62 fuelie problem??

[Jerry J.]

Hi... This is my 1st post. Have been reading this site for abt. 1.5 Years. The knowledge is absolutely incredible..I have learned a lot..

Problem is friend has a 62 fuelie, I have a 61.. When we turn the idle fuel screw in on the 62 very little changes, even when we seat the screw... On my 61 fuelie, when we change screw, engine stumbles, trips and stalls when screw is seated... The 61 idle fuel screw is turned out 2.5 turns and unit runs great. Is this a problem with the 62 or is it unique to that year???

Sorry for long post...Thanks, in advance... Jerry..

[G B.]

Calibration of enrichment lever stops

If an injection unit's enrichment lever economy and power stops are properly calibrated, the idle mixture screw will require less than one turn in either direction to produce a stumble. It sounds to me like the '62 unit has the economy stop set too close to the plenum (too rich).

You can get the stops properly calibrated by using a manometer or an exhaust gas analyzer. If your friend has the patience of Job, he could even use the Jack Benny calibration method: drive the car with various stop settings until he's happy with the way it runs. The last method is preferred by most members of the CorvetteForum. I'm sure someone there can advise you on how to perform trial-and-error calibration.

There are fuel injection repairmen all over the country who can do it with a manometer. If the engine is 100% stock Corvette, use a manometer if you want to be precise about the calibration. If the '62 has a modified engine (such as a 350 with an aftermarket cam and headers), you might get a better job with an exhaust gas analyzer stuck up your tailpipe. So to speak, that is.

Also consider that I could be full of crap about calibration problems. Maybe the '62 unit actually has larger replacement nozzles, or the idle mixture screw has the tip broken off, or the choke isn't releasing all the way, or...

[Roy B.]

Re: Calibration of enrichment lever stops

L/S is economy which determines the amount of fuel going in to the engine at idol and or at cruising speed, R/S determines the amount of fuel at throttle ( as you increase speed)

[Ed Jennings]

Re: Calibration of enrichment lever stops

I would agree that the economy stop is possibly too rich, but as Jerry points out there could be all sorts of other problems as well. My 62 will stumble if you turn the idle mix screw more than about a half turn in either dierection. Adjustment by the trial and error method is tedious at best, though it can be done, and if you don't know what you're doing you can really screw it up.

Jerry has the equipment and expertise to properly calibrate a unit and comes highly recommended....... Ya might want to give him a call.

[Mike E.]

Re: Calibration of enrichment lever stops

Another possiblity is that the large butterfly in the air meter is maladjusted. Check the setting in the ST-12 service manual.