500 Fuel Pump

[Tubacase47]

The seal in my pump is letting fuel into the crankcase. Can the seal be changed by taking the side cover off or does the pump need to be sent to a pump shop?

 

[Dieseltech]

All depends WHERE the fuel leak is. I'd start with the gear pump seal, PK 7910 first. If that doesn't stop fuel into oil then the four injection pump hydraulic head O rings need replaced, the top O ring leaks externally, the other three can leak fuel into oil when they fail.

 

[John Saeli]

Richard: I've never had to change those O rings, it was always the seal. How are the O rings replaced? Does the pump need to be removed? For future reference, I encountered a worn shaft where a new seal wouldn't seal, so I took the pump body to a local machine shop and had them bore into the pump body, the width of the seal, so the seal was on new shaft when installed. Very simple fix.

 

[Dieseltech]

Over time the head O rings get hard, and then fuel can leak past into the oil. The gear pump seal usually fails first though. I had two Cockshutt 570 PSB pumps this spring that both had leaking head seals. They can be changed on engine IF careful about timing the head, but it's best done with pump off engine.