30pict3 issues

Carbs & F.I.

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hambone
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Location: Portland, Ore.
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30pict3 issues

Post by hambone » Tue Feb 07, 2017 2:40 pm

HI.
Installed the "new" Bookwus carb on my '69 Bus. It acts like an 009 with the flat spot, most likely the accelerator pump. The throttle arm does not seat against the cam all the way without a light push.
Bentley says hook up a hose, measure output average of 10 pumps. Is there a driveway way to check this?
Car runs great at high RPMs but hesitates off of idle. Also runs well when cold, then the flat spot shows up when the engine warms up.
Also the idle air screw is almost fully seated. Is this related? Jetting?
Either way I think the carb has to come off for screwing around. Tempted to reinstall the 30/31 pict that has performed well for many miles... :salute:
http://greencascadia.blogspot.com
http://pdxvolksfolks.blogspot.com
it balances on your head just like a mattress balances on a bottle of wine
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asiab3
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Re: 30pict3 issues

Post by asiab3 » Tue Feb 07, 2017 10:31 pm

hambone wrote:HI.
1) The throttle arm does not seat against the cam all the way without a light push.
2) Bentley says hook up a hose, measure output average of 10 pumps. Is there a driveway way to check this?
3) Car runs great at high RPMs but hesitates off of idle. Also runs well when cold, then the flat spot shows up when the engine warms up.
4) Also the idle air (you mean the big brass screw?) screw is almost fully seated. Is this related? Jetting?
5) Either way I think the carb has to come off for screwing around. :salute:
1) Investigate this by removing the throttle cable and checking return. If good, loosen cable adjustment. If bad, check for binding throttle shafts and clean/lubricate.
2) Remove air cleaner rubber pipe and look down the carb, or use a good mirror and a flashlight. With quick stabs of the throttle, we should see a clean spray of fuel come out one of the brass fittings. This driveway test checks for fuel/no fuel, not output volume.*
3) If it runs well cold and balks when warm, I would assume the engine likes the extra fuel-to-air ratio that the choke provides. That's one clue that there's a fuel starvation issue.
4) How is the mixture (small) screw set? I find the "2.5 turns out" that everybody uses to be a poor base line. I have not found a "one size fits all" method to get the number of turns correct. Start five turns out on the mixture (small) screw and set the volume (big) screw to achieve your desired idle speed. Then turn in the mixture (small) screw until the idle is fastest and then starts to drop off. This is subtle, listen carefully. Go 1/4 turn back out on the mixture (small) screw and reset the idle speed with the volume (big) screw. If you note your current settings, and try this, how far off were you? Does it drive any better? Also if you noted your current settings, you can go back in case my procedure sucks.
5) I disagree right now. With a mirror, light, and small screwdriver, you can do a lot of testing in situ.

*We're looking for fuel here for function of the accelerator pump. There is a check ball or two in the accelerator pump circuit, and sometimes it can get stuck/varnished in place when a carb sits. This will allow no fuel into the accelerator pump diaphragm. Another "street" way to test this is to spray the accelerator pump with soapy water and stab the throttle. If the passages/balls are clogged, you might see bubbles, just like checking your bike tire or air compressor lines for leaks. This is my guess, as I've never had great luck getting "sitting" carbs to pop right into action without a cleaning. Gumout might work, but I had to do this once:

http://1967beetle.com/carburetor-rebuild/

Good luck, and let us know how it goes!
Robbie
1969 bus, "Buddy."
100k miles with me.
279k miles on Earth.

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Amskeptic
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Re: 30pict3 issues

Post by Amskeptic » Sat Feb 11, 2017 7:06 am

hambone wrote: throttle arm does not seat against the cam all the way without a light push.

runs well when cold, then the flat spot shows up when the engine warms up.

idle air screw is almost fully seated.

Slacken throttle cable a little and/or install a slightly tighter return spring.

Warm flat spot is likely to be a lean condition. Check main jet. Factory is 112, try a 117.

Idle air screw must be cranked out but good to help transfer circuit.
This carb needs a vacuum only distributor with a good vacuum diaphragm. No ifs ands or butts.
Colin

Image
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

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hambone
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Re: 30pict3 issues

Post by hambone » Wed Feb 15, 2017 12:28 pm

Yeah yeah. The problem is internal to the carb. OF COURSE I checked throttle cable tension etc you guys think I'm wet behind the ass-ears?
There is something binding inside, butterfly I haven't figured it out nor have I really tried. But I fixed the problem!
I re-installed the 30/31 PICT that I rebuilt 40k miles ago! It now runs like a greased hog!
Such a pretty 30pict3, what a shame that it runs like shit. I'm not really in a place for troubleshooting, this will have to wait another 10 years.
Thank you for the well-thought advice.
http://greencascadia.blogspot.com
http://pdxvolksfolks.blogspot.com
it balances on your head just like a mattress balances on a bottle of wine
your brand new leopard skin pillbox hat

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Amskeptic
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Re: 30pict3 issues

Post by Amskeptic » Wed Feb 15, 2017 7:29 pm

hambone wrote: you guys think I'm wet behind the ass-ears?
There is something binding inside,
This was Mike's carb, yes? Remember that Mike has enjoyed thoroughly testing me with all number of anomalies.
Colin
(have you had your ass-ears checked out? I am pretty sure there is a cure)
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

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