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Starter Motor Troubles

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tekspeek

Freshman Member
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I posted a query about a normally fuctioning starter motor failing about a week ago. Checked all connections and finally pulled the motor out.

I applied power to the motor and it simply sparked. I measure the resistance from the Positive (which of course is really negative) to the case. 1.0 ohms.

The brushes look good. Nothing abnormal about the motor. I chose not to dismantle the motor for fear I would induce other problems.

Any help?
 
Reinstall starter, then systematically do the following checks with the high tension lead removed from coil.
1. Remove the battery cables at battery and at starter and ground. Clean with Arm-n-Hammer bicarb and water, then with a wire brush, reinstall, test .
2. Test starter motor and solenoid: connect a jumper wire (heavyguage with alligator clips on each end) to the battery post of solenoid to the ignition switch side of solenoid--
a. starter turns normally, check next step
b. starter buzzes or turns slowly, bench test starter
c. no response, replace solenoid
d. if starter turns, but engine doesn't, check flywheel ring gear, if it's good, replace bendix

3. Check ignition switch, connect a test lamp (i made one out of an old tail light socket and again, put an alligator clip on each end) between the starter post of the solenoid and ground. Turn the ignition switch to start position and jiggle the key. If the lamp doesn't light when the switch is turned, check the ignition switch for loose connections, cracked insulation or broken wires. Repair as necessary. If the lamp flickers when jiggled, relace the ignition switch.
 
Since you already have it out, you might take it to a local auto parts store and have them test it. They may be unable to diagnose a problem but may at least confirm you have a problem with the starter itself.

Most of the major chains offer free testing. Some may be reluctant to test a starter that has the open pinion (like a TR4) but other shops don't care.

These things are pretty easy to service and a pretty robust design.

Used starters are pretty cheap and rebuilds are available I think. Some switch to the 'hi-torque' starter but I've never felt the need for that (in fact, those may spin the engine slower which I would think is not an advantage).
 
When the bushings go bad, the armature hits the field coil. When they rebuild the staters, they test for shorts, replace the bushings (if needed), turn the armature and replace the brush sets.

Bill
 
Thanks for the suggestions. I took the motor down to AutoZone - they were nervous because they didn't have a hook up schedule for a TR4 but we muddled through it and found a suitable connection. The motor turned about a half turn and blew the circuit breaker on the tester. We repeated this several times.

I found a local place that rebuilds/repairs starter motors. I dropped it off with them and will post the results.

Thanks for the inputs.

Pete
 
I did take the starter motor to a local motor rebuilder. I'm not sure what to make of the estimate. Basically they said I needed a new 'driver', bushings and 1 brush. $180. I have no idea what a driver is - maybe they meant me.

I retrieved the motor and pulled it apart.

What I found was that when disassembled the resistance of the Stator to ground was 350 ohms. That seems like a reasonable resistance - certainly not a short. The bushings and the brushes look good but when I reassembled the motor I measured the resistance of the 'hot' line to the case and found this to be shorted - zero ohms.

I'm thinking it could be the wires to the brushes shorting out but a)the repair shop would have seen this and b) I moved the wires around and did not see a change in resistance.

I don't know what else would cause a short - any ideas?

btw, I did purchase a starter motor on Ebay so I'm up and running (my wife was tired of popping the clutch while I pushed the car and I couldn't convice her that it would be good exercise for her to push and let me pop the clutch)

If there are any motor experts out there I'd appreciate your input.

Thanks,
Pete
 
Some of the veteran members here may remember me going through similar problems with my starter and rebuilder. In retrospect, I would have purchased a new starter instead of all the troubles with jump starting (I also had to get a neighbor first to help push it up a hill before I could get it in a downhill push mode, also with my wife as the clutch popper). I had my starter "rebuilt", tested and retested and "re-rebuilt" and finally had the drive mechanism welded together. I took that rascal starter in and out 7 times. Hope you have better and faster results!
 
[ QUOTE ]
I don't know what else would cause a short - any ideas?

[/ QUOTE ]

My starter failed with a short when the wrapping on one of the field coils abraded to the point that the metal of the field made contact with the body of the starter.

I found the exact one by disassembling the starter (with the field coils still attached), hooked up my ohmmeter (dead short) and fiddled with each of the field coils until tweaking one of them could intermittently make the short go away. Of course, once they were out the worn place on the wrapping (and other worn spots) were obvious.

I re-wrapped those spots with friction tape (the sticky cloth stuff) and all was fine again.

I had to use PB Blaster & a hammer-driven impact screwdriver to loosen those big phillps head screws that hole the field coils in place.
 
I believe George has ID'd the most likely short. If it is that don't get carried away with the tape there's not that much clearance between the fields and the armature. The armature sounds OK, just make a quick check on all segments though. Tell them not to get carried away if they think the commutator needs to be recut. I see too many where they've weakened the segments by removing to much. You're sometimes better off just clean with 250 grit paper and letting the new brushes seat themselves. They probably meant a new starter drive and those prices are all over the map. B.Victoria wants around a C note for one, but I see them go for $25 to 30 on ebay. Also check the the little interior return spring. They start out about 1.75" in length, but if it's lost a half inch it begins to lack the push to get the drive disengaged from the ring gear thereby causing more grief. If the bushings have any slop change them now. Other than that they really are bullet proof and better than the replacements on the market. Oh and throw some powdered graphite or moly on the interior spiral grooves of the drive mechanism.
Tom Lains
TS8651
TS58107
 
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