6.5TD STALLING - Air in Fuel Filter Housing

[Mudtrekker]

My 94 HD 6.5TD (Code F-HD) STALLS after about 1/2 to 1 mile from start. I bleed the air out of the fuel filter housing and it runs fine for another 1/2 mile or so. What is happening is it gets air accumulated into the fuel filter housing and stalls the engine due to no fuel reaching the FI pump.

According to older Forum posts, I checked & replaced the fuel filter first, no difference. Changed out the oil pressure switch on the top back on the the block (what a bugger to do, takes a real long 1 1/16 socket or a special socket that NAPA doesn't have), no difference. Still stalling.

Next step was the lift pump ($91.13 at Napa with AAA discount, much better than the Govt discount price). I checked it before changing it and it seems to be working. If I "prime" the fuel system by bleeding the air out at filter, it starts and runs fine, than I turn it off, and can hear and feel the lift pump pumping for a bit afterwards. If I open the bleeder valve on the top of fuel filter, it pumps out fuel 6 to 8 inches high after it bleeds the air out.

What is causing the air to accumulate in the filter assembly after running for a bit? This is real fun when it stalls at a lite during DC rush hour and I have pop the hood, open the bleeder, then crank the engine till it gets fuel and then fires up and get out again to close the bleeder valve! I've had lots of busy communters angry at me and have left fuel spots at several intersections near my home and work.

Not sure if this makes a difference but when I replace the fuel filter, it had a small round screen filter thing that fit onto the pipe that the Standyne fuel filter slipped over in the canister (a prefilter?). The new filter didn't come with a new one, so I reused the old. It fit onto the pipe into groves but was a kinda loose fit. When I slid the paper filter over it, it kinda slid down onto the pipe a bit like it was a little too big. Maybe it aged a bit. Would this make a difference?

I called 2 local dealer here in MD and 1st hadn't a clue so I called Crewell Chev in Gberg MD and they suggested it might be a FI pump and explained the extended warrenty on the DS-4 Electronic Pump. I told him that it had a new pump with less than 3000 miles on it. Beside how could a bad pump cause air to get into the system BEFORE it reaches the pump?

Next the Dealer suggested checking the fuel line between the lift pump and fuel tank. He said that it may have rusted a small pin hole that allows some air to get into the suction side of the fuel line before the lift pump. I told him I had to replace the rear brake lines because they had rusted thru along the frame rail. The dealer shop foreman said to pressurize the fuel tank with a air line and a rag around it into the fuel tank filler. Then check the lines closely next to the clamps holding the line to frame and if I found anything that looked like a fuel leak, that was likely the problem.

I havn't done it yet as we just started our first snowstorm here and my shop is not built yet. I still have the new unused lift pump if necessary.


Help me PLEASE!

You guys have always been a great help here on the Forum, I really appreciate it.

TIA,
Mudtrekker.

[pannhead]

take that advise,you are sucking air.....also make sure that the rubber o-rings were used when installing lift pump...there arent alot of joints so you should be able to narrow it down..another thing is that the fuel filter housing has several rubber o-rings that can go bad...the real nasty thing about an air leak is that a leak can suck air yet NOT leak fuel which makes it harder to track down.....good luck

[ucdavis]

The dealer had a good idea (the second dealer).
Air has to come from someplace. Suction side of LP is a good place to start. IIRC somebody had a similar problem w/pinhole in the dip-tube in the tank, which you could eliminate by filling the tank up into the neck. If trouble goes away, its in the tank; if not, then try the line from tank to LP.
Some report leaking back into system from a loose injector when the LP isn't working (IP has to provide suction to draw fuel if LP is NG, then sucks air to equalize when you shut down) but you seem to have eliminated LP because it after-runs.

[lupey6.5]

i would do some more investigating on how your filter housing fits together if anything is preventing the seal around the filter from seating properly you could be sucking in air right there or if you have been working the heck out of that bleed valve it could be sucking it in there--follow YOUR instincts after all its YOUR truck

[Scooby]

I am new to the electronic diesel, but have done lots of work on trucks and heavy equipment with mechanical systems. I have solved 'air leaks' before by installing an electric pump very similar to the lift pump on the 6.5 . From what I have seen, once you put pressure, even at just 5 psi like the lift pump does, you wont get air leaks cause the pressure is present to keep the air from getting in. Like was stated earlier, air can get SUCKED in in places where fuel wont leak out under low pressure. Your tank may have a slight vacuum on it- mine does each time I open the cap (not pressure- I'm sure!!)- not a lot of vacuum, just a small amount. I would guess that if you are sucking air, it would be between the pickup in the tank and the lift pump. Also stated earlier- check for that little oring especially on the suction side of the lift pump. You could try loosening the cap a little before you start out in the morning, and see if it still stalls. Dont forget to tighten it back up before water gets in !! Thats my .02 worth. [img]tongue.gif[/img]