Strange starter problem ...

[dekhelia]

Since I installed an AAZ engine a few months ago, I've had this weird problem with the starter motor. The unit was replaced with a new starter while I still had the JX motor, and there were never any problems then.

But since the AAZ, the starter has done this weird 'coughing' as the engine is being cranked. I've had a look at the exposed cam while the 'cough' occurs, and it actually stops briefly before the motor kicks in again.

The engine never takes any longer to start; in fact, as long as the IP timing is right for the external temp, it has always started very quickly.

But I do wonder if this 'coughing' and hesitating of the engine is going to be something that will become problematic, later. It's almost as if there needs to be an adapter, to get this starter to mate with the AAZ engine ... but I know this isn't necessary, as the AAZ is using the same clutch (new), flywheel and bell housing as the JX had.

All bellhousing bolts are tight. Starter is, as I say, newish. Battery is also newish. Neither gave a problem when on the JX.

Any thoughts much appreciated.

[ringo]

An easy job is to check your earth strap from gearbox to chassis is in good condition.
I had a similar weird sound which would result in a failed starter motor once a year. Turns out it was the earth strap.
Probably not your problem, but worth a check. Take it off, clean up the connections and re-install (if the braid is in poor condition then replace that).

Ringo

[dekhelia]

That's a good point. I'll check it first thing tomorrow, thanks. I did notice during the engine swap that the braid had a bit of a tenuous connection to the gearbox.

I've read that some people take an earth direct from the gearbox to the battery negative pole ... worth doing, or overkill, d'you think?

[ringo]

I think it's worth trying. Big bit of cable that though.

[dekhelia]

Update: installed a new earth cable from gbox to chassis cross member - made a massive difference, but not eradicated the problem altogether. The 'choking', sort of stuttering is still there (albeit much reduced), which makes me think that earthing is still the problem.

Going to take a big chunky cable from where the starter is bolted to the bellhousing, back to the battery -ve terminal (when I can find somewhere that does one), and see what happens then.

Who'd have thought that a simple earthing strap (or lack of one, or not enough of them) could cause such a problem? Einstein, or Faraday or whoever, should hang their heads in shame. Or something.

[ringo]

It's potentially too late as the damage may have already been done. Lets hope not.
It won't happen again though....

[dekhelia]

Hm, really hope not - that starter was only a few months old. Is that right, then, that a poor earth can actually destroy the starter motor?