Gas cap keeps loosing its seal

[lrlima]

1996 5.0 w/120k

I pulled a code (cant remember which one) but it was for a vacuum leak. Anyway, in my case it was a faulty gas cap. Replaced the gas cap and all was good for about 6 months. Then same code came back...put a little oil on the gas cap rubber seal and it fixed it for a while longer but the CEL came back. When I take the cap off, I dont get the hiss which I suspect tells me its not holding vacuum.

My question, does a locking gas cap help this problem or does it help hold the seal better? Or is there something obvious I can do to help this. Truck runs great though. Thanks

 

[Turdle]

Hmm,
I wonder if the purge solenoid vent tubes are clogged, or have fallen off, or split.
The purge solenoid is located in the driver side front fender well area, below the battery.Look for green plastic
--the vent and cannister are in the back-by the tank
I have seen things such as tires knocking the hoses off the solenoid valve-battery acid dropped on it causing a hole, you might take a look.

I have the part number for a locking cap, and I have my regular cap still. You can have it if you'd like to try it-

 

[MONMIX]

could this also result in a " check gas cap " light ?
Mine has been on for a wile and I keep checking it but the light never goes out.
I will open it from time to time and there is no pressure.

 

[MountaineerGreen]

Its P0442- small evap leak.

I have been chasing it for over a year now on mine. It comes on intermittently although I have replaced gas cap, purge solenoid valve (the one by the spare), the hose that runs from the front valve things to the upper intake manifold. I drove 3300+ miles and it never came on during my Moab trip, but I came home and the CEL came on the next day on the way to work.

Now, it hasn't come on for a few weeks now, haven't changed a thing. I just check my codes and clear em if its that one. Annoying if you don't have an easy way to do it though.

 

[lrlima]

Thanks for the replies, and thanks JT for the offer. I'll probably just go buy a locking cap today to see if that works. I wonder if it helps seal better anyway. At least I'm not alone with this problem...

 

[MONMIX]

no CEL, just a gas cap light for me.

 

[MountaineerGreen]

Do I have a gas cap light?? I've never seen it if I did.

 

[CDW6212R]

FYI, I have a locking gas cap on my 99 work truck, and the seal is definitely no better than the stock cap. I leave my truck at work occasionally, so I bought it for security. I got mine at Walmart, it's the good brand, it was about $24.

Don't buy a locking cap to gain a better seal, but the price of gas may be a good reason. Good luck,

 

[MONMIX]

Do I have a gas cap light?? I've never seen it if I did.

If you do it will light up when you turn the key on.

 

[Turdle]

If you do it will light up when you turn the key on.

You wouldn't mind looking at your filler in the AM for me?
I wonder if there is a switch actuator of some sort back there--

Where on the cluster is the light? I don't have one--

I always thought the clusters were the same from 96-01---ooops

 

[Turdle]

Locking gas cap