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73-87 Chevy _ GMC Trucks => Fuel Systems and Drivability => Topic started by: krigermoose on July 22, 2020, 12:55:12 am
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I'm a complete newb when it comes to wiring, and I've been trying to figure out the wiring for my carburetor. It's an M4MED on an '86 C1500 350. You can see in the image I attached, it's the connector that plugs into the device at the top of the carburetor. I traced the wires so it's easy to distinguish them; I am trying to find where the green wire goes.
Another wire I'm trying to figure out is where the electric choke connector goes. Right now I have it tapped into the fuse box, and it gets power when the key is on. I just want that wire to go to the right place.
Thanks for the help guys btw. My previous posts have only been questions and they've all been solved by you all.
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Hard to tell what kind of choke coil you have with the pic, but if it is electric, there will be a tab on the face of the coil cover. You will need a female spade termination to connect the wire to the male spade tab.
Sorry I can't help on the carb electric device, too new for me to even know what it does... ::)
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Sorry, could've worded that better. I have the connector for the choke, and it is an electric coil. I was wondering where the other end of the connection goes to. I had to get a new connector for the choke, I just don't know where to properly power it from. Maybe it's fine how it is which is tapped into the fuse box.
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GM electric choke operation for Q-jet carbs (http://forum.73-87chevytrucks.com/smforum/index.php?topic=36868.msg309686#msg309686)
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Unless you are preserving originality, what you have there is a shelf token ;D
M4MED is an acronym, Made for Making Engine Dead. Search that key term (M4MED) on the forum, for example: http://forum.73-87chevytrucks.com/smforum/index.php?topic=10151.0
The thing that looks like an MC solenoid is called the dual capacity pump solenoid. Basically it's something that breaks along with the other many things that fail on quadrajets. When "regular" Q-jets work properly they are pretty good carbuertors, however, they do nothing to improve overall power potential and are great at making you pop the hood, which is good if you don't regularly pop the hood. Think of it like this, they saved the same design and kept messing with it over and over again until it was abolsished. It is revered by many, but the feedback style carburetors and the like, or anything more than an electric choke is a non-supported, oboslote money dumpster and time waster. Do yourself a favor and look into a better option for fuel delivery.
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Unfortunately krigermoose lives in California like me and is subject to dynamometer smog tests with full Underhood inspection every 2 years which means he cannot remove or modify anything that has to do with the emission system. I believe this is a mixture control solenoid carburetor without dual capacity pump. All the ones I worked on at the dealer with dual capacity have an extra set of wires coming out of the side of the solenoid.
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Mike S is right, I do live in Cali, and this carb is actually brand new and I honestly just chose this because it is what I had originally. If there's anything I can modify on the carb right now that I can revert back to later temporarily for emissions testing, let me know but besides that I'm stuck with this thing... Thanks for the advice y'all.
I will look through some past threads as suggested.
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So you are going for emissions compliance. You are looking for the green wire? It should not be green, what color are the two wires going to the solenoid?
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Do you have a Q-jet without the solenoid? If yes, trade the top of that carb with your new one, after you remove the solenoid.
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Vile the two wires are very dirty and honestly I thought I saw green when I scratched some of it off, so maybe it's something else. The other wire I believe is orange...? As far as I can see.
JP, not a bad idea either, even though I don't have another carb without a solenoid I can run to a junkyard.
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Here is the problem with just swapping out the carburetor. California emission systems are unique in that they also have a full computer controlled ignition system. No vacuum advance and no centrifugal advance. the computer controls all timing based on inputs and conditions. If the original carburetor is not hooked up it will not go into closed loop. The ignition timing may default to a program that is not optimum or kind of like a limp mode. Also without going into closed loop the transmission may not shift as it should.You probably have a 700r4 so the TC clutch may not lock up. If you run it for any amount of time without being in fuel control you will most likely kill your cat converter. You may have to put an older distributor in and make sure you TC clutch locks up or wire it up differently until smog time.
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Where are they referencing the specs that they are basing the inspections off of on these old rigs? The VECI label? Running the vin will not decipher all of the originally equipped specs, so what is the basis?
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If it ever had a smog check in California and was entered as having California emissions the air resources board will have a data base on it and it will raise a red flag if it is entered as a 49 state truck. The smog tech has binders of books that he has to reference to inspect for equipment. Believe me they will fail it and he will have to go to a referee. There are shops that will “pass” it for fee but I wouldn’t go down that route. They are are already being watched and he could get caught up in it. I did smogs for 15 years in California. The state is very strict with smog shops.
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I was able to pass smog with my clapped out original m4med which ran horribly lean because of warping. The shop I went to didn't look at it too hard I bet, because I was just tested on a visual, nox, and whatever other parts of a basic procedure are. I failed once only because I didn't have vacuum to my EGR. So I think either I got lucky with the place, or the strict-ness of the inspection has changed.
Also, I do have vacuum advance. Correct me if I'm wrong but I don't think I have a computer controlled carb? And this is all stock as well.
Editing to add that I have a TH350C, missed that last part Mike S.
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That might be good news. That is a sign you have a 49 state vehicle as all calif equipped 1/2 tons with V8 engines were 305 and 700r4 transmissions with CCC emissions. No 350 or standard trans in 1/2 ton 2wd in California that year. 350 only and no 305 in 1/2 4wd. I’m really surprised that they did not require dyno test. You must be in an exempt county. Few and far between in California.
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You know what, they may have done a dyno test. Also, this truck came stock with a 305 which blew up. But yeah, very interesting that it still stands out with the th350
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Do you know if it is a California emissions truck or 49 state? Do you still have the glove box RPO placard you can post. Does the distributor have only the one set of wires going to the cap? If it was CCC it would also have a four wire connector coming out of the distributor housing going to the engine harness.