Starter on B7500

[OLD GAR]

The starter on my B7500 will not engage the bendix into the flywheel
The starter spins butt will not turn the engine over. I have switched the solenoid from a starter from another then changed a whole starter that was a recent purchase and no luck with all those fixes!

 

[Henro]

The starter on my B7500 will not engage the bendix into the flywheel
The starter spins butt will not turn the engine over. I have switched the solenoid from a starter from another then changed a whole starter that was a recent purchase and no luck with all those fixes!

Is this problem the same as you were having before you changed the starter motor?

If so, I would check the voltage between the battery connection at the starter and the starter case, to see if it was equal to battery voltage at the battery posts (not the battery clamps, but the posts themselves) and report back. Also report what the voltage is at the battery posts unloaded and when you try to start the tractor and the starter motor spins but doesn't engage the flywheel.

Maybe someone else has better ideas, but this is what I would do myself as a first step to evaluate the issue.

Some will advise changing things like the battery cables, but I personally favor taking measurements first rather than the shotgun replacement approach.

 

[North Idaho Wolfman]

How do the teeth on the ring gear look?

 

[mpsmdsr]

How do the teeth on the ring gear look?

 

[mpsmdsr]

does the starter have a solenoid like a car starter?

 

[North Idaho Wolfman]

does the starter have a solenoid like a car starter?

That's subjective... old ford starters had the solenoid on the fender.
But yes the solenoid on these is attached to the starter and activated / engages the starter and Bendix.

 

[North Idaho Wolfman]

The starter on my B7500 will not engage the bendix into the flywheel
The starter spins butt will not turn the engine over. I have switched the solenoid from a starter from another then changed a whole starter that was a recent purchase and no luck with all those fixes!

You're not just powering or jumping the starter are you? Thus bypassing the solenoid?

 

[GeoHorn]

I talked to OlGar and he says the ring gear teeth are fine. He bought new starter from Messicks and same thing…bendix/solenoid does not engage. He tested the spade connector with the start selected and has 12.8 volts at that point.

Very curious.

 

[North Idaho Wolfman]

I talked to OlGar and he says the ring gear teeth are fine. He bought new starter from Messicks and same thing…bendix/solenoid does not engage. He tested the spade connector with the start selected and has 12.8 volts at that point.

Very curious.

The only reason it wouldn't be engaging would be voltage is backwards, voltage is not being applied to both the starter and the solenoid at the same time, or there is some other damage!

 

[GeoHorn]

He jumpered from the starter motor connection directly to the solenoid so they would both be guaranteed currect and activated it…and it blew the 30 A fuse.

He’s 85 yrs old and a retired airline mechanic…. You’d think he could figure this out…but… ?

 

[fried1765]

He jumpered from the starter motor connection directly to the solenoid so they would both be guaranteed currect and activated it…and it blew the 30 A fuse.

He’s 85 yrs old and a retired airline mechanic…. You’d think he could figure this out…but… ?

Just wait until YOU are 85!
(I am 83)
Things get A LOT MORE difficult as old age takes control.

 

[GeoHorn]

Just wait until YOU are 85!
(I am 83)
Things get A LOT MORE difficult as old age takes control.

LOLOL… I’m gettin’ up there myself! OlGar and I are decades old friends (from an airplane type-club we both belong to) and I just hadn’t seen him on this forum…at least not recently …so I called him to tell him folks were responding to his posts and discussed it with him.

It’s difficult to fix things over the phone tho’. I stopped by his house a year or so ago when he complained his riding lawn mower wouldn’t engage the blades anymore and he couldn’t figure it out.
Turns out..it had an electric clutch (similar to an automotive AC compressor clutch) and vibration had simply broken the power—lead-wire where it entered the clutch-case. I removed the clutch cover and spliced the wire … no more problem. I admit I was surprised he hadn’t diagnosed that one… but perhaps he’s just gettin’ sneaky (it’s a 7-hour drive from here to there) about getting me to come over to participate and drink beer to celebrate.

 

[fried1765]

LOLOL… I’m gettin’ up there myself! OlGar and I are decades old friends (from an airplane type-club we both belong to) and I just hadn’t seen him on this forum…at least not recently …so I called him to tell him folks were responding to his posts and discussed it with him.

It’s difficult to fix things over the phone tho’. I stopped by his house a year or so ago when he complained his riding lawn mower wouldn’t engage the blades anymore and he couldn’t figure it out.
Turns out..it had an electric clutch (similar to an automotive AC compressor clutch) and vibration had simply broken the power—lead-wire where it entered the clutch-case. I removed the clutch cover and spliced the wire … no more problem. I admit I was surprised he hadn’t diagnosed that one… but perhaps he’s just gettin’ sneaky (it’s a 7-hour drive from here to there) about getting me to come over to participate and drink beer to celebrate.

Good on you for driving over to see him.
I too, suspect that may have been his intent.

 

[Henro]

The only reason it wouldn't be engaging would be voltage is backwards, voltage is not being applied to both the starter and the solenoid at the same time, or there is some other damage!

Interesting observation. We know the starter motor turns has did a second replacement.

Jumping from the main connection on the starter to the starter solenoid also caused the starter to turn but nothing else to happen as far as I remember. And I believe it was reported that the voltage at the starter when the starter was turning was something like 13 V or so, so there’s not significant voltage loss between the battery and the starter motor when this event is happening.

I don’t understand exactly how the Bendix on the starter motor works, but I get the impression if the starter motor is turning backwards that the Bendix will not extend. Is this correct? if so, I’m wondering if somehow the battery got hooked up backwards for whatever reason.

Maybe someone that knows can jump in here and tell us what would actually happen with the starter motor if the battery was hooked up backwards. Certainly the starter motor would turn backwards since it’s a series motor. I assume it is anyway.

The tractor may be old enough that hooking the battery up backwards may not cause significant issues, who knows?

 

[TheOldHokie]

Interesting observation. We know the starter motor turns has did a second replacement.

Jumping from the main connection on the starter to the starter solenoid also caused the starter to turn but nothing else to happen as far as I remember. And I believe it was reported that the voltage at the starter when the starter was turning was something like 13 V or so, so there’s not significant voltage loss between the battery and the starter motor when this event is happening.

I don’t understand exactly how the Bendix on the starter motor works, but I get the impression if the starter motor is turning backwards that the Bendix will not extend. Is this correct? if so, I’m wondering if somehow the battery got hooked up backwards for whatever reason.

Maybe someone that knows can jump in here and tell us what would actually happen with the starter motor if the battery was hooked up backwards. Certainly the starter motor would turn backwards since it’s a series motor. I assume it is anyway.

The tractor may be old enough that hooking the battery up backwards may not cause significant issues, who knows?

The starter does not use a bendix drive and the motor turns the same direction regardless of battery polarity.

EDIT: Strike the comment above on rotation. I looked at the parts breakdown and that looks like a PM gear reduction starter and in that case it would reverse rotation with polarity. The rest of my comments remain.

The starter gear is pushed into engagement by the action of the solenoid. In most modern designs that also closes an internal set of contacts that energizes the motor after the gear is extended.

This problem description is not adding up. Perhaps he is jumpering battery to the armature contact on the motor and not the solenoid itself. That causes the motor to spin but does not energize the solenoid.

Dan

 

[Chanceywd]

Just to confirm that reversing polarity with Dan. In changing an 8N to 12 volt you change from positive to negative ground. You can get 12 volt starter but the old 6 volt will work fine.

Bill

 

[Henro]

What Dan said makes sense when you think about it. The starter motor would be a series motor design, which offers very high torque at start. A series motor will run the same direction if polarity is reversed. The only way to reverse direction is to reverse the hook up of either the field or armature. Probably not easily done with a starter motor without disassembly at minimum.

On my starters I believe only the positive main terminal the battery connects to, and the starter solenoid activation terminal, are available externally. I would guess this is pretty standard, but I don’t know. So it seems unlikely the OP could be hooking the jumper to anything other than the solenoid activation terminal or the main power lug. Would be nice to see a schematic diagram of the motor internal connections to determine if there is some possibility of an electrical path between the solenoid activation terminal, and the armature/series field circuit.

Seems like we’re basing everything on the fact that two different starters were installed. I wonder if there’s any possibility that the original starter that was removed ended up being put back in place rather than the new one he got somewhere, especially if the "new" one was a used unit? I think at this point, I would swap the starters again and see what happens (marking one clearly first).

 

[TheOldHokie]

What Dan said makes sense when you think about it. The starter motor would be a series motor design, which offers very high torque at start. A series motor will run the same direction if polarity is reversed. The only way to reverse direction is to reverse the hook up of either the field or armature. Probably not easily done with a starter motor without disassembly at minimum.

On my starters I believe only the positive main terminal the battery connects to, and the starter solenoid activation terminal, are available externally. I would guess this is pretty standard, but I don’t know. So it seems unlikely the OP could be hooking the jumper to anything other than the solenoid activation terminal or the main power lug. Would be nice to see a schematic diagram of the motor internal connections to determine if there is some possibility of an electrical path between the solenoid activation terminal, and the armature/series field circuit.

Seems like we’re basing everything on the fact that two different starters were installed. I wonder if there’s any possibility that the original starter that was removed ended up being put back in place rather than the new one he got somewhere, especially if the "new" one was a used unit? I think at this point, I would swap the starters again and see what happens (marking one clearly first).

Please note I revised my comment about polarity and direction pf rotation. I was assuming a series wound motor but after looking at the parts breakdown it looks like its probably a PM motor.

In any event something about this problem description is fishy

Dan

 

[Chanceywd]

Please note I revised my comment about polarity and direction pf rotation. I was assuming a series wound motor but after looking at the parts breakdown it looks like its probably a PM motor.

In any event something about this problem description is fishy

Dan

I was agreeing with your original statement that changing polarity doesn't reverse rotation, and my experience with my 8n confirms it at least for an 8N.

Bill

 

[TheOldHokie]

I was agreeing with your original statement that changing polarity doesn't reverse rotation, and my experience with my 8n confirms it at least for an 8N.

Bill

Yes. 9N/2N/8N same as my B7200 - starter is a direct drive series wound DC motor. Looks like the US industry switched to gear reduction PM motors in early 90s and Japan may have been earlier. B7500s were built 2000-2004 and no field coil shown in the starter parts disgram....

Dan