Fuel Smell/Raw Gas Odor

Okay Guy's,

I need to come to the experts!

I have recently rebuilt my original V6 motor in my '71 CJ5. The motor runs great and the Jeep is in great condition.

My problem is this; I have a raw gas odor that I can't get rid of. I found several small leaks including a leak on top of the tank through the sending unit. I have repaired gas hose, replaced gaskets and have completely (visually) stopped all leaks from the rear tank to the motor on up to the carb. I replaced the fuel cap complete with a new gasket.

The motor utilizes the original oil bath air cleaner as well as the original 2 barrel carburetor.

What the heck can be causing a raw fuel smell? The smell seems to increase if I'm under a slight load, like driving up a long (slight) incline on the freeway.

I do have a vapor recovery system located in the left (driver) side rear corner. Could this cause an excessive fuel smell?

Please give me your thoughts.

Thanks, Pat

 

leaking gas cap?

 

can you feel any wet spots? try parking it up on ramps for a couple hours and see if you can find any spots

 

No not that. I placed a new gas cap complete with a tight gasket.

 

Heck Geoffrey,

I do better than that. I place it on my car lift and walk around underneath of it with a flashlight. I follow all the fuel lines and cannot detect any leakage at all!

 

Hard lines or rubber?

All in good shape, as you appear to have explained already.

 

I replaced my gas cap on mine with a replacement from walcks4wd.com and now every time I take a corner fuel sloshes out and it stinks like gas, until the fuel level is lower. if I reach down while driving I can actually feel the gas dripping off the gas cap. So just cause its a new cap doesn't necessarily mean it couldn't be the culprit. and when Im at the gas pump I do not top it off, I insert the nozzle all the way in and when it kicks off im done. Unfortunately someone in the world doesn't care about producing poor quality products. also another thing you could check is the float level in the carburetor or if the fuel pump is pumping too much pressure and flooding it.

 

It's a vented cap, it's designed to vent. It shouldn't be that bad though IMO. I only have leaked gas once at Odessa Canyon, I was starting to get real off camber, more than a city turn anyway.

 

do you have the underseat tank? if so and the filler tube body gasket is wore out then the sloshed out / vented gas will run back inside down the filler spout

 

If you can't see any leaks anywhere, you might try changing your carbon canister filter. If that doesn't help, there is a fuel shutoff valve in the expansion tank that the four vent tubes from the fuel tank run to. Two of those vent tubes go to the front of the tank and two are located in the rear of the tank. The shutoff valve is to prevent raw fuel from entering the expansion tank from the rear fuel tank vent tubes when driving or parking uphill. If your canister filter needs replacing and/or that shutoff valve is stuck open, maybe this could be the cause. The expansion tank would have to be replaced as a unit. This is from the FSM...hope it helps.

 

I think I'll have to check the float level. That's about all there is left!!

Thanks, Pat

 

Thanks a lot for some direction! I'll have to see about replacing the carbon canister. Just so I'm on the right track, this is found inside the unit located in the left rear corner of the vehicle, the one where two lines off the top of the tank go into.....correct?

Also, I'll have to check the other two ports coming out of the canister. If I recall correctly, there are two ports that have no lines attached to them. Could these require rubber lines directed down towards the rear of the vehicle?

Thanks again, Pat

 

No, a '71 with vapor recovery has a sealed cap. There's no point to having vapor recovery unless the cap is sealed.

When you fixed the leak in the sending unit, you may have started forcing fuel out somewhere else due to vapor pressure in the tank. The vapor recovery system is supposed to handle that.

Do you have the factory manual for your Jeep? The tank and the vapor recovery canister are shown in sections 4 and 4A.

 

The charcoal canister is located in the engine bay. The canister at the rear, by the fuel tank is the expansion tank. The fumes from the fuel tank go into the expansion tank and then up front into the charcoal canister. It's a closed system, so if any of the lines along the entire system are disconnected, gas vapors will exit to the atmosphere. There should be a line running from the expansion tank to the charcoal canister and then back out of the charcoal canister and through the PCV valve to be reburned. If any of the rubber hoses are missing, be sure to replace them with fuel hose. BTW, you are right about this being the place for experts. I'm not one of them. I just took their advice and bought a factory service manual.

 

Use GOOD fuel hose. A lot of the import stuff is marked for "fuel" but rots out in one season.

 

Take a look at these drawings from the 1972 manual. Pretty sure the '71 system is like this.





The tank at the back is an empty can that allows for expansion. There's nothing happening back there other than plumbing. The tap for a return line on the fuel sender is capped. The vent line with vapors from the expansion tank goes to the front of the car.

You have to have some way to draw the fuel vapors into the engine to be burned - so a hose for vapors has to go from the tank to the front of the car. Under the hood, you could have one of two types of connection. If the '71 225 is like the inline 6s in 1972, there will be no charcoal canister. The vent line from the expansion tank in the rear will go through the limit fill valve and into the valve cover. If it's like the V8s of 1972, there will be a charcoal canister under the hood.

 

Looks like I need a factory service manual.

Also, it looks like I need to attempt to find a charcoal canister under the hood. I'll bet that has been removed somewhere along the line.

Thanks again, Pat

 

Thanks a lot for the schematics Tim. I'll have to attempt to track these lines down.

Pat

 

You may have never had a charcoal canister. The 6s from 1972 had vapor recovery, and the vapors went directly into the valve cover - no canister. See figure 3. Your 225 may be like that. Notice the limit valve - that is meant to stop any liquid fuel coming up the vent line and going into the canister or engine (depending on the engine type). You'll definitely have something like that, and there may still be a line running along the frame from back to front for the vapor.

 

Okay, I'll check that out.

Thanks again!