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Fuel adjustment advice

Happy New Year everyone. I know its not the best day of the year to ask for help/advice, but I'm at the end on my patience/skills. I blamed a no-start problem on my 83 SC 3.0 on a fuel adjustment I made the previous night. Problem turned out to be a brand new pickup cable. By that time I had spent hours making fuel adjustments to try and start the car. Pickup problem has been corrected, I now had spark, but now I can't get it to start due to the fuel mixture screwup. How should I proceed to get it running again? I tried (and tried) to go from lean, with 1/4 turns, but no dice. If I raise the plate as its being cranked, I can get it to start briefly...4-6 seconds, but it will stall out again. Any advice would be greatly appreciated. Thanks!
Old 01-01-2018, 10:06 AM
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I'm by no means an expert, but this would be a good opportunity to check your fuel pressures (cold, hot, system,etc.)with a gauge just to verify that fuel pressure is not an issue. It's also a good time to verify that you have no vacuum leaks. Procedures for both fuel pressure tests and vacuum leak tests can be found via search.
After that, you can always calibrate the mixture via the factory method:
Pull one (or all) fuel injectors out and place in a jar while still connected to the fuel line. Jumper the fuel pump (procedure also found on search) so that it is running. Adjust the mixture screw so that you just barely get flow from the injector/s, then back off (counter clockwise) one half turn (180 degrees) on the mixture screw. If you have correct fuel pressures and no significant vacuum leaks, the car should now start and run. Once you get here, you can then play with the fine tune adjustment on the mixture (preferably hooked up to a CO meter to get the precise optimal setting.
I'm a rookie at this but other more experienced folks will chime in. Don't hesitate to ask questions, as in my case I have found that we have a community of not only experts, but friends willing to offer advice and time to help each other.

Last edited by 997at; 01-01-2018 at 03:34 PM..
Old 01-01-2018, 03:31 PM
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Thanks, the injector idea is good. I'm going to give that a shot. I've done a vacuum leak check with a smoke machine, and fixed a couple before this occurred. I've done a cold pressure test only, and it was in spec. It ran well when I shut it down. I'm so angry that i sabotaged myself! I'd just like to get the darn thing running. Thanks again.
Old 01-01-2018, 03:41 PM
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That sensor plate is really sensitive ...
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Old 01-01-2018, 04:36 PM
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And you know, I've read that it should "click". Mine does not click at all. Its as if it were a Allen head screw. I wish I could find a starting place, and at least get it running...even if its rough.
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Well, if its running with the air flow sensor lifted, turn the 3mm clockwise and the setting will be doing that which you did with your fingers to keep it running. Always know where you started with the 3mm allen so you can go back.
Bruce
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Old 01-01-2018, 06:27 PM
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There's a base setting for the fuel. The number one rule with CIS is don't mess with the fuel mixture until you know the system pressures are correct, the system is vacuum leak free, all the system components are functioning correctly in spec and your engine timing is correct.

You need to disconnect the safety switch plug on the back of the sensor plate, then wind the fuel mixture out ccw 1 to 2 turns, turn the ignition to on (not start) then lift the sensor plate. Turn the mixture screw cw until you just hear the injectors start to squeal. Don't do this for too long or you will fill the cylinders with fuel. Then wind it back ccw 1/2 a turn. That puts you in the ballpark. The problem now is that you don't know how much it's been adjusted for vacuum leaks and other problems so it may not start right away. I guess you would go richer cw 1/8 of a turn at time until you can get it to start. The screw does not click. They never did. Don't forget to plug the safety switch plug back in.

This thread is the best for CIS. It's a great place to start.

CIS Troubleshooting for Dummies

Last edited by gazzerr; 01-01-2018 at 07:11 PM..
Old 01-01-2018, 07:04 PM
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He already got it to start. He just needs to find the sweet spot. Start it and push on the sensor plate LIGHTLY to keep it running. Then adjust it so it stays there. I followed Bruce's advise above. It was a glorious day...
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Old 01-01-2018, 07:14 PM
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He should be able to find everything he needs off that thread. There's a number of ways to do it from using a gas sniffer on the exhaust (factory instructions) or reading the signal on the OXS test port pin (O2 sensor duty cycle). You can pretty much do it by smell and the lifting or pulling the sensor plate method and seeing how the engine reacts. The thread has a link to this method too.

The thing is chasing the mixture is absolutely pointless unless you know the whole system is up to spec. It will never run right.
Old 01-01-2018, 07:19 PM
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Thanks for the input everyone. I'm going to get a fresh start tomorrow. Good thing my garage is heated....I'm going to need it in this weather.
Old 01-01-2018, 07:27 PM
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Quote:
Originally Posted by enzo1 View Post
He already got it to start. He just needs to find the sweet spot. Start it and push on the sensor plate LIGHTLY to keep it running. Then adjust it so it stays there. I followed Bruce's advise above. It was a glorious day...
In other words, keep turning the mixture screw clockwise 'til you find the sweet spot where it keeps running.

Cheers,

Joe
Old 01-02-2018, 03:41 AM
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Its alive! I finally got it after several days of tinkering!!! And it is a glorious day! She's purring like a kitten. Thanks again to all for the advice!
Old 01-02-2018, 01:38 PM
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BTW, is it possible to purchase the basic equipment to adjust the fuel/air mixture, or is that something that cost thousands of dollars. What type would I need? Recommendations? I ask because I don't have anyone here in Shreveport that I'd trust to touch my car...and this is from personal experience. And its a 3 hour drive to Dallas....
Old 01-02-2018, 01:45 PM
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Quote:
Originally Posted by Bigdog1758 View Post
BTW, is it possible to purchase the basic equipment to adjust the fuel/air mixture, or is that something that cost thousands of dollars. What type would I need? Recommendations? I ask because I don't have anyone here in Shreveport that I'd trust to touch my car...and this is from personal experience. And its a 3 hour drive to Dallas....
You can buy an air fuel ratio (AFR) gauge for less than a couple hundred dollars. Do a search on Pelican or google to see your choices. Youíll need to plumb an o2 sensor into your exhaust- unless the 83ís have them already; not sure if or how you could run two things off of one, maybe someone can chime in?
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Old 01-02-2018, 02:00 PM
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Hi, I have a AFR, but thought that I'd need something more sophisticated than that. Is the AFR sufficient to adjust the fuel/air ratio?
Old 01-02-2018, 02:04 PM
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It appears Pelican doesnít list a simple wideband kit, hereís a link to what I was talking about

https://www.amazon.com/Innovate-Motorsports-3795-Wideband-Gauge/dp/B001QFH2RW/ref=sr_1_3?ie=UTF8&qid=1514934209&sr=8-3&keywords=innovate+wideband
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Old 01-02-2018, 02:05 PM
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Quote:
Originally Posted by Bigdog1758 View Post
Hi, I have a AFR, but thought that I'd need something more sophisticated than that. Is the AFR sufficient to adjust the fuel/air ratio?
AFR is the perfect tool to use to adjust your mixture, do it warm and at idle. Seems most folks recommend high 12ís to low 13ís.
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Old 01-02-2018, 02:07 PM
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Quote:
Originally Posted by Bigdog1758 View Post
Its alive! I finally got it after several days of tinkering!!! And it is a glorious day! She's purring like a kitten. Thanks again to all for the advice!
Every Bigdog has it's day.... glorious
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Old 01-02-2018, 02:25 PM
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i adjusted mine for years without AFR and it was fine, when I got the AFR gauge it was good.

set it as rich as it cant stand and not surge at idle and RPM does not drop down when letting off gas. disconnect the O2 when setting
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Old 01-03-2018, 07:42 AM
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T77911S: That's what I was thinking. There are people who say you shouldn't even touch the fuel-air setting without a test equipment, and others who do it by "ear" and are fine with it.
Old 01-03-2018, 09:13 AM
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