Help on bleeding fuel lines on 720 deisel

chas036

Member
I have 720 D that has not run in 20 years. The pony starts fine and I can turn over the diesel motor on decompression with no problems. I have emptied the diesel fuel from the tank, and removed the sediment bowl and cleaned it. I removed filter housing and replaced the two fuel filters. I reattached the fuel housing and reconnected all the lines and put new fuel in the tank. I removed the bleed bolts from the filters and opened the sediment valve, and NOTHING. Fuel will not flow. When I disconnect the line between the sediment bowl and the pump, the fuel flows fine. When I connect the line, there is no fuel flow past the pump. How do you bleed out the air if the fuel will not flow into the filters? Should the fuel flow freely through the pump?
 
open filter bleeders, then roll engine with starter motor let on decompression. after filters are full close bleeders and loosen line at each injector and proceeduntil you have fuel there. then tighten them and start as normal. Rd
 
Are you spinning the diesel engine over with the pony, or trying to let the fuel flow through with gravity? I think the transfer pump would have to be spinning to get everything primed, but maybe that's what you're doing.

One other thing you may want to check is the fuel line from the filters to the injection pumps. Mine was clogged with what looked like steel wool. It got into the pump bridge and pumps too. I have no idea where it came from but someone told me some filters are made with material like that. We thought maybe the previous owner let the filters in too long and they came apart. Cost me a set of rebuilt injectors.
 
I finally got oil to flow after blowing out the line from the pump to the filter. Looks like it was clogged after sitting for 20 years without running. Diesel motor started right up and runs great. I can't believe after 20 years, it runs so smooth.
 

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