DSM637

DSM637

Member
Good evening,

I recently replaced my starter motor and after 3 weeks, the engine will not turn over. I have bench tested the motor and it works fine, when placed back onto the engine, it may turn over for a second and then nothing. I have disconected the positive cable from the solenoid and earth from the chassis and put these cables staight to a battery, but nothing. Of interest, if I remove the plugs, the engine will turn over. The engine is a 1972 petrol. It appears to be an earthing issue and very minor voltage drop (starter motor model is NQS1302 = ERS00136 = STM1005).

I have renewed every thing from the solenoid to the earth strap on the starting system and thought originally it may have been hydrostatic lock, as the problem went after I had removed the spark plugs and turned the engine over. This however, is not the case now.

With the starter out, I can start the engine with the cranking handle, engine starts and charges fine (14 ish volts) and all electrics work ok.

Grateful for any advice.
 
Last edited:
Try refitting the positive cables then use a jump lead for a negative straight from the battery to the starter (or nearby, I used the bell housing) if it works you know its a poor earth. Alternatively do the same on the positive side to narrow down where you might have a bad cable or connection.
 
Hi Rubins4,

Thanks for the reply, I have used another battery and renewed both pos and neg cables, by-passed the earth and put the cable from the battery to the bell housing and various parts of the chssis, but the same fault. I have also renewed the earth strap from the battery to the engine and attempted to jump the starter from a car, but the jump leads get really hot, but no movement on the flywheel, I have also made sure that the clutch has been depressed too.

12 v from battery to solenoid and on turn of key, to the other side of solenoid and 12 v.
 
Hi DSM635, why did you change the starter? I suspect your new starter is faulty. I have had a couple of starters in the past that were fine when tested off the car but wouldn't work when a load was applied. Is it possible to return your starter and get a replacement?

Col
 
Yeah, wiring sounds OK, but hot jump leads suggest something bad happening. Who made the starter out of interest?
 
Col and Rubins4,

thanks for the reply. I changed the starter motor originally as the engine is off an old 1972 Air portable, which was reconditioned in 1986. When the engine failed to turn over, I took the starter off, stripped it and the bushes were near the end of their life, so given the age, I bought a new starter. When I put the new starter on, I had the same problem, until I removed the plugs. The engine then turned over (hence the hydrostatic lock solution). With the plugs back in, the engine started and no issues until now. The starter was bought off ebay and is an Elite pre engaged motor, compatible with 25605B,25605D,25668,25668B etc. I will contact the company on Monday and see if the have had issues with the motors previously.
 
It's always worth spending a minute or two counting the number of teeth on the pinion when changing starter motors. A starter motor with one tooth difference may work, for a while...
 
Col and Tall Ratbag, no ,I steer away from Britpart items and there are 11 teeth on both the old and new starter. I will look at cleaning the chassis up tomorrow to make sure the earth is good and then check voltage and see where I am at.
 
Good luck with it. It's faults like this that can drive you mad, it'll probably be something simple in the end though so hang on to that thought.

Col
 
Some thoughts, ...

I'm a bit confused [usually!], but, did you say pre-engaged starter motor?

It would be more usual to find an inertia starter motor on a petrol engine. If you have fitted a pre-engaged replacement, have you modified the wiring?

Mechanically, does the pre-engaged starter pinion approach the ring gear from the other side of the flywheel when compared with the normal case for an inertia starter where the pinion moves in towards the motor? Is the ring gear in good condition all the way round the flywheel? Is it correctly fitted against the shoulder on the flywheel? Is the flywheel fitted concentric to the crank centre - i.e., if you rotate the engine, does it run true?
 
Its a long shot but I have heard of new old stock starters only working for a short while because the brushes stick due to the inhibitng oil drying out. Its worth a punt to just squirt WD 40 into the brushes, I know its an insulator but it seems to free them up.
 
As as per Tall Ratbags comment, you don't have pre-engaged starters on petrol series, they are standard starters with a spreader solenoid fixed to the inner wing so now, I'm confused as well.

Col
 
Blackburn,

you are right, that is the starter motor in question, so apologies for the error..........
 
I think the answer lies here =>

DSM637 said:
... I have also renewed the earth strap from the battery to the engine and attempted to jump the starter from a car, but the jump leads get really hot...
Click to expand...


This starter is shorting - you are in effectively turning your jump leads into a heater!

Replace starter
 
Tried the WD 40, but no luck, thanks for the post Stretch, I have spoken to the company that have supplied the starter and they asked if I had bench tested it, told them I had, so they have asked me to return it and they will test it and let me know their findings.......
 
Pity the WD40 didn't work, there's not a lot in a starter other than big wires and the brushes and the brushes sticking or dirt on the commutator seem to be most common problems (with the starter)
Bad connections on the big cables are the real ememy. I took every lead off mine and bench soldered the ends, made a huge differnce.
 
Good evening, apologies for not replying earlier, returned the starter motor and the company bench tested it, it is fine, they have replaced the starter, but it has the same fault. Due to the poor weather, I have not had a chance to look into the fault more, but I will look at removing the starter and putting it back on as square as possible, incase it is catching on the flywheel teeth. On looking in at the flywheel, it all looks fine and I can turn it over with the cranking handle, with the engine running, there appears to be little or no untrue running from the flywheel. I may take the engine out over the weekend and engage the motor to see what is happening.
 
Could you describe what does happen? Does the starter turn and not engage the Bendix? Does it engage the Bendix but crank too slowly? Does it not turn?
 
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