I have a 1981 4640 which doesn’t work well when it is below 50 degrees. Once started, it starts fine for the rest of the day. The problem is that the engine is not spinning fast enough to start. It will rotate slowly for about ten seconds and then stop. After that, I have to wait about a minute to try again. The only way I can start it is to jump, sometimes I even have to double-jump. I have new StrongBox 6volt batteries and good cables. Everything on the tractor is factory-made. What do i need to check?
On our 4430 and 4640 I replaced 6v batteries with two 12s with + to + and – to – leads and ran pos to starter from both batteries and – also. I know this is not a factory, but it eliminated all the problems with the starter and alternator. They also take off better thanks to increasing the speed of the starter. I used a stud 31 battery with 700 CCAS at 0 degrees with more amperage than this, and the batteries don’t seem to deal with vibration either. It may not be the politically correct way, but it has worked for us.