30 PIC help wanted

E

Ernie

True Classic
Maybe this belongs in NFC, but I'm looking for help from knowledgeable Fiat guys.

As a favor for my wife's horse vet, I'm working on his 1963 Volkswagen beetle.
His "mechanics" haven't been able to get it running for several years of trying.

My remaining issue is a slight hesitation just as the throttle is advanced.

Since I got the engine running I've rebuilt the carburetor and cured an air leak at the carb base. The engine starts and idles fine.

Am I just too used to my own weber carb applications where I get immediate satisfaction? Barring lawn mowers, I haven't work on a single barrel anything since the '70s.

I see Jeff Stitch has these carbs for sale occasionally, so I'm thinking some of you guys might be able to set me straight.
 
If you start your thread with:
Ernie said:
Maybe this belongs in NFC
Click to expand...
Then ask about a 63 Bug.... You already know it belongs in NFC. Please help the mod team out by putting NFC posts in NFC.
 
But, but, in my defense, I'm seeking help from our favorite weber carburetor guys.

On the other hand, I don't want to let you down. I've never moved or deleted a thread, but I'll look into how to do it.
 
Don't worry, most people who use Xweb usually use the "see new posts" option which includes NFC.

Ok, to your issue. The hesitation when moving off idle is usually related to the accelerator pump on the carb. I find quite often the diaphragm is cracked or old and is either not working or leaking air.

Now, some other potential issues could be, courtesy of a quick google search with AI. Idle Screw turned in 1/8 to 1/4 too far. I have not seen this before, but.... Fuel pressure. Now, I have seen this before and had it happen to me also. Remember, the carb needs 2.5 to 3.5 psi all the time. For me, I had a bypass on the line to keep the fuel always flowing, but I did not restrict it enough and was running out of pressure. Finally, vacuum leaks. I see you said you got it resolved, but maybe another session with the smoker to ensure it is good may be beneficial. On Weber DCOE's, they like to leak really bad around the throttle plate rod at the bearings on the side. Most don't seem to see this as in racing, it is either idle or full throttle.

Hope this helps, and keep the questions coming.
 
Thanks for the reply.

You've mentioned some of the things I worked on. The pump diagram was replaced as part of the rebuild. Even before I got the engine to run I had low fuel pressure due a grubby fuel filter.

O'Reilly helped with that, but right away another trip to town because proper fuel pressure exposed fuel line leaks.

Once I solved the ignition problems and had the engine running, I ordered the carb kit because revs would cycle up and down, and I realized there was an air leak at the base of the carb.

The carb kit, combined with flattening the carburetor base makes the engine start, idle, and run well. It's the very slight hesitation just off idle that has me guessing.

That's why I asked in my first message if maybe I'm expecting too much. This engine is 36hp, single barrel, putt, putt.

Or, is there something else I should check on this carburetor?

The only piece of the rebuild kit I ended up not using was the needle valve. The one supplied with the kit was machined differently and used some combination of copper gaskets I couldn't figure out. With the old one back in, I've seen no indication the float or needle valve is related to this hesitation.
 
Ernie said:
As a favor for my wife's horse vet, I'm working on his 1963 Volkswagen beetle.
His "mechanics" haven't been able to get it running for several years of trying.
Click to expand...
Sounds like those "mechanics" should be fired & the vehicle perhaps taken to an old-VW-specific shop.

Ernie said:
My remaining issue is a slight hesitation just as the throttle is advanced.
Click to expand...
fastx19 has already noted most of the go-to fixes, but you might also recheck the timing & the ignition points condition (wear) & proper gap.

Ernie said:
I see Jeff Stitch has these carbs for sale occasionally...
Click to expand...
For the record, I have never had any VW Solex 30 PICT carbs, nor offered any for sale.
 
It sounds like the mixture may be leaning out as you go through the transition region. That condition can often be solved by increasing the size of the idle jet. I would also check to make sure that the float level is set correctly as that can affect the transition.
 
I've taken the carburetor apart again to check everything. I was just getting to the float checking part and may revisit swapping the needle assembly.

Yeah, Jeff, you got me. I totally forgot I wasn't working on a weber carb. If I had remembered that, I probably would have come here with my questions in the first place. Old brain cells.
 
As Don indicated, it is that transition region from idle into the main circuit which is getting you. Now, the idle does not turn off right away, it actually goes a little bit into the main circuit before coming on full. So, something there is amiss. I know 0 about solex carbs as well, so I think you are seeing theory at this point.

I was just looking at a diagram of one, and that transition is going to be caused by potentially 3 things. 1. Too Rich at that point, 2. Too lean at that point, or a sudden drop in airspeed into the engine at that point. 1 and 2 can be fixed by ensuring the fuel/air ration is right. I use the Propane trick as an easy to determine method of rich or lean. Use a small propane torch, unlit, and if you introduce propane into the carb at idle and it speeds up, you are lean, if it stumbles, you are rich. Now, if there is no change, then you might just simply have a design issue with the intake where at a certain RPM is does not have sufficient flow for what is required. I doubt this though.
 
Here's the latest news. I completely went over the carburetor again and mounted it back up.

Surprisingly, the engine ran worse than before, bucking under a bit of load. So, I reread the tweaking instructions for the rebuild kit I bought. This resulted in tossing out what I learned from Pierce Manifolds many years ago regarding setting for best lean idle.

Overlooking the fact that the instructions referred to the mixture adjustment as volume control, I did it their way.

Success.

Thanks to everyone who chimed in.
 
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