GM feedback carburetors

Sean Owner Cornville, Arizona Posted   Latest  
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1981 Chevrolet El Camino 3.8L (A) 3-spd (THM350C)

I had this sweet El Camino get towed in last week as a no start after sitting for 6 months. He inherited it from his dad, so no known history, just that the fuel gauge read half tank 6 months ago when he parked it. Quick check showed no fuel getting to carb after 30 seconds of cranking, and fuel gauge reads half. I hook up a pressure/vacuum gauge, and see it varying between 1 psi, and 1 in/hg, so it appears that the fuel pump diaphragm is intact. I let it sit until Wednesday, then finally I push it in. Pressurized the tank with a small amount of shop air while cranking, and we now have 3.5 psi, still no start, but it will run off of ether. No fuel being squirted by the accelerator pump, and carb looks very clean, like a recent overhaul. Carb is a E2ME Dualjet.

Got the authorization to rebuild the carb, and tore it down, to find it bone dry inside, not even the evidence of evaporated fuel. Check the check valve in the filter, and I can blow through it. I figure if there's a problem, I'll run into it on the reassembly. No issues at all, got the mc solenoid adjusted to spec, the air bleed set, reinstalled the carb, and it fired right up. This morning, I hook up the old brick to adjust the carb, and found codes for tps, and mc solenoid, even thought the solenoid is clicking. wiggle the connector, and it quits. Check the tps, and it's stuck at 4.88 volts. I go, and order a pigtail for the mc, and a new tps, them go back, and decided to perform the base adjustments while waiting for the parts, and found the o2 stuck at .454v, so off to order a new o2 as well. I replaced the ect, and pigtail yesterday while the carb was out, because it had the typical bare wires. 

As I am waiting for parts, I realized that this thing had to have been rebuilt in the last couple of years, and whoever did it only set up the carb, and nothing else, not even testing the tps. Very interesting that they only did part of the job, because these carbs are complicated, and require gauges to set up correctly. I am only 39, and have been in the industry since 2001, so I shouldn't even know how to do these carbs, but 20 years ago, I had an 81 Camaro with the E4ME, and it wouldn't pass smog. I messed with that thing so much, and finally got it to where it was getting 18 mpg, and would pass smog with flying colors.

How many of you out there would be able to make this thing run correctly when done? How many of you would tackle this job as a learning experience, and tool up to do it?

+3
Rusty Owner/Technician
Oakham, Massachusetts
Rusty
 

I would and I do a few carb repairs now because few folks know what they are doing. I'm 63 :-) Your fuel pump test indicates a faulty pump BTW. It should pull at least 15" of vacuum if the outlet is wide open and it should make at least 7 PSI. A compound gauge hooked to either port "cycling" between pressure and vacuum indicates a leaking check valve.

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Jaime Diagnostician
Ocala, Florida
Jaime
 

If I rebuilt one I've done a thousand of these carbs. At one point I was doing 3 a day (full rebuilds) and 3 tune-ups (Plugs, Caps & Rotors, if the last 2 were needed) per day. Like Rusty said, you probably have a bad fuel pump. I suspect the pump may have leaked into the engine oil, and not back to the tank though. Either way, change the pump and you shouldn't have the hard/no start

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Sean Owner
Cornville, Arizona
Sean
 

I've done plenty of those pumps, so I already know that trick with the bolt. I pass that one on whenever I can, because nobody ever showed me, and I used to fight the pushrod. I'm one of the few around that will even work on the older vehicles, and I do probably 6-8 carbs a year. The least favorite one I have ever worked on was the Varijet in the 1984 S-10 I used to own. I could never get that

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Cliff Diagnostician
Santa Maria, California
Cliff
 

I would do it in a heartbeat, Though not a learning experience for me. I still have all the tooling to do them. Granted the stuff is in a cardboard box in the nether reaches of my toolbox. I still do about 6 to 8 Carbs a year and I am picky which models I do rebuild do to the lack of readily available parts like the old days. Kudos to you for taking it on! I have been in the industry since

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John Instructor
Beaver, Pennsylvania
John
 

Rebuilt more of those than I can count. How are the throttle shaft bushings? BTW no fuel at all in the bowl? The needle valve was probably stuck in the seat.

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Charles Instructor
Fitchburg, Massachusetts
Charles
 

OH! yes I do recall the process and we actually had a "Clean Room" within our shop so that a rebuild couldn't get contaminated. Really Though it was so that we could keep the odor from the cleaning tanks and we also rebuilt Diesel injector pumps, which the room was set up for. Funny that you ask I was digging into my tool box and when I opened the top left draw I had a flashback and was

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Danny Technician
Losangeles, California
Danny
 

I've rebuilt a bunch of them. I'm sure I could put one together blind folded. That said, I would never repair another one for a customer. However, I might do it for a friend as a favor. The last one I worked on was a CO failure. It had a TP Sensor that read reference voltage on the signal line. That put the ECM into WOT mode. Apparently the carb had been taken apart numerous times. The

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Glenn Owner/Technician
Houston, Texas
Glenn
 

I've got Rusty, beat I'm 70 and still at it. I've done a ton of these also. However in my area in houston tx, i would not consider this job unless the tank is cleaned and fresh fuel added. I'm pretty sure that even on that old C3 system there is a .450 bias volts on the O2. but if he's keeping the car a new O2 is not a waste. I do have an old Line 9 catalog if you need any part #s and I still

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Sean Owner
Cornville, Arizona
Sean
 

Both Autozone, and Oreilly's stock carb kits, and floats. Choke pull-offs are usually in Phoenix, so I can order the parts, tear it down, and drop it in the bucket, then be able to reassemble the next day.

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