Gas cap question

[viperman]

It appears that the M715 gas cap is the same as an M-37 and even the Duce is this correct?

Thanks

[brute4c]

The caps are the same...well...some of the caps have a lever on the inside that can be rotated when fording...closes the cap vent...and others dont.
The M715's use the non vented one...though the other can be used if you want.

[george walker]

Brute is correct, the fit is the same the application is not. The early design caps on m-38,38A1 m-37 dueces etc had a vent valve in them, which had to be closed before fording to keep out water. Around the mid 60's this valve was deleted, the tanks on later vehicles were vented another way, so the correct cap for 715 is a non vented cap even though a vented type will fit. As well early vehicles should not be fitted w/ a nonvented cap since their tanks are vented that way.

[brute4c]

Just to add an FYI...the M715 tank is vented through a hose to the air cleaner that comes off the side of the filler neck.

One problem to watch out for on that vent is overfilling of the tank where fuel gets in that vent hose...must have happened to mine before I got it...it had most of a tank when I picked it up...on the 60 miles ride home, the truck quit...like it ran out of gas...after checking some stuff under the hood, we tried removing the gas cap on a whim...it sucked in air like crazy. Problem is that the vent hose leaves the filler neck, drops low and then rises again at the air cleaner. The low area between the 2 ends is a catch for any excess fuel that is in the filler neck. When the low spot has fuel in it, there is no longer a path for venting the tank and there I was on the side of the road.

Went home, took off one end of the line and had a ton of crappy looking come out...problem solved since.

[fisherman]

So my venting gas cap is not stock then?

[viperman]

Thanks guys real good info.........
my cap is ok, but ratty.................
I just thought I'd look for a new one

[brute4c]

Theoretically none of these truck should have come with the vented one BUT it is well known that Jeep has a "tradition" of using whatever is on hand...kind of how some of the lae model trucks got the early style turn signal setup...if one or the other was available, it got used.

[randyscycle]

Mine has the vented cap with the valve too. I suspect that caps were replaced with whatever was laying around on the supply shelf too.

On another note: Since I have not tried to fill my tank at the station yet, what is the best way to avoid overfilling? Just watch until gas is at the bottom of the neck/elbow?

[brute4c]

Yep...thats my method.

I have seen people fill their truck right up to the top of the filler neck...of course that fills thevent...but you can hear the tank getting full and see it too...pay a little attention and you wont overfill.

[Binford]

You'll fill it until you can see gas in the bottom of the neck/elbow, but then it will take another several gallons and not seem to fill any further! I'm talking like 5 more gallons!

At least it's easy to see....