Fuel tank leaking.

[Tuesdak]

What are the common things I need to look for?
Just filled the tank and ran 20 miles or so. Park nose up on a 7% or better driveway. Found good leak under the tank coming from the back strap area - the area near the fuel pickup and return unit. Still drips when the truck is level. Have not confirmed if the pickup assembly is leaking etc. as I only see the strap by it is wet. Nice noticeable puddle was left.

Past 3 fill ups have not leaked.

 

[Prairie Dog]

There are two possible sources of the leak that I know of.
Hopefully someone else will comment with pictures but back in the day, our 03's often had an open nipple on the top of the tank. With the tank in the truck you can't see it of course but you can reach up from the front and feel for it. It's situated in a low spot on the top of the tank and is a 90 degree plastic part. Most were just open to the elements and water and dirt got in. I was one of the rare lucky ones and mine had a molded-in cap on it. This connection was used as a vent or return line or something of that nature on gassers and should be plugged for us. You can either attach a fuel line to it and use it as another vent or just plug it off.
Secondly (and most likely IMO), the sending unit/fuel line assembly is installed with a collar that is similar to a lid on a large mason jar. They were often loose and you can reach up with your hand and just turn to tighten it if your strong enough. Mine was loose and I had to use a large flat screwdriver against one of the plastic ridges of the "lid" and tap it a few times with a mallet to get it snug and stop the leaking. Both my old 93 and my present truck had a leak in this location because the lid was loose.

Scott

 

[AnOldBiker]

Never had that year, but had a leak on my '06 and found on the top of the tank are 2 vent valves (1 front / 1 back) that equalize the tank pressure to atmospheric as the level raises and lowers.

With the tank angled in the right direction to put the level towards either the front or back half of the tank that your checking:
1. check the hose on the nipple and see if it is leaking fuel, if so, the float is bad and the unit might need replacing or cleaning.
2. If it's not that, there is an o-ring for this unit seal into the tank.

That was my problem. The o-ring had a crack and all I needed to do was replace a $1 o-ring.
There are 2 units on the tank and they can allow debris in. The hose I believe is a 3/8" ID, and you can install cheap plastic in-line filters to correct this. Just make sure you check them once in a while or you can cause a vacuum action on the tank.

 

[MLee]

Do a search on the vent hose for the tank. This hose should have been put on before delivery to keep out water that collects in this low spot, and contaminates the fuel with water. Get a hose and run it up high, to be used as a vent. When this newer design came out the owner was blamed for water in the fuel system which required a lot of injectors to be replace at the owners expense. Not covered by the warranty.
And your leak is as suggested when full. my older one done the same thing, loose sender ring.

 

[Tuesdak]

It was a loose sender ring. Used a long screwdriver and a BFH. It was going to chip a corner off the ring, tighten it, or break it. It tightened it 1/4 turn. Problem solved.

I will look up the vent hose and also put a CAT water separator element in the system. The CAT water separator saved an injection system for me in the past where the other IDI diesel that didn't have one wiped the pump and injectors with some bad fuel.

 

[rscurtis]

If you haven't done the vent modification on your truck, you'll be surprised how much easier it becomes to actually fill the tank, and you'll appreciate the additional travel range. My signature truck will go 200 miles of highway driving before the needle even moves from the "full" mark.