Hello everybody,
I'm having a weird problem with my Q-jet so I'm hoping somebody could get me on my way.
I've rebuild the Q-jet with Cliff's SR rebuild kit. I rebuild it almost down to the letter and set everything as it should: Lean stop, rich stop and idle air bleeding valve. No problem so far.
I put the E4ME on the engine ('81 Corvette) and drove it around till coolant and oil were hot. After that removed the aircleaner and tried to get the dwell as close to 30 as I could but there is the problem. I also have my dual A/F meter in the exhaust and the A/F meter has some simple output that it is sending to the ECM so it can control the lean/rich situation.
Now the problem. Dwell is always at 25! The needle is searching a little (maybe 1 or 2 degrees total). But my A/F meter is saying i'm running rich at 11.5:1. So I turned the idle screws in until the mixture was around 13:1 to 15:1. The vacuummeter is around 20Hg (sometimes a little more) and I checked for vacuumleaks (when it was running lean) no problem there. When I'm driving slowly acc. to 30mph the mixture is at 12.5:1 (not 14.5 as it should be) so it is running rich again. When going back to idle the mixture is leaning out to around 14:1.
When I was back at the garage I looking inside the carb from the top with a bright flashlight and could see the plunger isn't moving! And that would explain the rich condition when driving. So I took solenoid out of the carb and replaced it with another one (I tested before putting it in!).
On this one the dwell meter still said 25 degrees well it was a horrible idle with a 18:1 mixture. When I "flash" the carb with my hand (to decrease intake air) the idle was going up. This means the A/F meter is right! Checked again with my light and the plunger was moving up and down (could also hear the sound. Again set idle to around 14:1 and dwell still at 25. Driving around and again the same thing in the beginning I see the mixture around 14 or 15:1 but after a few minutes I'm back at 12.5:1. And yes after checking the plunger again dead in the water (at full rich)
First I was thinking the dwell meter was broken, now I'm hoping the dwell meter is broken... When I set the key to start the engine the ECM (check engine) light is working and after starting it goes out. The ECM light is never on (even when I disconnect the CO sensor in the exhaust the light doesn't come on). When I remove the connector from the solenoid at the carb then the light goes on (but the mixture stays the same...)
Day two (today). Took the A/F ratio stuff out yesterday (after removing the ratio meter the dwell meter still said 25 no improvement in above idle rpm's.
Today I put some 300 miles on the vette so when I was driving it back into the garage I was thinking, well hotter then this isn't possible. So I connected the dwell meter and now it was at 40 (still hovering around 1 to 2 degrees). When opening the throttle I can see the meter going to 30 so something is working (same thing the day before). So I put the idle screws 2x 1/2 turn IN, no change in dwell. Put a cloth on the intake to rich up the mixture. Still 40 dwell.... Hmmm. Well anybody an idea? As I changed the M/C solenoid I think the carb is about right so the problem could be the ECM (or PROM?)... or something else?
So if somebody can point me into a direction please do!
Greetings Peter
