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Was talking to a co-worker that also has a 6.5 turbo diesel about my fuel issue...

Mezmorized

Mezmorized

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He said that both times that problem happened to him turned out to be a pinhole in the return line. Please explain that one to me... How could a pinhole in the return line cause the "misfire"? How can the return pass air to the IP? I can understand the feed line (and I suspect mine to have a pinhole between the tank and the LP), but I don't see how it can cause the issue when it's just returning air to the tank?
 
Pinhole in return would cause a fuel leak externally, but would have no bearing on operation beyond that; the return is pressurized albiet very low pressure so when engine is running no way for it to suck air and that then causing operability issues, more to your buddies story I think
 
You guys are missing the boat.

GM put a dip tube on the return line to keep it submerged in fuel. When you shut off the engine and air leaks like a throttle shaft seal, etc. will allow air into the system as the leaky rotary vane IP transfer pump and sometimes lift pump allows fuel to drain back to the tank. This causes the fuel system to have air in it. Return line who cares? However the air in the return line allows air back into the IP and causes hard starting overnight. It is all because fuel will drain back to the tank allowing air into the IP. This is why the return line is run to the bottom of the fuel tank and ANY air leak anywhere in the system is a problem. Leaking injectors, or sticking, or worn out, can also be a source of air and hard starting. (Been there got the t-shirt.)
 
Ok, but my issue here is not hard starting over night... It "misses" while running, to a point some times where it will have hardly any power. Floor it when that happens and all I get is a bunch of shaking, smoke and barely any rpm's.

When I start it after bleeding the air out of the FFM, it runs good for a could of minutes then goes back to doing the same thing.
 
WW is correct I have solved air problems in the return line before. This sounds like fish biting to me I would start with LP test then Check ffm for leaks before the fuel lines. They can be a bear look for wetness, pressurize if you have to or evaporate smoke tester.
 
Agreed if it isn't a starting issue then the return line isn't much of a concern other than if it is restricted.

Fuel pressure and vac gauge combo can help.
Sounds like you have a kinked hose, plugged tank sock, or air leak on the suction side. (I don't know for sure if a kinked hose on the return side would affect the system or not.) With the air you don't have a LP issue alone or at all - it would be in combo with another problem.
Remember with a restriction the IP pump is strong enough to pull a vacuum that can boil diesel fuel and the boiled diesel will look like air. This can cause the lift pump to loose prime as it literally vapor locks the lift pump.

With a kinked hose behind the FFM my engine would randomly misfire then stall without smoke. It would have air (boiled diesel) in the return line.

I would make sure the LP is operating and stays operating. This allows you to concentrate on air leaks before the lift pump including the o-ring at it's inlet. Then check the pickup assy for pinholes and a plugged tank sock. Again, check for kinked hoses before you drop the tank. A hot hose expands and makes the kink more restrictive.
 
But thanks for mentioning the tube War Wagon... I'm installing an aux. tank in the bed of the truck. I started a thread that got moved to a section that hardly anyone posts on LOL. Anyway, I installed a fitting at the top of the tank for the return line. I'm doing it that way for a few reasons. First reason is: If I run straight off the aux. tank and my problem is solved, then I know it's between the main tank and the LP. Second reason is: I already have the aux. tank, so instead of dropping the main tank, I'll install the aux. tank (since I've had it for 2 years LOL ).

Both tanks will be running to a fuel filter with separate inlets and I will be able to shut off one or the other. Hence why the return line needed to be installed in the aux. tank.

The fitting on top of the aux. tank is a 1/4 NPT bulkhead fitting, so I will be able to install a tube going to the bottom of the tank. :)
 
Before I condemn a lift pump I test it as I unhook it. I pull the exit line and attach a hose to a container and hot wire it to see if I have any flow.

If no flow then, I pull the lift pump and try running from container to container. This is usually how I find a plugged tank sock. I've sen a lot of times people swapped lift pumps for no reason only to find it was a tank sock issue
 
When you do run the lines for the new tank, buy the fuel line rated for biofuel. Even if you don't run it they will outlast the regular lines. Once new tank is in use if it solves the prob I would drop the factory tank, pick up Leroy's sending unit, loose the sock, and replace the lines with the same bio rated rubber. A lot of fuel filter housings have multiple source lines, put it in pre lp. Truck is almost 20 yrs old and you plan on keeping a while anyways, right?
 
I have first hand experience on what hes saying. I had some weird problems, miss fires, stalling and some times hard starts. I went through everything and could never figure it out. A few weeks later fixing something else I noticed my frame was a little wet but not leaking bad enough to see anything on the drive way. It was a tiny leak on the return line. I fixed it and everything went away and it ran prefect ever since.
 
Ok, I am now running on auxiliary tank ONLY and it has no issues at all. The "missing" is no longer present. Brought it up to about 2200 rpm a couple of times and still no issue. It also seems to fire up a lot quicker than before. I have not road tested it yet, I need to plate it for the summer first. My next issue is finding out why my GP controller quit. I don't want to just change the controller and cross my fingers. I want to check the circuit and see if I have power from the signal wire to the controller to start with. I'm assuming there is a fuse as well, just have to track it.
 
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