CAT 3126 rough idles then dies

I have a 1998 Freightliner FL70 with a 3126 in it. The truck has ran great until recently. This problem has been intermittent......someitmes it starts right up then other times it will take a second (acts like it has air in it) rough idle then die. The only way it will start again is if I take the seconday filter off and fill it full of fuel (there is no primer pump on it).

I've recently replaced the fuel tanks, new suction side fuel lines, changed the oil, new fuel filters. I also replaced the fuel pump solenoid. It will run great one day then do this the next.

I cannot find a fitting that will fit into the port by the secondary fuel filter to take a pressure reading on the fuel pump.

Ideas or suggestions......my CAT certified guy is a ways away and I'm trying to avoid having it towed. I can change parts or take stabs at it here at home. My gut tells me the fuel pump but could it be some sort of sensor or HEUI pump?

Suggestions...?

 

I have thought about the fitting (regulator) on the back of the head. Tomorrow I will take it off and clean it out. I haven't done it because its so hard to get to or see.

No codes or check engine lights whatsoever. New oil change and filters (CAT filters).

Thanks.

 

Today I replaced both the speed sensor and timing sensor ($123 they come as a pair).

I will let you know the results.

Thanks,