John Deere surging

LMP1953 · Dec 29, 2019

The engine on my John Deere 850 diesel was surging up and down and now won't start. I checked my fuel filter and it seems okay and I will replace it tomorrow. Anything else it could be besides a plugged fuel filter?

David G · Dec 29, 2019

My guess would be air leak on suction piping or plugged return

Bob · Dec 29, 2019

Injection pump on an 850 is "returnless", but there's a "leakoff" line from the injectors.

The "returnless" pump makes them a bear to bleed if they get run out of fuel, or otherwise get air in the injection pump.

Bleed screw is in pump inlet fitting, and repeatedly opening it a bit without starting engine will let air that rises out of internal injection pump passage purge out, and fuel in.

The fuel filter head they used is sort of "wonky", with an internal fuel shutoff.

Filterhead can plug, or failed O-rings can cause clogs or air leaks.

If it hasn't been run out of fuel and just needs to be bleed, I would first check/replace filter.

If no help there, verify a good gravity flow of fuel up to the filterhead, if that's OK, look for internal problems in the filter head.

LMP1953 · Dec 29, 2019

Never been run out of fuel. Will check other options. Thanks.

John Deere surging

LMP1953

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David G

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Bob

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