Starter motor failure mode
31 Oct 2012 20:41 #1
by dandjcr
David and Janet Ribbans - Oka 148
Oka148 profile here.
Visit our technical and travel blogs: here.
dandjcr created the topic: Starter motor failure mode
Forum Home > OKA Maintenance > Starter motor failure mode
Tony Lee
Member
Posts: 539
I know Peter has swapped his starter motor with a geared type, but given that most of us probably have the standard issue, just what is the failure mode of the standard units.
Brush wear?- fixed by regular renewal?
Instant failure of windings??? Solenoid??
Bearings/mechanical???
--
Tony
picasaweb.google.com/114611728110254134379
October 18, 2011 at 5:00 AM Flag Quote & Reply
Peter_n_Margaret
Member
Posts: 198
Mine was still working fine when I replaced it, but sometime in the past it had had a thump and had broken the bell housing which had been welded up.
Given that the OE starter is about half a metre long and weighs about 200kg
I reckoned that the chances of it happening again were sufficient justification to bin it for one that was a fraction of the weight and length.
--
Cheers Peter, OKA196 Motorhome. www.oka4wd.com/xt196.htm
October 18, 2011 at 7:45 AM Flag Quote & Reply
T & D Morris
Member
Posts: 29
Tony
Ours filled with water and mud and the auto electrics that serviced travel about OKA’s wanted $1200 to repair it with no guarantee.
We purchased a new unit for $550 called a 1SKRA and short time later a spare.
This was in 1999 and it's still working well.
This unit has an external solenoid and I was told that on full flex the front tail shaft can knock off the solenoid, but it hasn’t yet.
The details are PJL Industries 08 9479 1866.
ISKRA 1M295 STR 12v 2.8kw 10T T/S PERKINS R/H AZJ 3144 JD Type
Weight 12 kg
--
October 18, 2011 at 11:20 AM Flag Quote & Reply
Dandj
Member
Posts: 367
Tony, our starter motor failed in Eucla just a few weeks ago and left us stranded for a few days. It's an awful feeling to turn the key and get only a click, (or in our case nothing at all). The solenoid had failed and they are not repairable on the roadside (they have 2 windings inside but I'm not sure why yet) .
I got a spare sent out from PJL in Perth but frustratingly, that didn't fix the problem, but at least we now had a click. It seems that the armature had also failed in some way, maybe the brass commutator being too worn for the brushes to seat properly.
I bump started the Oka (which is quite easy) and drove to Robin in Coolgardie without switching off and replaced the armature with one from another failed unit and all was well.
We just got back home about an hour ago but soon I'll get the broken armature tested and machined and we'll see what the problem was. Heavy current machines like these are pretty reliable so failure is usually dirty or worn commutator or brushes, worn bearings or solenoid failure (it's close to the exhaust in our case but in others it hangs down below). Mechanical failure, other than impact, would be rare, after all a starter motor would normally only operate for less than a minute per day.
Robin's failed one was actually due to the brush springs shorting out to the housing (they are very close and can also move about) so ensure there is insulation around them to prevent that.
I shall also dissect the failed solenoid (with an axe if necessary) to see what went wrong so I'm better prepared next time. I had spare brushes but no spare solenoid.
The brushes in ours (also an Iskra) are spot welded on so replacing them isn't easy. I haven't done it yet but i'd probably cut the leads off and drill a small hole in each lead and bolt them together using M3 or 4 bolts. You'd need a big soldering iron or gas torch to do it otherwise.
--
David and Janet Ribbans, Oka 148
October 18, 2011 at 4:51 PM Flag Quote & Reply
Hal Harvey
Site Owner
Posts: 510
Terry's IM295 appears to have been superseded by the IM315, according to the PJL site. The later one is a little shorter and a little more powerful. Parts appear to still be available for the earlier model.
Ten kilos to stash somewhere if you're going to take a spare, which would of course guarantee you'd never need it. Wouldn't it be good if you could just make a little voodoo model of one to serve the same purpose?
--
Hal
October 18, 2011 at 7:35 PM Flag Quote & Reply
Dandj
Member
Posts: 367
Hal. I think I would take a working solenoid and brush plate as spares next time, but have the armature machined and/or tested before leaving. That would save most of the weight at minimal cost with only a bit more risk. But if I had a spare working armature I'd probably take that too...
Taking a starter off and disassembling it is only a 10 minute job once you've done it a couple of times, as I have now. The top bolt is the awkward one to access. Disconnect the battery first to avoid a light show.
A starter is a single point of failure but one where the risks can be mitigated. Hindsight, mutter mutter...
To paraphrase Edison: "I have not failed, I have successfully found 10 ways of repairing a starter motor that don't work".
--
David and Janet Ribbans, Oka 148
October 18, 2011 at 8:39 PM Flag Quote & Reply
James & Usha (THEByleDuct)
Administrator
Posts: 161
This discussion piqued my interest in what I had on board. A quick look and photo later came up with an OEX starter with part number DXS498. It cross references to a Denso SNJ026. I'll have to go through the files Tim left me to see when it was put in. As far as I'm aware it has worked well so far. These should be easy enough to find a spare solenoid for I should think. Good ideas here. Thanks!
--
OKA #072
October 18, 2011 at 9:36 PM Flag Quote & Reply
Tony Lee
Member
Posts: 539
Hmmmmmm! No single failure mode that couldn't also happen to a brand new geared unit.
I may rely on the fact that 123 is relatively young at 90,000km so should last a few more starts yet.
At least there are options to get the OKA started unlike our MH on a Ford Transit chassis that failed in the middle of Morocco because arcing battery connection hade wiped the ignition key security code. Only needed 5 minutes with a laptop to recode, but that first required a 300km round trip to pick us up and take us to the nearest Ford dealer.
S'pose my next question might be "how can you tell when a ceramic clutch needs replacing"
Perhaps in another topic
--
Tony
picasaweb.google.com/114611728110254134379
October 19, 2011 at 7:56 AM Flag Quote & Reply
Hal Harvey
Site Owner
Posts: 510
You've already put that out there Tony - re ceramic clutch.
--
Hal
October 19, 2011 at 9:30 AM Flag Quote & Reply
Dandj
Member
Posts: 367
Tony, now I know why there are 2 windings in the solenoid. One heavier coil pulls in the plunger to engage both the pinion and contactor for the motor supply, and the other, lighter winding holds the plunger in while the motor rotates. This article explains it all quite well. Logically, the lighter winding should be the one to fail first due to heat etc, but does logic apply?
BTW the most common problem I've had with starters is dirty contacts, either on the motor itself or the starter battery. All connections (inc. battery ground) should be checked before blaming the motor. Also check the start relay to ensure the the start signal actually reaches the solenoid from the key switch. Our intermittent starter problem up Cape York last year was a loose solenoid connection.
I used to have an isolating switch in the starter battery lead for quick isolating but they can't handle the 100's of amps of starter current and go high resistance so I removed it. I put a large wing nut on the battery terminal bolt as a quick release instead.
--
David and Janet Ribbans, Oka 148
October 19, 2011 at 9:56 AM Flag Quote & Reply
Tony Lee
Member
Posts: 539
Hal Harvey at October 19, 2011 at 9:30 AM
You've already put that out there Tony - re ceramic clutch.
Ah yes, not only the short term memory is going bad, but the long term one is failing as well.
Thanks Hal.
--
Tony
picasaweb.google.com/114611728110254134379
October 19, 2011 at 3:15 PM Flag Quote & Reply
Tony Lee
Member
Posts: 539
"Logically, the lighter winding should be the one to fail first due to heat etc, but does logic apply?"
Pretty commonarrangement and even most common single phase motors use a start and run winding.
Failure is usually the pull-in coil and it happens when the contact that should transfer the current from the pull-in to the hold-in coil just at the point where the solenoid contacts are closed, fails to transfer - usually because of wear. This means that the pull-in coil is left carrying a large current for seconds instead of milliseconds - and eventually burns out.
--
Tony
picasaweb.google.com/114611728110254134379
October 19, 2011 at 3:20 PM Flag Quote & Reply
Dandj
Member
Posts: 367
I've now cut open my failed starter solenoid to determine the fault.
If anyone is interested in what's inside a starter solenoid, I've written up some notes on our blog.
--
David and Janet Ribbans, Oka 148
October 30, 2011 at 12:28 PM Flag Quote & Reply
James & Usha (THEByleDuct)
Administrator
Posts: 161
Brilliant! "To reassemble, simply reverse the disassembly process"
--
OKA #072
October 30, 2011 at 2:20 PM Flag Quote & Reply
Tony Lee
Member
Posts: 539
Well my OEM starter hasn't got an external solenoid housing, so adding a heat shield can be taken off my far-too-long to-do list.
--
Tony
picasaweb.google.com/114611728110254134379
November 1, 2011 at 4:05 PM Flag Quote & Reply
oldfosil
Member
Posts: 3
As a retired Autoelectrician who spent a great deal of time repairing startermotors of the OKA vintage I would advise replacing them with a gear drive unit as soon as possible. They weren't much good when they first came on the market, gear drive units are far more reliable. Just remember it's not IF it's going to fail, but, WHEN it's going to fail. ( usually at THE most inconvienient time)
November 2, 2011 at 4:19 PM
Tony Lee
Member
Posts: 539
I know Peter has swapped his starter motor with a geared type, but given that most of us probably have the standard issue, just what is the failure mode of the standard units.
Brush wear?- fixed by regular renewal?
Instant failure of windings??? Solenoid??
Bearings/mechanical???
--
Tony
picasaweb.google.com/114611728110254134379
October 18, 2011 at 5:00 AM Flag Quote & Reply
Peter_n_Margaret
Member
Posts: 198
Mine was still working fine when I replaced it, but sometime in the past it had had a thump and had broken the bell housing which had been welded up.
Given that the OE starter is about half a metre long and weighs about 200kg
I reckoned that the chances of it happening again were sufficient justification to bin it for one that was a fraction of the weight and length.--
Cheers Peter, OKA196 Motorhome. www.oka4wd.com/xt196.htm
October 18, 2011 at 7:45 AM Flag Quote & Reply
T & D Morris
Member
Posts: 29
Tony
Ours filled with water and mud and the auto electrics that serviced travel about OKA’s wanted $1200 to repair it with no guarantee.
We purchased a new unit for $550 called a 1SKRA and short time later a spare.
This was in 1999 and it's still working well.
This unit has an external solenoid and I was told that on full flex the front tail shaft can knock off the solenoid, but it hasn’t yet.
The details are PJL Industries 08 9479 1866.
ISKRA 1M295 STR 12v 2.8kw 10T T/S PERKINS R/H AZJ 3144 JD Type
Weight 12 kg
--
October 18, 2011 at 11:20 AM Flag Quote & Reply
Dandj
Member
Posts: 367
Tony, our starter motor failed in Eucla just a few weeks ago and left us stranded for a few days. It's an awful feeling to turn the key and get only a click, (or in our case nothing at all). The solenoid had failed and they are not repairable on the roadside (they have 2 windings inside but I'm not sure why yet) .
I got a spare sent out from PJL in Perth but frustratingly, that didn't fix the problem, but at least we now had a click. It seems that the armature had also failed in some way, maybe the brass commutator being too worn for the brushes to seat properly.
I bump started the Oka (which is quite easy) and drove to Robin in Coolgardie without switching off and replaced the armature with one from another failed unit and all was well.
We just got back home about an hour ago but soon I'll get the broken armature tested and machined and we'll see what the problem was. Heavy current machines like these are pretty reliable so failure is usually dirty or worn commutator or brushes, worn bearings or solenoid failure (it's close to the exhaust in our case but in others it hangs down below). Mechanical failure, other than impact, would be rare, after all a starter motor would normally only operate for less than a minute per day.
Robin's failed one was actually due to the brush springs shorting out to the housing (they are very close and can also move about) so ensure there is insulation around them to prevent that.
I shall also dissect the failed solenoid (with an axe if necessary) to see what went wrong so I'm better prepared next time. I had spare brushes but no spare solenoid.
The brushes in ours (also an Iskra) are spot welded on so replacing them isn't easy. I haven't done it yet but i'd probably cut the leads off and drill a small hole in each lead and bolt them together using M3 or 4 bolts. You'd need a big soldering iron or gas torch to do it otherwise.
--
David and Janet Ribbans, Oka 148
October 18, 2011 at 4:51 PM Flag Quote & Reply
Hal Harvey
Site Owner
Posts: 510
Terry's IM295 appears to have been superseded by the IM315, according to the PJL site. The later one is a little shorter and a little more powerful. Parts appear to still be available for the earlier model.
Ten kilos to stash somewhere if you're going to take a spare, which would of course guarantee you'd never need it. Wouldn't it be good if you could just make a little voodoo model of one to serve the same purpose?
--
Hal
October 18, 2011 at 7:35 PM Flag Quote & Reply
Dandj
Member
Posts: 367
Hal. I think I would take a working solenoid and brush plate as spares next time, but have the armature machined and/or tested before leaving. That would save most of the weight at minimal cost with only a bit more risk. But if I had a spare working armature I'd probably take that too...
Taking a starter off and disassembling it is only a 10 minute job once you've done it a couple of times, as I have now. The top bolt is the awkward one to access. Disconnect the battery first to avoid a light show.
A starter is a single point of failure but one where the risks can be mitigated. Hindsight, mutter mutter...
To paraphrase Edison: "I have not failed, I have successfully found 10 ways of repairing a starter motor that don't work".
--
David and Janet Ribbans, Oka 148
October 18, 2011 at 8:39 PM Flag Quote & Reply
James & Usha (THEByleDuct)
Administrator
Posts: 161
This discussion piqued my interest in what I had on board. A quick look and photo later came up with an OEX starter with part number DXS498. It cross references to a Denso SNJ026. I'll have to go through the files Tim left me to see when it was put in. As far as I'm aware it has worked well so far. These should be easy enough to find a spare solenoid for I should think. Good ideas here. Thanks!
--
OKA #072
October 18, 2011 at 9:36 PM Flag Quote & Reply
Tony Lee
Member
Posts: 539
Hmmmmmm! No single failure mode that couldn't also happen to a brand new geared unit.
I may rely on the fact that 123 is relatively young at 90,000km so should last a few more starts yet.
At least there are options to get the OKA started unlike our MH on a Ford Transit chassis that failed in the middle of Morocco because arcing battery connection hade wiped the ignition key security code. Only needed 5 minutes with a laptop to recode, but that first required a 300km round trip to pick us up and take us to the nearest Ford dealer.
S'pose my next question might be "how can you tell when a ceramic clutch needs replacing"
Perhaps in another topic
--
Tony
picasaweb.google.com/114611728110254134379
October 19, 2011 at 7:56 AM Flag Quote & Reply
Hal Harvey
Site Owner
Posts: 510
You've already put that out there Tony - re ceramic clutch.
--
Hal
October 19, 2011 at 9:30 AM Flag Quote & Reply
Dandj
Member
Posts: 367
Tony, now I know why there are 2 windings in the solenoid. One heavier coil pulls in the plunger to engage both the pinion and contactor for the motor supply, and the other, lighter winding holds the plunger in while the motor rotates. This article explains it all quite well. Logically, the lighter winding should be the one to fail first due to heat etc, but does logic apply?
BTW the most common problem I've had with starters is dirty contacts, either on the motor itself or the starter battery. All connections (inc. battery ground) should be checked before blaming the motor. Also check the start relay to ensure the the start signal actually reaches the solenoid from the key switch. Our intermittent starter problem up Cape York last year was a loose solenoid connection.
I used to have an isolating switch in the starter battery lead for quick isolating but they can't handle the 100's of amps of starter current and go high resistance so I removed it. I put a large wing nut on the battery terminal bolt as a quick release instead.
--
David and Janet Ribbans, Oka 148
October 19, 2011 at 9:56 AM Flag Quote & Reply
Tony Lee
Member
Posts: 539
Hal Harvey at October 19, 2011 at 9:30 AM
You've already put that out there Tony - re ceramic clutch.
Ah yes, not only the short term memory is going bad, but the long term one is failing as well.
Thanks Hal.
--
Tony
picasaweb.google.com/114611728110254134379
October 19, 2011 at 3:15 PM Flag Quote & Reply
Tony Lee
Member
Posts: 539
"Logically, the lighter winding should be the one to fail first due to heat etc, but does logic apply?"
Pretty commonarrangement and even most common single phase motors use a start and run winding.
Failure is usually the pull-in coil and it happens when the contact that should transfer the current from the pull-in to the hold-in coil just at the point where the solenoid contacts are closed, fails to transfer - usually because of wear. This means that the pull-in coil is left carrying a large current for seconds instead of milliseconds - and eventually burns out.
--
Tony
picasaweb.google.com/114611728110254134379
October 19, 2011 at 3:20 PM Flag Quote & Reply
Dandj
Member
Posts: 367
I've now cut open my failed starter solenoid to determine the fault.
If anyone is interested in what's inside a starter solenoid, I've written up some notes on our blog.
--
David and Janet Ribbans, Oka 148
October 30, 2011 at 12:28 PM Flag Quote & Reply
James & Usha (THEByleDuct)
Administrator
Posts: 161
Brilliant! "To reassemble, simply reverse the disassembly process"
--
OKA #072
October 30, 2011 at 2:20 PM Flag Quote & Reply
Tony Lee
Member
Posts: 539
Well my OEM starter hasn't got an external solenoid housing, so adding a heat shield can be taken off my far-too-long to-do list.
--
Tony
picasaweb.google.com/114611728110254134379
November 1, 2011 at 4:05 PM Flag Quote & Reply
oldfosil
Member
Posts: 3
As a retired Autoelectrician who spent a great deal of time repairing startermotors of the OKA vintage I would advise replacing them with a gear drive unit as soon as possible. They weren't much good when they first came on the market, gear drive units are far more reliable. Just remember it's not IF it's going to fail, but, WHEN it's going to fail. ( usually at THE most inconvienient time)
November 2, 2011 at 4:19 PM
David and Janet Ribbans - Oka 148
Oka148 profile here.
Visit our technical and travel blogs: here.
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