Alrighty, my dads 92 started getting air in it when left overnight, start then die, crank for a bout 30 sec and it would fire up and be fine till left over night again. Well it started getting worse, would do this if only left for a couple hours, and now even 5 minutes. It has a brand new return line kit and viton o-rings, and a new lift pump.

I started diagnosing it and found first that a return line had come loose, i fixed it, although it struck me as odd that it did not leak diesel. Fixing this made the truck get the air out alot faster, aka only takes about 15 -20 sec. of cranking to get it to fire. Buut, is still getting air in.

Next, i put clear line on before and after the lift pump. There were no bubbles before, but where after. Replaced lift pump, starts even faster after dying due to air, and sometimes wont die, just stutters pretty bad.

Im going down to look at it again here in about 5 minutes. Im going to put clear hose on the IP cover return line. And replace the rubber line that goes from the hard line to the lift pump. I did not verify that air was not coming in from there.

The IP itself does leak a little, not drips or anything, but is wet around what i think is the advance plunger... anyhow, the rod on the left side. Could this cause air in the system? My dad needs his truck, and he cant afford to take it in, im more than up to fixing it, but he needs it for long trips and im running out of ideas as to what it is.

Thanks in advance for the tips and or tricks guys.

Mike

 

Hairy,

It sounds simple, but mine did exactly the same thing, and it was the fuel heater electrical fitting on top of the fuel filter. It barely leaked fuel (practically undetectable), but sucked up air when sitting.

Just a thought,

Mac.

 

I didnt get a chance to look at it tonight, ended up adjusting the brakes on the 63 and putting shocks on mine. But i had thought about it. It is bone dry but that doesnt mean it cant suck air, if i dont find anything its getting a new o-ring. Also, when he had a shop change the FF they dropped the bowl and fubar'd the drain petcock, but thats been some time ago now, however it does seep. Plan is to switch his with mine and see what happens. Thanks for the input, much appreciated.

 

my '87 6.9 is doing the same thing. I have replaced most of the return lines and o-rings. I still got the one in the back to go. You mentioned the hard line coming from the tank. Should it slide freely inside the rubber line going to the manual pump. I was checking my fuel lines last night for a leak. I noticed that hard line coming from the tank, going in to a rubber line and it slides freely I couldn't pull it out.( didn't try too hard though). It don't have a clamp or anything on it. Could I be getting air in from there? Thanks, Tony,

 

in total frustration a year ago i completely went thru my fuel system and found 2 problems.

one was the flexible return line from the tee on the back of the motor to the hard return line on the frame rail.

the second was a pinhole in the hard line on the rear tank. dirt and moisture had gotten trapped in the crevise of the quick disconnect fitting. the hard line looked merely pitted but beadblasting revealed the hole. the quick disconnect itself was probably ok but the o-rings within are another potential problem on a 20 year old truck.

kevin