I have a Q-jet on a truck I'm working on. It has the electric enrichment solenoid on the right front of the carb. The connection is a two wire plug. One wire connects to a matching connector in the main loom. The other has a connector but I can't find where it should go. It wasn't connected when I got the truck. There is a broken sensor in the water neck but I have tried to buy one but noone knows what it is nor can they match it up to my extra connector. I know there a lot of guys here who would know this so let me know if you can help. Thanks in advance,,,, Matt

Hummm, two weeks and nobody responded.

Could you give a better description of this other connector? Is it from the carb, or in the harness?

All GM CC carb vehicles have a diagnostics connector in the harness, green with a single wire, that just sits there. Weird way to do it, but that's what they did.

The thermostat housing sensor is either the "CTS" (coolant temperature sensor) if electrical, or "EFE TVS" (early fuel evaporation thermal vacuum switch) if vacuum. The CTS is absolutely essential to giving the computer the info it needs to run the engine correctly.

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Your description of the wires doesn't completely make sense...

That isn't exactly an "enrichment solenoid"; it's the computer's method of controlling fuel metering. The computer is supposed to be constantly switching it on and off whenever the engine is running, at a rate of about 7 or 8 pulses per second. It can vary the percentage of the time that it holds it on, from about 20% of the time to about 80%. If the computer (via the O2 sensor) detects that the mixture is too rich, it holds the solenoid "on" for a greater fraction of the time, and if it sees "lean", it energizes it for a lesser fraction. Without that hooked up, the carb will go to full rich; the actual control range isn't that great, so it might still run OK, but it will get terrible gas mileage.

The 2 wires that go to it are: a pink with black stripe, which is a particular ignition feed that's in common with all sorts of other things, it comes from a splice in the wiring harness where it's joined to its source alnog with about 5 or 6 other such wires; and a blue one, that should go straight to the green connector that five7 mentioned, and then on into the pass compartment to hook to the ECM.

The sensor in the top of the water outlet has to be the coolant temp sensor. There should be a yellow and a black wire going to it. The original connector on most vehicles is round with 2 concentric contacts, it is a piece of horse dung; most of the replacement sensors have a different style of connector, and should come with a mating pigtail in the box.

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The connector is a small oval with two wires. One wire comes out of the main harness and the other is about 8" long and has another connector on it. The truck isn't here right now so I can't check wire colors or what the other connector looks like. I think I'll have the truck back next weekend to change the oil and finish welding the exhaust. I rebuilt the engine and I also thinnk I have a vacuum line wrong too because it is shifting strange. It winds pretty tight before it shift out of first and hesitates during the shift. I know it has a vacuum operated sensor that affects the shifting but I haven't got into that problem yet.
Thanks,,, Matt

I posted same time as RB83L69 so after reading his post I can add a bit more info. This truck doesn't have an O-2 sensor,never has had one. RB83L69's description sounds very close though as far as I can remember other than the lack of O-2 sensor. I just put new exhaust on after putting in the rebuilt engine and the new Y-pipe didn't have any provision for an O-2 sensor either.
The truck is an 86 chevy with 305. I tried to buy a CTS for it and they gave me the two post piece you describe but it won't fit the connector I have that comes from the connector on the carb. Maybe when I get the truck back I can take some pics and show all what I'm dealing with.
The full rich carb also makes sense because mileage has sucked and it plugged the catalytic converter which is why I had to replace exhaust system.
Thanks,,, Matt

If your truck never came with an O2 sensor in the exhaust then it didn't come with a computer controlled carb either. There's no point in putting on a carb that the ECM can alter it's fuel curve if the computer has nothing to reference (O2) to check it's adjustments against.

Some early-mid 80s GM trucks DID have "ESC"- electronic spark control- that has a computer controlled distributor but not carb. I believe they have a coolant temp sensor, and maybe even a throttle position sensor in the carb but no provision to run a M/C solenoid. This is from WAY WAY back in the archives of my cobweb-infested brain so don't take this as gospel.

I could almost beleive that! It does have the ESC distributor. But then where does this plug really go especially since it fits this carb. It does make sense since there would be no other way for the ecm to determine rich/lean. I have another Q-jet from a 79 vintage 1 ton van that I could put on and not have to worry about the thing on the other carb. I also have an old HEI with vacuum advance which I could bypass the ecm altogether. I'd probably have to rejet the carb since it was from a 350 but that shouldn't be too bad.
Really I'd like to know how it's all really supposed to be just for my own knowledge.
Later,,, Matt

What year is this truck, and what size (1/2 ton, etc.) and engine?

I have an '84 G20 (3/4 ton) van, originally 305 (350 crate longblock put in later) that has a computer, a distributor with a 4-wire flat connector AND vacuum advance, with a TH700R tranny. The carb has NO computer connections (not even TPS). The sensor on the thermostat housing is the EFE TVS only - no wires. A.I.R. to the manifolds only, no O2 sensor.

Perhaps that's what your truck originally came with, and someone put a CC carb on it thinking it needed the computer control.

The truck is an 86 Heavy Half camper special. The engine which matches ID numbers, is a code H, High Output 305. It's possible a prior owner did switch carbs. The distributor is a vacuum advance ESC unit. There isn't a TPS or an obvious place to mount one on the carb. My Haynes manual is where I read it was an enrichment solenoid. I thought I understood it all way back last year but my memory has fuzzed out since then and I couldn't figure out the wires then either.
The wire that comes from the main harness appears like a factory splice into the wire it attaches to. Just like what RB83L69 describes in his reply. There's just no place for the other end of the carb connector to go, at least I haven't found it yet. I assumed it would go to a sensor of some kind. There may be another connector in the main harness it needs to go to. On the water neck is what appears to be a standard temp sender from the 70's but the contacts are broke off. Also on the neck are two different temp vacuum switches with 4 or 5 vacuum lines to each one. Some of the lines are from the evap can others go to the air pump and related stuff. The vac advance also comes from one of these.
Like I said earlier, I'll try to get the camera out next weekend when the truck is here and take a few shots as well as a shot of the vac diagram.
Thanks for the help and ideas,,, Matt

It's probably the right carb. Somebody fiddled with the wiring, most likely.

For example, when I got this van, the DEALER had disconnected the 4-wire distributor connector and jumped two of the wires together! I undid that jumper, and it wouldn't run. Plugged the connector back in, ran again.

Good luck. Hope you can find a wiring diagram to help figure it all out.