1976 Eldorado Choke Pull Off

awadecki · #1 (**permalink**) 02-17-09, 02:16 PM

Any idea how to adjust the choke pull off on a 1976 Eldorado carb? I don't have the manual with me, and it looks like there are two vacuum diaphrams on the passenger side of the carb. My car runs rich when I first start it when it's cold. Choke closes just fine, but car misses unless I open the choke slightly with a screw driver, then it smooths right out. I thought there was a screw to adjust it, but I don't see one, and this Quadrajet has a different setup than my 72 Oldsmobile with a choke heater.

submariner409 · #2 (**permalink**) 02-17-09, 11:27 PM

Don't have a 2-diaphragm QJ in front of me......One of the cans will immediately pull the choke butterfly open about 1/8 to 3/16" as soon as the engine fires and establishes manifold vacuum. Either the small vacuum hose is cracked or the can is toast or the lever travel is restricted. Track down your vacuum lines from the carb through any TVS (Thermal Vacuum Switch) to the manifold and distributor. They have a tendency to get brittle and crack. Plenty of easy fixes for this one.......rubber vacuum line in a blister pak from your local parts house......just check for the correct ID hose. (The other can is probably an unlocker for the secondary air valve.)

awadecki · #3 (**permalink**) 02-18-09, 01:48 AM

Thanks.

The choke butterfly moves freely. If I push it open manually, it moves a linkage that goes to the back canister. However, this back canister isn't pulling the choke off at all (I'm guessing it should). In that case, what's opening the choke? It does open, and when I tap the gas it opens by itself, but it just isn't opening enough when the engine is first started. It does open when the engine is first started, it just doesn't open enough and the engine runs too rich.

Sorry, I'm a naive 26 yr old who understands and can repair TBI/PFI systems, but haven't yet gotten to know the mess of linkages on a Quadrajet carb. This is my first carbureted car.

submariner409 · #4 (**permalink**) 02-18-09, 01:00 PM

That pulloff canister should have vacuum hooked up to it somehow, maybe with an inline thingy that looks like a tiny inline fuel filter......a vacuum delay can. The total choke pulloff is controlled by either an electric or manifold heated bimetallic spring in the black covered round thingy on the right (passenger) side of the carb. The adjustment for that is by loosening the 3 screws around the edge which hold 3 spring clips. Turn the black cap until the choke butterfly is just barely closed, cold (about 40 - 50 degrees F). When you first start the car, press the accelerator down once, which should set the choke and fast idle cam. Start the car and vacuum should immediately pull the choke butterfly open 1/8" or so, and, as the engine/carb warms, the butterfly should slowly open fully.

Find a 8x11 paperback book on Quadrajets by Doug Roe (?) in a local speed or car parts house or search Jeg's, Summit, or Performance Automotive Warehouse.