Engine/Transmission (1998.5 - 2002) Fuel Tank Over-pressurizing

[SConklin]

My fuel tank is overpressurizing, and causing the cap to overflow with fuel. I have switched caps even, and it is the same. Can the tank be pressurized beyond the vent's capacity? Where is there another vent other than the cap? Or is something else wrong? I have a FASS on it too running 15-17psi.

 

[Thomas]

Your diesel fuel tank should be open to the atmosphere at the vent at the rollover valve on the top of the fuel tank model year 2002. Check for a cap left on at manufacture, a clogged vent, or a malfunctioning rollover check-valve.

 

[csutton7]

how long have you had the truck and two, when did this start--after some mod or just on its own????



did you install a separate return line for the excess fuel--



should be very little pressure as stated by Thomas..... chris

 

[HEMI®Dart]

More info on the vent:

http://www.dodgeram.org/tech/dsl/ISB/low_power.htm

 

[SConklin]

That link says that if it's not venting properly, it should have a vacuum. I have the opposite - it's building up pressure! What would cause this? I have the return from the FASS returning with a T-fitting into the fillup vent, like it's supposed to.

The truck had been sitting all winter, and I just got done putting twins, and reinstalling the head. I don't see how either of those could have any effect. Fuel pressure is constant all the time, and the FASS has been on for a while (never did this before). It just started when I got my truck running after sitting all winter.

 

[Thomas]

... I have the return from the FASS returning with a T-fitting into the fillup vent, like it's supposed to...

Is the fillup vent the item indicated in the attached drawing?



There is no way to pressurize the tank with the vent at the rollover valve (mentioned in my initial reply) functioning properly unless you increase the volume of the fuel in the tank very rapidly.



This recent thread explains the venting of the tank including the vents in the fuel cap.

 

[csutton7]

truck has been sitting all winter--



the FASS system has been on for awhile--



truck has been sitting all winter--



better check the vent return and see if something has got it plugged or is it kinked--



I'd start the truck--remove the cap and see what the fuel is doing---is it getting directed the wrong way all of sudden and coming up and out the cap(kinked or clogged) ---or does it flow back into the tank as it should---put the cap back on and see what happens---how much fuel do you see coming back to the tank, if you can see it---chris



how full is the tank--

 

[SConklin]

I'll check the return flow, and mess with the level in the tank, and see if it has any effect.

Can the rollover valve just go bad?

Thomas, yes, that's where the return is piped into.

Also, I know it's not the cap's fault, because I've tried two different caps, and the same result.

 

[Cooker]

Rollover valves do clog with dirt and debris over time and don't fo their job properly. I have replaced a few now on a several different trucks.

 

[SConklin]

Just filled up with fuel at the pump, and when I started the truck, it knocked really bad for a second, started up, and billowed white smoke (A LOT), and started gushing fuel out of the top of the tank, and the fuel cap. I also checked the oil, and although it is brand new (so it is pretty clear to begin with), it also seems to be very thin. Although I cannot smell any fuel in it, I suspect that it may have some. Also, the vapor coming from the fuel tank seems to have a crankcase vent smell to it, like oil - not fuel.



Is it possible for the oil and fuel to be mixing somehow? I had a friend of mine suggest that a seal on the injection pump could be bad, and allowing crankcase oil/vapor into the return line of the injection pump.

What other way could they be mixing? I know the connector tubes could be leaking, or the injectors, which would explain the knocking, but could that explain the pressure in the fuel tank too? I've never heard of that happening before...

 

[randrade]

My 02 had a similar problem, after i had installed a set of new 275RV injectors. I stop the truck and could hear air coming from the gas cap. Friend who is a diesel mechanic suggested something was up with the injector or poss the copper washers or maybe the o-rings. I bought all new washers,o-rings and reinstalled and the problem went away Hope this helps

 

[HEMI®Dart]

Sconklin,



see this old thread:



https://www.turbodieselregister.com/forums/showthread.php?t=94613&highlight=Fuel+tank+pressure

 

[SConklin]

I think that may be it. I had one injector that was difficult to install. It was just very tight and had to be forced into it's position. It may not have been lined up just right (everything fit, and torqued down correctly, so if it were off, it would be just off an imperceptable amount - but maybe enough to cause leaks). That thread from Hohn sounds just like my truck though, and everyone seems to be pointin to the injector. That would explain the knocking, and potential fuel in the oil too.

I have new injectors coming in this week. I'll hold off on driving it, and install these injectors. Hopefully, if everything goes right, that should be the answer... I really really hope so... This truck is getting very frustrating and depressing.

 

[csutton7]

when changing your injectors did all the copper washers come out with the old injectors??? did you install new copper washers on the new injectors?? do you have the injector lines and return line hooked up properly to the VP?? read below



I'm not sure the crossover tube would align properly if there was an extra copper washer still in the bottom of the injector hole of if you forgot one--but maybe it would just enuff to get things tightened up--now if this one injector or more are not sealing then that may account for oil/fuel mixing--



concerning the pressurizing I think that something has to be wrong with the FASS system or you possibly have the return line off the VP 44 hooked to the wrong port--ie you have the return line hooked to an injector port and an injector line hooked to the return port--in fact the more I think of this the more I think this may be it---chris

 

[bmoeller]

Your problem sounds just like what we had happen on the combine we were running in the fall of '03.



The injector hold-down was installed upside down on the #1 cylinder. Swelled the tank up big time. Did plenty of damage.

 

[SConklin]

The hold downs are installed the right way, and the VP44 lines are all hooked up properly. And I know there is only one copper washer per injector.

I think that the injector is just jammed in so tight, that it may not have lined up exactly right, or pressed down quite enough. My guess is that the copper washer is just a hair too loose, and it's causing it to blow by. Sound like a plausible answer to all these problems?

 

[csutton7]

bmoeller--good point---chris

 

[csutton7]

well if that one injector isn't sealing then that very well could be it--guess we know what you'll be doing shortly--keep us posted--chris

 

[pro99]

Hey SConklin your on the right track with the injectors. I had a few come in for this same concern at the DLR I work at. It's best that you remove all the injectors and take a look at the copper washers and o-rings. Sorry to hear you have to do this but you know what they say you have to pay to play :{ good luck on your findings... ...