Zenith questions and bog off idle ?

cnavarro · 06-11-2005, 06:46 PM

I took advantage last night that it wasn't too hot and there was a good breeze at home. Starting tinkering with the aux enrichment adjusting screws and the accelerator pump screw. Up until this point, I had popping at idle and to a lesser extent, on decel. I could live with that. It's annoying that when I go to accelerate from idle, it bogs (cough cough and sputter) then comes to life once you get it out of the bog by 1750 or 2000 rpm (where the torque convertor locks up- it's a sportomatic). I turned both aux enrichment screws out 1/2 a turn and the acc pump screw 3/4 turn. It's much happier, no popping at all at idle and almost inaudible occasional pops on decel. Engine was idling perfectly at 600 rpm and I bumped it up to 800, just until the alternator light goes out when the sporto is in gear and at a complete stop. It still seems to have to think about moving when I give it gas and occassionally bogs (without any sputting or coughing). All done with engine at operating temperature. I'll see in the morning how it feels when it's cold. The same symptoms were present when it is cold and to some extent worse. All the usual have been attended to- valve adjustment, points, cap, rotor, plugs, new wires, timing is at 35 degrees @ 6000 rpm per the spec for the '70 2.2T.

What is the proper method for adjusting the acc pump and both the aux enrichment screws? I'm assuming that turning the larger of the two aux enrichment screws richens up the mix (based on my nose smelling the exhaust). As far as the smaller of the two screws, turning it out seems to lean it out (further CCW, the more it pops). Are these observations correct?

About the bog- the dissy is not the original one, but a bosch retrofitted by Stoddard. It seems that the idle advance is a little retarded, somewhere about 0 degrees to give me the 35 degrees @ 6000. Could that lack of timing be the cause of the bog at idle? If so, what can I do to the dissy to correct this?

project 911 · project 911's Garage

Charles-

I've got a 70 2.2 with Zenith and Bosch dizzy.
The Zenith pump diaphrams can go bad, and the nozzles can get plugged, but in my case it is all in the timing. For some reason mine has always had the bog if I set the timing to 0 degrees as shown in the manual. I finally just started timing it by ear by starting at zero and making slight changes and blipping the throttle until it responded crisply. I always get mixed up with which way is advance and which retard, but mine is set so the Z1 mark on the pulley is about 1/4 inch to the left of the mark on the fan housing. It still shows 30-35 degrees at 6000rpm.

Allenk · 06-12-2005, 06:01 AM

Same for me as project 911. It seems to me, if it were your acc. pump adjustment, you would get popping out the carb from leaning out. Unless of course you are way rich at idle, but you would be popping out the exhaust from so much fuel.

jstobo · 06-12-2005, 07:12 AM

The factory manuals have the best write up on the Zeniths that I have found. That said-Haynes has good Aux Enrichment instructions. They are out of the Factory manual. If you have zenith's my advice to find someone with the factory manual and copy the appropriate pages. Good Luck

limble · 06-12-2005, 07:32 AM

Charles,
I have the Zenith manuals. Send me an e-mail.
thelancials@msn.com

cnavarro · 06-14-2005, 07:09 AM

Thanks Mike for the manuals. I spent a while this morning syncing the carbs and re-doing the slow idle adjustment. I'm very happy with the results and the car now idles at 850 on the dot and doesn't smell like it's pouring out gas either.

Will adjusting the aux enrichment system tune out the bog at 1250-1350 rpm? Seems to me that it's way too rich. I did bump up the timing closer to 0 degrees at idle, but it's probably a few degrees retarded from 0, as i'm trying to keep the advance limited to the 35 degrees at 6000 (it's actually closer to 36 at the top end now). I don't have access to a CO meter, so will this be futile without such a device?