Did you check for fuel when it started hard?

Im curious about this one too, my VW does this and my Monza did this when it ran, about ten years ago.

_________________
I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

It turned nasty outside today - cold and windy. Got home late so decided to try one thing - I uncapped the nipple that is the vent for the fuel bowl. I depressed the accelerator peddle once and hit the ignition - she tried to start. I did not pump, but depressed the peddle about half way - she lit right off and settled into a nice smooth idle. Now, does this make sense? The fact that it had, essentially, no venting of the fuel bowl, was preventing things from happening like their supposed to, i.e., the accelerator pump not being able to squirt like it's supposed to? Does this make any sense?

dave

...well the pump will sqirt in any case, if there is fuel available. The vent blocked could make it more difficult for the fuel to flow to the various discharge ports. Keep us advised. I bet the choke could use some tweaking, too, but I'm glad it acted better for you.

D/W

_________________

If it ain't broke, fix it!

Tilt! The bowl vent isn't supposed to be capped. On a '72 or later car, it's supposed to run to the charcoal cannister (to the crankcase via the fitting on the fuel pump body casting on a '71 and on a '70 California car). On a '70 non-California and all '69 and earlier cars, the fuel bowl is supposed to vent to ambient. If it was capped, that will cause problems, but no, it won't in itself prevent the accelerator pump from working.

Dan, the cannister you mention - would that be the same cannister that the fuel tank vent line runs to?

I was just thinking that with that vent line capped, that the accel pump would still work, but perhaps, for some reason, not quite as well as it should - kind of like blowing into a straw with the other end plugged, then blowing into it without the other end plugged (I know, dumb way to look at it, but that's the way I see it in my feable mind ). I did'nt check to see how the fuel stream looked cause it is pretty cold and I just didn't feel like it tonight. But it did act much better.

dave

The very same one, yep. In the right front corner of the engine bay. In order for it to work, it has to be hooked up correctly. There are three large ports and one small one on the cannister.

Large tank vent line connected to the "TANK" port
Large carb bowl vent line connected to the "CARB" or "BOWL" port
Large purge line connected between to the "PURGE" port; the other end of this line tees into the PCV hose
Small purge valve trigger hose connects to the one and only small port on top of the cannister purge valve near the "PURGE" port; other end of this line tees into the vacuum advance hose

HA! I beat you to it while you were asleep, Dan (scroll way back). You're tripping from the corned beef acid, man...

D/W

_________________

If it ain't broke, fix it!

OK, some things are starting to make sense, now. The engine was missing a lot of lines when I got it and some were there, but not connected to anything. Hmmmm. I'm gonna have to find some "Ts" somewhere.

dave

OK OK OK OK OK...... With that bowl vent capped would the bowl not be pressurised with the car sitting, forcing the gasoline through the jets down into the carb throat, effectively emptying the bowl?

Ever seen a jerry can that has been left out with both caps tight? Swells right up like a balloon.

But even when the fuel bowl is empty the fuel pump should fill it in no time. I took my carb off a few times and changed the jets (tweaked the stepup rod bracket on the BBS) and even with an empty bowl the car lit off after about a second of cranking. So why would you have to crank and pump for ages to get it started?

_________________
I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Suprisingly not all veicles had the carb bowl vented to the charcoal canister. I had (might still have ) a Carter BBD from a late 70's slant that had a cap on the bowl vent nipple. I later did find in the factory service manual (vacuum hose routing charts) that some applications did indeed have the bowl vent capped.

Hmmmm. Steponme - good question. That's what I'm trying to figure out. My thought is, like you eluded to with the gas can, is that if the vent nipple was blocked, then pressure might build up and with no where to go, you would be unable to introduce anything else into it, i.e., the built up pressure would tend to force fluids (fuel) out and not let it in. Make sense? But it was much better last night. The weather is supposed to improve after today, so hopefully I can get on it when I get home after work - or this weekend - and take a closer look at the choke system.

dave

No. There is an internal vent as well as the external one. The only way the bowl could become pressurised is if both internal and external vents were blocked. The internal vent is the angled tube protruding through the inner sidewall of the air horn.
Not if the pump's weak or there's an air leak in the line upstream of the pump, see above.

True, but the one in question in this thread...should.
Yep, their internal bowl vent design was reworked to compensate...sorta. The "no external bowl vent" carbs tend to be a lot more persnickety with hot starting and hot idling.