Fuel Filling Problem with Freightliner Chassis

[DynamaxGS]

I'm a new owner of a 38 ft 2004 Dynamax Grand Sport on a Freightliner FL-70 chassis. It is a beautiful rig with less than 15K miles on it but it has one aggravating flaw: the rig cannot be fueled normally by inserting the fuel nozzle in the filler tube and setting the latch to fill and cut off automatically. At some point fuel will spurt out of the filler tube in a big gush before the nozzle can detect the fuel and shut off. You only have to get doused with diesel fuel once to know that you have to figure out a way to prevent it.

I've tried opening the other tank filler tube (it has two 45-gal tanks with fillers on each side of the cab), filling as slowly as I can, etc. but it always tends to overflow. It takes a good half hour to get as much diesel in the tanks as I can but I can never get it more than about 80% full and I'm not making any friends with my RV colleagues who are waiting for the pump. I've started to fuel only at off hours or where there are many free pumps so as not to alienate others.

I can't believe that Freightliner designed this system this way; there has to be some glitch somewhere (venting, interconnecting tube from tank to tank, etc.). The previous owner briefed me on this. I went ahead and bought the rig because it is so outstanding otherwise, the price was right and on the theory that I could find the problem and fix it. The previous owner had taken the rig to Freightliner during the warranty period but they said they could not find anything wrong with it. Before I take it to another Freightliner facility, I thought it would be worth checking this forum to see if anyone else had ever experienced this type of problem. Any ideas?

[wolfe10]

Hopefully, someone else with the FL-70 chassis will respond, but as you know the population of RV's on that chassis are fairly limited.

When I called Freightliner, they said they do not have a technical support group for the truck chassis as they do for the RV chassis in Gaffney.

Their suggestion was to take it to a Freightliner dealer who could both look at the problem and also research any applicable factory bulletins that address the issue.

About the only suggestion I have is to carefully trace all the fill and vent lines and make sure none are kinked or blocked.

The good news is that as many FL-70's as are on the road, this kind of issue is unlikely to be accepted by commercial vehicle operators, so either there is a "fix" or you have a unique issue such as blocked or kinked line.

Brett

[Guest Wayne77590]

I've sent you a message regarding a forum that I think I saw this type of information on.

I think it had something to do with changing out the neck (Filler Tube) going to the tank.

Good luck.

[Charlieanddawn@gmail.com]

First do not use the truck pumps only the auto/RV pumps. The fill tubes are almost at the same height as the top of the fuel tanks on many rigs. The top of the tank fills up very quickly when using the truck pumps. Not enough air can escape from the tank when filling at a fast and pressure builds up and spits the fuel in the filler tube back out.

Another answer is to learn the amount of fuel your rig is going to need at different gauge readings and slow down ( a lot ) as it gets close to the amount your going to need.

No vent tube is big enough to vent all the escaping air. Look at the size of the fuel fill on big trucks the large fill tube allows air to escape.

I have had fuel spit back at me many times and I have learned that the best answer for me is using the Auto/RV pumps that fill slower and know how much I am fuel I need.

[DynamaxGS]

Brett - Thanks for looking into this. Your suggestions, plus some sources provided by Wayne suggests that this is a venting problem. I will check soon to see if the vent tubes are properly sized and connected to the filler tube ports. From what I've read it appears that the worst case is that the service center has to drop the tanks and install a larger vent tube and check valves. Hopefully I have a kinked/blocked vent tube that can be easily rectified.

[DynamaxGS]

Charlie - Thanks, and yes, you only have to get doused once on the truck pumps to know that they have way too much volume. I have consistently used the auto diesel pumps since that first dousing. It seems to me that a properly designed fuel system should allow you to insert the fuel nozzle in the fiiller tube, set the latch to the slowest fill rate, and expect it to shut off properly without a spill. This isn't possible with my tanks. I use the smaller pumps, pump fuel manually as slow as I can and I still get fuel blowing out the filler tube. I've started to use a small flash light to see into the filler tube and I'm learning to "listen" to the fuel to know when it is getting to the maximum level. This can't be even close to right. After some research and assist from other contributors, I'm pretty sure there is a major problem with the venting in my tanks. Thanks again for the comments.