Engine/Transmission (1994 - 1998) Beloved Air Leaks/Low idle setting

[MrWill12]

Well the want to do list is running into and crossing over the have to do list.
My idle seemed to have fallen off after adjusting it a 2nd time within 12-16 months so I adjusted it a 3rd time on Wednesday. This has started me thinking if there is a problem with the lift pump, the throttle linkage, fuel solenoid or air leaks. (Or a lovely combo package).
With this in mind, I just changed the fuel filter on Thursday, in a mad rush to finish, topped of with Diesel from my usual spot, added some read about and "suggested" AMS Oil cetane booster (not my usual thing) and took off on a camping trip and travel about 150 miles up and down some Appalachian Mountains well into WV.
I goto crank-up the truck the next day and it is stumbling and putting out the "air leak" white smoke. After 20 seconds it has leveled itself out as best as I could tell.
The next morning I decide to hit the throttle a little before I start it, Thinking maybe it is the linkage sticking causing the lower idle issue, It starts then it still stumbles and I hit the throttle a little and out rolls fuel rich black smoke. WTH! This rig never even hazes.
So, Since my fuel gauge has never worked since I've owned it (My wife just loves telling me my fuel light is on, she's always on an 1/8th tank #@$%!) my plan is to remove the bed and go in and address the fuel gauge sending unit and the rubber lines going into and coming out of of the tank. What suggestions do you all have about what I should address while I'm in there with the bed off? (Draw straw, etc..)
Thanks

 

[CRodi]

It's no where close to the fuel tank, but I'm wondering if you checked the fuel supply and return lines that run from the engine to frame. They're located near the firewall area. Sometimes they rub and chafe against the firewall. You don't necessarily have to see leaking fuel from there to have a problem. I've heard from others that a slight air leak, without signs of a fuel leak is enough to cause a problem.

I replaced mine a long time a go, strictly as a preventative measure. Marine grade and bio fuel compatible fuel lines are available as a kit, either from Geno's or directly from Larry B's.

 

[MrWill12]

Yes, your right. I have heard the same about the fuel lines next to the firewall.
I sprayed down the engine with some diluted Simple Green and rinsed it off to get a better look and to check for any leaking fuel around the preheater or hoses nearby. It started up this afternoon without much fuss and after running around I came home to do a visual.
On closer inspection of the rubber hoses, where the return line changes from metal to rubber, the writing on the rubber hoses appear pretty new and where they come into contact with the firewall they are surrounded in a plastic conduit. I am the third owner of this truck and according to how fresh the writing on the hoses appears they have been replaced.

I did find a hose clamp loose on the return line under the intake manifold. Engine too hot to do anything other than look. Crazy hard to reach. Look like you have to remove the fuel filter and bracket to have a chance to get access to this area. That would be a little to easy if thats it.

 

[surfbeetle]

The rubber lines from the engine to the frame are best changed from underneath with long extensions to reach everything. It's truly a pain in the butt. I have done it several times. The fuel lines from Larry B's and Geno just take longer to deteriorate but they do eventually. Also there's the right angle hose at the fuel heater as well as the heater itself that often needs attention. Good luck.

 

[hsmith]

Unbolting the mc and laying it to the side gives some valuable working room also.

 

[GAmes]

Just remember that air leaks are on the suction side of the pump and rarely leak fuel. Everything you need to know, plus some. http://www.cumminsforum.com/forum/94-98-engine/58777-joe-gs-fuel-system-writeup.html

 

[MrWill12]

Hey GAmes,
That is a good write-up I found that myself kickn around in here.
I have not had any problems since the trip. Now that I think about it the terrain that I was in, I am really starting to believe that it is in the draw-straw, if I understand the anatomy of the in tank unit. The reason I say this, going into the camp ground there is a pretty steep climb, 22-25*ish, and I had traveled about 125 miles. This would have been enough to drain 1/4 tank of fuel plus the incline allowing the fuel to move to the back of the tank...allowing for a large void in the front of the tank where air could be pulled in if there was a hole towards the top-half of the draw straw.

 

[MrWill12]

Just remember that air leaks are on the suction side of the pump

Makes perfect since when you say it. I have had trouble with power equipment when the take up fuel line get cracks in it and the the fuel level gets low.
Why do you think so many guys say that by replacing the fuel return line remedied their problem. Maybe cause they replaced more than just that one line?

 

[wcjp]

on my 96', I had multiple air leaks. The two biggest were the fuel preheater gasket and the soft line to the lift pump. The lift pump line was the last line swapped. I had spent the day off swapping all the usual suspects. Didn't get to the lift pump soft line until late in the day. It was not planned to replace it. It was the only item left that could be causing a problem. Once removed I sliced it in two. I could see daylight through the sides. It did not leak fuel. At the time it was a 2wk minimum wait through Chrysler. I ended up buying Coast Guard approved Marine grade diesel line. I place a decent size loop that would clear the steering linkage and not kink. Never had another problem with air leaks.