07-20-2019, 08:16 AM
The V92 DD engines have fuel coming from the tank to the first filter, the fuel then goes to the engine driven gear pump with a built-in relief valve. The fuel then is routed to each head and passes by each injector before returning through a restriction to return to the tank. There is supposed to be a check valve in the line going to the first filter. Given the age of these coaches it is possible that it leaks a little or more which is why you want to have the primary filter, in particular, off as short a time as possible. This is enabled by having a filled filter handy when removing each filter.
Jon Kabbe
1993 coach 337 with Civic towed