Fuel related dying, strange fuel bowl action

[JTodd]

Truck has run flawlessly until Saturday. Fired it up just like normal Sat Morning, let it idle for a minute or two as I cleaned the snow off, and started to back out of the spot. I got about a foot and it dyed. No warning of any kind. It took a bit to get it started and then it would miss, even at idle. It has sense died more than a couple times as I try to diagnose the problem. Sometimes it misses, sometimes it just dies.

I replaced the fuel filter (the new style from NAPA is ridiculous. They obviously did not realize the little spout on top was for bleeding, instead it is now just a little crank handle to tighten the bleeder) and the lift pump. The LP was only a year old, but after the new filter, it seemed like the next place to look. It seemed to have an intermittent thing going on. In addition to those parts, the PMD is 6 months old, the battery and starter a year old, and the glow plugs about 2 months old. I took on some fuel from a truck stop Friday morning - about 1/2 a tank, but it ran fine Friday after that. I added fuel conditioner, anti-gel to eliminate that problem.

Basically, when it dies, I open the bleeder on the fuel filter and bleed it a couple times. Sometimes it fires up quickly, and sometimes it takes some cranking. That increasing speed cranking like it just not getting enough fuel. One odd thing I have noticed is that when I open the bleeder with the key in the 'off' position, fuel spurts out much the way a shaken bottle of coke does when you start to open the lid, fizzy. It seems like there is air spurting out along with fuel, and it is under pressure, even with the key off. With the bleeder open, I can hit the key and fuel starts to come out as it should. If I hadn't had the problem before changing the filter, I would think that is the problem. The next thing to try is the fuel pump relay. After that - any suggestions?

[Warren96]

If you open the filter bleeder and foam comes out, there is a hole in the suction line from the tank to the lift pump. Look under the truck and see if you can see a wet fuel mark on either fuel line, or on the frame.Normaly your truck shouldn'nt smell of diesel fuel, it reeks of fuel when you have a air leak. I hope you read this before you buy a relay. My 1994 model did the same thing. Good luck and keep us posted.

[JTodd]

yeah, I bought a new relay before getting your post. Now I have a relay and LP in my spare part bin. I will check for leak along the frame.

[JTodd]

It looks like there is a leak either in the rubber hose or at the joint between he hose and the solid fuel line. How hard is it to drop the fuel tank? It looks like that is the best way to get at those lines. Off hand, any one know what size rubber hose that is? While I am there, what else should I do?

[Warren96]

First you have to find a home for all that fuel in the tank so you can get it unhooked from under the truck.Don't try to take the tank off with any fuel in the tank! You cannot believe how unstable that is. Next you want to be sure not to bend the supply and return lines on the top of the tank, as they are welded to the sending unit. Then unbolt the straps, and gently lower the tank a little until you can get the fuel lines and the gauge wires off. I used some wooden blocks under the tank to lower it a little at a time. Is the top of the tank damp from fuel? then you might have to replace the sending unit. Take your time doing it and you wont have any problems.Use lots of liquid wrench or PB Blaster and let it soak in good.When you do have a fitting that comes apart be carefull of the small O ring inside. It needs a soft touch, and maybe some silicone grease when you tighten it up. Good luck and let us know it goes. It can get frustrating, take your time.

[JTodd]

Man, that was one of the most un-enjoyable jobs I have done. Garage is full of race car parts and other stuff, so was only able to get part way in. It took me a lot longer than anticipated and it was around 12 degrees when I finally finished. It was hell getting the tank unstuck from the rubber insulator. For those coming after, at the rear corners of the tank the seam flange is thicker and can be pried against. I used one of those 'L' shaped flat bars and was able to get it to come down. Until finding that sweet spot, I was very worried about denting the tank instead of loosening it. I found that with a couple of 2x4s laid flat, I didn't need to disconnect the electrical connections. I had read that the entire filler neck comes down, but I saw that that was not going to work. I disconnected the filler hose and the vent hose from the top side, (not the tank side) and was able to snake that out that way. Getting it back in was a chore because the hoses were so stiff from the cold.

The leak was either in the rubber hose or the solid line right at that junction on the frame rail. I did not realize until dropping the tank that the hoses have crimped on flare fittings. I ended up cutting those off the solid lines and using hose clamps and the proper size hose. 3/8 id for suction and 1/4 id for return. I had enough hose that I ran them up the frame rail far past where it was wet from leaking, cut the solid line and again used hose clamps.

Once done, I quickly bled the filter bowl and fired it up. Runs like a champ. I am a bit concerned about the hose clamps, especially on the return line. I don't know how much pressure that is under. I thought about a compression fitting instead of hose clamps, but could not find anything that would fit at the hardware store. At least for now stainless steel hose clamps will have to work.

Thanks for the info and the moral support.

[JohnC]

I am a bit concerned about the hose clamps, especially on the return line. I don't know how much pressure that is under.

Same pressure as the tank: almost none.