fuel mix problem adjusting

What year/model/version? (I assume it is a US Bosch CIS model?)

 

OK -- but is it a US version, or is it a euro version that has been "converted" (quasi-Lambda) for US importation?

Have you:

1. Verified that you do have spark on both banks during engine running (or during starter motor cranking if the engine won't run at all)?

2. Checked to see if the frequency valve "buzzes" whenever the fuel pump is running = it should (i.e., unplug the safety switch, turn the key "on", listen, or feel, to confirm the fuel pump is running, and the feel the frequency valve to see if it is (correctly) buzzing.

Also, for background, when you were manually adjusting the mixture (and things seemed to be working), were you able to "swing" the unplugged O2 sensor voltage from 0.1~0.2V (lean) to 0.8~0.9V (rich) and back again?

 

That would make sense if it was previously tweaked up with a failed cutoff valve diaphragm (allowing extra oxygen into the exhaust upstream of the O2 sensor/sampling point during warm-running - so extra fuel is wrongly added to compensate). Are you saying that you needed to make (and did make) a huge "lean" tweak after replacing the cutoff valve? Since you describe that all the other systems are perfectly well, and it was running previously before (even if poorly), I'd just try going back in the other direction a bit towards where it was (i.e., add a little richness). The next fallback position is to set the mixture screw per the Mondial 8/QV WSM initial procedure using the "remove a FD output line/turn mixture screw rich until some fuel comes out/turn another fixed amount from there" method (but I'd just try a little blind hunting first before resorting to that extra BS ). Good Hunting!

 

AS Steve said, base setting( with fuel pump running) remove an injection line from top of fuel distributor. Watch for slight fuel output, maybe a drop every 10 seconds,if no fuel comes out adjust so just a small amount rises out of the port. Put line back on and run engine. Without a Gas analyzer you are left with turning adjustment screw to the left until it runs rough, then to the right until it runs rough, then finding the middle where it will run smooth.This is a method to use if you want to get it close without a 4 gas analyzer. Once again all other systems must be in order so you are not compensating for vacuum leaks, timing issues, etc.You are probably looking at minor adjustments at this point, of maybe one turn or less. Tepps

 

~0.8V is no sin .

How does it run when you plug the O2 sensor in? (I.e., does it warm idle OK as the O2 voltage makes the larger closed-loop swings from lean-to-rich and back?)