Carb question, need to dump little gas in carb just to get car started Options

[angerosa]

The story picks up here...

So last you knew I was using my phone at the inspection station to make the last post. Lets rewind to Tuesday... I got a call from the carb rebuild kit vendor telling me that there were two different accelerator pumps for my carb and asking which one I had so he'd know which to include in my kit. He said one was much longer than the other. I thought to myself this must be my problem all along... I have the wrong one in my carb. I paid the extra $10 to have him include both pumps and a few more dollars for priority mail. Remember I'm trying to make it to a show on Sunday.

In retrospect it didn't make much sense that I had the wrong pump all this time. My car didn't run bad the first several years I had it.

After a really hectic week I was excited to receive the kit in mail on Friday. I ripped open the package only to discover that the longer accelerator pump was the same one I already had. I set it aside to enjoy a pre-arranged, Friday night dinner with the in-laws.

At about 8 this morning I went outside and started giving the carb a gasoline bath. I wanted to put the same accel pump back in because it looked to be in good condition. The spring also looked to be just fine.

I wanted to just clean out the inside of the accelerator pump reservoir because it looked a little dirty. I was hoping I could find some other adjustment to get the cam closer to the accel pump actuating arm. When I got everything back together it lined up perfectly! It was just some gummed-up grime that was holding the button in and the gasoline bath had cleared it out. I mounted the carb back on the intake and made some small adjustments to the fine adjustment screw in the actuating arm so that the accelerator pump is actuated with the smallest push of the peddle. I also put the tension spring on a little tighter. I had an issue where my carpet was keeping the peddle from fully returning to the neutral position which made the car idle a bit higher when that happened. Now it doesn't do that. Here's what it looks like now.


Much better right?

Runs much better. Here's my problem now...

My car runs 95% better but I still don't know how to tune this thing. When I got everything back on my car I still had an issue where it was dying out when I hit the throttle. I found that if I tuned the screw for Primary idle jet a tiny bit, it got rid of that. See earlier in my thread the diagram of my carb that kg6dxn posted...
Should I be turning that screw?
What knobs should I be tweaking to tune this carb?
What jets should I be adjusting if any?

The only symptom I have now that I would try to get rid of is that when I'm in the wrong gear, the car bucks and backfires a little bit. For example if I'm in 3rd going slowly up a hill and I nail the throttle, the car bucks instead of slowly accelerates to speed like I would expect a FI car to behave. This is not really a huge problem but I bet with the right adjustments I could get rid of it.

Oh and by the way...

[Mike Bellis]

Now you're at the point where you find the achilles heal of that type of carb setup. The biggest challenge is tau. The effect of the long runners is tau or fuel that falls out of suspension and runs down the walls of the runner. VW solved the problem in the Bug with an exhaust tube running next to the intake runner. The extra heat helps keep the tau from forming.

The bucking could be either too much or too little fuel due to tau. Most likely to little fuel in suspension. As the fuel on the wall makes it to the combustion chamber, it is liquid and not aerated. This can make it run like it's lean while blowing excess fuel out the exhaust. You will not get a good burn with liquid gas.

As far as tuning you will need to find jets for the carb and get a wide band AF meter or use the seat of your pants method.

Bottom line, you will need to play with it but it may never be perfect.

[angerosa]

Thanks Mike - makes a lot of sense. There is a strong gas smell when my car is idling. Always been there so I'm probably running rich. What I'm looking to figure out is what dials on my carb are adjustable or should be adjusted. Are jets always something that should be all the way in or should I be able to adjust them?

[ThePaintedMan]

I agree with what Mike is saying. The longer intake runners on the Type 4 makes a single carb setup far from ideal, regardless of how the carb itself if setup. That being said, people have made them work for a long time, even if it is an imperfect option.

It sounds to me like when you open up the throttle like that, the secondary is providing too much fuel - similar to flooding. As Mike said, without an AFR gauge, you can't know for sure, but in that case, you would need to first identify the size of secondary main ets, then source one a size (or several sizes) smaller.

Adjusting the idle mixture won't make much of a difference, if any on the top end (or when you "punch" it). If the car is running rich at idle, you should be able to dial some of that out though.