Troubleshoot weak start on Deere 650 tractor

[beachcruiser25]

Hello all,

New member here, long time lurker. Lots of useful information here and would like to thank all the active members for creating such a lively community.

I have an issue with my John Deere 650 compact tractor. With a new battery, i'm having a weak start, the tractor will turn over once or twice per key turn but wont start. It turns over completely but doesn't appear to have enough amps or CCA's to get it to spin fast enough. The tractor is old and its wiring is a little worse for the wear and i believe the problem is in the wiring somewhere but just want some second opinions. I've done a couple tests that provide the following data:

Battery is new and good, roughly 12.7v with mutlimeter
Voltage drop test from battery + to starter + connection reveal a voltage drop of 0.3v
Voltage drop test from battery - to tractor frame at battery cable connection point reveals voltage drop of 0.1v
Glow plug light will turn on consistently
When turning from glow plug light on to start, tractor will turn over intermittently, sometimes not at all

I purchased the tractor used a couple years ago and it ran fine. However, its been put away in a covered shed for a year now.

My primary questions are what would be the best methodical way to test the wiring to be sure of good connections? Also, the starter on the tractor doesn't have apparent solenoid + and -, i've attached a picture of a replacement part. If someone could tell me where to jump on it to bypass the ignition/solenoid that would be helpful? Finally, if someone has the service manual (#tm1242) and could copy a picture of the wiring diagram ill be your best friend. Ive attached the best grainy photo from the web i can find. I will get some pics of the tractor up asap to help with diagnostics. Just fyi, this wont be a drive by thread, i will be checking periodically.

 

[Kubota 2350]

I've found most all starting problems are related to poor connection, loose or corroded cables.
Check both ends of the battery cables to start with.

 

[beachcruiser25]

Im thinking the same thing. I did check both battery cables and there was some corrosion. I cleaned them and applied some dialectric grease prior to doing the voltage drop test on both. The info above is after cleaning the cable connections. I agree the wiring is the likely culprit though.

 

[George2615]

Welcome to TBN...........................

I know you say the battery is new but that doesn't mean it can't be defective. When was it new? recently, when you bought it a couple years ago, or when you parked it in the shed a year ago. If it only cranks once or twice there could be a problem with the battery. Pull the battery and take it to an auto parts store to have it load tested to start with. If new and it tests bad it should be replaced under warranty where you bought it.
Then remove and clean the ground connection where it attaches to the frame and the battery end connection.
Pull and clean the cable connections at the starter.
Thoroughly inspect the positive and negative cables. Its possible they could have corrosion inside the protective jacket coating. Replace if needed.
You could also pull the starter and have it tested at the auto parts store. This is assuming the starter solenoid is attached to the starter.
If all this checks good the you may have an ignition switch problem either internal or external. Check for corrosion on those cables going to the switch.

 

[beachcruiser25]

George, thank you for the reply. The battery was purchased last week. I doubt the battery is defective because i had an older spare battery i also tried to start the tractor with that gave me a similar result before (stupid of me to buy the new battery i know). I may have to pull the starter like you suggest but the symptoms are more pointing towards an electrical issue as the starter will engage and turn the motor over, just not fast enough. I would also like to note that when i was trying to get it to start, with the weak turn over, the battery jumper cables became quite hot after a dozen or so attempts. Really wish i could get that wiring diagram, looks as though i may have to drop $120 to get a manual.

 

[George2615]

A service manual would be a good investment.

 

[Jnf]

A service manual would be a good investment.

I have found on several starter that a slow to no start to be cause by worn front or rear bushing in starter housing, have replaced them and it almost always fixes the problem. Sometime a bench test does not load starter and it will check good without load.

 

[Agvg]

Picture of the starter? what is the voltage drop between battery ans starter when you try to start?
Can you check the brushes and se if they are worn out or stuck?

 

[beachcruiser25]

Agvg, i will try to get pictures today of the starter and tractor. Unfortunately it is at some rural property and not my primary residence. The voltage drop between the battery + terminal and the positive cable attachment to the starter is 0.3. I may have to pull the starter to give it a rebuild/cleaning and check the brushes like you suggest

 

[Oldtink]

Yes I agree 100% with getting a service manual from JD.
I had a 650 for 28 years. My electrical problems always ended up being loose spade connectors in the wiring harness. Especially the safety start circuit. Years of vibration, I guess.
Anywho, the starter solenoid is on the bottom of your picture, motor on top.