Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

M4MED Function

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kiowamec:
Okay I finally got my M4MED stripped down. Man there is quite a few parts inside these carbs.

Studying the booster circuit it appears that the solenoid operation simply diverts fuel from the pump back to the fuel bowl. This setup seems to be more of a reducer of pump shot rather than a double pump shot as the model signifies.

Can someone confirm this shed some light on this?

Schurkey:
Chevy engine in a pickup truck or van; early-to-mid-'80s; electrical connector on the carb but not computer controlled?

Yeah, that's the way I understood them to work.  Cold engine gets full pump shot, warm engine gets reduced pump shot.

Maybe I'm wrong.

Cliff Ruggles:
That's pretty much how they work.  We use a lot of those castings to build our custom large cfm carbs from.  That system can be blocked off internally and a standard late model airhorn installed on them......Cliff

kiowamec:
The solenoid does operate on 12 volts correct?
I think I will leave it in and put it on a switch.
I will be using a Wide-band to set it up so I will be able to see what works best.

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