Spitfire IV starter fails to disengage

[Ray Perkins]

The starter motor developed a tendency to stay engaged after the engine fired.

I removed the starter and the teeth on the pinion were horribly worn, so I bought a new starter assembly from James Paddock. When I fitted the new motor the same problem seemed to occur - although the sound was different; with the old motor the noise was a graunchy rattle, with the new one more of a high-speed whine.

With both motors the Bendix moves freely.

I disconnected the coil so that I could turn the engine over without it starting. When I turned the key the starter engaged cleanly and tuned the engine over as it should, with no unwanted noises, so the problem occurs at the point when the engine starts.

I am at a loss as to what to do next! Any advice gratefully received.

[Brit car fan]

It could be the solenoid sticking, such that the motor is still running after engagement. This could account for the repeated problem with the replacement motor kit as it would not have had anything to do with the motor. Perhaps try removing the rubber cap and spraying some switch cleaner into the solenoid. Could check function by disconnecting the motor and checking that it clicks on and off ok.

Dave

[Ray Perkins]

Hi Dave,

Thanks. I hadn't thought of that. I'll give it a try.

[Ray Perkins]

Starter motor fails to disengage...

Right. I have replaced the solenoid and this makes no difference.

I am coming to the opinion that this is a problem with the positioning of the Bendix relative to the flywheel. I see from the Rimmer Bros catalogue that there should be a shim fitted between the spacer and the starter motor. This has been absent, but to my mind, fitting a shim will reduce the clearance between the Bendix and the ring gear, when I need greater clearance

Are there any measurements I can make to check the positioning of the starter motor?

[Ray Perkins]

Starter motor fails to disengage...

Right. I have replaced the solenoid and this makes no difference.

I am coming to the opinion that this is a problem with the positioning of the Bendix relative to the flywheel. I see from the Rimmer Bros catalogue that there should be a shim fitted between the spacer and the starter motor. This has been absent, but to my mind, fitting a shim will reduce the clearance between the Bendix and the ring gear, when I need greater clearance

Are there any measurements I can make to check the positioning of the starter motor?

[RobPearce]

If the motor is really "failing to disangage" then replacing the solenoid wouldn't be expected to make any difference on a Bendix starter. Dave must have either assumed it was pre-engaged or interpreted your problem differently.

Ayway, the shim is not usually required but gives better engagement when the teeth are a bit worn. I very much doubt your problem is anything to do with positioning.

Just to clarify... the noise your getting is after the engine starts *AND* you've released the key? Because the period between engine start and you letting go is expected to have a high speed whine as the motor spins up to its natural free-running speed... because it has disengaged. A sticky solenoid can prolong this effect. If the bendix gear hasn't disengaged then the noise would typically be more tortured, since the motor is being over-speeded by the engine.