Starter Motor Failure?

[JohnP]

I have had worsening problems with the starter over last few months. Often with it sticking engaged and having to rock the car to disengage it.
However, now I am getting the click of the solenoid and nothing else and I have noticed the starter cables getting very hot very quickly (not just close to connections but throughout). Rocking car is not producing the usual clang of the motor disengaging.
A test with an Ohm meter is showing more or less open circuit between starter motor side of solenoid and ground (with battery disconnected).
I am assuming that I am looking at a major short, probably through a failed starter.
Anybody here have another view?

Looking forward to your ideas.
John

[oldelanman]

I would suggest you check the mounting bolts. Loose bolts could cause misalignment and the sticking you have been experiencing and if a bolt has now fallen out altogether or a lug broken off the starter may be jammed completely. Also check that the cable hasn't come off the starter and is shorted out on the chassis.

[Craven]

A normal working starter motor has a very low resistance between its 12v (in) terminal and earth, low enough to read a dead short on a DIY meter.
I would suggest your starter pinion is now jammed in the flywheel as very very high current flows if the motor is not rotating.

[JohnP]

Thankyou for this advice.

I have taken another look, and I think I can see the spigot from the shaft of the starter motor - or is there a cover?

Anyway - it is not rotating when the engine is turned over by hand. Therefore, if it is the shaft of the motor the starter must not be engaged I think. Of course, if it is a cover, which I seem to have seen on some exploded views of these starters then it is not telling me anything.

Seems that next step for me (with limited garage and inspection facilities) is to gather a posse of mates and bump start it.

If it then starts again with the starter motor it is down to the garage to get the bendix serviced, and if it doesn't then off to the garage for a new starter motor.

I am pretty certain that the power cable is not shorting direct to earth by visual and tactile inspection.

Does this make sense?

With thanks.

[2cams70]

On the end of the starter the armature shaft usually has a square end on it. Try to turn it using a spanner or shifter. Normally that will free a jammed starter but best to remove the starter later when convenient and check the condition of the ring gear and starter pinion teeth. You can also remove the inspection cap on the bellhousing to view the starter pinion and ring gear. It's a press fit into the bellhousing but it will normally tap out using a large screwdriver and mallet.

[alan.barker]

When you change the bendix it's a good idea to change the oilight bush for the starter shaft.
Alan

[Slowtus]

Notwithstanding all of the advice given - all of it good - I would take this opportunity to swap it for a Japanese starter.

I first did this back in the '80s and have done it on every Ford block since, you will have to make up an adaptor plate and fiddle a little with the wiring but it is well worth it.

The problem, as noted, is that the bolts come loose + to the weight of that massive starter and the rest you know.

PS never once had a problem with this conversion

[alan.barker]

When i had the problem of Starter jamming i found there were cracks in the alloy fixing flange. I took a flange in good condition from a spare duff Starter. Fitted a new oilight bush from AES and new Bendix gear.
No problems since and now good for another few years.
Alan

[Bigbaldybloke]

It?s pretty easy to remove the starter and have a look if you have ramps or a suitable jack and stands to get under the car, it?s just the cable and two bolts which can be undone with a socket and a long extension. The cause of a starter jamming is often a worn ring gear on the flywheel, usually in the area just before the engine reaches top dead centre. The bendix spring can also weaken or the bendix get fouled up with muck. It has been known for people to fit the incorrect gear to the starter with the wrong number of teeth which also causes it to jam. Also the thin plate between the engine and gearbox bell housing locates the starter in the correct position and if this is damaged or missing the starter motor can be misaligned.

[2cams70]

Sometimes a ring gear worn in a specific location only is also an indication of a worn engine. Th uneven compression results in the engine always stopping in the same position so the portion of the ring gear that the pinion engages in is always the same and hence wears excessively.

[JohnP]

For the record:

It would seem that the bendix was almost certainly stuck and eventually released. It is not certain whether or not the open circuit I was detecting with the AVO, nor the heating of the cables was present whether the motor was stuck or not (although I guess that would be immaterial).

Once we geot everything moving again, we confirmed thtat the motor was not running well and a replacement seems to have done the trick - for now.

Next time I have to crank for a long period to prime carbs I shall check the temperature of the leads for interest to determine if the very high current pull occurs when the motor is cranking properly or just when stuck.

Thanks to all for your comments and hope they help other forum users in future.

JP

[Craven]

Good feedback, the current in a DC motor stalled or start condition, as a rule of thumb, is around 10X the running current.

[rgh0]

Good feedback, the current in a DC motor stalled or start condition, as a rule of thumb, is around 10X the running current.

Car starter motors especially old style ones such as the Elan standard Lucas unit run in "start" or near stall condition continually and draw very heavy currents and can only run for very limited periods without overheating the motor and cables.

If you crank a twink with a standard starter and cables for any period it all gets very hot. It just gets hotter quicker if the starter stalls

cheers
Rohan

[Craven]

Not sure how a starter motor defies the electromagnetic principles of back EMF, but there you go.