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RocketSurgeon
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Joined: May 26, 2005
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Location: Roseville, CA
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 Posted: Tue Feb 10, 2015 2:29 pm Post subject: Fuel shut off valve? |
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Question for the gurus.
Did a 71 bus come equipped with an in line fuel shut off valve?
http://www.thesamba.com/vw/classifieds/detail.php?id=1127717
Follow up question. Are new fuel pumps today built with an internal shut off valve? The origional rebuildable ones do.
My bus has a tendency to flood. Not terrible but it stinks. I've swapped the needle valve, replaced the float, double checked the float level, swapped the carb, went back the origional carb, checked the idle shut off solenoid, replaced the pump, checked the pump pressure, checked pump volume....
Everything is to spec. The bus runs better than it ever has! It takes a few too many cranks at startup and reeks for a minute after.
Diego
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Last edited by RocketSurgeon on Tue Feb 10, 2015 2:38 pm; edited 1 time in total |
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Brian
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| Posted: Tue Feb 10, 2015 2:32 pm Post subject: |
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Pretty sure they did not come with one.
New pumps are just pumps. I would stick with the mechanical one and just get a fuel pressure regulator. Not the spin cap one, but a quality one.
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RocketSurgeon
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Location: Roseville, CA
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RocketSurgeon
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| Posted: Tue Feb 10, 2015 2:46 pm Post subject: |
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Thanks goat. What kind of regulator are you talking about?
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Brian
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busdaddy
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Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Tue Feb 10, 2015 4:52 pm Post subject: Re: Fuel shut off valve? |
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The short answer from what I can tell is yes, the anti gravity feed valve was added when the fuel pump changed from the rebuildable style to the roundish topped ones. Most got ditched the first time any fuel line work was done as the uneducated saw it as just another peice of power robbing smog equipment.
Desertbusman tried one a couple of years ago when he (like all of us) was experiencing vapor boil in the lines when parked thanks to our fine modern fuels. I can't recall the full results of his testing but in the end he went with a solenoid at the tank outlet IIRC.
Here's some reading for you:
http://www.thesamba.com/vw/forum/viewtopic.php?t=523787&highlight=flooding
Brian, what do you mean by "solenoid in the carb"?
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Wildthings
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| Posted: Tue Feb 10, 2015 5:43 pm Post subject: |
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| Brian wrote: |
Yea if you have an electric solenoid in the carb you're good to go.
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Not sure what you are meaning, but the idle fuel cutoff will not prevent fuel from leaking past the needle valve. |
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RocketSurgeon
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Location: Roseville, CA
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| Posted: Tue Feb 10, 2015 8:28 pm Post subject: |
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Sorry brian, your not goat 
I think Brian means to say a 34 pict vs an older 28 with no solenoid cut off.
So can we say that those with an older rebuildable fuel pump ( with the built in valve) still experience ethanol fuel boil?
I also want to mention I went from 1/4" fuel line to 3/8 gates baricade line. Thinking less fuel in the line would help... somehow... It didn't.
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airschooled
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| Posted: Tue Feb 10, 2015 8:44 pm Post subject: |
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I've always wanted to try to rebuild an old pump for this exact reason.
You tested your fuel pressure? What was it?
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RocketSurgeon
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| Posted: Tue Feb 10, 2015 8:48 pm Post subject: |
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2.8 psi
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busdaddy
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| Posted: Tue Feb 10, 2015 8:57 pm Post subject: |
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| RocketSurgeon wrote: |
| I also want to mention I went from 1/4" fuel line to 3/8 gates baricade line. Thinking less fuel in the line would help... somehow... It didn't. |
More room for boiling.  How did you even clamp it on there?
Modern cars keep thier fuel under constant high pressure and use it through tiny fuel injectors, it's made to vaporise easily from droplets, since it's under pressure and circulates constantly less ingredients are required for preventing low temp boiling.
A few have suggested a bleed back to the tank to relieve the pressure from boiling, a Tee near the carb and small carb jet shoved into the return line is the simplest method I've seen proposed, so far no actual long term results posted by anyone as to if they actually did it and it worked. Adding a return (preferrably above the fuel level) is one of the major sticking points with this idea.
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RocketSurgeon
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| Posted: Tue Feb 10, 2015 9:09 pm Post subject: |
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Sorry I meant 3/16" 
I don't know if I like the idea of atomizing fuel outside the carb with a jet or other small orifice. That might turn what would have been a fire into a bomb 
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kreemoweet
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| Posted: Tue Feb 10, 2015 11:32 pm Post subject: |
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| RocketSurgeon wrote: |
| Did a 71 bus come equipped with an in line fuel shut off valve? |
I think not, nor did any of the early Bays. The Bentley manual makes no mention of such a device. The VW parts manual makes no
mention of any such device. The Bentley shows that the 68-70 busses had the "round-top" VW/Pierburg rebuildable pump, which does
not have a shutoff valve (whereas the "square-top" used in other vehicles did). The '71 bus pump shown there appears to be identical to the pump
used on '71 and some '72 bugs, which did not have a built-in shutoff valve. The mechanical pump used on carbed late bays appears to
have many parts identical to those used in the "square-top" Pierburg pump, and does have a fuel shutoff valve.
It's hard to tell what VW was thinking: that the fuel tank being so close to the carb would mean parking on a steep hill wouldn't result in much
elevation difference (and hence gravity pressure difference)? Anyway, VW decided the carb float needle valve did not reliably stop gravity flow of
fuel, but nevertheless continued to perform its main function (regulating flow from fuel pump output) quite well. Perhaps they did when brand-new,
but not too long ago I disassembled half-a-dozen used needle valves, and 5 of them had a very pronounced groove worn in the "needle" (which is more
of a cone than a needle) where it contacted the very narrow seat chamfer, so they probably did not provide a completely tight seal.
FYI, I have 2 aftermarket Brosol pumps of unknown vintage, one alt-style and one gen-style, and blowing mightily into the inlet results in zero flow
from the outlet, so they either have cutoff valves inside, or else the check valves are extremely strong, totally unlike the stock pumps VW used, whose
check valves were mosquito-weight.
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Last edited by kreemoweet on Wed Feb 11, 2015 12:06 am; edited 2 times in total |
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busdaddy
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| Posted: Tue Feb 10, 2015 11:35 pm Post subject: |
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The jet is in the sealed return line you add back to the tank to act as a restrictor so fuel pressure is maintained when running but bleeds off as soon as the engine stops, then when the lines get hot the pressure doesn't build and overcome the needle and seat. 
Spraying fuel overboard would be a bad idea.
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RocketSurgeon
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Location: Roseville, CA
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| Posted: Wed Mar 18, 2015 11:07 pm Post subject: |
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Ok, I've reached my boiling point... This needs to be solved.
Here is my first experiment.
A tee before the pump and after the pump. The tee after the pump has the return end filled with JB weld and I have drilled a #76 (0.5mm)hole through it to releve pressure back to the tank line. If it works I will have to make it more elegant. Right now it looks like a hose clamp bomb. And is a fire hazard...
I will report the results.
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airschooled
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RocketSurgeon
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| Posted: Wed Mar 18, 2015 11:25 pm Post subject: |
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Although the installation looks similar, I'm going in a different direction than the original valve.
This was part of the inspiration.
http://www.thesamba.com/vw/forum/viewtopic.php?t=389630
I just want to bleed off the pressure that builds in the line after the pump after the engine is shut off.
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airschooled
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| Posted: Wed Mar 18, 2015 11:34 pm Post subject: |
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| RocketSurgeon wrote: |
Although the installation looks similar, I'm going in a different direction than the original valve.
This was part of the inspiration.
http://www.thesamba.com/vw/forum/viewtopic.php?t=389630
I just want to bleed off the pressure that builds in the line after the pump after the engine is shut off. |
Ahh I see the similarities. But I think as our fuels boil and increase pressure, the stock valve would have the same effect, through a different method. Yours would bleed 100% of the excess pressure off, while the stock would only bleed off anything over a set value (probably close the the 3psi of a good pump.)
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