Midnight Oil Workshop
New member
Hi, My official factory service manual (and every other parts reference) shows that the fuel pump in my 1996 Force 120 uses 2 round diaphragms that consist of 2 pieces each - one clear plastic backing disc - and one black rubber valve disk - that are sandwiched together and attached to the pump with a clip in the center of each diaphragm. When I disassembled my pump to rebuild it, I found that it only has the clear plastic backing disc - but is missing the black rubber diaphragm itself. (it's been like that for years and the engine ran). My rebuild kit came with both pieces, so I installed the diaphragms as indicated in the manual - with the black rubber diaphragm aganst the pump housing and the clear piece on top of it to hold it down. When I went to start the engine I got no fuel and the engine didn't start. So, I disassembled the pump again and removed the black rubber diaphragm to put it back the way it was and the fuel flowed normally again.
The engine runs okay with only the plastic backer for the diaphragm, but it does stall after idling for a minute and I have to pump the fuel ball to get it going again. No noticable probelms at higher speeds. I have seen youtube videos of people rebuilding this same pump and they also only use the plastic backer for the diaphragm - omitting the black rubber piece. Can anyone shed light on this issue? This pump is powered by engine compression - which is on the low side, but runs just fine otherwise.
Could the slightly low (about 105psi on all cylinders) compression cause my fuel pump to not function with both pieces installed for the diaphragms?
The engine runs okay with only the plastic backer for the diaphragm, but it does stall after idling for a minute and I have to pump the fuel ball to get it going again. No noticable probelms at higher speeds. I have seen youtube videos of people rebuilding this same pump and they also only use the plastic backer for the diaphragm - omitting the black rubber piece. Can anyone shed light on this issue? This pump is powered by engine compression - which is on the low side, but runs just fine otherwise.
Could the slightly low (about 105psi on all cylinders) compression cause my fuel pump to not function with both pieces installed for the diaphragms?