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Fri Nov 15, 2002 3:14 pm

I went to replace the fuel gauge sending unit in my 77 bug and as soon as i loosened one screw, gas came streaming out like the tank was pressurized. Is this normal? If it is, how do you release the pressure to remove the sending unit, and if not, what could cause the problem?

Although its a 77, the engine is a cabuerated '73 with stock mechanical fuel pump. Most (if not all) the smog control stuff is removed (I know for sure that the charcoal canister in the rear is removed, and all the other small tubes from the tank dont go anywhere)

Fri Nov 15, 2002 3:46 pm

Take the fuel cap off before you do any fuel system work. This will release all pressure. Yes, it's normal. That's vent caps are made. Amazingly enough, even though I give you this piece of advice, I somehow forget this about 50% of the time.

Sat Nov 16, 2002 12:07 pm

I forgot to mention that I did take the fuel cap off - does this mean that maybe another hose from the fuel tank to the filler neck may be disconected (ie clamp shut somewhere)?

Sat Nov 16, 2002 6:11 pm

If it is similar to my 74, upon lifting the cargo matt, you will see two hoses. One is the big hose that you pour gas into the tank and the second one is a thiner hose that is connected below the big hose. This hose catches any overflow when filling up. If you disconnect this hose at the tank it releases all the presure. Make sure that your fuel level is below half.
Good Luck

Sun Nov 17, 2002 10:32 pm

You shoud NEVER have pressure inside the fuel tank, and the VW should NEVER use a vented gas cap.

If the charcoal canister stuff has been disconnected, what you need to do is....

1. makes sure the hole in the fan shroud is blocked up (it provided air to the charcoal canister) - so you don't loose cooling air. The hole in the air cleaner (from the canister) should be blocked off too. The third line from the canister runs up to the front of the car - this is now disused but can be left in place (it was the actual vent line to the tank with this "emissions" venting).

Up front at the fuel tank - you have the main filler neck and close to that - a 3/4" breather. This breather should have a T in it for a thin line - this thin line will now become the main vent. Your tank may have one or two thin vent outlets in the rear left corner of the tank. Both of these (if you have them) should have a thin line running around the back of the tank to a point close to the T in the 3/4" breather. Now you take a long rubber fuel line and connect it to the 3/4" breather, then make a new T connection close to that for the line around the back of the tank (if your tank has it), and then run the long line up-and- over the instrument cluster so it's the high point in the system, and then back down the left side of the tank (there may be a slot in the bodywork under/left of the tank) and so under the bodywork. It just hangs down under the car there. If you have an expansion box/tank next to or above the tank - this is disconnected completely.

This arrangement replicates the "pre emissions" venting system, where everything is vented through the up-and-over vent line.

You must never take a short vent line from the 3/4" breather straight down the right of the tank - you'll get fuel smells in left corners. A vented fuel cap may also cause fuel smells in hard left cornereing (as I said before - the VW does not use a vented gas cap.)

Sun Nov 17, 2002 10:33 pm

Sorry - forgot to add my sig to the last

Rob
Rob and Dave's aircooled VW pages
Repairs and maintenance for the home mechanic
http://www.geocities.com/aussiebug1970/

Wed Nov 20, 2002 5:19 pm

Why dont you want vented gas caps?

Wed Nov 20, 2002 8:11 pm

69 beetle said:
>Why dont you want vented gas caps?

As I said in my post above...
"A vented fuel cap may also cause fuel smells in hard left cornereing... the VW does not use a vented gas cap."

The filler neck is only slightly above the level of the tank and so in left hard corners the fuel flows up the filler and out the vented cap into the recess. So you get a fuel smell inside the car, and then your girlfriend/wife wants you to buy a Toyota :-)

Rob
Rob and Dave's aircooled VW pages
Repairs and maintenance for the home mechanic
http://www.geocities.com/aussiebug1970/

Wed Nov 20, 2002 8:13 pm

Yea thats happened to me before, only my car is white and you can see the gas stains, I thought other that that obvious reason is that the presures would screw the engine. Thanks though... !