1973 T4 Dual Carbed Engine Idle Issue

[thewalrus]

I'm having an issue getting my bus to idle after starting and warming up. It'll start right up on the first try, then idle for a few seconds and then die down and stall.

1973 1.7L dual carbs.
Timed to 8.5* AFTER TDC (Per the Bentley)

So far I've done the following:
Checked for Vacuum leaks
Clean battery connections
cleaned and replaced the cap and rotor
checked spark plugs
Sprayed the carbs with carb cleaner (Rebuilding them is on my winter to-do-list)
Swapped the coil
Swapped the distributor
Swapped back in the solid points (I had Pertronix electronic points)

NOTHING I've done so far has helped or changed the symptoms. The only other thing I can think off is to swap the vacuum advanced cans. I dunno. I'm scrapping the barrel here. I really should know this.

Original Distributor:

Close up:

Broken rotor I found while inspecting (REPLACED)

Replacement distributor. I think it's for a F.I. Super Beetle (??)

Side by Side. Original on bottom:

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'73 Transporter 1.7L Dual Carb

[Spike0180]

What is with the sheet metal screw in the bottom dist?

I would suggest looking into your fuel delivery. Make sure your fuel filter is clean and you're getting good clean fuel.
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Brutis Patches Izabich: 1970 VW Transporter - 1776cc DP
Current State: Projects never truly end...
Location: Grosse Pointe, Michigan
Other cars: 2003 F150, 2003 Jetta GLI vr6-6sp

Sambastic: adj; the quality of being nit picky, elitist, expecting everyone to do things the way they believe is best with no regard to situation, "sambastic"

[thewalrus]

[Wildthings]

Try static timing your engine at 7.5° BTDC, if you are static timing your engine to 8.5° ATDC your timing is going to be extremely retarded. Once you get it running set your timing to 28° BTDC @ 3500+rpm with the hoses off and plugged. Ignore the book timing unless you have a new out of the box distributor. Do check that the vacuum retard can holds vacuum many, as most will not at this point in time. If the retard can will not hold vacuum you need to remove the retard hose and plug the vacuum port on the carburetor.

Also an engine that starts and then dies may have a bad vacuum leak.

[lil-jinx]

Set it as Wildthings said,but remove and plug the vacume line at the retard side of the vacume can.
If you want to set it as per the book,then the retard side has to be working.
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https://www.thesamba.com/vw/forum/viewtopic.php?t=620186
https://www.thesamba.com/vw/forum/viewtopic.php?t=668799
1974 Bay Westfalia. she likes to be called Ethel.
1968 Dune Buggy
1974 parts bus
A smart man learns from his mistakes,a very smart man learns from other's mistakes.

[aeromech]

I doubt it’s a distributor issue because it starts and runs. I’m thinking it’s fuel related. Either correct fuel mixture or fuel supply. Fuel mixture could also include fuel atomization. Try removing the air cleaners and using a spray bottle squirt some gas down the throats when it tries to die. Let us know what happens

Edit: I guess we assume stock dual carbs with chokes? Are the chokes opening?
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[lil-jinx]

This may help
https://www.thesamba.com/vw/forum/viewtopic.php?t=173175
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https://www.thesamba.com/vw/forum/viewtopic.php?t=620186
https://www.thesamba.com/vw/forum/viewtopic.php?t=668799
1974 Bay Westfalia. she likes to be called Ethel.
1968 Dune Buggy
1974 parts bus
A smart man learns from his mistakes,a very smart man learns from other's mistakes.

[thewalrus]

I fixed it! I swapped out the vacuum advanced can and it idles perfectly now. Timed it to 7.5* BTDC and it super smooth. Just went for a test drive and it drove very smooth and had lots of power. Thanks Samba!!

One more question, how come a worn in/ used distributed should be timed to 7.5* BTDC but a new one is 8.5* AFTER TDC? Is it just from wear-and-tear on the internal parts?
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'73 Transporter 1.7L Dual Carb

[Wildthings]

The original distributor specs assume that everything in the distributor works as it did when it left the factory, that is just not a good assumption any more. The best way to time your engine is to set the timing at 28° BTDC @ 3500+ rpms with the hoses removed and plugged. This mimics the full throttle, high rpm condition when you are asking the most out of your engine.

The vacuum can on the distributor can fail to hold vacuum which is very common with dual vacuum cans, but can also happen with single vacuum cans. The cans can also just freeze up, sometime just from an accumulation of dirt with age and sometimes bees will build nest in them. The centrifugal advance mechanisms also wear and freeze up with time. Few people lubricate them with any regularity and there are both fiber and metal thrust washers that fail, along with some plastic parts that get brittle and fall apart.

People have gotten used to the idea that a car will drive several hundred thousand miles and need little work along the way, that was just never true with vehicles built 40+ years ago. ACVW's were not even close to being the best of their era, but they were one of the easiest to repair which made up for a lot.

[thewalrus]

Looking for Idle Issue answers and I found my own thread

OK... It's giving me idle issues again and I've done the following:
Checked for Vacuum leaks and replaced all vacuum lines
Sprayed the carbs with carb cleaner
Adjusted the valves (Thanks Mr.D!)
Removed the ENTIRE Smog System and plugged up holes in Heads and back of Carbs
Installed rebuilt distributor (Had it rebuilt over the winter here: http://www.sparkingplugs.com/)
Cleaned the battery connections
New Spark Plugs
New Points
New Rotor
New Cap
New Wires
New Coil
New Fuel Filter (Wasn't clogged)
New Air Filter

After all this is did fire right up and idle OK. Once it was warmed up, I timed it to 7.5° BTDC and it idled very smooth there. I attempted to test drive it and the carbs started backfiring on every stroke. I realized I had forgotten to plug the brake booster line back in and once I did.... the entire system went to shit. It wouldn't idle at 7.5° BTDC, it wouldn't rev, and it eventually died out. I checked the brake fluid reservoir and it was completely empty. The "B" light on the dash wasn't on either.

Is there any chance the Master Cylinder is shot and causing a massive vacuum leak in the engine? When it was running fine I did notice a very slight pull to the right when braking.
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'73 Transporter 1.7L Dual Carb

[skills@eurocarsplus]

1) who gives a shit where idle timing falls...it's pretty irrelevant unless you're getting smog checked. you don't drive at idle, so it's a non issue. in a perfect world, you could get it close, but we aren't in a perfect world.

you could have a ruptured booster, or a bad hose going to it.

for a sanity check, cap off the booster vacuum nipple on the engine. report back. if it runs fine after that, your problem lies in the booster circuit. if it still runs like a bag of shit I would triple check for vacuum leaks. you could have worn throttle shafts, a plugged jet, etc etc
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[Wildthings]

If it idled with the brake booster hose disconnected, I would think it would be running puke rich with it connected.

[orangebug60guy]

[thewalrus]

[orangebug60guy]

[thewalrus]

So which line is busted? Is there a way to check the one-way valve on the brake vacuum lines?

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'73 Transporter 1.7L Dual Carb

[orangebug60guy]

Big Jack,

Check out where the arrow is pointed. Its the red tube in your picture.

Also check the valve. The arrow on the check valve should be facing towards the carbs.
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[thewalrus]

Is this what I'm looking for?

http://www2.cip1.com/ProductDetails.asp?ProductCode=VWC-191-611-933

Also the "G2" hose in that diagram goes to the right side valve correct?
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'73 Transporter 1.7L Dual Carb

[skills@eurocarsplus]

that check valve won't help ANYTHING if the booster or it's lines are no good. it's there to 1) hold vacuum for 1, possibly 2 pumps of assisted braking AFTER the engine dies and 2) to help protect the booster from a backfire

again, CAP off the vacuum port and report back. if it still runs like crap, you have other issues
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[thewalrus]

I double checked my spark plug wiring and had one backwards.

It fired and idled much better after that. It seemed comfortable around 7.5-8° BTDC. No smoke. No carb backfires. I capped the retard vacuum line and it didn't make any difference also. I let it cool down for the night and I'll see how it is after work today...

Fingers crossed!
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'73 Transporter 1.7L Dual Carb