Aircooled Vanagon Dual Carb Setup Vapor Lock

[82bessieblue]

Hello all,

First time poster, long time searcher of the Samba. I looked through the search function and couldn't find a solution to my particular problem (described below), so if anyone knows of a post that already deals with this, please point me in the right direction!

Now with that being said, here is my current setup:

1982 Aircooled Vanagon 2000cc
Approx. 124,000 original miles, overall great shape
Dual Solex Kadron Carbs (installed by PO)

My problem:

When I go to start the van in the morning, it pretty much fires up easily with little hesitation. After driving for about 20 minutes or so around town, parking, and then trying to start it again, there is quite a bit of hesitation. I usually have to floor the pedal (probably not the best idea, but it works) for it to start. Also during this period, there is a relatively strong smell of gas vapor. Its been doing this for the past several months now. Also, not sure if they are related issues, but I opened up the engine compartment just after engine shutoff, and the carbs were fairly hot to the touch. I disconnected the fuel return line (I recently replaced all fuel lines in the engine compartment), and there was quite a bit of vapor pressure built up in the lines. The PO had put in an old thin filter set up in the return line, so I removed that and it has helped reduce the fuel pressure.

To me, it sounds like the carbs are getting vapor-locked shortly after engine shutoff, thus flooding the engine. I've got the carbs tuned as lean as possible for now... The fuel air intakes are just K&N air filters that suck in warm engine compartment air, so I'm wondering if I were to route in cooler outside air this would help vent the vapors and cool the carbs?

[MarkWard]

It might be the fuel boiling in the bowls. Some will wash down the throats and can flood the engine. Holding the pedal on the floor increases air flow and compensates for the over rich mixture.

You probably want to add isolater blocks between the intakes and carbs. This will reduce the heat soak.

Not sure of your fuel supply setup. If it requires a return, the fuel pump may be overrated. You need 3 psi to run the carbs. The cheap diaphragm pumps work well in this application. Nothing wrong with a return, but it should be returning off the carb supply, not a regulator. This allows some circulation of fuel that helps cool the carbs slightly. You might also try lowering your float level. This will help the problem of fuel running down the throats. My bet is if you got the engine hot and looked down the carbs with the engine off it will look wet.
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[82bessieblue]

Hi Mark, thanks for the info!

I agree its probably the fuel boiling... the carbs are almost too hot to touch after driving over 30 minutes... seems like a potentially dangerous situation. My family and I use this as a weekend camper, so I want to be especially careful.

The Solex's both have insulator blocks installed... I'll have to see if they make thicker ones, but I'll have to watch out height clearance for the carb air breathers, they already touch the bottom of the engine hatch as it is.

I'll look into a diaphragm pump for this... The PO had swapped out the FI-rated fuel pump for a smaller metal box-shaped fuel pump with a VW logo on it, maybe it was from a bus... Any recommendations on diaphragm pumps?

Currently the return does run directly off the bottom of the carbs/top of intake manifolds. Since i removed that in-line filter off the return, it seems to flow quite a bit better.

Now that you mention it, the butterfly valve does look a bit wet after shutoff... I figured that was somewhat normal. I'll try lowering the float levels and see what that does...

Eventually once this engine dies, I'd like to swap out with a TDI of some kind...

[MarkWard]

Busses used a mechanical pump bolted to the side of the case. I am speaking of the Type IV engines. I would not go about swapping fuel pumps till you measure the fuel pressure you have currently. Too much pressure, will overcome the floats.

Might be worth using a temp gun and measuring the base of the intake, the isolator, and then the carb itself. This will give you some sort of reference. Yes, its pretty tight under the deck for dual downdrafts with air filters installed.

Back in the day, vapor lock was a condition where the fuel would vaporize in the fuel lines. It did not really relate to the carbs themselves. Do make sure your metal lines are not near any heat source.

How about posting a picture. You can not beat the simplicity of points and carbs. Dual carbs take some patience to get right, but once they are setup with good linkage, they really are a nice option. Are some fuels less app to boil?
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[82bessieblue]

Did a bit more research, looks like the PO removed the original mechanical fuel pump and just added an electric pump. I found it online, looks to have a psi rating of 3.5. I'll look into checking that directly though. I like the idea of adjusting the float arms, I'm guessing I should try and bent those further down into the bowl?

Thanks for clarifying vapor lock, I was a bit confused with that one, guess I should change the post title! And once I did some research on the Kadrons, I eventually got comfortable with getting them tuned in properly. Its actually kinda fun playing around with the idle and air/fuel mix ratios.

I think the PO was definitely going for simplicity, which I am happy about... aside from this relatively minor issue, ole Bessie Blue runs like a champ!

I'll try and get some photos of her and the dual carb setup when I get home. Thanks so much for your input so far! This really is a great community and resource!

[Howesight]

I agree with Mark - - your fuel pressure is too high. The Kadrons' float valves are being overcome with excess pressure which is dumping fuel into the engine. This "floods" the engine on re-start which is why you end up needing to open the throttle wide open to clear out the liquid fuel in the intake ports and the cylinders. You might also have a leaking or loose accelerator pump nozzle.

Here's a helpful link:

http://kaddieshack.com/kadron_rebuilding_instructions.html

In any event, use a high quality fuel pressure regulator and that will help considerably.
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'86 Syncro Westy SVX

[bobbyblack]

Air cooled engines are very susceptible to heat. All of the vapor lock problems I had were related to missing tin, or poor seal between engine and body. Check your perimeter to be 100% certain that the seal is decent. I've had to resort to duct tape, or inner tube rubber screwed between sides.

I also agree 100% with the high pressure answer tho.
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'87 Westy 'Flossie','86 Westy 'R1','86 tintop GL - Subi2.2 'J2','83.5 stock tintop L 'ZoomBus','74 Karmann Ghia, '63 Notch

[Wildthings]

Ethanol laced fuel boils easily on a hot soak, all of my carbureted rigs have problems with this these day. What you need to do is cool off the carbs. The first thing to do is make sure that no hot air car recirculate back into the engine compartment and that the thermostat is allowing the flaps to open fully. Having the timing set correctly at 28° BTDC @3500+ rpm, hoses off and plugged helps as well. Using the stock spec may well cause your engine to run way hot as the stock spec assume everything works factory new, which isn't likely to happen this many years down the road.

With dual carbs you can install the thick phenol FI gaskets between the heads and the manifolds, and you can install additional phenol gaskets between the manifolds and the carbs. Having both sets of phenol gasket is fine during the summer months, but may cause problems in cold weather if you do not have an intake air preheat system.

You can also add thermostatically (or timer) controlled fans to cool the carbs after shut down. This is what I have on my T-181 with a stock center mount carb. Another thing people have done it add a fuel return line to bleed off the fuel pressure after shutdown, this will keep additional fuel from being forced into the carbs as the fuel in the lines boils. Busdaddy has a post on how he did this in the Bay Window Forum.

[82bessieblue]

Wow these are great ideas I never even thought of really. So I bought a fuel pressure test kit from the FLAPS this evening. I'll give that a check tomorrow and take a read with the IR gun after driving too. Any specific temps I should be staying under?

I'll take a look at the thermostat tomorrow as well and see what thats doing.

It does have fuel return lines from both carbs, that were previously blocked by a bad filter which I've removed and seems to help a bit.

I was actually thinking of some sort of thermostat fan to use to remove the excess engine heat, can you elaborate more on the carb fan setup that you use?

Overall the engine compartment is fairly well sealed, and the tin is in very good shape but there are a few gaps/holes that i'm sure would benefit from reseal.

[82bessieblue]

So, I have some updates on this...

I disconnected the fuel line just upstream of the carbs, the pressure gauge read around 5.5 - 6 psi... I'm guessing that may be the problem, and need to install an in-line adjustable fuel pressure regulator?

Also checked the engine compartment temp about 20min after shutting off the engine with an IR gun. Top of engine block read around 175 deg F, while the carb exterior (float bowls) read around 115-125 deg.

Going to ask around the FLAPS to see if I can come up with a regulator. Here's my setup:

[MarkWard]

I do not see the linkage rod for the flaps that are operated by the thermostat in your pictures.
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[Wildthings]

[82bessieblue]

You're right, I noticed that this afternoon. Originally the fuel lines were just laying on the block, almost too hot to touch, so I worked on rerouting them and installed a fuel pressure regulator this evening, hopefully that will help cool them down a bit.

I will do more investigating tomorrow, but my guess is the flaps have probably been removed by the PO. Does anyone supply these? Whats the best way to have them reinstalled? Remove top engine tin? Looks like a jigsaw puzzle!

[Wildthings]

Not a particularly easy job to add the flaps with the engine in place, but it can be done. You can use a mirror or boroscope to look down through the hole in the #4 tin to see if the flap is covering the oil cooler or not. If in the correct position the flap will totally block the view of the top of the oil cooler.

[Backtotheeighties]

For future reference on an old post- to reduce the height for vanagon engine lids try Pontiac GTO tri-power air filters. k&n have equivalents.
I am guessing the original kadron mesh housings were designed for using Chevy Corvair sized filters. There are other equivalents but watch the inner diameter doesn't foul the breather. MANN have made the oe kadron paper ones obsolete, and filters for US made cars are not easily found in the rest of the world.
Eliminate the bracket over the carb mouth. Two long cap head bolts through new holes in the lid into carb. Weld /bung the ol center hole. Increases airflow.