Cat C15 Fuel Problem

intersting. If your filters are filled, then it doesnt seem to be draining back to tank. Do you have a hand pump primer on filter housing or a block off plate? I hjad same issue with c12 and full filters. First replaced check valve in filter housing, that didnt work. Replaced the whole filter housing (160 bucks from cat). that didnt work, took offf block plate and installed cat hand primer pump. That fixed it. Only have to prime when changing secondary.
Maybe bad block off, bad primer pump diaghpram or filter housing.

 

Check all the fuel lines. I had one dry rot and it would seap out overnight. Wasnt dripping fuel anywhere, but the seapage was enough for it to lose prime. Replaced fuel line and never had another issue

 

Luckily the line i had dry rot was in a spot that was easily seen. Return hose, just looked wet but when i would bend the line the cracks were visible and it would drip out. Follow your lines all the way back to the tanks.

 

Your primary fuel filter will always be 60% full when checked as fuel will always bleed back past divider valve
(Under center rear of bunk, on crossmember) and into tanks.
If it's full, to the top, is being fed fuel from upstream ( next stop is pump) and or secondary fuel filter housing.
Primer pump is commonly an issue, more so with the addition of bio blend fuel, which is, for the most part, alcohol, which dries rubber ( like in the hand primer pump plunger!!! )
I'm not one to throw parts at a truck without proper diagnosis, but if the primer is old, replace it, its life is done anyway.

 

Check the return fuel line back of the head
the o ring goes bad it happened to me once

 

If all fuel lines check out and you have replaced the check valve and transfer pump. My guess is you have an injector leaking off over night. Does it smoke alot at first when you do get it started ?

 

Just a fyi, i have the same engine and my fuel filter is always full when i change em out.

 

Its a mbn. Doesnt have a hand primer.

 

It should , unless someone removed it.