We have 2 old Cummins 5.9 buses, 1988 and 1989 we use for school shuttles and we have a problem with then cranking but not starting after they sit over night. In order to get them to start we have loosen the injector lines. We have replaced the fuel pump, filters and have checked for leaks nothing found. Any help.
Which pump does it have on it? They were available with an inline pump that is Bosch or a rotary pump that is much smaller. The inline pump has six injector lines with the lines coming straight out of the top and rotary pump has the lines coming out of the back of the pump. Of course you probably already know that, but they have different little differences that can cause the problems you are describing.
I has a check valve that holds a little pressure in it so it will start. It should be on the left side of the injection pump itself, look for a banjo fitting like an 18mm. Not on the rear of the injection pump. What kind of chassis is under these buses?
there is a housing that the racor filter threads on to. by pass it with a hose and see if your trouble disappears. and you always check the under hood filter if its low on fuel after it sits a few days then u know if there is a leak