I did use the search feature looking for this topic, but found nothing. The mixture control solenoid on my Rochester E4ME Quadrajet has stopped working. It no longer makes the tale-tale clicking sound when the ignition switch is turned to the "on" position. I pulled a code 23 which lists an open or shorted M/C solenoid as a potential problem. Since the solenoid no longer clicks, I am pretty sure it is the culprit. At any rate, it apparently must be replaced. I checked the fuses and they are OK so I know there is power.

Some time ago, I took the top off the carb to replace the TPS but did not pay any attention to the solenoid except to be careful not to disturb the metering rods. What is involved in replacing the solenoid? Are any adjustments or settings required during replacement? Are any special tools or instruments needed to do the job? What holds the solenoid in place - clips, screws, what? Are there any helpful hints or tips that can make the job easier? Any potential pitfalls or potential unpleasant surprises that I need to be aware of? Or would I be better off leaving it to a pro?

Thanks in advance for any help.

Did you test the MC solenoid with an ohm meter to see if the solenoid is open? If the solenoid is good, it may just be a bad connection.

The air horn has to come off the carb to get access to the MC solenoid, just like when you changed the TPS. There should not be any adjustments necessary after you put the air horn back on.

Thanks for the response Ernie. Currently, the carb is off the vehicle and on the work bench. I tested continuity on the solenoid and it checked perfectly. It is not open. I also tested one of the electrical terminals to ground and got no reading, so it is not shorted (at the carb. anyway). I applied 12 volts to the solenoid and got one click each time I "made" the connection. In normal operation, while on the engine, the solenoid can be heard clicking repeatedly as soon as the ignition switch is turned to the "on" position. When the engine starts, the clicking cannot be heard so I do not know if it continues to click while the engine is running.

I disconnected the battery on the vehicle to test the plug & wires to the ECM for ground. One leg shows no continuity to ground but the other shows perfect continuity (0 ohms). This leads me to think the leg with no ground is the positive lead and the one with the perfect ground is the negative lead while the solenoid itself is above ground (insulated from the carb itself).

If I replace the solenoid, is there any adjustment necessary? A vague reference on another site leads me to suspect that an adjustment to the lean and rich stop has to be made when the solenoid is replaced?.

I am considering remounting the unit and checking for bad connections.

I am considering remounting the unit and checking for bad connections.
Based on you checks of the MC solenoid I would tend to agree. Do you have a scanner to plug into the ALDL so you can monitor the MC dwell? I would verify that the ECM is trying to control the dwell. If it is then you probably have a bad connection somewhere between the ECM and the MC solenoid.

The MC solenoid should have 12V on the pink and black wire as long as the ignition is on. The ECM provides the ground to energize the coil. If you don't have 12 volts at the pink and black wire, check the 10A fuse for IGN/ECM.

Both the ECM fuses are good. I tested both with an ohm meter. I also reset the ECM by leaving the fuses out for a couple minutes (10 seconds is all that is required). I will check for 12 v. at the pink and black leads. Thanks for the info.

I tested the voltage on the pink and black wire today. I got 12.3 volts across the pink and black lead and engine ground with the ignition switch on and engine off. Will reinstall the carb, check connections and test with scanner. Seems to be narrowed down to poor connection somewhere or bad wire between ECM and M/C solenoid. Will let you know what I find.

Thanks for the input.

...I got 12.3 volts across the pink and black lead...
Try the scanner first to see what the ECM is doing. Then get a test lamp and hook one side of it to 12V and the other side to pin 18 of connector C1 of the ECM. That's the MC solenoid signal. If you can verify the ECM is working then it must be in the wiring harness.

I'd try running a separate long jumper wire from pin 18 of connector C1 on the ECM direct to the other side of the MC solenoid. That would bypass all wiring in the harness for that circuit. There are two large wire connectors on the ECM called C1 and C2. C1 has pins with numbers 1-22 and C2 has pins with letters A-U. I'd cut the wire currently on C1-18 (Lt. Blu?) about three inches from the connector, and splice in the new wire out to the MC solenoid. Good luck.

>I'd try running a separate long jumper wire from pin 18 of connector
>C1 on the ECM direct to the other side of the MC solenoid.

Before doing that, simply disconnect the battery, then remove both plugs from the ECM (NEVER, EVER unplug the ECM without first disconnecting the battery!!!). Then use the ohmmeter to check that the grounded side of the MCS is no longer grounded. The ECM grounds that wire about 10 times per second while the other side of the MCS is always (with the ignition on) connected to battery power. You should not have measured "a perfect ground" on that lead before; that indicates something shorting it. It's barely possible that the ECM driver for the MCS was blown somehow.

If you have an old-time dwell/tach, you can connect it to the green plug in front of the carb and a nearby GOOD ground and monitor the signal applied to the MCS. I have a 10-foot length of two-conductor cable that I install when I want to monitor my dwell from inside the cabin while driving. With the ignition turned on but engine not yet started, you'll see the meter wiggling due to the "keyed" grounding signal.

If you don't have a dwell/tach, you can use an old analog-type voltmeter. To calibrate the meter, hook it up to the green plug and ground, then set it to at least 12 volts DC scale. Turn on the ignition and it should be wriggling at some voltage. Carefully note the voltage at the center of the "wriggle-zone"; that voltage that you see will represent about half of the full reading that you will note after about 30 seconds when the ECM stops providing the MCS signal while the engine is stopped. When the engine's running and warmed up, the reading that you should see, if the carb is set up properly, is just a little bit LESS voltage than the "wriggle-zone".

OHOHOH, I KNOW WHAT'S THE PROBLEM.... you've somehow grounded that green plug!!!! That green plug should NOT be connected to anything other than a test dwell/tach meter when you are wanting to monitor the dwell. Have a looksee: I bet it's fallen onto something that's grounding the metal prong inside. If that's not it, maybe the wire to the plug has frayed and is shorting to the intake manifold somewhere up front.

Mixture Control Solenoids are extremely reliable and very, VERY rarely require replacement. The plunger on the "piddle" valve can wear a spot on one side but there's nothing in the MCS itself to wear out.

Also, it was said earlier that there aren't any adjustments to make after replacing the MCS: that's incorrect. There is one funny-looking, spring-loaded screw that holds the MCS into the carb bore; the screw has extremely fine threads (something like 60, maybe 72 threads per inch). That's the lean-stop screw. It's head has two flats. There is a tool kit available from Textron (try your local NAPA store, ask for the CCC carb adjusting tool kit) which includes four special drivers, one of which fits that screw head. Another Textron CCC carb calibration kit has a set of tiny rulers and gages used to set the adjustments in the carb. One of those gages looks like a bent-up pencil clip from yesteryear and is used to set the spring-loaded MCS body a certain distance inside the carb bore, by adjusting the fine-thread screw. If you remove that screw, you will lose that precise adjustment and your MCS dwell will be off. IF you do not buy either of the Textron driver or gage kits, then you CAN try removing the screw using pliers but I'll guarantee you that you WILL break off that special double-flat head on the screw using pliers. If you want to try anyway... make a mark on one side of the screw so that you can reset it to the same place. Now, drip a drop of oil onto the screw, letting it drip down along the screw into the threads. Next, put your fingers on the MCS's mounting flange that the screw is holding down, and press down with your fingers; the MCS should move down 1/8" to 1/4"; this will relieve the heavy spring pressure from the screw. Now you can, while carefully counting turns, screw the screw CLOCKWISE, INTO the carb, while carefully counting turns. GENTLY screw the screw inward until it bottoms out, keeping pressure on the MCS all the time to prevent that heavy spring from pressing against the screw's very-fine threads. Now write down exactly how many turns you screwed the screw down, such as 6-1/8th turns. Be as exact as you can.

Now that you know where you'll have to reset the screw, you can back it out all the way (while keeping pressure on the MCS to prevent the spring from pressing against the screw threads) and finally, lift out the MCS itself.

If you don't relieve the spring tension of the MCS from the screw, you run the serious risk of stripping out the threads for the screw inside the carb body. Years ago, there used to be a repair kit but I haven't been able to find any for some years now. So if you strip those threads, yer pretty much SOL. If that should happen, there ARE a few things you can try, such as putting a small strand of wire inside the screw bore, which will force the screw against the other side of the threaded bore and perhaps cut the threads a bit deeper into the side of the threaded hole. I've used a strand of wire, a strand of very small (0.020" diameter) solder, and once I cut a small slice of alumunum foil, rolled it into a tube, stuck it in the hole, then threaded the screw into the foil-lined hole.

But I'll be willing to bet that ALL that happened in your case is that the green dwell plug has fallen into a place where it's being grounded. Not to worry: the ECM, itself, grounds that particular wire, so all you're really doing is bypassing the ECM's ground; no damage should result to anything.

Hope that helps!

Spanner, I think you may have hit the nail on the head! Today, I was looking at that very plug - the green one for the dwell/tach connection and observed it to be in bad shape. In fact, it is badly mis-shapen. Don't know how it got that way, but it is quite possible that it is shorted. I'll check it out tomorrow and let you know what I find.

The fact that I got a good connectivity reading from the negative side of the solenoid to engine ground has been puzzling me ever since Ernie said the ECM furnishes the negative voltage to the solenoid. It just did not make sense and was turning my brain to mush. Years ago, I was an electrician in the Coast Guard and my background told me something was hoaky. I know that if the solenoid is getting negative voltage from ground (essentially bypassing the ECM signal), then the solenoid picks up just once as soon as the ignition switch is turned to the "on" position and stays energized until the ignition switch is turned to the "off" position regardless of the number of times the ECM pulses the solenoid. A short in that green plug would explain the goofy ground.

I'll let you know what I find.

Spanner, I think you may have hit the nail on the head! Today, I was looking at that very plug - the green one for the dwell/tach connection and observed it to be in bad shape. In fact, it is badly mis-shapen. Don't know how it got that way, but it is quite possible that it is shorted. I'll check it out tomorrow and let you know what I find.

The fact that I got a good connectivity reading from the negative side of the solenoid to engine ground has been puzzling me ever since Ernie said the ECM furnishes the negative voltage to the solenoid. It just did not make sense and was turning my brain to mush. Years ago, I was an electrician in the Coast Guard and my background told me something was hoaky. I know that if the solenoid is getting negative voltage from ground (essentially bypassing the ECM signal), then the solenoid picks up just once as soon as the ignition switch is turned to the "on" position and stays energized until the ignition switch is turned to the "off" position regardless of the number of times the ECM pulses the solenoid. A short in that green plug would explain the goofy ground.

I'll let you know what I find.

.... has been puzzling me ever since Ernie said the ECM furnishes the negative voltage to the solenoid....

"I know that if the solenoid is getting negative voltage from ground (essentially bypassing the ECM signal), then the solenoid picks up just once as soon as the ignition switch is turned to the "on" position and stays energized until the ignition switch is turned to the "off" position regardless of the number of times the ECM pulses the solenoid. A short in that green plug would explain the goofy ground.

I'll let you know what I find.

It doesn't get "negative voltage to ground"; it's actually grounded by a transistor switch, similar to a pair of relay contacts, inside the ECM. When it's NOT grounded, you can measure 12 volts on it because there is 12 volts applied to the pink-black wire of the solenoid, which goes through the solenoid coil, and appears at the other wire of the solenoid when it's not grounded by the ECM. Again, that green plug connects directly to that end of the solenoid coil itself, so you can actually monitor whether the ECM is switching the solenoid on and off or not. In your case, it sounds like either the green plug or its wire is accidentally grounded somewhere, most likely to something on top of the intake manifold and possibly due to high heat. If so, then all you should have to do is eliminate the inadvertent-ground and you'll be back in bizness :o) If not, then disconnect the battery then unplug the ECM, then unplug the solenoid, and then measure the resistance to ground of the green plug; it should be infinite. If it's still zero, then that wire is shorting to ground somewhere, most likely inside the harness somewhere but most likely someplace on the harness where you may have other damage to the wiring from high heat. My '83 Malibu has several such "burned" areas along its harness that I have no idea how they happened as the harness doesn't seem like it's long enough to have fallen down onto the exhaust manifolds.

If the short goes away, then plug the computer back in and measure the resistance again (leave the batt disconnected). If it's now zero ohms, then that driver circuit inside the ECM has somehow gotten fried and you'll hafta find another ECM. I have an ECM-PROM Interchange Manual and can tell you what others will interchange directly but the fact is that you can most likely use ANY ECM for a 229-V6 G-body of '84 or '84 and there's likely to be no noticeable difference. You can't use an ECM from '82, though, as those were somewhat simpler/less capable than '83/'84; and the last year of the 229 V6 was '84 so anything later is also out, not to mention that '85+ ECMs were even fancier/more capable than '83/'84. You should be able to find another '83/'84 ECM fairly easily, and it shouldn't cost more than $40 at the very highest. I won't even look at them if they're over $30, myself.

But ECMs are pretty reliable, unless somebody's been playing around a lot with the engine harness, hooking things up here and there with pure abandon, not having the vaguest idea what's what or what they're doing.

Today, I checked the green dewll plug that was badly mis-shapen. It was shorted AND one of the legs was in direct contact with the thermostat housing. Just like you suspected, that was the culprit. I cannot prove it, but my mechanic MIGHT have damaged the plug last month when he replaced the valve guide seals and adjusted the valves. I cannot imagine how he could have gotten that close to the plug, let alone use enough force to mash it up, but I cannot think of any other way it could have happened. Who knows, I may have damaged it last year when I changed out the thermostat, but I learned a long time ago not to be heavy handed with fragile mechanical/electrical systems.

Oh well, the problem is solved and I want to thank you and Ernie for your assistance. Boy, am I glad I didn't jump in blindly to change the solenoid. Right now the carb settings are perfect.

What a great web site!

Glad that's what it was! Yer lucky it wasn't the hot wire to the solenoid that was shorted; I had that heppen a cupla years ago when I changed the intake gasket on my full-sized wagon. Although I very carefully lowered the intake in place and *thought* I ran my hand along the wiring harness that runs behind the passenger's side head, and also along the rear edge of the intake to check that no wires had gotten caught under the intake, it happened the hot wire that feeds 12V to all the solenoids on the engine DID get caught under the right rear corner of the intake, running right across the water port. When I was all done and tried starting the car, it would start then as soon as I released the key, it would stop. Then I realized some of the idiot lights were no longer lit with the ignition turned on. The ECM's 10 amp fuse was being blown. That caused one HECK of a lotta head scratching for a coupla hours before I finally dug out the CSM and started going through the schematic to see what all was on that fuse that could possibly be blowing it. After another cupla hours, I FINALLY realized that 12V feed line to the engine's solenoids and schtuff was shorted. Digging into the wiring harness and carefully unraveling the tape, I FINALLY found the dang wire snaking underneath the corner of the intake manifold ;o((((

Wound up cutting the wire on both sides where it disappeared under the intake, then splicing it back together. I took the chance of leaving it there instead of yanking the intake again because it seemed that the wire was not causing a coolant leak despite running across the gasket surface. I figgered "What's to lose: if it turns out to be leaking, I'll just hafta do it again!" And sure nuff, here it is almost three years later and it's still water-tight :o))))

Anyway, glad you got if fixed!