I have a 1988 F700 with the 6 cyl diesel. I sat for a few weeks, maybe no more than 3 and now it won't start after previously running and starting fine. We currently think there is sludge in the lines and possibly fuel injectors because the priming pump feels like it is pulling against a vacuum. Previously it moved fuel with no problems. We removed and cleaned out the tank, and replaced both fuel filters and the water separator, hoping that would alleviate the problem, but did nothing - bringing us to the clogged injector conclusion. Any ideas?

 

Probably not a clogged injector.

pull a fuel line off the pump and see if it drains fuel from the tank.

Make sure the fuel solenoid is working. Unhook it and put it into run position if its not moving..

 

I can see the solenoid and remove it just fine, but I have no idea what you mean by putting it in the run position. Is it a physical positioning or do I need to send a current through it to activate the solenoid? And after putting it in run, do I reassemble with it that way? Is the assumption that if it's stuck, then physically moving it would fix the issue?

 

This is a new holland engine right? 6.6 or 7.8L?

If so the solenoid physically moves a linkage on the fuel pump. Turning the key from on to off should move the the fuel shutoff lever back and forth.

 

The solenoid has 3 things going for it. Off, run, and start. Off is obvious. Run will only hold it in the running position after hitting it with the high amp draw of 'start'. The 'start' will kick the solenoid on, and is not for keeping it running. It's a higher current than the 'run'.
You can leave the key in the run position, and physically pull the solenoid lever, and it should stay there. The 'start' will take 2 people, the key operator, and the observer. No need for removal,unless it's actually bad.

 

its the 6.6 - and we bought it with the idea of a locally owned bio-diesel company in New Orleans a few years ago (the truck is a 1000gal tanker), but never got off the ground. Problem is, we are moving to california, and may now just be trying to sell it. So we were trying anything possible to get it running to make it sell that much faster.

 

The solenoid seems to be working fine. Any other suggestions?

 

Did you blow out the lines from the lift pump back to the tank?