[bestgenman]

I’ve changed filters on dozens of 8V Detroits during my business days servicing generator sets.  It has always been a practice to never remove both filters at the same time.  Doing so allows air to enter as the fuel runs backwards out of the lift pump.  The lift pump is after the primary and before the secondary and Detroit gear pumps do not do well with self priming.  

Occasionally, air would enter and the fix was to install the new primary (being the first filter in the flow of fuel), and use any device that would pull a vacuum at the secondary.  Sometimes it is necessary to remove the inlet line to the secondary as a good access point. Once the lift pump has fuel all is usually well.

[jimg]

When I replace fuel filters, I have the new filter in the engine compartment area and fill the new filter with fuel before removing the old filter. I immediately screw on the new filter filled with fuel. This is done on both primary and secondary filters. After completing the filter swap start the coach and bump the throttle to about 1000-1200 rpm’s and it may be sluggish for a second or two then clears out and engine runs as it should.

[Guy]

Thanks guys.
Funny how doing anything on a car or pickup doesn't get me nervous, but this Newell really makes me unsure of myself working on it. So far everything I have attempted has worked out fine  due to your advice... 
Would not attempt Newell projects without you Gurus.

[77newell]

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.

[Guy]

Thanks guys. I did it as you suggested, one filter at a time, pre filled with diesel. Fired right up and ran great. Next up , draining coolant, filling with distilled water. run to temperature, and drain water and replace with  Peak Final Charge (OAT).

[Tf175]

It appears that this thread is exactly what I am experiencing now . I am thinking the return line deal looks good , presume that pumping fuel into the return will fill the pump , filters , etc in reverse . Wondering about the check valve blocking the flow of air/fuel ? And what was the fix for the coach at the rest area ?
Holding the fuel line up and filling it seems a good thing as well .
Chris

[Tf175]

Occurred to me I didn't read the bit about pumping and return line carefully enough... one should connect inlet side of pump to return line , pump into tank ? 
... Duh 
Chris

[Glenn and Laureen]

I replaced both fuel filters on my DD6v92 today after reading this thread. Had my son standing by with the new filter filled with diesel and immediately screwed it into place after removing the old one. X2, then started the engine right up and ran smoothly with no problems. Thanks to all for the guidance.

[Tf175]

Good result , Glenn . The problem I had was due to trying to run the new fuel /water separator without filter element. I was concerned about the extra restriction of the element , but failed to read ALL the instructions and missed the bit about the check valve blocking flow with element removed . Lesson learned .
Glad your engine is making Detroit Music ! 
Chris