Jamming Firefly starter motor

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tedmunds
Posts: 6
Joined: Sat May 26, 2012 5:40 pm
Name: Tim Edmunds

Jamming Firefly starter motor

Postby tedmunds » Wed Jul 25, 2018 11:44 am

On three occasions now my starter motor has jammed when trying to start the car. There is no obvious common factor and it can be cured by taking the starter out and putting it back. When jammed the engine cannot be turned on the starter handle and taken photographs of all the ring gear in situ does not show any damaged teeth. Any ideas?

DeaneHarding
Posts: 9
Joined: Fri Aug 09, 2013 9:18 pm
Name: Robin Gilbert

Re: Jamming Firefly starter motor

Postby DeaneHarding » Sun Jul 29, 2018 2:08 pm

The usual cause of a jamming starter is wear/damage on the flywheel and/or starter pinion teeth. A distorted starter motor shaft or worn bearings will also cause problems, as will any looseness in the motor mounting. The starter should be a good fit in the housing and cover, including the locating peg and its hole, often damaged.

Ray Spain's "Repair Manual for Alvis Cars 1932 - 1939" is good reading for the frugal owner, even if some of the 1950s techniques described are frowned upon in these affluent days. It states that "Starter jamming may also be caused by the Bendix pinion going too far "into" the flywheel. This can be cured by fitting shims or washers between the pinion and the Bendix casing."

As the manual notes, a jammed starter can sometimes be freed by putting the car in top gear and rocking it to and fro, a technique I have used with success. Don't do this with the ignition on!

Peter Martin
Posts: 160
Joined: Tue May 22, 2012 5:26 pm
Name: Peter Martin

Re: Jamming Firefly starter motor

Postby Peter Martin » Wed Aug 01, 2018 10:23 pm

Random thoughts;
1 Is the battery in good shape/fully charged
2 Does the pinion move freely on the shaft ,some advocate light oiling others claim clean dry moving parts, I prefer the former.
3 Does the starter motor kick & throw the pinion forcefully if you remove the motor and connect it direct to a battery . NB lots of big sparks when you complete the circuit ,be careful
4 Assume pinion teeth are in good shape and not ragged & worn down

Good Luck

shaun matthews
Posts: 25
Joined: Mon May 21, 2012 9:30 am
Name: shaun matthews

Re: Jamming Firefly starter motor

Postby shaun matthews » Fri Aug 03, 2018 4:57 pm

A broken starter pinion return spring can cause this , It will work 95% of the time no probs then jam solid at the worst possible time (My Sp20 did so driving off a car ferry in Denmark!) Turning the engine backwards will not free it- The only quick fix is to slacken the starter bolts 6 or 7 turns and it will then free - You'll have to bite the bullet and pay our friends in Kenilworth a significant fortune for a replacement but its quite easy to change once your credit card has recovered from the battering.

Good luck


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