I asked over on cummins forum awhile back...(ive been dealing with this for about a month now). Few weeks back the raptor fuel pump that the last owner of my truck put in died on me so i swapped it with a fass. Trucks a 96 12v. 191 dvs, 64/71/14 turbo, 5x14 injectors, built trans. Ever since the truck has been nothing but a PITA. Starts hard after sitting, when it starts it idles like crap, cant rev it without it sputtering and missing. Whole truck shakes while idling and i can even drive the thing for a little while. A good amount of white/ blue smoke comes out of the exhaust that stinks of raw fuel to the point where it burns your eyes. Timing has been checked and rechecked and rechecked again, 15.5*. Changed injectors along with all sealing washers and hardware. Injectors are 5x14's. I replaced the return line up to the tank (as close as i can get to it without dropping the tank anyways). Changed fuel filter. My gut is telling me its air getting in the system with it being most problematic after it sits and losses its prime. But i have no clue where the air could be coming from at this point. Fuel heater assembly and pre filter screen crap is al long gone. Can anyone think of anything. Im at the point where im missing work because i cant drive my truck. And honostly id sell it at this point but it wont run good enough to sell

 

You need to quit playing with it and drop the tank..your air leak could possibly be the fittings on top of the tank module itself....close as you can get, ain't good enough

 

Yeah thats my next step. Need to wait for someone to give me a hand. Thanks for the reply. Just seems odd to me that all this happened after i changed the fuel pump. Only thing i can think of is with the new pump and actually pushing fuel with correct preassure something that was weak before just gave out

 

You can also very easily loosen the bed on the off side and take the tank side bolts out. Watch for the wires, but very easy to access the tank by lifting the bed. Most times, that is the route I take as I am usually alone working on stuff.

 

Alright ill try that. Just noticed under close watch that my bleeder screw on top of the filter is leaking. Gunna get that fixed asap. Prime source of fuel/air leak right there

 

You have possibly found the leak there but.. do you have a fuel pressure gauge? if so is it a mechanical one? If it is you will have an isolator that has a bleed screw in it, under the bleed screw should be a ball bearing that often gets dropped when the screw is taken out. The screw will seal enough to prevent a leak but will allow air in when the truck sits.

 

Thanks for the reply buti do not have a pressure guage, (i know should have been my first thing to install). That will be the next thing i install