Rebuilt carb by one of Cliff Ruggles former employees. Runs and drives well. Drinks fuel.


Have never been able to get the dwell set. Hangs at 6 degrees in closed loop. I've tried idle air bleed across full range, as well as starting with idle mixture screws 3 3/8 turns out, then one full turn (twice) out from there per GM manual.

It's as if the ECM is getting a bad reading somewhere else, such as TPS or something. No idea.

When I drive it the dwell will sometimes climb to around 30 degrees, but bounces around and never gets above 35. And I have no explanation for why it will periodically climb during driving.

Hold hand over carb can make the dwell climb as the car chokes down.

Any ideas?

 

When was the 02 sensor last changed? Those old single wires only last like 20K miles.

Also worked on a TBI Astro or G-Van once that was drinking gas, forget which that had a 4.3L. The 02 was dead lean, the fuel trim BLM maxed out. Got to checking and it had adequate fuel pressure, injectors were working well, timing at spec, etc. Eventually, I clamped the air hose off before the diverter valve. Instantly the 02 sensor voltage jumped up, the BLMs dropped like a rock and it ran well. The Air system was never diverting with a warm engine, pumping air into the manifolds all the time ahead of the 02 sensor which sensed the added air as the engine running lean.

 

Ok. Good information. Will check if AIR is involved. Start there. Also check for vacuum leak. Easy enough to change O2 sensor at some point too. Thank you.