mep-803a fuel cap vent

[m32825]

So I got a new fuel cap and now I can read the writing that says vent open and closed, also that vent closed is for vapor lock and fording. I searched through the TM 9-6115-642-10 operator's manual but see no references to the fuel cap vent. Did I look in the right place? Do any of you guys ever turn it to the closed position? Thanks!

-- Carl

 

[Guyfang]

Unless you are going to ford a stream, or use the gen set as a fishing sinker, put it in open, and forget it's there for the rest of your life. No place is it in any gen set manual mentioned. Sadly, in one instance, someone did just that. Closed 7 gen set fuel caps, and thought it was a good joke. I spent several hours " enjoying " the joke. We all assumed that since all the sets would not run, the common denominator was fuel. All the sets were running on Aux fuel. Then someone asked me why there was a vacuum on the fuel tank. Then it was clear. Probably the guy who did it was standing in the room with us. Real funny.

 

[m32825]

Thanks for the info, Guy, that must have been frustrating! Did the units start and then slowly die as the vacuum built, or not even start?

-- Carl

 

[Guyfang]

In the beginning they started. Then ran, slowly died. Would not start later. Some, that were not super air tight, sat a while, and started again, but then died. It was in a sister unit. They had the problem a day or two, before they gave us a call, 5 KW's. I have twice seen the fuel tank collapsed, from this problem. Should not even call it a problem. An "oversight".

 

[Light in the Dark]

I've only encountered units with the fitting closed that have been 'preserved'. Otherwise... they have all been open. A small, easy to overlook detail for the casual owner.

 

[dav5]

I thought I had read everything on the 803A but obviously I have more to learn. I have been cranking it right tight. So I assume you turn it to the first resistance and not to the final stop?
I think what saved me was that I have an aluminum insert on the top of the tank that the wellnut fits into[ which doesn't seem to be present in any other 803a that I have seen] that is impossible to seal even after installing new wellnuts.

 

[Light in the Dark]

Look at the underside of the fuel cap... you will see a little butterfly valve. This can be set to OPEN or CLOSED (if you are moving equipment over terrain, etc).

 

[m32825]

Pictures... better late than never!

-- Carl

 

[Guyfang]

To make it better, I have seen them with NO open or closed printed on the cap. In the early 70's, I ordered caps, because we were supposed to get ready to do a load up on C130's at Gibelstadt. The Zoomies did not want to let us on the birds, with fuel in the gen set tanks, without new fuel caps and we had to turn the valve to closed. Well, we had the new caps, and when we looked, nothing. The valve was there, but not marked open/closed. So we lied.