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Re: vintage CIS warm-up issues Posted by Dana [Email]  (#2822) [Profile/Gallery]
(more from Dana) on Sat, 20 Jan 2007 03:48:03
In Reply to: vintage CIS warm-up issues, MS, Fri, 19 Jan 2007 19:08:25 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Most of the items you list are on the right track. During the first couple of minutes at very cold temperature, the cis control system is "locked" at a fixed fuel enrichment value until the oxygen sensor has been allowed to warmup by heated exhaust gases. Then the CIS control turns on (this is where you are having a problem). If your warmup regulator heater resistance is ok, getting 12VDC, clean of deposits, and checks out ok for back pressure readings to the fuel distributor when cold...then I would suggest checking to see if the CIS is controlling within the mid range and if not...adjust the fuel enrichment to achieve this. Its control must be able to swing between warm and cold weather. There is a possibility that the enrichment setting is fine to achieve proper CIS control during warmer weather but then can not enrich the mixture enough during cold (i.e. you are fine during normal inspections during warm weather). My guess is that the enrichment screw was just a bit too lean but one can not tell when the cis system corrects this within its extreme control range. It is the reason to have the frequency reading of the modulating valve...to check that it is running at 50% duty and there is enough control range above and below this value...i.e. 35% to 75%.
The other thing to check is the short term enrichment during the first two minutes of cold driving. It is the manifold vacuum switch which activates the cold start valve in short spurts during the first couple minutes of driving (this is the additional function of the cold start valve other than for just starting....) Hope it helps...Dana
posted by 207.68.60...
, Sat, 20 Jan 2007 03:48:03 <-- Viewing This Message, Sun, 21 Jan 2007 15:14:56
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