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AFC Fuel Mixture Too Lean, Type 1

Greetings.

About a month ago, I burned the #3 exhaust value when the seat came loose. Before the catastrophe, one mechanic told me that the whistling sound was normal in older cars. Yikes! This was the third set of heads I've replaced in less than 30K miles.

I've wondered if the engine was running way too lean. The air-flow regulator adjustment screw is all of the way in. I've searched for intake leaks, but none have turned up. Another mechanic believes he can adjust the mixture by changing the air-flow meter spring adjustment...which he has done twice, but the engine still shows signs of running lean. The values are tight after a few hundred miles.

I'm frustrated enough that I'm considering replacing the engine with a carburetor fed model.

1) Has adjusting the return spring of the air-flow box been shown to be fruitful? 2) Is there some advice available for locating air leaks? 3) Do older AFC engines run lean and there's nothing we can do about it?

Cheers.

Reply to
beewoolie
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Spring tension will indeed control mixture, but unless he has an exh analyzer what will it be adjusted to? Color of plugs?

Heads on those engines usually go a long while without failure; could there be a cooling problem?

Yes, those engines were designed to run lean.

Speedy Jim

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Reply to
Speedy Jim

Weren't the FI engines in the '75-79 Type 1s equipped with different cylinder heads? Where did you get the cylinder head from? Is the engine running too hot? Are there any vacuum leaks on the left side of the engine? Are you sure that injector is spraying out properly? How is the fuel pressure and the fuel filter? Does that engine run a catalytic converter or EGR valve?

Reply to
dave AKA vwdoc1

IIRC, the heads are the same except for a boss for the head temperature sensor.

The last ones I bought were from MOFOCO. They were for a carbureted engine, but they drilled the boss for me. The new ones that the mechanic put on are rebuilt Brazillian models.

That could certainly be the case. I've been thinking about ways to find out. I have access to an industrial IR thermometer. I'm not sure it's terribly accurate.

Not that I've been able to detect. I've wondered this as well. I've been thinking I should get some carburetor cleaner and spray it on the engine while it is running to see if the engine reacts, suggesting that there is an intake leak.

I had them serviced when I put the MOFOCO heads on the engine.

I replaced the fuel pressure regulator about 30K miles ago. It was a little wonky at the time. Replacing it made the fuel pressure much more even. The filter isn't that old,either. I certainly could replace it, but there isn't any reason, ATM, to suspect it.

There is a catalytic converter. It was built for California. The EGR valve has been disabled because the linkage broke. AFAICT, there was no way to fix or replace the linkage.

Yeah. The mechanic says that he deduces the A/F mixture by the plug color. Kinda dicey if you ask me. Not that it isn't accurate, but it takes some time to verify and I don't think he ever did this.

How would I know? Checking the engine temperature?

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Reply to
beewoolie

Yes, a cyl head temp gauge might be a good idea.

And the heads are indeed different. The FI heads used smaller diam exh valves with larger stems than the carb heads.

Jim

Reply to
Speedy Jim

Thanks Speedy, I thought I might have remembered incorrectly or something. lol

Mofoco had bought all of Topline's air-cooled machinery when they stopped rebuilding these engine parts. I think that Topline only sell new parts now. I am not sure if Mofoco has the greatest quality control so I usually purchase new air-cooled cylinder heads from another source. ;-) I have a local auto machine shop for rebuilding engine components. They seem to do very good work.

Also are you using the correct distributor? I seem to remember that certain distributors might have #3 cylinder firing slightly differently than the others. Of course I am not sure if this is correct, but the reason is to keep the #3 cylinder running a little cooler than it could ordinarily run. Of course make sure the #1 spark plug lead is at the #1 spark plug notch at the distributor too. ;-)

An exhaust leak right at the #3 exhaust port might create problems for the valves too as cool air might be drawn in hitting that hot exhaust valve. Cooling fan the correct one? Tin all correct and fitting properly? Good supply of fresh air getting to the engine? I think that the Type 181s (The Thing) also had engine cooling problems so one of the local guys at Battered Bugs created a fix for that.

Thinking out loud!

Reply to
dave AKA vwdoc1

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