Fuel tank problems

[poolmike]

So my wife and I were cruising on the PA Turnpike on Saturday. All was well until suddenly I was loosing boost/power and I was watching my fuel gauge drop quickly. We got it to a rest stop where I discovered that the return hose blew off the the motor, hosing down the undercarriage, the turnpike, and a few cars behind me with some 20ish gallons of diesel. $$$Lovely$$$. I put the hose back on with a new clamp and went on my way...wondering WHY it happened. Anywho, whenever I release the fuel cap, there is a crap-ton of pressure coming out...or is it air being pulled in? The tank appears to be caving in on itself. I will look into this a little more tomorrow when I have time. I am wondering if the fuel cap is supposed to be vented, and maybe it is blocked?

 

[Hit The Road Jack]

So my wife and I were cruising on the PA Turnpike on Saturday. All was well until suddenly I was loosing boost/power and I was watching my fuel gauge drop quickly. We got it to a rest stop where I discovered that the return hose blew off the the motor, hosing down the undercarriage, the turnpike, and a few cars behind me with some 20ish gallons of diesel. $$$Lovely$$$. I put the hose back on with a new clamp and went on my way...wondering WHY it happened. Anywho, whenever I release the fuel cap, there is a crap-ton of pressure coming out...or is it air being pulled in? The tank appears to be caving in on itself. I will look into this a little more tomorrow when I have time. I am wondering if the fuel cap is supposed to be vented, and maybe it is blocked?

poolmike,

I experience the same pressure sound (seems to be suction) when removing the fuel cap for Diesel addition...

 

[poolmike]

Check your tank and make sure it isn't caving in on itself. I will check my vent tube and make sure it isn't frozen/plugged up, or maybe it has some type of valve on it that is failing.

 

[abittenbinder]

There are 3 valves on top of the fuel tank. 2 are rollover/vent valves and one is a pressure/vacuum compensating valve.

The fuel return circuit to the 647 fuel tank has a integral preheat valve that directs return fuel to either the tank directly or the fuel tank cooler before entering the tank. Doktor A

 

[poolmike]

Ahh...so probably a failing pressure compensation valve.

 

[yellowmike]

I have a friend who just bought a used 2006, 2500 with only 25,000 miles on the clock and he is having the same problem. He called me up and said that he was getting ready to take the sprinter for a drive and noticed a small puddle of fuel under the tank. he opened up the fuel cap and said that he noticed a lot of pressure had built up and it was released when he undid the cap. What did you guys come up with for answers for this problem????

 

[seadawg]

I have a 2004 and if the tank is the same layout in order to fix any of the hoses etc. on the top you are going to have to drop the tank. It is pretty easy to do with an empty tank ( not the case when I did it) so if you are having problems don't fill the tank. I bought all new hose clamps and some extra hose when I took the tank down here is a link to the process. https://sprinter-source.com/forums/showthread.php?t=12741

 

[offgridnick]

Hello Seadawg i read your interestring post about leaks and dropping the tank but now I'm confused---- all very well but does anybody know
what exactly was the cause of the problem Poolmike described as pressure (or maybe vacuum) in the tank? I THINK that was in the first post
titled "Fuel Tank problems" Did we get off the subject or did I miss something? Nick In BC

 

[offgridnick]

Hey PoolMike-----we seem to be off and running in several directions following your first post---when you find the specific cause of your
pressure in the tank causing leak (hose blowing off) could you please come back to this thread and let us know? Much appreciated.

 

[seadawg]

I thought that Doktor A's comment on the three valves on top of the fuel tan were the answer/ Perhaps I jumped the gun. If the tank is imploding then it would seem that the vent was not working. The return line would then have to push fuel into an already high pressure situation which would cause the weakest link to open. That is what I understood.

 

[offgridnick]

Seadawg--sorry I see your point now-------Doktor A says the vents are atop the tank, therefore the only fix is to drop the tank to test. I got
off the track reading about dropping the tank to fix leaks. One question for \poolMike tho: exactly which fuel line (return) was it that blew off
on the turnpike? The small one near the BACK two cylinders? So then, when you put it back on. the leak stopped, but the tank pressurized?
I don't mean to be a PITA, just trying to get the whole picture. Thanks, Nick.

 

[Germanvehicles]

Hi, I was just wondering if and how anyone actually fixed this pressure/ vacuum (most likely vacuum) in the tank issue. I have been having this same issue for 7 months and it was not always occurring but over the past few months it has been getting so bad that my engine shut down for the first time and then multiple times thereafter. Now I just leave the fuel cap off and it starts up fine and runs fine. I know Doctor A said there are two vent valves and a pressure compensating valve on top of tank and it seems if that blue pressure compensating valve is not functioning properly the tank will not vent and you will get this pressure/ vacuum in the tank. It must be a vacuum, as when the fuel cap is on tight my pump shuts down, as fuel is being delivered some air must come in to displace this delivered fuel and if not then a vacuum must occur. When I open the fuel cap then it starts right up with no issue other wise I can't get it going.

Here's the problem I am having. It seems that the pressure compensating valve is not working correctly and must be change but when I went to 4 different dealerships to order the part they could not find it. One dealership was able to find what looked like the part in the diagram but when I got the part it was not even a valve at all and just a 90 degree screw on fitting, that did not even exist on my tank. I went to some other Dodge and Mercedes dealerships and the same thing happened. I would like to resolve this problem, but does anyone know the part number(s) Mercedes or Dodge of this blue pressure compensating valve on the top of the tank or better yet can tell me where I can definitely buy it from (or what they did with there old one to fix this issue)? Can you please tell me, how did anyone resolve this issue about pressure/ vacuum in the tank.
Thank You

 

[glas1700]

My 2006 parts manual shows two vent valves, 5133917AA & 5133918AA. They are both right angle parts and may or may not be what you need, but they're the only valves shown.

Byron
07 Navion

 

[Germanvehicles]

Hi Byron,
Thank you for the reply. The numbers that you have posted are the ones that many dealers have given me. I have ordered the 5133917AA part which seems like the right one from there diagrams (it is on the correct section of the tank) but when I got the part it was wrong and the real kicker was that the part does not even exist on my tank. Dodge calls this a "valve" but when I got it and examined, it was only an elbow fitting and no valve. The second parts number 5133918AA is an elbow on the expansion part of the tank and connects to the vent hose which in turn connects to the filler tube. I did not order this one as it seems wrong away unless every dealership has the parts mixed up which I did not think they would. In any case the part they sold me was not even on my fuel tank so it can't be a mix up for the expansion tank elbow.

I have attached two pictures below of what the part looks like that they have given to me and the diagrams the Dodge and Mercedes dealers have. From what I am reading on the forums it seems that the correct valve is a little blue valve that connects to the 2 rollover/vent valves that is connect all together and then vents through this third blue pressure/ compensating valve.

Thanks again for your response as it is very much appreciated.

Trevor,
05 Dodge Sprinter 2500 High Roof