I bought a book on Webers - "Weber Carburetors" by Pat Braden. It has a good section on carburetor troubleshooting and a section on rebuilding 5 different Webers. They are IMPE, DGAV, DFT, DCOE, and IDA3C. At first I figured that the DGAV, being a two barrel carburetor, would be most similar to the DCD. I now believe that the DCD is much closer to the IMPE except that some things are multiplied by two. Can someone confirm this for me?
So far, I have been able to correct the power problem. The symptoms of the power problem were: 1. Reving in neutral is just fine 2. Anything but slight gas pedal pressure caused the engine to bog while driving 3. Could only 'tease' the car up to about 40 mph 4. Lose speed on the slightest incline After cleaning the main jets, the power problem has disappeared. The main jets are accesible from the outside of the carburetor underneath the 10 mm nuts. The jets were covered in some sort of green slime that came off in chunks.
Now to the idling problem. The symptoms of the idle problem are: 1. When I push in the manually operated choke, the engine dies 2. Adjusting the idle mixture does nothing 3. Can't get the engin to idle below 1500 RPM NOTE: Some of the symptoms above may be due to the high idle speed screw setting I've removed the carburetor cover assembly and removed/inspected the three brass fittings that sit within the triangle formed by the two barrels and the float bowl. I suspect that two of these fittings are emulsion tubes, and the other is the idle jet. Correct? Which is which? I pulled these three items and they all looked VERY clean - so I left them alone. The bottom one third of the float bowl was covered with what looked similar to the lime scale that is found on a water faucet. I easily wiped this stuff off - essentially just dissolving the stuff in the gas left over in the bottom of the float bowl. This did not adversely affect the carburetor at all (AFAIK), and I'm assuming that this crud has run through the carburetor by now.
Then I unscrewed the idle mixture screw and blew some carburetor cleaner (through the tiny plastic tube attached to the aerosol can) into the idle orifice. This seems to have helped a little, in that now I can get the engine to idle about 800 to 1000 RPM. However, the carburetor now does not like to make the transition from idle circuit to main circuit. The Weber book calls this the progression circuit. When the car is in neutral, the engine can be 'teased' to get from idle to high rpm, but when driving the car, the engine will stall as I step on the accelerator. The potentially dangerous situation can be remedied by a pull on the choke to keep the engine alive.
Any thoughts here? Should I recheck my work? Anything else to look at? I've checked into a rebuild kit and having the carb rebuilt. At $30, the rebuild kit seemed to be the way to go, but I'd prefer if I could resolve the carburetor problem without having to pull the carburetor completely apart. A professional rebuild (Pierce Manifolds) should run $125 to $150, so I think I'd consider a new 32/36 DGV (as its seems more common and easier to get parts for it) before getting mine professionally rebuilt.
One more thing, the Weber book recommends 3.5 lbs of fuel pressure. I checked my fuel pressure, and It looks like 1.5 lbs to me. I've considered an electric fuel pump, but would prefer to remain stock in this regard. I'm not opposed to non-original stuff on the car. It's just that it brings with it the hassles of wiring, additional electrical load, that awful buzzing, etc. Since I've seen the power improvement, I've been less focused on the fuel pressure issue as a source of the idling problem. Opinions?
Brad Sahr brsahr(at)imation.com