Hello all! I know there is a lot of info out there about this subject. Believe me, I have been scouring through that info until my eyes hurt. I recently purchased a 1987 D150 LE with a 318 for my son for his first vehicle. I knew there would be repairs needed and I have done quite a bit to it. It has been running well until a week ago. It died on him on a busy highway and i had to rescue him.

Anyway, I have, prior to this, already replaced the plugs and wires, cap and rotor. I can't seem to find a vacuum leak. The air pump is not there. I tried a reman spark control unit (the one behind the battery) no luck. The same story, engine fires right up but idles like garbage and dies. Have to throw it into neutral and feather the throttle to keep her running. So I think I need to ditch the lean burn. From my research, some places say just get a kit like this https://www.jegs.com/i/JEGS/555/40500K/10002/-1 and some other info says I also need to replace the carb.

I can't find a definitive "this is what you need to do" to handle this issue. I'm hoping the gurus here can help be get down to brass taxes here. Thanks for any help.

 

Every single vehicle I've had with the lean burn system, I pulled it and converted to regular electronic ignition. You might have other issues, but convert it first. Even if the carb. is bad, it will still run better with regular ignition. The hardest part of converting is replacing the distributor and getting it timed right. You'll need to find a vacuum port for the advance on the distributor, but other than that, it's mostly replacing one part with another. You'll need a distributor wrench (it's just easier to do with one, but you can get by without it), wire cutters, a volt/ohm meter, a few other basic tools, some dielectric grease and an afternoon. Since you've replaced the plugs and wires, those are good to go. You won't need to replace them for years or 30,000 miles.

I'm not sure what spark control you replaced as the lean burn unit is a weird shaped thing on the drivers side of the air cleaner. There are a couple of control units, one is the voltage regulator I think, behind the battery. The brain box looks like the square box in the ad you mentioned. Now, if you DON'T have the lean burn unit on the air cleaner and you DO have the control unit on the fender well behind the battery, you don't have lean burn. Without a picture I can't tell for sure but you may just have electronic ignition. If your ballast resistor failed, it may or may not run and they fail without notice. If you jump a wire across the terminals and it starts, it's a simple little thing like a ballast resistor. Ballast resistors on these are notorious for failing. When I drove an old Dodge, I always carried a spare wrapped up in a towel in my tool box. Check the ballast before you throw more money at it. They are cheap. If it's bad, you saved a chunk of change. If not, you aren't out much and now have a spare.

 

Hey, thanks for the response and info.

So I don't have anything on the side of the air cleaner, only the box behind the battery in the left fender. There is no vacuum advance on my distributor, just a 2 wire plug. I don't have the 5 wire module from the Jegs link. The box behind the battery I tried replacing was referred to as the spark controller in several places so that's why I tried it. I checked the 537 vacuum lines and while there are some minor issues I don't think there is a bad leak somewhere causing this, but I have been wrong once or twice in my life The PCV valve seems fine.

The engine fires right up every time. Sometimes it sounds like it is idling fine but it seems to get a bit worse as the engine warms up, goes into a rougher idle. So driving I have to kick it up into neutral and giver her a little throttle to keep it running. Seems to run normally while in motion. It will run at idle, it is rough until it dies if you let it sit. One of those things a 16 yr old kid generally doesn't know how to deal with, hence his panic when it died on him on the way home from school. I was able to drive it home with the above method.

 

It may be a lean burn, the unit looks like one but I've never seen one like that. My old '88 Diplomat had it on the air cleaner. Just to make sure, before you buy a new ignition system, replace your ballast resistor and hook a vacuum gauge to the intake. I'm looking at those headers and wondering how well the exhaust is flowing.

 

So I took more pics. I went to the parts store and the ballast resistor they showed looks completely different than what looks like a ballast resistor on my engine. I'm assuming that's what it is? If that's my resistor I need to figure out where to find that.

Also, there is a pic of a lone vacuum hose coming off a "T" that is not connected to anything. I can't tell if it is supposed to go to something or not. I illustrate in the pics where the other lines in the "T" go to. One goes to a solenoid on the right side and the other goes to a 90 deg elbow that I have been connecting to the port on the air cleaner in another pic. I also uploaded a video to you tube of the engine running if that helps.

 

The white rectangle looks like a timer for the electric choke. The ignition ballast resistor will look similar but will be mounted on the firewall. there are two types. One with a single connector on each end and one with two connectors. Replacements usually only have one on each end. The hose may go to the bottom of the air cleaner. If you don't want to hook it up, put a golf tee in the hose to stop a vacuum leak.

 

Ok, so I scoured the engine bay and there is no ballast resistor and no ignition control module. All there is is a voltage regulator, the dual vacuum solenoids, a couple relays and plugs and that's about it. I don't see any obvious places where there is something missing. So I think I'm going to buy a timing light and check that. I've been a diesel tech for nearly 25 years but it's been at least that long since I last played around with an old gas engine with a carb, lol

 

Read up on the lean burn systems here Sound like you have a miss in the video. New plugs wires cap and rotor along with a carb rebuild would improve things. Or get rid of that boat anchor intake(and emissions crap) and put on an edelbrock with a holly 4 bbl carb! The distributor doesn't have vac advance but if the plug is the same you can use the standard electronic ignition set ups on prior year vehicles to the lean burn. Check out the link here it is for the install of the electronic ignition but all you need is the ballast resistor wiring and the ignition module.

 

I replaced the cap, rotor, plugs and wires a couple months ago. Along with engine and trans oil and filters and the rearend oil. It has been running pretty well until recently when it died on my kid, like I mentioned before, and the current issues started. It always fires right up, but like in the video, it sounds like a miss. From my research it seems like about half of the emissions stuff has been removed over the years but parts of the system are still there possibly causing me problems now, I don't know. I just looked under the distributor cap and it's pretty rusty inside where the pickup is. Maybe that's an issue.

I would love to do an intake and carb but that's nearly $1000 and I only paid $1200 for the truck and probably put $600 into various repairs and such so far.

So if I go for the kit you linked with the distributor, ignition module, ballast resistor and harness how much of the rest of the emissions system can I eliminate? Or is that kit used in conjunction with the lean burn system? Where do I source the vacuum for the distributor from? Doing other research, do I need to replace the carb or just plug off things that aren't used anymore?

 

Rust inside the distributor is bad mojo. When you use the kit, it will have the entire ignition system.Make sure you follow the wiring diagram for power. As for vacuum, in the video, it looks like a vacuum hose goes to the back of the carburetor at the base. This may work and you can put a tee in it. Otherwise, the one photo of the white rectangle shows a plug where a vacuum manifold would thread in. Head over to a bone yard and see if you can score a few off Mopar V-8's. I've seen them with anywhere from one to many ports for vacuum. Often with a large central port for the power brake booster.