Stalls under load.

[Xevin]

-72 Campmobile

2.0L GD engine solid lifters. 6rib trans
Weber DFEV 32/36 carb from PO days.
Bosch SVDA distributor with Pertronix points replacement module. 8000 miles.

Last valve adjustment and oil change was 500 miles ago February 2020.
I haven’t run the bus in the last few months.

Issue- odd stalling.

Went to exercise the 72 yesterday. Started fine and idles fine. I pull out of driveway in reverse. No issues. Put it into first gear and drive about 30 yards and it stalls. Started it up, idles fine. Drive off 30 yards put it into 2nd gear, stalls. Perhaps I need to warm it up a bit. I usually don’t need to warm up this bus to drive it. Unless it’s in the 30s. It was Sunny and high 60s yesterday.

Start up again. Drive in 1st and 2 around the block everything seems and acts normal to this bus.

Get on freeway (Only 2 blocks from house). So I go down the on ramp in 1st gear and shift to 2nd it stalls. WTF. Start car up and let idle. No problems starting or idling. Rev RPMs up and down, no problem. Limped it home. Maybe 1.5 miles back to home. I had to play this game about about 15 times to get home.

When I say stalls, most of the time it would politely show me the idiot lights and have no power. Just dies.

Occasionally, it would impolitely “Buck” in 1st gear to let me know it’s about to stall and die.

The bus always started fine and idled fine regardless. I did adjust the idle screw to raise the idle. The idle would raise and lower as it should when twisting.

Thoughts of a leaking intake boot (I use Vanagon intake boots clamped on runnners) , Pertronix module taking a piss, flooding/float issue, dirty carb, and clogged fuel line crossed my mind.

So where to start trouble shooting? I’m thinking I start with cleaning carb. Is there another easy test to eliminate issues first I should look into?

About 4 years ago (10k miles ago) I had a dirty carb issue. The bus would run great with load and RPMs up but when I’d come to a stop light it, would die. Cleaning all the passages with carb cleaner solved that issue. I then installed a rebuild kit for good measure and maintenance.
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[aeromech]

Bucking and the type of carb you are using sounds like carburetor icing to me. That said, it sounds like you’ve been running this combo for a while and this just started. So if it will run under heavy load you must be getting fuel. The longer you idle the colder your intake runners get. Reach down and feel them and you’ll understand. That’s not good. Can you repeat the problem in your driveway or do you need to be moving? If you can repeat it then take a hair dryer and shoot warm air into your air filter. See what happens. You can also use the hot air on your intake runners and see what effect that has.
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[pioneer1]

My experience was a clogged fuel line/ filter. Enough gas would seep thru between each fail to fire up the engine for a few seconds.
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[Xevin]

Thanks Aeromech. I don’t thinks it’s icing. I’ve run this bus in just about all ambient temps, humidity, and altitude conditions one could think of. Never an icing issue. I can’t replicate the issue in the driveway.

Pioneer1, I could see that being an issue. Especially since it’s been sitting longer then usual. Just weird it happens under load. I can idle and rev it all day long and it purrs as normal.
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[airschooled]

Sometimes a wonky fuel pump will allow enough fuel to gravity trickle out for easy idle/1st gear operation, but give up under load. Fuel pressure testing would be good, as well as a filter inspection.

Robbie
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[Jeff Geisen]

To the OP, anytime an issue like yours crops up I will check dwell and other ignition system functions before getting into the abstract art diagnosing fuel delivery shenanigans. A bad condenser or coil can cause symptoms similar to those you are experiencing. If you are running Hall type or another style ignition system module there’s still everything else to check out even though points are not present.
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[TomWesty]

I will bet my whole bitcoin fortune on it being a plugged fuel filter or the like. Super cheap easy fix....Classic symptoms.
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[busdaddy]

[Xevin]

[Wildthings]

Maybe you have some water sloshing around in the tank? If so adding ISO-Heet should get you running. It just takes the tiniest amount of water to momentarily clog a carb jet.

[Ryan P]

I had a similar issue and determined it was carb icing. Letting it warm up longer helped. Wildthings directed me to check my thermostat. My thermostat had failed and the flaps were always open not allowing it to warm up.
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1969 Beetle
1972 Camper
1977 Beetle (Standard)

[Xevin]

Tonight after work the puzzle got the best of me. Some great suggestions here. One thing stood out in my mind. A clog/starvation of sorts. Maybe debris, water, or something else.

So about an hour ago, I said fuck it. Fire it up and ran it around the block and see what happens. While idling in driveway (less then a minute) I did release the gas cap and twisted it back on. I also took off oil cap (just barely to see if idle changed) Crank case pressure seemed good, as it wants to suck the cap back on. Nothing changed idle.

Off I go. The bus plays like it normally would. I can shift through first and second in the neighborhood like normal. The weather is 41* and 71% humidity.

Side note. My thermostat flaps have been wide open the last couple years. I have a working thermostat from Awesome Powdercoat I put on 5 years ago. I did a lot of testing with flaps operating and just wide open. Made no difference with the progressive Weber set up I’m running.

To continue my test drive. I take a couple laps around the block. All seems normal. I jump on freeway and run through the gears. All seems normal. Bus performs just as I know it does.

Thinking I got crud to take care of in tank and its time to change fuel filter. Plus, I need to run the bus more often.

Thanks all for the suggestions. I’m going to run it right now and see what happens. It is my favorite VW to drive. Crust and all.
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[Xevin]

Took the bus out. Fired up just like normal. Drove 5 miles. Freeway and sides roads. All is good.

However..........my gen/Alt light comes on when starting and not oil light.

Yesterday, the oil light and gen light always came on and shut off as one would expect while starting. Ugh.
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[Abscate]

You just got some junk inthe carb from sitting, and I bet it has cleared.

You can check for water in the gas by letting the car sit, then draining off500 ml into a clear glass container , look for cloudiness or layering - you won’t find any ,though.

You also might have bumped the alternator light wire off the back while checking stuff, too. Cheap things first!
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[Wildthings]

It has become my standard procedure to added FI/Carb cleaner to the tank when I first fire up a rig that has been sitting for months. Even supposedly ethanol free gas doesn't seem to age all that well these days.

[aeromech]

Found a rag inside a tank once. Similar symptons
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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

[RWK]

My interior gas tank coating began coming off after many years, caused the same thing,idle all day long but would not run past half throttle or under load.
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[airschooled]

Get up under there and gently wiggle the oil light with the key on, engine off.

Yup, you remember the necessary Yoga posture…

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[Xevin]

^^^^ I do remember
Checked it out this morning. Oil light works now as it should.
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[timvw7476]

hope it was debris in an idle jet.
but in the past when stalling between gears, it's been leaking distributor advance can, or bad gasket at intake manifold to head joint (loose bolts) or
leak at the power brake booster junction at the engine tin for me.
Frustrating stuff, but inexpensive stuff too. Also a good reason to check torque
of manifolds & heat exchanger nuts at the same time. Keeps it running & sounding nice.