Gas cap problem

[path1]

Why does my “gas cap off” light come on. Gas cap is on right, and the light came on, OK time for a new gas cap. Old cap looks good, but OK we’ll get another and see, maybe rubber gasket is bad. Put on new gas cap, after about 3 min “gas cap” light goes off. OK good. When we got back home I put on “old” cap (because it is locking type) and guess what, no more problems for the last 3 tanks.

I thought it might be me not having cap on right. Then I thought it might be some hose starting leak. Then I thought I’d post this here to see what others think.

2003 Ford Triton 5.4 in class C.

[C-Leigh_Racing]

Ok, well what if every time you stop for a fill up & screw the cap off & theres vaccumm in the tank, which does not affect the engine operating, but will affect the gen set operation unless you leave the gas cap loose so it can build a vaccumm, then the gen set will operate. What is going on there.
Neil

[wa8yxm]

Have a somewhat related problem (Check engine code p0455 which is "Evaporative Emissions Control Systems, Major Leak" And the most common cause "Gas Cap Off"

Posibilites include all the following:
Defective gas cap
Defective sensor
Defective vacuum pump
and in my case: Sticky solenoid valve

After a couple months driving with the occasional light on.. I have not seen the light for some time now (Save when starting the car) as the solenoid freed itself up with enough exercise.

Alas, you may need a pro's tool box to diagnose it less you have tried a new cap.

[rockhillmanor]

When we got back home I put on “old” cap (because it is locking type) and guess what, no more problems for the last 3 tanks.

That's because that is the CORRECT one. Those cheapies gas caps from the local store do not work and do NOT play nice with the on board computers.

I found out real quick there are 2 types of gas cap covers you can buy. The cheap one and the real expensive one.

The real expensive one is the correct and only one that works according to manuf specs.

I went to the store and just grabbed the cheapest one only to find out they don't work. Hold on to your pocket book when you find out what the correct one costs!

Seriously though go to a parts store and have them look up the correct oem one for your MH. Problem will be solved. Not having the right gas cap affects other functions also. Like you won't pass emissions with that other cap either. Gotta love them computers.

[BTPO1]

Fiverwheel wrote:
And some times it just waits for you to spend money on a part...then fixes itself:)

How true!

[Fiverwheel]

And some times it just waits for you to spend money on a part...then fixes itself:)

[BTPO1]

Sometimes there is a small piece 0f debris that keeps it from getting a proper seal which brings in the light. Sometimes just taking it off and putting it back on will do the trick. Some tell you to turn it till it clicks a few times. JMO

[enblethen]

I would look for the sensor. It should be around the vapor canister.