Fuel Cap

timjuhl · Posted: Sat Oct 27, 2012 1:31 pm Post subject: Fuel Cap

I have two different fuel caps that fit the filler of my M38A1. One is the well-known "fording" cap, the other one is pictured below. Are they both "correct" for the M38A1? Perhaps the latter used on Jeeps without the fording system installed?

Thanks!

Tim

_________________
Tim Juhl
1952 M38A1
1946 Aeronca L16A Army Liaison Aircraft

evanso1975 · Posted: Sun Oct 28, 2012 4:05 am Post subject:

from Ryan's M38 Reference Guide, that type entered production August 1951. The "fording" type (with the internal valve) entered production in 1955.

So, the type you show is correct for post-August '51 M38, and M38A1's built before or during 1955.

Owen.
_________________
Owen

1951 US Air Force M38
1944 F-1 1/2-ton Airdrome Trailer
1940 C15 Chevrolet CMP 11-cab
1939 DKW KS200 Motorcycle
MVT # 19406

timjuhl · Posted: Sun Oct 28, 2012 6:57 am Post subject: Fuel cap

Thanks Owen. I still have much to learn.

I had searched online for caps and found some similar but was confused a bit by the fact that this cap has a slight dome shape and a tiny hole in it.

It certainly does seal well.... Just needs to be stripped and reprinted. It came with a rusted M38A1 fuel tank circa late 1952.

Tim
_________________
Tim Juhl
1952 M38A1
1946 Aeronca L16A Army Liaison Aircraft

BCA · Posted: Sun Oct 28, 2012 8:10 am Post subject:

Tim, I have never seen an "early" "Pressurized Open Slowly" cap with a hole drilled in it. Check you cap closely- does it look like someone drilled in a vent hole. ... Brian

evanso1975 · Posted: Sun Oct 28, 2012 9:57 am Post subject:

Didn't pay much notice to the hole in your cap. Embarassed

I've never seen one with the hole drilled in it either. Mine's a slightly earlier model, but the operating principle should be the same:

No hole. The picture in Ryan's guide of your fuel cap type doesn't show a hole either. Thinking about it, a hole drilled through the cap would tend to void the "pressurized" statement.

Owen.
_________________
Owen

1951 US Air Force M38
1944 F-1 1/2-ton Airdrome Trailer
1940 C15 Chevrolet CMP 11-cab
1939 DKW KS200 Motorcycle
MVT # 19406

skyjeep50 · Member Joined: Feb 20, 2007 Posts: 606 Location: Illinois

The hole was drilled in the one cap as evidenced by the stamped wording on the cap - "pressurized open slowly". The fuel system can't be pressurized by expanding fuel vapors if there is a hole in the cap so it must have been drilled after manufacture. Perhaps some PO Bubba had problems with fuel delivery so he suspected the tank wasn't venting correctly or he took off the fording vent line...so let's put a hole in the cap!

Which begs the question - who was Bubba? I wouldn't think the military would drill holes in fuel caps after they stopped putting fording systems on jeeps - they had the vented version of the cap. And did they leave the fuel vent line and brake vent line that goes to the air cleaner? I would think that hole would have the potential for letting in water and dirt being exposed as it is.
_________________
1951 M38

timjuhl · Posted: Sun Oct 28, 2012 6:43 pm Post subject: fuel cap

I gave it a close looksee - the hole was definitely added later - it is just slightly off center, not the kind of thing you would expect from the factory.

My tank is vented thru a line to the air cleaner so an extra hole is not needed. I'll have to give some thought as to what to fill it with.

I haven't seen any caps that look exactly like mine - as you can see from the photo, it is slightly domed with a flattened edge about 1/4 inch wide. it also has tiny grooves around the circumference, extending half way down from the rim of the cap.

Tim
_________________
Tim Juhl
1952 M38A1
1946 Aeronca L16A Army Liaison Aircraft


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