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  #91  
Old 10-17-2018, 01:46 AM
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Originally Posted by MIPS View Post
It's just a variable position electronic actuator that pushes or pulls two pins in the carb body that control how rich or lean the engine runs.
Holy shit, that is awesome! On paper, assuming everything is working properly, it should have almost comparable performance and emissions to an equivalent fuel injected engine. Well... you know, kind of... not really, but it's still awesome. I'll grant, I don't know a whole lot about old carburated cars, but I never knew that mixture adjustment was a thing, at least not on stock cars. And not on an AMC. That's pretty advanced tech for AMC back in the day.

And it's further reason why it's so upsetting to me when people disable these systems. That's literally something that's good and helpful! Good for fuel economy, the engine, AND the environment!
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  #92  
Old 10-17-2018, 08:46 PM
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I think my plan after the car is on the road and I am positive the ECU is properly serviced I will throw the car on an old AirCare dyno to see that it says, then do the nutter bypass and try again. I am starting to now get curious exactly which way the emissions, performance and economy goes. According to the official documentation the ECU/ECM/CEC (I'm running out of things to call it but for all purposes I am referring to the emissions computer) keeps the air/fuel ratio at 14.7:1 with a physical either/or adjustment for high-altitude driving but no fine tuning outside of using a wideband O2 sensor and adjusting components not monitored by the computer, else it just tries to compensate for the changes.

My goal today was to inspect and test the stepper motor. It's held onto the BBD with four torx screws. The only warning is that while the pins are loosely retained by a plastic disc on the motor assembly there is a spring that can fall out and easily get lost. If it is not on the center pin in the photo below, make sure it's still hanging out of its recess in the carb body.



When the key is in and turned on the ECU will initialize the stepper motor by advancing the pins out to a full-closed position and then pulling them back. That is what happened on my unit so it's safe to say the ECU, the stepper motor wiring and the stepper motor are functioning. The motor is made up of two windings with taps at each end and in the middle. Refer to the wiring diagram on the last page. End-to-end resistance should be around 140-150 ohms with each half of a winding being half of the total value and no continuity to the exterior casting. The readings should be identical when comparing one winding to the other. It all tests good.
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  #93  
Old 10-17-2018, 10:06 PM
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I suppose the book must have a procedure for adjusting the carb... there must be a 'neutral' or 'test' mode, some method of setting the stepper motor to whatever position it's supposed to be in for making adjustments. Hell, it might be as simple as unplugging it while the ignition is off.
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  #94  
Old 10-18-2018, 08:47 PM
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When on in open-loop there are several fixed positions the pins can be in depending on several on/off sensors. The manual states how to enable each mode for testing and that various carb adjustments can only be performed under certain ones. If you cannot reach the specified mode there's 20 pages of logic flowcharting to test each component in the CEC individually. I guess this is why people hate the BBD electronic carbs so much. If the emissions system is not working the adjustment instructions are useless and you are forced to fudge some things to get it close enough, or just do the nutter bypass and get another carb because computers are hard.




I think my major strength here is that I'm approaching this from the opposite direction. Whereas most skilled mechanics of this era vehicle (and most jeep people) really don't know much about electronic emission systems my background is early computer theory and digital electronics so this is all making total sense to me as opposed to how the carburetor in general works.

Again, I want to point out that the AMC repair manual is amazing. It's twice the thickness of your average Haynes manual and is pretty much identical to that of the average phonebook. It's like reading a tome.


Last edited by MIPS; 10-18-2018 at 11:07 PM.
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  #95  
Old 10-19-2018, 02:28 AM
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And this is why I despised working on computer controlled cars with carburetors.
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  #96  
Old 10-19-2018, 09:25 AM
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nvm

Last edited by init4fun; 10-21-2018 at 08:32 AM.
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  #97  
Old 10-19-2018, 09:44 AM
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nvm

Last edited by init4fun; 10-21-2018 at 08:32 AM.
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  #98  
Old 10-19-2018, 04:44 PM
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Quote:
Originally Posted by MIPS View Post
I think my major strength here is that I'm approaching this from the opposite direction. Whereas most skilled mechanics of this era vehicle (and most jeep people) really don't know much about electronic emission systems my background is early computer theory and digital electronics so this is all making total sense to me as opposed to how the carburetor in general works.
I would be taking a similar approach. It's pretty safe to say my knowledge of those things isn't as extensive, but still.

Around '96 there was a new tenant in my old building who knew how to work on EFI, which I think ticked off the super who could fix just about anything else on a vehicle. However, the super serviced arcade machines regularly and often worked on TVs and other electronics, so go figure.

Last edited by Jon A.; 10-19-2018 at 04:47 PM.
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  #99  
Old 10-20-2018, 12:07 PM
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Finished cleaning and verifying some cabling and slapped the stepper back in for a test. Success.

https://www.youtube.com/watch?v=b_BOvlLOrP0

The car sounds WAY better now at idle and you can smell it's not running as rich. Still not perfect but I think that might just be the O2 sensor needs to be replaced.
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  #100  
Old 10-20-2018, 10:57 PM
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Sweet!

O2 sensor, but also perhaps those vacuum switches. You might want to get a vacuum gauge and test those switches to see that they open/close at correct vacuum (or at all). Nice that it says right on the wiring diagram how much vacuum they switch at. Vacuum gauge is a good thing to have for a carburated car, anyway.

Last edited by MadMan; 10-20-2018 at 11:24 PM.
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  #101  
Old 10-21-2018, 09:25 PM
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Great to see somebody fix one right instead of trashing ever little bit of emissions control. This is what made most 70's-80's vehicles so intimidating to me, that sea of vacuum lines and "doo-dads".
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  #102  
Old 10-27-2018, 05:06 PM
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Dug through the parts bin and pulled out the screws, original hoses and check valve for the VsV and reinstalled everything back up to the Sol-Vac solenoid. Ran a vacuum check to see if the CeC was properly actuating the solenoid and then plugged the hose until the sol-vac is replaced.




So that now leaves one last plugged vacuum line (which you can see above I taped shut because the rubber plug has cracked and was leaking) which I can only assume is for the cruise control. I went back into the bin again and was unable to locate the vacuum reservoir. I can only assume it was misplaced but at least replacements are easy to source. I did however find a length of vacuum line that was about two feet long and while it's not the original T-shaped bracket the cruise control kits came with there was a similar looking L-shaped metal bracket but it did not fit where we saw the one above pictured and the hose was not long enough to reach that side of the car. It had to of been located somewhere near the throttle linkage as Madman suggested. I had to step back and look at what I HAD and what I was MISSING.
Looking directly above the linkage is the firewall with a mouse chewed bulkhead seal. Next to it is a ground point....and another unsealed hole through the firewall.....Hmmmmm...




Aha! The bracket mounted here as an aftermarket/dealer installation! The other screw was in the parts bin.




Okay, so now the actuator is reinstalled where it should be, the linkage is where it should be (but needs to be replaced) and the vacuum hose routes to where a vacuum reservoir would of normally been, which is right next to the plugged vacuum line. So now we have all the vacuum lines and mysterious cabling figured out.

Last edited by MIPS; 10-27-2018 at 05:19 PM.
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  #103  
Old 10-27-2018, 09:05 PM
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Ah ha! I love being right ^_^

That's a really janky looking bracket. I wonder if maybe this car had the cruise thing all the way over on the passenger side, and someone replaced it with this unit and made a bracket for it. Alternatively, it could just be that way from the factory/dealer. We are talking about the company that uses radioshack toggle switches on the dashboard.

Anyhow, just buy one of those ball chain connector thingies and put the two halves of the chain together. It's like a light chain, except the slightly larger diameter ball chain.
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  #104  
Old 10-27-2018, 10:45 PM
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I'll just replace the entire ball chain with a new piece as it looks to be repaired once already.

I'm just more baffled by how inconsistent the service manual is on the cruise control. I can see in other google images the actuator has a vacuum reservoir but the Popular Mechanics article doesn't indicate one as part of the kit.
Likewise I was expecting the large diameter hose to be manifold vacuum. Wrong. It's the smaller diameter vacuum port. The larger diameter hose runs inside the car and to the brake release switch which until now I didn't completely recognize as having a vacuum port on it, since it's bolted to the brake pedal.



Worse yet I still cannot tell if this was aftermarket or dealer. As mentioned the kit and AMC's package are the same thing. All the parts cross-reference even though for example AMC lists a different inline speed sensor while Dana and Popular Mechanics list what I have now which is a magnet strapped to the driveshaft while the speed transducer is bolted next to it.

Whatever. If it works it works.

Last edited by MIPS; 10-28-2018 at 02:36 PM.
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  #105  
Old 11-04-2018, 03:56 PM
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The thing is with forums, especially ones that aren't very busy, is that they get hit real bad with spam bots. Because they don't want to find a real solution to the problem, the admins just check the box that says all accounts need admin approval... and then they always forget to check if there's any new members pending. I wouldn't be too mad at them, they probably just don't check the thing very often.
Two months of this crap and now I'm watching registrations get rejected within hours. I'm positive whoever is moderating registrations has their head completely up their ass.



I have not seen this kind of paranoia since I screwed with Flat Earth Society forums a decade ago.
If they don't take this last registration, get f****d EaglesDen.






Ahem. Anyways....
On a more positive note, the Cruise Control is now reinstalled completely. Those black gobs on the chain were actually bits of shrink tube someone was using to smooth the cable out where it passed through the opening for a second cable linkage. I replaced that with a hollow bolt for hanging a ceiling light. Replacement chain was $4 from The Home Depot.



Last edited by MIPS; 11-04-2018 at 05:02 PM.
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