sluggo42

When I bought my truck, the guy told me that the gas cap was worn out and was triggering some code that turned on the check engine light.
He is using a locking cap that is fine, and the old cap is still there. I find the locker to be a major pain in the ****. Is there really a code that comes from a worn out gas cap that isn't sealing as well as a new one?

camelracer

It' true. The OBD systems in all vehicles nowdays monitor for loose or leaking gas caps and will set a code and turn on the check engine light. It may take a few start cycles to turn the light off after it's repaired.

Thomas

The fuel tank on your 24-valve Cummins/Ram is open to the atmosphere via a vent at the rollover valve on the top of the tank. If the pressure inside the fuel tank is anything other than atmospheric pressure, you have a problem. There is no system or circuitry on your Ram to monitor anything about the fuel tank (and its cap) other than fuel level.

infidel

Not true. The cap is designed to hold 3psi pressure or vacuum.
I have no idea if there is a sensor or not in 24 valve but have read of many people turning off the CEL by tightening their cap. It could be that this function was only used on a limited number of model years.

Scramblinman

Yup, in Washington State, they even check the fuel cap with a vacuum gauge as part of the emissions test.

Can anyone else hear the vacuum seal being broken and air rushing into the tank when they loosen the fuel cap?

Thomas

This is true—most likely because P/N 5278632AA CAP, Fuel Filler is the only filler cap listed in the model year 2000 (Mr. Sluggo's year) Mopar Parts Catalog. The same cap was used for gasoline & diesel fueled Rams. The evaporative emissions control system on the gasoline fueled Rams requires the vent functions on the fuel cap.

Part number 52127666 VALVE, Fuel Tank Rollover Safety is used in the fuel module in the tank of diesel powered Rams. When the truck is upright, the valve is open to the atmosphere. This is easy to verify with a new rollover valve in your hand. The only time the vent functions on the fuel cap would come into play will be if the vent on the rollover valve is clogged by debris or careless vehicle assembly.

bigdav160

Thomas is correct.

No evap system on the diesel and no trouble codes/CEL associated with it.

curts99

a trouble code being set on a diesel for a loose gas cap no way not on that year model not sure on the newer ones. on a gas vehice yes i see it all the time at work a evap code and the gas cap is loose. not the case on a diesel you can drive without the cap and no code will be set.

sluggo42

I find it hard to believe that with the FP issues that there would be a vacuum on the tank. I could see it if they somehow pressurized the system to help out the VP44.

Devin_01

Well I tapped into the vent line on the filler hose for my aux. tank and my truck hasent set any codes or gave any problems.

piperca

No such problem with diesel. I ran with my cap loose for many miles, when I was having a problem with my rollover valve not doing its job and creating a vacuum in the tank.