Liquid Check Valve

[Mick]

Ok Jeep gods, found another potential problem...

I have a 74 CJ5 , with a AMC 304 that I bought about six months ago... When I bought it, the fuel gauge never worked. So today, I dropped the fuel tank to change the fuel level sender... The tank dropped really easy, cleaned up nicely, all complete with a new fuel level sender... I found the problem to be the ground was no longer connected to the old fuel level sender... But now, on to the curiosity...

In my inspection with the fuel tank dropped, I traced the fuel lines, vent lines, etc... I noticed that the liquid check valve had all three lines connected to it... As I was following the one line that leaves the check valve, I noticed that it was capped off... Upon further research, it appears that this line should go to a charcoal filter, which is no longer installed in Jeep... I also noticed that no rollover valve was never installed...

So... Here it comes... Should I leave things the way they are?!? No rollover valve and a liquid check that is plugged off... Or should I buy a rollover valve and charcoal canister and install them?!?

 

[rr41mag]

I put a fuel filter on mine

 

[hole]

Roll over valves come in handy in case you do roll it over IIRC the roll over valve is obsolete, not sure about the check valve. Again IIRC, someone on this forum had a post about finding a roll over from a DeLoren(sp ?) parts website, and someone else retro fitted one from a Nissan. Try doing a few searches to see if they pop up.

 

[Torxhead]

A layout of the rollover/check valve system can be found in most Jeep CJ repair manuals.

 

[jdarg]

I have a 75 w/ the same setup.

AMC didn't start using separate separator/check/rollover valves until 76 or 77 IIRC. That one unit in the rear fenderwell of your 74 serves all purposes.

There's a free 75 FSM online that describes testing and operation of it. Just google 1975 jeep service manual and you'll find it.

 

[Saddle Tramp]

I think the rollover liquid check value are important and should be maintained. Here is what it should look like from a 1977 OEM Service Manual.

 

[jdarg]

The 74 has a different setup than the 77.

 

[NorthwestCJer]

The roll over check valve is only operational if the entire system is functioning. If your charcoal canister is not properly hooked up, then the roll over and liquid valve will not do their function properly.

 

[jdarg]

I disagree, at least wrt the unit the OP has in his 74. Those have a needle valve/orifice that closes the vapor line upon inversion - whether or not anything is actually hooked up to the vapor line. Its mechanically actuated by the position of the valve, not by vacuum, etc.

The only detriment to the OPs current setup is the vapor is venting to atmosphere, which should still be fixed because if nothing else it causes the garage to smell like gas if its parked indoors, and of course the effect on the environment.

OP should just connect the line to the can again and he is good to go. Adding another rollover downstream from the 74's unit would be redundant.

 

[Mick]

Jdarg: I agree with you regarding my 74... Upon further research, my 74 never came with a rollover valve, only a liquid check valve...

The kicker is, the vent line on the liquid check valve is also plugged off... So, it is not venting to atmosphere... I was wondering if I should add a charcoal canister and reconnect the vent line to the charcoal canister...

 

[Torxhead]

I have always thought that the book got it backwards when they identified the check valve and the rollover valve. That plastic valve, whatever it is called, will close off when filled up with fuel like when having a full tank and going down a steep hill or an actual rollover. If it doesn't close off, fuel will run out thru the charcoal cannister, creating a fire hazard. The valve allows filtered air from the cannister to the fuel tank to replace the space used when fuel is drained out of the tank. If it doesn't provide that air to the tank a vacumn will form in it creating a problem with the fuel flow to the pump and can stall an engine. To check the fuel tank vent system, remove the gas cap after a drive and there should not be the sound of air rushing in to the tank. Anyway I think that other valve labeled as a rollover valve is just a back up valve. Thanks for sending in that pic Saddle Tramp.

 

[jdarg]

I would if it were mine.

Not venting the tank will also causing fuel delivery issues due to the pressure differential. My guess is PO made up for that by running a vented cap if its capped?

 

[Mick]

Ya... I see what you are saying about venting the tank. I will check the gas cap and see if it is a vented cap... If not, then I will purchase a charcoal canister and install it for fuel tank venting...

Thanks everyone!