with 12V (yep, I understand that's not under load)
- I reinstalled it back onto the engine
- I then completely bypassed the solenoid by connecting my battery (lose on my garage floor at the moment) directly to the starter via jumper cables.

With every attempt to get the engine spinning it'd either:
- do nothing for a second, then spin maybe 1/8 rev and then stop again, or
- spin 1/8 rev, then stop
It never got into any kind of continuous spin (which it what I think should happen here, right?).

I even tried it with my battery charger - set in ~ "jump start mode" - connected to the battery, and got the same behavior.

Don't those results isolate the issue to the starter? I suppose I could repeat the test using my car battery instead of the tractor battery just to make sure it's not a battery issue.

FWIW - when I had the starter apart I was able to confirm proper connectivity, i.e.
- one set of opposite pairs of brushes went to the bottom plate (GND)
- the other set of opposite brushes went to the bolt that the cable from the solenoid goes to (12 V input).

The only thing I didn't test that I probably should've was the resistance for those pairs of brushes.

[Oak]

I would confirm your battery is in good condition but it does sound like it's the starter motor from your tests.

[ironman]

Originally Posted by gbonawitz

- I reinstalled it back onto the engine
- I then completely bypassed the solenoid by connecting my battery (lose on my garage floor at the moment) directly to the starter via jumper cables.

With every attempt to get the engine spinning it'd either:
- do nothing for a second, then spin maybe 1/8 rev and then stop again, or
- spin 1/8 rev, then stop
It never got into any kind of continuous spin (which it what I think should happen here, right?).

I even tried it with my battery charger - set in ~ "jump start mode" - connected to the battery, and got the same behavior.

Understood that you were connecting your positive battery/charger lead directly to the starter's cable terminal.
But where did you connect the negative when using the charger?
Is your negative battery connection to the chassis clean, bright , and tight?
Is your motor making a good ground connection to the chassis?