I have an 84 D100 pickup with the Lean Burn system on it. Someone before I got it has unhooked several of the wiring harnesses, I assume because something wasn't working. The carburator wires were one of the things that were unhooked. There is a gremlin in the ignition that every couple weeks causes it to not fire. I have spent hours trying to figure out what is wrong, only to have it start working on its own until the next time it quits. I have read an article about switching the Lean Burn system to a regular electronic ignition, and it says you need to replace the carb to make it work. When the ignition is working, the truck runs good and gets good gas mileage. Is there any reason why the carb wouldn't keep working if I replace the ignition system? Thanks for any help.

The vacumn ports are different on the non lean burn carb. The LB ECU does most of the carbs tuning(if it works at all).......Take it from one who JUST went thru this dis the lean burn and go to HEI or Mopar ECU.
You can PM me and we will get together and talk.
Frank

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

Welcome on the board. Yep, making problems is what the Lean Burn system does best! You should remove it if your local emission laws allow it. Where is the truck registered, and what kind of emission tests must it pass, if any? Regular Mopar electronic ignition or (better) HEI, incorporating an advancing distributor and a carburetor equipped with a vacuum advance port, will greatly improve everything about how the truck runs (better performance, driveability, mileage...).

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Too many people who were born on third base actually believe they've hit a triple.

It doesn't have to pass an emissions test. That is how it got into the shape it is. Whoever had it before me would just start cobbling until it would run. I do the same thing at times, but I am trying to get rid of some of the rats nest that is there now. When I started working on it, there were wires and vacuum lines dangling everywhere.

It is the most gutless vehicle I own, but it will get 20 mpg (in warm weather) with all the wires and most of the vacuum lines from the carb unhooked and plugged. I thought that was pretty good. I have another pickup to use if I need hp.

I didn't put in all the details in my original post so I thought I would tell the whole story.

When I got this pickup ($300; to be a spare vehicle), some things were already unhooked. My son drove it for over a year, patching and cobbling the wiring whenever something wouldn't work. A friend drove it for 6 months doing the same thing. Now I am driving it to work every day, trying to get the mechanical things in halfway decent shape (the body is a lost cause). Last weekend I fixed several minor things in the engine compartment,one of which was running a vacuum line to a shutoff valve on the dash to manually control the heat riser valve and the air control valve in the air cleaner for faster engine warmups in cold weather. They had been disconnected also. When I was done with everything I tried to start it and had no fire to the distributor. I spent 3 or 4 hours trying to figure out what was wrong. I finally gave up and put everything back together to take it to my neighbor who runs a mechanics shop. I decided to try starting it one more time, and it started like nothing was wrong. It has done this before, but it would start after sitting a few minutes.

I drove it all week, and Saturday I replaced some worn water hoses; the starter, because the gear was badly worn and was kicking out more and more; and put on a manual choke because the automatic choke wasn't working right since the weather turned cold. I did the choke first, and it started right up in 20* temps. I then spent about 3 or 4 hours taking off the other parts, getting new ones and putting them on. When I got done I tried to start it, and no spark again . I thought I would adjust the pickup coil a little closer to see if that would help. I only moved it halfway, but that was apparently too much, because when I tried cranking the engine it snapped some teeth off of the plastic distributor gear . It was 5 o'clock when that happened and I was mad and just quit.

I pulled the distributor out on Sunday and found 3 teeth missing on the gear. I spent a few hours reading other peoples ignition swap experiences and gathering other information. I decided since I had the distributor out, now would be a good time to change the ignition system over to HEI if I was going to. Most of the vaccum lines had been taken off and the ports plugged on the carb before I started working on it and it runs fine (when the ignition works). I was getting about 20 mpg in warm weather with the everything unhooked, which is why I was wondering why I couldn't still use the old carb (at least for now) if I changed the ignition.

Today I ordered the new distributor (with mechanical and vacuum advance), GM HEI coil, and GM control module. I will give another update when I get everything installed.

FWIIW, I had a similar intermittent problem with my lean burn system and pulled the plugs from the bottom to the computer module on the air cleaner and cleaned the pins and plugs with a scotch bright pad and contact cleaner; no more problems.

You don't have a feedback carb do you?

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'81 D150 with "Lean Burn"

Deja vu! Same year truck, same problem. When I got it, the intake had been replaced with one from an older truck or industrial slant (yellow) and the carb had been replaced by a Holley 1920. Ran like crap! I found charcoal inside the carburetor. Yep the cannister had ruptured. Might want to take a look at yours

As for the ignition, once I changed the distributor it was run some times, and others it was hard to start and ran like crap. Ignition box was part of the trouble. Replaced it and it started much better. Still runs like crap. I suspect multiple vacuum leaks. You might do well to check for those too. the lean bum had many flaws, and that was but one.

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If it was easy, everybody would be doing it.

I don't have a multimeter at the moment (I am going to get one soon), but after all the events happened that I wrote about, I used a test light to check the computer input wire. It was relatively slow to light up and not that bright, as compared to a good voltage source, so I am thinking it was not getting adequate voltage. It was probably exaggerated by bad connections as you suggested.

I am not sure, but I don't think so. There is 2 wires coming out of the carb both going to the same plug. I didn't really look for it, but I didn't see the other plug that goes to it. There are several vacuum ports on the carb, most of them already plugged off when I started working on it. Is that enough info to tell if it is a feedback?

I have looked inside the carb and it looks fairly clean. there was a little varnish that a few shots of carb cleaner took care of.
Concerning the vacuum leaks, there was one line that wasn't plugged when I first looked under the hood after everyone else had been driving it, but I plugged it before I started driving the truck myself. As I said in my earlier posts, it runs good and gets good gas milage. It would start good in warm weather. When the air temps started getting colder, it didn't want to start as well. A small shot of ether and it would start right up and stay running. I put the manual choke on it and that significantly helped helped the cold start problem.

Is it a purge solenoid, or an idle solenoid, that the wires attach to? (i.e. is it near the hose to the canister or is it the thing that stops the throttle shaft from going counter-clockwise?)

There is a temp sensor in the head connected to the ESA. I guess if the condition of the sensor, or the wiring, were such that they were telling the ESA that the motor is warm, it'd make for hard starting cold.

Looking at the carb from the drivers seat, the wires come out the right side. The throttle shaft is at the back. Does that help?

I thought I would give a little background on my pickup.

The man I bought it from had parked it on top of a hill and forgot to set the e-brake or put it in gear (manual trans). It rolled down the hill (backwards) and through the woods but didn't make it to grandma's house. Somehow it didn't make any direct hits on its journey, just a lot of sideswiping. That is why I got it so cheap. During the time that my son was driving it, someone ran a stop sign and he hit their car. A couple days later an adjuster from their insurance company came to look at the damage. They are looking at a pickup that looks like it came from a wrecking yard from front to back, and decides there was $1000 damage done in the accident to my $300 pickup. I told my son to go find someone else to run a stop sign.

I bought a radiator for less than $200, then using a sledge hammer along with a chain and some binders, we got the sheet metal bent back in the right general direction (well almost). We have 2 bungees holding the left headlight in place, and it even stays aimed right uness you hit a really big bump. Before the accident, my son had taken a paintbrush and wrote "treebasher" on the back and both sides of the bed. It is painted tan and brown, which hides the rust fairly well. It is truly one of a kind.

That'd be a purge solenoid. I don't know if that could affect cold starting if it, or it's wiring, were not in working order.

Is the vacuum modulator on the ESA still hooked up (you mention a lot of capped off vacuum lines)?

It is a manual transmission. What is an ESA?

Electronic Spark Advance...the lean burn 'computer.'

There are a couple things mounted on top of the engine that had vacuum lines running to them at one time. One looks like a metal can about 4" in diameter and 3" tall. If I remember correctly, that can had the vacuum lines still hooked up, but the wires were unhooked when I started working on it. It is totally out of the system now. If that did have something to do with the spark advance, I think the distributor I ordered (with mechanical and vacuum advance) should take care of it now. The parts have arrived, but I still have to get them and put them in.