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HARD starting JD 4840
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JD 9400
Posted 12/6/2016 06:23 (#5679119 - in reply to #5678789)
Subject: RE: HARD starting JD 4840


Southern Pa.
ccjersey - 12/5/2016 22:50

There used to be electric destroking kits available for the 20 and 30 series tractors etc. The pumps mostly use the same size plug where the destroking valve screws in, so unless there is something else in the way to prevent installing one, you should be able to do it.

The steering wheel trick doesn't destroke one, it is doing the opposite, making the pump pump oil, but preventing it building high pressure. It works......just not as good as destroking it. With a good tight system with no internal high pressure leaks one revolution of the engine and the pump builds pressure and destrokes. If the 3 point leaks down, move the lever so it stays down until the tractor starts.

You might have a leaking SCV on it. If you can use a blank plate to replace each one in turn and try starting it, you might find an internal leaking SCV and recover some hydraulic capacity in the process. Of course there are other possibilities for the leak, that is just a simple one to eliminate with just a blank cover and a wrench or two. While the SCV's are off you could put a kit in them and stop the external oil leaks that should have nothing to do with the tractor starting.


X10. SCV' s leaking internally are a common problem on older tractors. Another way to check your SCV's for internal leaks is to run the tractor on some job that DOESN'T require using the SCV's. PTO work, three point hitch work, pulling gravity wagons, etc. Get out of the tractor periodically, and feel the SCV's. The one (or more) that is warm/hot to the touch compared to others is the culprit. If you are not using the three point, the three point hitch lift cylinder housing is a good reference point. (Not the ASSIST cylinder/s)
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