Hints and Tips - Starter Problems

From: Joseph
Sent: 28 July 1999
Subject: Starter Dilemma

Collective wisdom of the prewarrior group required.

The starter in my PB engine jams. I have taken to the generator shop twice. I have checked all circuits (starter push peddle on firewall. fusebox etc etc.) for continuity. Out of the car, the starter spins freely when 12 volts applied. In the car, when one applies power directly from the battery, the starter freezes. The fellow at the shop placed the gear on the wrong way the first time, in other words, spinning away from the body rather than towards the body of the starter. This rectified, still no go.

a.) either there is a dead spot on the armature that spins fine without load and when placed under load, can't take it and stops. or

b.) something with the way the gear is hitting the teeth on the flywheel.

History: worked just fine for about a month but then progressively, the starter would just fail on me after taking a ride of 2o minutes duration. i.e., froze on me. Push starting the car was OK however.


From: Lee Simmons
Sent: 28 July 1999
Subject: Re: Starter Dilemma

I have had this problem before and it was solved by replacing the bearings. Seems that they had worn some and when hot there was too much slop in the shaft movement. When cold or without a load it works fine but hot and load it binds.

Lee C. Simmons

From: David Cochrane
Sent: 28 July 1999
To: Joseph
Subject: Re: Starter Dilemma Joseph,

It sounds as if there could be some resistance in the circuit that measures OK with an AVO (ohm-meter) but goes high resistance when you try to pass high current through it. Have you checked the battery and its connections? Especially the battery to earth. A simple way to check is to turn the headlights on then operate the starter. If the lights go very dim or go out, that is your problem.


David C

From: Guy Weatherall
Sent: 28 July 1999
To: Joseph
Subject: RE: Starter Dilemma

The contacts in the starter switch may need cleaning as they may test OK but are unable to pass heavy current. The other thing to check is the continuity of the earth loop back to the battery (battery to body, body to earth strap, earth strap to engine).


From: Joseph
Sent: 29 July 1999
To: Guy Weatherall
Subject: Re: RE: Starter Dilemma

<<The other thing to check is the continuity of the earth loop back to the battery (battery to body, body to earth strap, earth strap to engine).>>

This is what I was thinking

From: Joseph
Sent: 29 July 1999
To: Lee Simmons
Subject: Re: Starter Dilemma

<<solved by replacing the bearings.>>

When I queried the electrician regarding this, he emphatically stated there was plenty of stability in the shaft and that the starter bushes were solid and the shaft running true.

It seems that the ground may be the culprit so I am going to check that first.


From: Joseph
Sent: 29 July 1999
To: Bill Hoskins
Subject: Re: RE: Starter Dilemma

<<ring gear working out of true on the flywheel.>>

Engine just rebuilt by Mike Allison and no grinding was going on initially.

>have you checked the armature shaft for straightness?

Yes as did the rebuilder of the starter.

> how about voltage drop across the starter when under load?

This may be a culprit. I will check the ground.

starter originally 12 volts, or 6 (with a battery tap)? 12 volts

From: Joseph
Sent: 29 July 1999
To: David Coch
Subject: Re: Starter Dilemma

<<Have you checked the battery and its connections?>>

The battery is a brand new Diehard.

I am thinking it is the grounding now.


From: Dwyer
Sent: 12 August 1999
To: Joseph
Subject: Re starter dilemma

1. I discovered recently from the Owner's Manual that there *should* be a spacer plate on J and P starters. It's 1/8 thick and the same shape as the starter flange. However I doubt that lack of it is your problem as our car has run or rather started ok for the last 30 years without it! Since the engine is totally in pieces at present for reconditioning, I can't actually try it, but it will increase the lengthways engagement of the gears and act to reduce the pressure and hence wear on the teeth.

2. After the aforesaid 30 years there is some wear on the teeth in the two preferred stopping areas: I wouldn't call it severe. After all, at best the engine is only about 6:1 compression so that's not hard to turn from rest. I will however rotate the flywheel when it goes back together so as to use the least worn sections - and remake the timing marks to avoid future confusion.

3. If the starter occasionally fails to turn the engine I'd vote for worn commutator segment, one open circuit winding on the armature, or even sticking/worn brush. We had this symptom for some time: if you put a spanner onto the squared end of the shaft at the front of the starter and rotate the armature maybe 30 degrees then try starting again off it goes. We had the armature rewound.

4. If the starter never turns the engine, but spins fine off-load, I would suggest that you have a high resistance in the car starter wiring. Measure the voltage on the starter terminal when the starter is supposed to be turning the engine: if it's near to 12 volts you have an open circuit as 3. above. If the voltage is low, there is high resistance somwhere. Measure voltage to chassis at each point back to the battery to find where the voltage is being lost. There will be a drop in starter voltage due to normal losses, but it's not huge. For the reasons above I can't check on our car, but I would guess you'd see over 8 volts on the starter when it's spinning the engine.

5. On the same theme check the connexions to chassis at both the engine and the battery. You need a good heavy braid or cable of at least 10mm diameter, and clean *tight* connexions.

6. I know it's obvious, but is the battery #proven# to be good? Will start another car? Due to the limited use that we give our cars the batteries tend to fail for lack of exercise, and the first thing that goes is the capability to deliver that big current to the starter. Everything, even headlights will work fine, but the damn' thing won't start!

Please advise the end of the story: this is how we all learn.


Dave Dwyer
MG J2/PA engine

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