JD 850--no fuel delivering to middle injector

Niji · Sep 27, 2017

Hey Folks--so, I just replaced a head gasket and front crank seal on my JD850 (3 cyl Yanmar diesel). I only took the three metal fuel lines loose at the injectors--did not mess with the other ends or the injector pump at all. Got it all back together and now the front and rear cylinders are getting fuel when I crack and bleed them, but the middle one is not. It was running fine when I parked it to do the new head gasket. It seems like very odd timing for an injector pump to decide to poop the bed, and it also seems odd that I'd get fuel delivering fine to two cylinders but not the third. Any insights would be much appreciated--especially if they don't involve buying a new injector pump! (Just sayin'/hopin'). Thanks!

winston1 · Sep 28, 2017

Don't suppose it should happen but I would start bleeding back at the filter with plenty of fuel in the tank and work forward. Certainly would be a cheaper try than a new pump. Also try tapping lightly on the pump. Outside chance a plunger is stuck in the up position. When you unhooked the lines you may have relieved the pressure on the #2 plunger while in the up position so it is possible it could stick up.

Kustrud · Sep 29, 2017

Niji said:
Hey Folks--so, I just replaced a head gasket and front crank seal on my JD850 (3 cyl Yanmar diesel). I only took the three metal fuel lines loose at the injectors--did not mess with the other ends or the injector pump at all. Got it all back together and now the front and rear cylinders are getting fuel when I crack and bleed them, but the middle one is not. It was running fine when I parked it to do the new head gasket. It seems like very odd timing for an injector pump to decide to poop the bed, and it also seems odd that I'd get fuel delivering fine to two cylinders but not the third. Any insights would be much appreciated--especially if they don't involve buying a new injector pump! (Just sayin'/hopin'). Thanks!

If you're getting fuel at 2 out of 3 I would think it's air in the system somewhere.

Spanner · Sep 29, 2017

http://www.tractorbynet.com/forums/parts-repairs/386143-jd-850-no-fuel-delivering.html

California · Sep 29, 2017

I just thought of something: If the #2 plunger is stuck at the top of its travel - maybe compressed air into the other end of the fuel delivery tube could force it back down.

winston1 · Sep 30, 2017

California said:
I just thought of something: If the #2 plunger is stuck at the top of its travel - maybe compressed air into the other end of the fuel delivery tube could force it back down.

After more thought on my earlier statement: Each plunger in the pumps has a delivery valve (check valve) on the discharge side that keeps the pressure on the injector side. If working correctly, you could not blow air back through there. Nor should loosening the injector lines relieve pressure on the plunger. I do know the plungers are capable of sticking and have stuck up and that is possible what is happening. Should that be the case I believe you would have to remove the delivery valve in order to move the plunger back down. That is unless tapping on the pump would do it.