when i back my truck in on a slight grade i dont get air in my fuel and it will start like its 70 degrees out after sitting for as long as it wants. but when i pull in to the same grade i will develop air in my fuel from somewhere and it starts rough. any thoughts? ive already gone threw pretty much the entire fuel system but the tank and interior tank parts.

 

the suction tube in you tank is were i would start

 

These 12v trucks are notorious for loosing prime due to a leaking Return line, Fuel heater and Overflow Valve problems. The reason I mention is due to the fact the tank wont really cause a loss of prime in most cases. As far as in the tank parts a broken or cracked plastic pickup tube or a leaking module. If the tank was full it would eliminate the problem.
Have you replaced the fuel heater?

 

yes all the rubber lines are new, new overflow valve, brand new lift pump, injectors, fuel heater gasket and strainer and it will only lose prime it its sitting on a grade where the motor is higher then the rest of the truck. if i back it into my parking spot its fine.

 

So you didnt eliminate the fuel heater? did you vacuum check it? If thats the case all thats left is the tank! Might just install a draw straw and eliminate the hassle of diagnosing the module. The module is an obsolete part unless you can find one aftermarket or another application that will work.
I've seen the float assembly cause issues but for the prime to fall off from the pump back something has to be leaking further towards the front. It really wouldnt make sense if it were in the tank. I vote fuel heater leaking at the plug.

 

what plug? i just had the whole heater and lift pump assembly off and cleaned/ put new gaskets and strainer and put new teflon tape on the pipe fittings. but i agree it has to be closer to the motor. or is the heater right off the back of the pump and what i cleaned was just a pre fuel filter?

 

The fuel heater is known to "disintegrate" internally. It causes a massive air leak that will not leak much fuel, even when the tanks pressurized it tends not to leak if the heater is plugged in. Just for checking sake I'd pull the prescreen back off and delete the heater. There should be a thread around here showing pics. It's pretty simple, take the heater allen screw out, replace the screen bowl with the gasket and your ready to roll.
Normally this causes a no start or complete loss of prime most of the time.

 

One more vote for deleting the fuel heater, I got rid of mine last fall and I've been driving my truck in -40c (-22f) with no problems. Just remove the bowl on the bottom and remove the plastic disc with the plug coming out of it. You will have to remove the thread extension from the center, then reinstall the bowl with a new gasket and strainer. I would also replace the lift pump to fuel heater line while your in there.

Also make sure the electrical wires that you disconect aren't going to touch anything.

Try this first and if you still get problems try one of the other suggestions.

 

alright ill give that a try! thanks guys. also will i notice any starting differences with the heater plugged? i still have my intake manifold heater working so i wouldn't see it making a big difference. ill look for more info on how to plug it, but it sounds like i pull the bowl off and remove the screen filter and lock nut, then what? or more or less what do i plug and how does this keep air from entering my fuel.

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alright did a quick seach found alot of people have deleted it but no real descriptive info on what to do once the bowl, locknut, and screen are off. is there a plug i will see up in there?

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good news found a good right up with pictures! last question, please tell me i can delete the fuel heater without having to take it off the block. The metal fuel lines where a PIA to get back on haha.

 

You should be able to remove the heater without removing the lines, just pull the bowl off then if you look up at where the bowl threads on, you will have to unscrew the threaded extension/adapter that holds the plastic heater section on. Once you have the heater and threaded extension/adapter removed you can reinstall everything exactly how you removed it, just leave the plastic heater and threaded extension/adapter out.

Some more info for you:

http://www.dieseltruckresource.com/d...r-t230687.html