Autolite 2150 mixture adjustment

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Aug 9, 2009 | 07:22 PM

yankeerebel

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Autolite 2150 mixture adjustment

I've got an Autolite 2150 on a '77 F-150 351M. Complete rebuild of the carb and it still has issues. Starts fine, high idles fine, comes off high idle o.k., high idle screw lands at the 'V' on the cam, choke kicks in when engine is warm and opens fully and idles relatively smooth at ~750 by ear only. I wired the choke to the 'S' terminal on the alternator and checks out at about 10V.

I've checked for vacuum leaks with a can of ether but don't notice anything. I have a worn throttle shaft with a bit of gas seepage and a little vacuum loss there but no diagnostic tools to know how much. The idle will vary a little and randomly cycle up and down but nothing unworkable.

The exhaust smells of unburned fuel and stings my nose. Truck drives o.k. but frequently stalls at stops on the road especially when the engine is really warm. When I play with the mixture screws I get no change in idle whatsoever. Checked the spark plugs but they don't show any signs of over-richness however, I have not put many hours on the engine at all.

What could be my problem? I'm running out of ideas.

Thanks in advance.

Aug 9, 2009 | 07:34 PM

steponit

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check the autozone site repair section

Aug 9, 2009 | 07:39 PM

fmc400

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Joined: Apr 2004

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From: Austin, TX

Little or no response to the idle mixture setting is indicitave of a vacuum leak. I highly suggest getting a vacuum gauge. With this tool, you can dial in your mixture exactly.

Aug 9, 2009 | 07:46 PM

yankeerebel

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FMC400,
where does this vacuum gauge attach? Will my worn throttle shaft be enough to cause these symptoms?

BTW if it had not been for your post about adjustments to the 2100 I'd have given up by now, THANKS!

Aug 9, 2009 | 08:13 PM

montana_highboy

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Joined: Apr 2008

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From: Big Sky Country

Quote:

Originally Posted by yankeerebel

where does this vacuum gauge attach?

You want to read manifold vacuum (below the throttle blades).

Aug 9, 2009 | 08:29 PM

Jermafenser

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Joined: Jul 2001

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From: MD

Quote:

Originally Posted by yankeerebel

FMC400,
where does this vacuum gauge attach? Will my worn throttle shaft be enough to cause these symptoms?

Anywhere there is a full time vacuum reading. This can be the vacuum tree at the back, the manifold vacuum nipple just northeast of the thermostat housing. I use this as it's the most convenient place to hook a vacuum gauge. However, not all trucks came with it, tho (it may be there for some emissions applications).

I'm not entirely sure how the throttle bore wear will affect the fuel and/or air mix. My 2150 has throttle shaft wear as well (over 200k miles) and I've got a vacuum leak as well that I haven't found where. It idles slightly rough while in gear, and it's hard to get it in gear without dying if it's not fully warmed up. But the exhaust burns nice and hot and doesn't smell like unburnt fuel.