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slow turnover

Posted: Sun May 27, 2018 5:21 am
by poppydog
I know that this is not a Db tractor question but I feel that this is a problem that could possibly affect any type and there are so many of you out there with wide knowledge of tractors in general that you may be able to help me.
As well as my 990 I have an old nuffield and now for some reason when turning the key the starter turns the motor over slowly. When I use starter cables off another vehicle battery as a booster it still turns over slowly. Have had the starter overhauled but no difference.
Any ideas much appreciated.

Re: slow turnover

Posted: Sun May 27, 2018 6:25 am
by cobbadog
Sounds like a voltage loss somewhere or the starter needs to be checked over again. Talk to the person that did the rebuild and let them know of your problem, that just might twig something in their memory and they should correct it for you at no charge. A bench test by that person should confirm what is happening.

Re: slow turnover

Posted: Sun May 27, 2018 7:20 am
by ollek
Bad cable connections (both plus and minus) between battery and starter motor is the first thing to look for. If you connect the starter cables to the tractor battery poles, then the current have to go trough the tractors battery cables. Try to connect the slave battery directly to the starter motor, but be careful, the tractor will start to move if in gear..

Re: slow turnover

Posted: Sun May 27, 2018 9:47 am
by KevinC
I have had a similar intermittent problem on a fordson major. After turning it over feel to see if any of the cabling is hot or at least warmer than the rest. It does sound like a bad contact. You could just take all the cables and wires off one by one and clean them and their contact point making sure there is no paint,grease or mud between the them. By all the wiring I mean all that associated with the starting circuit so it wouldn't take too long and it would eliminate that as a potential source of the poor performance.

Re: slow turnover

Posted: Sun May 27, 2018 5:06 pm
by ollek
After removing the cables I would file and sand all the contact faces clean as the problem is most likely corrosion.

Re: slow turnover

Posted: Sun May 27, 2018 6:45 pm
by Gard
Measure the voltage difference between the hot stud on the starter motor and the + battery post while someone is cranking the engine. This should be a small number like less than 1 volt. Do the same thing from the ground on the starter to the battery ground. This should help narrow down the fault. Check the voltage across the battery when it is cranking and this should be close the voltage between across the starter motor. If you have close to 12 V across the motor when its cranking, I would suggest bringing it back to the starter shop. When I got a new starter I had the shop build me some nice new heavy cables, he advised me they would be a lot better than the generic ones from the auto parts store.

Re: slow turnover

Posted: Mon May 28, 2018 6:41 am
by rid54
As has been ponited out, allt joints in the current's path from battery to ground could introduce a resistance and so a poor performance of the starter. Such "joints" or contact points exist inside the solenoid as well, the main contacts that actually power up the starter.

If all cables and such are OK, the problem is in the starter itself. There could be a short or break in an armature winding, badly seated brushes or poorly finished surfaces of the commutator segments. If all the external connections are OK, you may have to take the starter back to the shop which did the overhaul and have them check it.

Re: slow turnover

Posted: Mon May 28, 2018 1:17 pm
by ollek
I think we can rule out problems with the starter motor, as poppydog wrote " Have had the starter overhauled". The solenoid is also most likely checked by the workshop that did that starter motor check out. The most important thing is to check that the current supply and the ground to the starter motor are in order. This is in fact something that has to be checked and fixed before the starter motor is even removed from the tractor.

Re: slow turnover

Posted: Tue May 29, 2018 7:40 am
by cobbadog
That is very true ollek but I have had faulty electrical items after a rebuild and even a brand new generator that was suitable for the bin but returned and it was replaced under warranty, so we do need to cover all possibilities.

Re: slow turnover

Posted: Tue May 29, 2018 9:05 am
by poppydog
Thanks guys thats given me some things to check.

Re: slow turnover

Posted: Tue May 29, 2018 9:27 am
by ollek
It is most important that all connections between the battery and the starter motor are checked BEFORE the starter motor, old, new or repaired) is blamed for the problem