My 7700 diesel runs good most of the time but it every once in a while it will run doggy. Ran it hard for 6 hours the other day and then headed home and it quit on me a few times. Seems to be getting air or something. Everything obvious I have done. I changed fuel filter a few hours earlier. No obvious leaky lines. It has the two tanks. Seems to do this more often when down to second tank. Is there something on the injection pump that I am missing such as a screen? or a check valve that is sticking? Is the pickup in the second tank a problem? Need some help. Thanks.
- Thread starter jhwis
- Start date
My 7710 does the same thing when working HARD and only have fuel in the lower tank. Am told could have a small leak in the line where it does not have a problem when fuel is in the upper tank, but can suck air when it has to pull fuel up from the lower. Could also be the lift pump.
Odds are the lift pump is shot. When the top tank is full, gravity works it's magic and keeps her in fuel but when the lift pump actually has to lift it.... you get the staggers and jags..
I'd open the bleeder on the filter head when the lower tank is down a good ways, then operate the hand primer and see if it will lift fuel. If it won't, you've answered the question.... provided the inlet isn't plugged in the siphon... but given that it seems to work ok with fuel up top... I'd say that is unlikely.
Rod
I'd open the bleeder on the filter head when the lower tank is down a good ways, then operate the hand primer and see if it will lift fuel. If it won't, you've answered the question.... provided the inlet isn't plugged in the siphon... but given that it seems to work ok with fuel up top... I'd say that is unlikely.
Rod
Destroked 450
Well-known Member
- Location
- Harned, Ky
Sounds like a weak lift pump, fuel from the top tank transfers to the bottom tank and all fuel is drawn from the bottom tank to the engine. With the top tank being higher than any other part of the fuel system any leaky lines or fittings that would allow air to be sucked in would leak fuel when both tanks are full.
With all fuel drawn from the bottom tank any thing floating around in the bottom tank that could plug the pick up could give problems at any time even with both tanks full.
Shouldn't be the problem was it's not related to the amount of fuel in the tanks but, have you checked the oil in the injection pump to make sure it's not low and plungers are trying to stick from lack of lubrication.
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