Hard Starting 7720

To start my 7720, I have to pump the hand plunger 20-30 pumps. If it sits for more than an hour I have to do this to get it started. I can hear my lift pump pumping and it seems to have good power once it is started. Is there a way to fix this without taking off the injection pump?

Been there done that with a cat engine on our wheel loader. We went round and round trying to find out why it would lose prime. After messing with injectors and fuel lines, we found out that the vented fuel cap was plugged solid, so as the fuel was sucked into the pump it created a vaccum so when the pump was shut down with the motor, it would draw back the fuel in the lines to the tank. Probably not your problem but worth a try, cost us a lot of time and effort. Some one with knowledge of those pumps could help you better, could be a check valve in there sticking or something

It is not the injection pump. The fuel is bleeding back to the tank when you shut it off. It will just take some time to fix it and usually not much money.

You need to work your way back from the injection pump on the supply side. Usually the line form the pump to the filter body is fine. The trouble usually is at the fittings on the fuel filter base. Check an make sure the elbows are tight in the base.

Also there is a CHECK valve on the inlet side of the filter base. It is supposed to stop the problem your having. Take it off and disassemble it. You used to be able to get a rebuild kit for it. I am not sure if you still can.

If all is well tat the filter then work your way down to the fuel tank. Your getting air into the system that is allowing the fuel to run back to the tank. So it may not show fuel but will leak air.

If all else fails I have gotten another check valve assembly and installed it under the fuel tank right on the electric fuel pump there. It is easier to hold a column of fuel rather than vacuum against air.

I had a JD 7700 I could not stop for bleeding back. So I put the second check value under the tank never had any problems after that.

replace the check valve on the filter first . less than 4 bucks from Deere this fixed the trouble on my 7720 and 4430