Spitfire mk3 starting issue

[Sandy Gibson]

I’m having a starting issue and I’m not sure how to identify the exact problem.

When I go to start the engine, sometimes it spins and starts as normal but other times the starter engages but can barely manage a couple of chugs turning the engine. The Bendix gear is new and always engages.

The battery is good and all external connections seem to be sound.

I suspect the starter motor may be faulty but not sure how to test it.  I could do a bench test but I think it would probably only act up under load.

I am reluctant to go for a new motor and discover the fault lies elsewhere and having looked a a couple of YouTube videos, I don’t think I’m up for trying a repair myself

 

[Pete Lewis]

are you loosing any coolant  ??  bore filled with coolant will make it struggle

but simplest option is a failed field coil on the starter makes it erratic and mimic a flat battery 

unless you can mount and appliy a stalling load to the starter  you wont prove anything on a bench running light 

Pete

 

[Sandy Gibson]

Thanks Pete.   I’m sure I don’t have any coolant leak into the bores (or I’ve got bigger problems than I thought!)

It is the intermittent nature of the fault that was throwing me but it does exactly mimic a flat battery so your suggestion sounds good.

Sandy

[Pete Lewis]

and dont discount the solenoid  they can be very green and crappy inside  

have you tried jump direct from battery to the main starter lead terminal ??

Pete

[Sandy Gibson]

I had assumed that if the motor spins fast enough to engage the Bendix the solenoid must be OK.

Will try a direct feed next time it happens.

Thanks

Sandy

[NonMember]

Depending what you mean exactly, reluctant cranking can be due to odd things.  My Spitfire had an occasional issue with only getting half a rev of cranking before stopping.  It turned out to be a sticky centrifugal advance in the disi. When stuck fully advanced, the ignition kicked back hard enough to stop the starter motor dead.