Over-running starter motor - JCB 8014 digger

[patrickr321]

A bit flummoxed by the following problem:

Intermittently, the starter motor on my JCB is over-running, metal on metal noise, still turning over in key-off position. Not good. Only way to turn off is disconnect battery.

I've had the starter motor out and bench tested it, thinking it was a dodgy solenoid. Connect up 12v supply to the main terminal. Then apply 12v to the ignition connector and the pinion shoots out and turns; it flies back in when 12v removed from ignition connector. So seems to work OK.

I've checked the voltage to the ignition lead: Reading 0v with key off (actually a small amount of voltage leak: 0.05v); 12v with ignition in 3rd position (ie. start). So that seems to work OK.

Any other ideas as to why it's sticking on?

Interestingly, it happens most when starting from cold.....

Thanks

 

[box]

Strip, clean and lube the starter while you've got it off. Just because the starter bench tests fine, doesn't mean it's throwing out and retracting correctly on the machine with the load/drive of the ring gear.

Also make sure the one way clutch is working correctly.

If it's got a removable solenoid cap, remove it and check and clean the solenoid contacts and plunger.

Failing that, could be a faulty ignition switch or starter relay (if it has one).

 

[patrickr321]

Strip, clean and lube the starter while you've got it off. Just because the starter bench tests fine, doesn't mean it's throwing out and retracting correctly on the machine with the load/drive of the ring gear.

Also make sure the one way clutch is working correctly.

If it's got a removable solenoid cap, remove it and check and clean the solenoid contacts and plunger.

Failing that, could be a faulty ignition switch or starter relay (if it has one).

Thanks for all that. I'll take it off and clean it up, inspect the solenoid etc. It's odd that it's sometimes getting power when the key's in the off position and continuing to run. Of course, when I check for voltage at the ignition terminal after the event, it isn't there - or is 0.05v. Is it possible it's getting an occasional short in the solenoid that makes the starter continue to run?

 

[ACEngineering]

Thanks for all that. I'll take it off and clean it up, inspect the solenoid etc. It's odd that it's sometimes getting power when the key's in the off position and continuing to run. Of course, when I check for voltage at the ignition terminal after the event, it isn't there - or is 0.05v. Is it possible it's getting an occasional short in the solenoid that makes the starter continue to run?

its most likely cause either the contacts inside the solenoid are burnt and welding themselves together or you have a mechanical issue with the gear not sliding out of mesh ie its too stiff on the sliding parts.

if you had wiring problem i would expect it to have melted all the looms etc.

 

[patrickr321]

its most likely cause either the contacts inside the solenoid are burnt and welding themselves together or you have a mechanical issue with the gear not sliding out of mesh ie its too stiff on the sliding parts.

if you had wiring problem i would expect it to have melted all the looms etc.

Hi

Thanks for this. I've had the solenoid off and there's no access to behind the contacts. I can see the plunger etc. The fronts of the starter motor pinion teeth are worn and I've noticed that there is some burring on the flywheel. Before refitting, is it a good idea to gently file these down? It sounds as if I need a new starter and solenoid?

 

[ACEngineering]

Hi

Thanks for this. I've had the solenoid off and there's no access to behind the contacts. I can see the plunger etc. The fronts of the starter motor pinion teeth are worn and I've noticed that there is some burring on the flywheel. Before refitting, is it a good idea to gently file these down? It sounds as if I need a new starter and solenoid?

you can file the burs off the teeth yes but remember they are supposed to be angled to allow the gear to mesh in easy.

you cant get in the solenoids to see the contacts normally, some you can unsolder and pull apart but really at that stage there is little point in bothering just fit a new one.

 

[patrickr321]

Now the question is whether to go OEM or JCB......

And is it a good idea to lube any of the parts when fitting (if so what lube?) - or avoid lube?

 

[ACEngineering]

Now the question is whether to go OEM or JCB......

And is it a good idea to lube any of the parts when fitting (if so what lube?) - or avoid lube?

No need to lube anything on a new starter no.

Genuine JCB or OEM is the same thing even if your buying the OEM part elsewhere its still original equipment spec.

There will be loads of starters that will fit it as in bolt on, they will mostly all be copies and possibly several different KW ratings some not fit for your purpose.

 

[patrickr321]

No need to lube anything on a new starter no.

Genuine JCB or OEM is the same thing even if your buying the OEM part elsewhere its still original equipment spec.

There will be loads of starters that will fit it as in bolt on, they will mostly all be copies and possibly several different KW ratings some not fit for your purpose.

Thanks. Sorry, I meant "copy". You're right, there's loads of copies out there. Seems the one I'm replacing is a copy too - not original. Difficult decision as the copies are around £100 and a JCB one is £260 + VAT.

 

[ACEngineering]

Thanks. Sorry, I meant "copy". You're right, there's loads of copies out there. Seems the one I'm replacing is a copy too - not original. Difficult decision as the copies are around £100 and a JCB one is £260 + VAT.

honestly surprised the jcb one is that cheap.

 

[suffolksmallholder]

I am lucky to have two local Auto Electrical Co’s reasonably local to me. One in Lowestoft and one in Yarmouth.
Over the years I have had sterling service from both, repairing Bosch, Lucas (Prince of darkness trophy winners from 1066 to 2024) and Valeo starter motors.
If you are lucky to have a competent independent Co, let them do the overhaul as it will save you a heap of pi55ing about and at the end it will work as it should.
FYI, you’ll have change left from £100 which will make you smile plus a years warranty.
What’s not to like
SS

 

[patrickr321]

I am lucky to have two local Auto Electrical Co’s reasonably local to me. One in Lowestoft and one in Yarmouth.
Over the years I have had sterling service from both, repairing Bosch, Lucas (Prince of darkness trophy winners from 1066 to 2024) and Valeo starter motors.
If you are lucky to have a competent independent Co, let them do the overhaul as it will save you a heap of pi55ing about and at the end it will work as it should.
FYI, you’ll have change left from £100 which will make you smile plus a years warranty.
What’s not to like
SS

Thanks, I'll look into whether there's somewhere local...... cheers

 

[patrickr321]

Agggh. I've just replaced the starter motor with a new JCB one, after filing down the burrs on the flywheel gear to give the best mesh possible. Digger started fine a few times but I've just had the starter stick on again briefly and continuing to turn (briefly) with the key in the "off" position! Now seriously don't want to start it again in case it trashes the teeth of both the starter pinion and the flywheel gear. I don't understand why it's sticking on. If it was getting mechanically stuck, shouldn't it all disengage and stop when I turn the key to the off position?

I've also tested the ignition switch again with a multi-meter and it seems to work as expected. 12v when in start position. And 0v (or thereabouts) when in the run or off position. Surely this should also indicate that the starter relay is also working correctly? - or could that still be faulty even with these readings?

 

[Lazy Sod]

You must be slipping, @ACEngineering, you haven't suggested fitting an Iskra starter yet.

 

[ACEngineering]

Agggh. I've just replaced the starter motor with a new JCB one, after filing down the burrs on the flywheel gear to give the best mesh possible. Digger started fine a few times but I've just had the starter stick on again briefly and continuing to turn (briefly) with the key in the "off" position! Now seriously don't want to start it again in case it trashes the teeth of both the starter pinion and the flywheel gear. I don't understand why it's sticking on. If it was getting mechanically stuck, shouldn't it all disengage and stop when I turn the key to the off position?

I've also tested the ignition switch again with a multi-meter and it seems to work as expected. 12v when in start position. And 0v (or thereabouts) when in the run or off position. Surely this should also indicate that the starter relay is also working correctly? - or could that still be faulty even with these readings?

Multi metre test is a waste of time, simulate a load on it like a 55watt bulb if you want to test it.