'74 bus, carb leaking
Posted: Mon Oct 01, 2012 11:30 pm
I opened the garage door to the near-overwhelming smell of petrol. Under the bus, passenger side, was a nice fresh pool. It seemed to emanate from the carb and not the line. Up up up the carb I looked, trying to find the point of highest egress. It was dripping off the low end of the arm for what this diagram unhelpfully implies is called "pump"; the low, bent end of 44 in other words but gas doesn't run through there so it's coming from somewhere else, right?
Clamping the gas to that carb stopped the dripping. The general area tidied (removed the air filter stuff) and cleaned up, I had my better half turn the key to 'on' to get the electric fuel pump running--fuel line unclamped now of course. Drippity-drip-drip gas was almost running out of...somewhere...not clear to me where. Key off. Carb off. The intake manifold was brimming with gasoline like a mug of coffee filled by an overenthusiastic waitress.
Okay, okay, I took the carb off and got gas all over the place even though I was holding it vertically. I called Halsey (it's past time when any but a West Coast shop would be open, see? And I know that name "Halsey" from all the scuttlebutt around here) and he said the waitress is prolly the float valve overenthusiastically stuck open, so I should take the six screws off the top of the carb and have a look. "Six screws? There're only five," I said but didn't argue further with Halsey, who was quite insistent. Maybe six is his lucky number. He also told me that aftermarket fuel pumps are more than happy to destroy float valves, which can "barely take 3 psi", what with their whopping 6+ psi and all. His advice on that point: install a 2 psi pressure regulator. As this problem didn't rear itself for ca. 1,000 miles with this pump and these carbs (or for ca. 13,000 miles with this same pump and a Weber regressive), I'll sit on this nugget until told otherwise.
It came off easy even though I only removed five screws--I used my imagination to remove the mysterious sixth for good measure--and the float looked fine. The float valve looked happy too, not backing out or anything. Muir shares a story in the Idiot Book about a similar situation where he managed to blow air through the float valve even holding the carb upside-down; I didn't have the same experience and can only get air through it when upright. Given Muir's surprise at his ability to get air through the upside-down carb, I assume mine was the desired result. Other advice Halsey and Muir independently offer is to knock on the top of the carb, more precisely on the top of the float bowl of the carb, with a plastic screwdriver handle to try to unstick the valve. I'm past that point.
Not quite sure where to go next I figured why not just put it back together? On went a new carbtop gasket (they sure don't seem to try too hard to get all those holes to line up with the holes on the carb, do they?). On went the carb. Again with the better half and the key and no leaky leak!? Hmmmm. My luck is never that good, plus wtf in the first place? I pushed the butterfly open and no gas is running down into the lower part of the carb--that's where I'd see something like that happening, right? The pump ran for a nice long while, and nothing.
Naturally the 1-2 valve cover is full of gas so that's another mess I cleaned up. The oil too--I almost forgot that one. What a disaster that would've been. (A curious thing when I drained the oil: At first, for a while, it's clearly just good ol' oil. But just as I catch myself thinking, "Well this is a waste of some 500 mile-old 20W-50" out runs gas gas gas. So I think that it's because gas floats on oil; naturally the gas would come out second. But then, it switches back to plain oil again. Huhn.)
It all got put back together, except the air cleaner stuff, because I'm gonna check in the morning and see if it's decided to start leaking again (i.e., the whatever's wrong in the carb is wrong again). Is that a decent line of thinking? I didn't put any oil back in it because what's the point if it leaks again, or so goeth my reasoning.
Thoughts? Observations? Criticisms? What parts do I need to get on deck?
Clamping the gas to that carb stopped the dripping. The general area tidied (removed the air filter stuff) and cleaned up, I had my better half turn the key to 'on' to get the electric fuel pump running--fuel line unclamped now of course. Drippity-drip-drip gas was almost running out of...somewhere...not clear to me where. Key off. Carb off. The intake manifold was brimming with gasoline like a mug of coffee filled by an overenthusiastic waitress.
Okay, okay, I took the carb off and got gas all over the place even though I was holding it vertically. I called Halsey (it's past time when any but a West Coast shop would be open, see? And I know that name "Halsey" from all the scuttlebutt around here) and he said the waitress is prolly the float valve overenthusiastically stuck open, so I should take the six screws off the top of the carb and have a look. "Six screws? There're only five," I said but didn't argue further with Halsey, who was quite insistent. Maybe six is his lucky number. He also told me that aftermarket fuel pumps are more than happy to destroy float valves, which can "barely take 3 psi", what with their whopping 6+ psi and all. His advice on that point: install a 2 psi pressure regulator. As this problem didn't rear itself for ca. 1,000 miles with this pump and these carbs (or for ca. 13,000 miles with this same pump and a Weber regressive), I'll sit on this nugget until told otherwise.
It came off easy even though I only removed five screws--I used my imagination to remove the mysterious sixth for good measure--and the float looked fine. The float valve looked happy too, not backing out or anything. Muir shares a story in the Idiot Book about a similar situation where he managed to blow air through the float valve even holding the carb upside-down; I didn't have the same experience and can only get air through it when upright. Given Muir's surprise at his ability to get air through the upside-down carb, I assume mine was the desired result. Other advice Halsey and Muir independently offer is to knock on the top of the carb, more precisely on the top of the float bowl of the carb, with a plastic screwdriver handle to try to unstick the valve. I'm past that point.
Not quite sure where to go next I figured why not just put it back together? On went a new carbtop gasket (they sure don't seem to try too hard to get all those holes to line up with the holes on the carb, do they?). On went the carb. Again with the better half and the key and no leaky leak!? Hmmmm. My luck is never that good, plus wtf in the first place? I pushed the butterfly open and no gas is running down into the lower part of the carb--that's where I'd see something like that happening, right? The pump ran for a nice long while, and nothing.
Naturally the 1-2 valve cover is full of gas so that's another mess I cleaned up. The oil too--I almost forgot that one. What a disaster that would've been. (A curious thing when I drained the oil: At first, for a while, it's clearly just good ol' oil. But just as I catch myself thinking, "Well this is a waste of some 500 mile-old 20W-50" out runs gas gas gas. So I think that it's because gas floats on oil; naturally the gas would come out second. But then, it switches back to plain oil again. Huhn.)
It all got put back together, except the air cleaner stuff, because I'm gonna check in the morning and see if it's decided to start leaking again (i.e., the whatever's wrong in the carb is wrong again). Is that a decent line of thinking? I didn't put any oil back in it because what's the point if it leaks again, or so goeth my reasoning.
Thoughts? Observations? Criticisms? What parts do I need to get on deck?