Starter motor issue

[Tandem]

Hi-
Sole Mini 14 engine, turn ignition, starter motor turns, but very slowly to a stop.
3 x 85amp batteries in parallel - all showing 12.5v - when tested with multi meter.
Fact it turns, albeit slowly, suggests it may be connections, or starter assembly....
Where to start?
Any advice appreciated.

 

[geem]

Take it off and give it to an auto electrician. I once did that with similar symptoms. The auto electrician couldn't believe it ran at all. The insides were a mess of verdigris and carbon dust. It was perfect after a rebuild

 

[Refueler]

Absolutely ... as per 'geem' .....

My Perkins starter is over 400 quid IF you can find one ... so gave to local guy ...

He stripped, cleaned, rebuilt the spiral on the shaft (built up where it chipped and ground back), new springs, replaced the flyer ........... 100 euros and she is like new.

 

[andsarkit]

I don't know where you are based but the Plymouth Alternator and Starter company are good. They rebuild and test units at the site and stock a vast range at reasonable prices.
PAS starter
I have used them a couple of times and been very happy.

 

[Baddox]

The battery voltage of 12.5V is a little low. If you have a multimeter, you could check what the voltage drops to when the starter motor is turning.
Another quick and easy thing to check would be the voltage drop across the wiring from battery to starter during cranking.
If all is OK, then get the spanners out to remove the starter.

 

[MoodySabre]

If you don't know how to check the voltage drop then read here How To Perform A Voltage Drop Test - Help With Automotive Circuit Diagnosis
The low the voltage reaching the starter then the lower the amps that make it turn. Bad battery connections can cause this. Checking connections is the first thing to do. The batteries may read a reasonable voltage with a multimeter but still be inadequate under load. A property battery tester will tell you. Know a friendly garage who will lend you one? Start with the easy things.

 

[GunfleetSand]

Could you ‘prove’ your starter by using jump leads from battery to ground and live feed to starter motor?

 

[William_H]

Could you ‘prove’ your starter by using jump leads from battery to ground and live feed to starter motor?

Yes a jump start to battery from a good battery. (take it out of your car.) wold confirm battery problem or starter itself. (or wiring) Or as said check battery voltage while cranking should hold above 9v. ol'will

 

[AntarcticPilot]

The battery voltage of 12.5V is a little low. If you have a multimeter, you could check what the voltage drops to when the starter motor is turning.
Another quick and easy thing to check would be the voltage drop across the wiring from battery to starter during cranking.
If all is OK, then get the spanners out to remove the starter.

An experience I had may help. The batteries weren't charging when the engine was running. I had a check round, and the usual culprit, a loose connection, was OK. Poked around a lot more, but couldn't see anything. It was only when I got quite rough with one of the connections from the alternator to the starter that I discovered that the wire had corroded to a sort of red powder inside the insulation. There was absolutely NO external sign, and I had to be quite violent before it snapped.

My point is that the heavy-duty wires connecting the starter motor can be in a bad way without there being any external sign. It can also take quite a lot of force to discover that the wire has corroded!

 

[Tandem]

Yes a jump start to battery from a good battery. (take it out of your car.) wold confirm battery problem or starter itself. (or wiring) Or as said check battery voltage while cranking should hold above 9v. ol'will

Thinking the batteries could be the issue I actually added a fully charged 85A car battery to the existing 3 with the same result.

 

[Tandem]

An experience I had may help. The batteries weren't charging when the engine was running. I had a check round, and the usual culprit, a loose connection, was OK. Poked around a lot more, but couldn't see anything. It was only when I got quite rough with one of the connections from the alternator to the starter that I discovered that the wire had corroded to a sort of red powder inside the insulation. There was absolutely NO external sign, and I had to be quite violent before it snapped.

My point is that the heavy-duty wires connecting the starter motor can be in a bad way without there being any external sign. It can also take quite a lot of force to discover that the wire has corroded!

Will check this possibility along with the other thread suggestions before taking the starter motor off.

 

[GunfleetSand]

I found this video to be fairly clear if what you’ve got is not obvious and as above maybe some corrosion in a cable giving voltage drop. Also check all ground connection from battery to engine.

 

[Refueler]

Interesting posts ... just one comment :

When voltage of a battery is low - the amps demanded of it increase in proportion as the load works on WATTS ....

Its usual that a fully charged battery av=ctually delivers LESS amps than a lesser charged to do the same job. Of course a starter will spin faster on a higher voltage and in so doing ask more amps - but NOT at same differential as the higher voltage compared to lower.

 

[Refueler]

Leads .... the usual culprit.

How often do we check .. clean and refit our leads ... common poor connections are ground to engine ... +ve on alternator ... +ve on starter ... even battery connections.

When poor start / charge is found - first thing is to disconnect and clean in turn major connections to m,ake sure least resistance ... anhd not uncommon to find the ring end or cable is on its last legs ...