70 Westy Stalls When Warmed

[stevo]

I have a 70 bus DP 1600, 34Pict-3 with 1-273 on the flange, plus an 034 single vac distributor that starts easily and runs until the choke is fully warmed, then stalls without fail. The idle cutoff solenoid tests positive with its clicking sound when ignition is on. An old friend said its bad gas but I'm skeptical since it has a full fresh tank anyway. Are there suggestions for me to consider so I can get past warmup, then later look at improved performance by swapping components?

[Abscate]

Put a vacuum gauge on it and check for leaks.

That red cap doesn’t look too “ sealed up”

Your 34-pict 3 was designed To run with a dvDA distributor, you can’t just throw what ever fits in there
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[wagohn]

To get beyond the "bad gas" theory, you could rig up a gravity fuel delivery with fresh gas.
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1976 VW Transporter, 2.0 FI Engine

[Abscate]

If it is a daily driver or been running ok , solar flares are more likely a cause than bad gas.

It’s a fools diagnosis on a running car
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[busdaddy]

Once it's warmed does the idle improve if you manually close the choke plate slowly?, or get worse?, or is there a spot where it gets better and then falls off?
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[aeromech]

Sounds like a vacuum leak. Check your boots
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Lead Mechanic: San Diego Air and Space Museum
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VW Type 2 1971 (3 ea.) 1978, 1969
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[Wildthings]

How cold is your intake manifold when this happens? It should be very warm after a couple of minutes of running.

[Abscate]

At 10 o/c to the red vacuum cap there is a large 1cm plug in the back of the carb. Those are notorious for loosening up on the 34 PICT3, and will cause running problems like you described.

Sniff and see if it smells like gas at all. If. So, it needs to be removed, sealed, and peened.
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[stevo]

This bus wasn't a daily driver but it does have a tank with 80% or more fresh gas. Both the red and black plugs to the rear of the carb are super tight. Once it is warmed the engine cuts out really fast. Anticipating that I returned the choke cam as it was quickly dying, once it passed the past tooth on the cam. Doing that prevented stalling.The spot where it falls off is immediately after that last tooth - fully warmed choke. Right before the last tooth it is running fine. While it was idling i sprayed carb cleaner at the boots and the base of the carb, no changes.

The intake manifold is not warm. Between the boots and the upright to the carb the manifold is cool; at the upright below the carb it is typically chilly. The 1cm plug had gas on it, but I also just sprayed it with carb cleaner. It is snug tight in there.

[SGKent]

best to set your idle mixture and try again. Cup your hands like you were going to strangle the carb. Move your hands in slowly towards the top of the carb from about 1' away. As you get closer does the RPM go up or down? If the RPM goes up then the mixture is too lean. If the RPM goes down then the mixture is too rich. When you have it adjusted properly you can get your hands very close to it without the engine changing RPMs.
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[aeromech]

Can you please post 3-4 nice shots of all angles of your engine? This could be something as simple as a missing hose. Sure sounds to me like your engine leans out and dies when the choke plate if fully open.
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[Wildthings]

With the ignition on, if you disconnect the idle fuel cutoff can you hear it click?

[stevo]

[Wildthings]

Have you checked the idle jet to make sure it isn't clogged?

[stevo]

[Wildthings]

[stevo]

On the intake right below the accelerator barrel nut is not one but two short pipes welded there. I only noticed one this whole time, figuring it was for a vacuum gauge. This morning I noticed the second one behind it shooting up at an angle. Perhaps it is for a brake booster. When I clog the second one (barely seen in the photo above) with a finger the idle increases. The remnants of whatever had clogged it before felt aged and rotted out. It is likely I'm not only looking at one, but two situations causing it to lean out. Earlier suggestion that a hose might be disconnected points right there.

[stevo]

2X post

[stevo]

Now that it is idling and the carb and distributor adjusted I took the bus for a test drive for over two miles to the post office. Going from neutral to first gear is awfully sluggish. Seems to want an extra abundance of gas. From first to second gear it is about the same. Higher gears, less problems. Power lacks climbing hills, especially in second. Abrupt stops at stop signs and red lights cause stalling.

I put a vacuum gauge on it and found it spikes and holds at 15 during warmed idle. I sprayed carb cleaner at the intakes, DP boots, and carb base including throttle linkage. No changes in rpms. What am I missing?

[Wildthings]

I would dump some Techtron or Lucas FI cleaner into the tank and see what effect it has. Might not fix your problem, but it is about the cheapest thing you can try.