JD855 cannot keep prime on fuel system

   / JD855 cannot keep prime on fuel system #1  
B

bayfarm

New member
Joined
Jul 17, 2013
Messages
6
Location
Sugar Grove, IL
Tractor
JD 3020 JD 855
My JD 855 will not keep prime. After priming and bleeding air from system it starts and runs until all fuel in filter is used then quits. Bad fuel pump??? Once it is primed appears to pumping fuel but will not sustain. Any insights would be appreciated.
 
   / JD855 cannot keep prime on fuel system #2  
Disconnect fuel line into filter housing and turn on key and see if it’s pumping a good flow, not just gravity feeding.
 
   / JD855 cannot keep prime on fuel system
  • Thread Starter
#3  
Thanks, that was next on my list. If good flow - what next?
 
   / JD855 cannot keep prime on fuel system
  • Thread Starter
#4  
JD855 fuel problem. This is later model with mechanical fuel pump, Original problem: Will not stayed primed. Identified additional trouble: fuel oil is getting in crankcase oil. Fuel seems to flows into crankcase when tractor sits after running. Pumps out of valve cover breather hose on next start up.
Working down the list of troubleshooting from tech manual. Checking fuel shut off, valve clearance, Fuel pump leaking, warped heads☹️ Any other thoughts, places to start?
I am leaning towards looking at fuel pump first. I do not have pressure gauge for inspection. Has Steady flow of fuel when pulling hose to filter and cranking starter. Seems normal?? What should I look for when removing fuel pump that indicates trouble?
Thanks in advance for assistance.
 
   / JD855 cannot keep prime on fuel system #5  
Bayfarm, when my vehicles were of 50's and 60's vintage I saw a couple mechanical fuel pumps get a pinhole in the rubber diaphragm causing fuel to leak into the engine. Haven't been involved with tractors that long so I didn't even know they came with mechanical pumps any longer but I imagine they work on the same principal. On automotive pumps the top was removable so you come inspect the diaphragm for a hole. Maybe yours is to..........Don
 
   / JD855 cannot keep prime on fuel system
  • Thread Starter
#6  
DonRybak said:
Bayfarm, when my vehicles were of 50's and 60's vintage I saw a couple mechanical fuel pumps get a pinhole in the rubber diaphragm causing fuel to leak into the engine. Haven't been involved with tractors that long so I didn't even know they came with mechanical pumps any longer but I imagine they work on the same principal. On automotive pumps the top was removable so you come inspect the diaphragm for a hole. Maybe yours is to..........Don
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Thanks. My thoughts also, just have not got that far yet in the search. Will keep all posted.
 
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