Here’s one I'll try on you guys. Have a problem with my Weber 23/26DGAV - need help from those of you with a thorough knowledge of the beast. It is running about the right mixture at idle and kind of rich at medium to heavy throttle, but intermittently rich but mostly very lean at light throttle! Looking for suggestions.
Have a '71 with about 30K on rebuilt engine. Bought the carb very used and don't know its history, but rebuilt it with the proper kit. A friend of mine rebuilds classic European race cars and knows quite a bit about Webers, so has been my source of information so far.
Since putting on the rebuilt carb (with proper manifold) was having a slight stumble when at light throttle, as in going down the road at 65
mph. The engine has all new high voltage components, Pertronix and coil and ran well before the change of carburetors (as well as one would expect on a very old dirty Solex.) The stumble was a problem, so have checked for vacuum leaks, idle adjustments, timing etc.
To get a handle on what is going on, have installed two 18mm nuts on the exhaust collector pipe just behind the Y to mount O2 sensors. (yes, I know - why two. I decided to do a little checking on things, wanted to
compare two sensors.) I have also borrowed a friends Hall meter, which agrees with the reading of my O2 sensors with a digital voltmeter.
The carb has all the regular jets installed - 170 on Primary, 180 on Secondary, with a .50 idle jet. Idle mixture screw is adjusted farther out than I would expect - maybe two turns or more. Mixture is running about midscale on the Hall, and can be adjusted normally though not as quick a change in engine speed as I would think would happen. Float level was set correctly during assembly.
Under mid throttle (midway on one barrel) to full throttle it is running rich, about 0.92 volts on the sensor, into the rich side of the Hall. Another clue, but I'm not touching that until I get the low throttle
stuff worked out.
And now the important part........
At light throttle (anything above idle to maybe 1/5 thottle or less) the engine is running VERY lean, almost to the point of misfire most of the
time, though I have seen the Hall and my meter jump up toward slightly rich then back to lean. It sort of flutters between very lean and slightly rich. Most of the time it's running very lean - like zero on the Hall, less than 0.100 volts on the digital meter. Very discouraging.
If I pull the manual choke out slightly (I have an adapter to replace the water choke) the mixture stays rich at all throttle setting. It takes just a little movement of the choke plate, and then the car is running slightly rich all the time, the same as when at mid to full throttle.
I changed the idle jet from .50 to .55 and then .65 with no real change. Except the other day realized that the way the carb is laid out, the jet is on the Secondary side! Am I mistaken? This carb has the electric fuel cutoff solinoid, which seems to go where the Primary side jet would be if were like in all the Weber books I have. Does the jet on the secondary side feed the primary idle?
The mixture seems to jump around a lot, but runs lean most of the time while running with light throttle.
I have also checked the current draw of the fuel cut-off just to see if an intermittent coil was the problem, but the current is constant (about
I have checked things over, have run out of ideas and looking for any others.
Frank ('71 with wierd Webber.)