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Researching the lean burn igntion system

9K views 22 replies 9 participants last post by  Speed Dragon 
#1 ·
I just bought a 1987 D150 with the 2 barrel 318 and I'm new to this site. My new(to me) truck runs & drives great, very smooth, and is all stock, the engine was replaced a few years ago with a Jasper reman. It still has the lean burn ignition and feedback holley carb (also replaced with a reman) and has none of the problems associated with the lean burn system I read about so often. It also still has the original cat convertors (even the little mini-ox one is still there) and a recently refreshed smog pump system with new hoses, diverter valve, etc etc. It's really a very nice, unmolested truck that looks, runs and drives very well.

However, there is no oxygen sensor anywhere, and I can find no evidence that their ever was one. Did all of these systems use an O2 sensor? The truck runs so well (and even gets decent mpg) that I'm not going to do anything other than try my best to keep it maintained, but the lack of the O2 sensor has me scratching my head. Can anyone offer any information about this?

Thanks
 
#2 ·
I know that 85 86 and 87 did not have O2 sensors as long as the engine was not TBI. If you are running stock it is not needed. People that run mild and over weld a bung on and use an A/F meter to fine tune engine performance.
 
#4 ·
Nope, no O2 sensor on those. TBI was introduced on the 88 models, and I think they went to 93 then went to multi-port FI. The lean burn computer isn't that sophisticated.
 
#7 ·
Air Charge Temp Sensor?

Thanks for the replies. That's what I needed to know about the O2 sensor.

On a related issue, does anyone know if the lean burn system used an air charge temp sensor? There is a brass plug that has been installed in the intake manifold behind the carb that doesn't look stock. And their happens to be a one-blade wire terminal nearby that isn't hooked to anything. I'm thinking someone removed the AIT sensor for some reason, but don't want to spend the $12 on a new one if that's not right. Any help is most appreciated!
 
#8 ·
The plug was probably for a tree that would provide a vacuum source from the manifold for various things. Either things were removed or there were enough vacuum hookups at the carb to run everything, so the tree wasn't needed anymore.
 
#10 ·
Speed Dragon said:
My '87 Diplomat has an O2 sensor, 318 2bbl w/ LeanBurn. If I remember right, it should have an O2, especially if it has a FB carb.

So they do have o2 sensors on them..sure it's not just the cali. model? :D
 
#11 ·
As I have said...they do NOT have O2 sensors in the three model years I have mentioned. They do however have charge temp switches located (looking at the truck from the front) located just behind the carb and to the left. There will be two wires one a female connector for the ground and another 3mm rubber booted power connector. Cost in auto parts is usually $35 so try getting it from the Jyard as most never went bad. Just always remember to twist the boot left to right to unstick it or you could break the conn inside.
 
#12 ·
I have an 87 D150, 318, auto, standard 1/2 ton pickup. Sounds like the same as you have...There is no O2 sensor, and as far as I can see, the carb is non-feedback. The computer, that sits on the left fender area, just seems to regulate the spark advance, and sends a signal to a relay for the TC lockup.....Its really pretty basic, thank your lucky stars it aint more complicated. I have my EGR valve unhooked, and the belt for the smog pump has been off for a couple years. No problems. I have a factory shop manual, I can look up more info if you need any........What I`m stating here is just off the top of my head, without getting into details.
 
#13 ·
DiverDwnPowrRam said:
As I have said...they do NOT have O2 sensors in the three model years I have mentioned. They do however have charge temp switches located (looking at the truck from the front) located just behind the carb and to the left. There will be two wires one a female connector for the ground and another 3mm rubber booted power connector. Cost in auto parts is usually $35 so try getting it from the Jyard as most never went bad. Just always remember to twist the boot left to right to unstick it or you could break the conn inside.

I didn't think so either until speed dragon said his LeBaron did. Maybe they were on cars/ certain cars only and not on trucks, but speed dragon knows what an O sensor is.
 
#14 ·
Maybe the trucks were different, but I doubt it. More than likely, there were different versions of the Lean Burn, one w/ O2 and one w/o it. And I don't think my Diplomat is a Cali model, I'm second owner, and the original owners bought here new as far as I know.

Trucks may have been different, I can't remember if I've ever seen a truck w/ an O2, but EVERY car I can remember seeing w/ Lean Burn had an O2. I'll have to remember to look next time I'm in a junkyard :)
 
#15 ·
There were several versions of the Lean Burn,ESA,ESC,SCC,etc systems. TBI did not come out until 1988 in the 318 only...360 was included in 1989.
Don't get a solenoid on the carb confused as they also used bowl vent solenoids and other solenoids. You can have Lean Burn without a feedback carb.
The Lean Burn may use any of the sensors listed.
The one wire O2 sensor is Mopar part# 4301375


Description and Operation
The Electronic Spark Advance provides electronically controlled spark advance and eliminates the need for mechanical and vacuum advance controls in the distributor. The Spark Control Computer uses as many as six sensors to monitor the engines conditions so that it can fire the spark plugs at the proper time.

SPARK CONTROL COMPUTER (SCC)
The Spark Control Computer is the heart of the entire system. It gives the capability of igniting the fuel mixture according to different modes of engine operation by delivering an infinite amount of variable advance curves. During cranking, an electrical signal from the distributor is fed into the computer. This signal will cause the computer to fire the spark plugs at a fixed amount of advance. Once the engine starts, the timing will now be controlled by the computer based on the information received from the various sensors.
The amount of spark advance is determined by three factors, coolant temperature, engine speed, and manifold vacuum.

The computer determines spark advance in the following manner:

1. Coolant temperature modifies vacuum advance schedule. There is a different schedule for hot and for cold engines.
2. Advance from vacuum is programmed into computer. In a cold or warm engine spark advance depends only on amount of manifold vacuum. In a hot engine spark advance depends on both manifold vacuum and engine speed.
3. Advance from speed is programmed into computer and depends only engine speed.

SENSORS
The Electronic Spark Control System incorporates the following sensors:
1. The Hall Effect Pickup assembly, located in distributor, supplies basic timing signal and engine speed to computer.
2. The coolant sensor, located on thermostat housing, gives computer information on engine temperature.
3. A carburetor switch located on end of idle stop tells computer when engine is at an idle.
4. The vacuum transducer is located on the Spark Control Computer and tells computer how much vacuum engine is producing.
5. The oxygen sensor (used with Feed Back carburetor only) is located in exhaust manifold and informs computer about oxygen in exhaust so it can alter air/fuel mixture.
6. A charge temperature switch (on 6 cyl. engines only) is located on intake manifold and monitors intake air temperature.


The Holley model 6280 carburetor(Feedback), utilizes four or five basic metering systems. The idle system provides a mixture for idle and low speed conditions. The accelerator pump system provides additional fuel during acceleration. The main metering system provides an economical mixture for normal cruising conditions. The power enrichment system, which combines a mechanical and vacuum operated power valve, or uses a modulated vacuum operated power valve, provides a richer mixture when a higher power output is required. Some models use an O2 feedback solenoid that is responsive to the oxygen sensor.
In addition to the four or five basic systems, there is a fuel inlet system that constantly supplies fuel to the basic metering systems and a choke system which temporarily enriches the mixture to aid in starting and operating a cold engine.
 
#16 ·
Well usually you are right Chump but unfortunatly you are wrong in this case. I owned an 85 LWB 318 no O2 sensor. I traded this for the 86 3/4 LWB 360 I still own...no O2 sensor. Both also did not have computers (in the sense of the 10 pin modules) but both did have the dual modified ECU on the driver fender. Not trying to be a smartass but I own two trucks on these years and you can see my engine rebuild on another thread...I like mild over stock but I retain the stock look for restoration.
 
#17 ·
My '85 van has a slant six with ESA. No O2 sensor and no feeback carb. The only thing on the carb. that is electronic is the idle stop solenoid.
 
#18 ·
I'm still not sure that the trucks didn't come w/ an O2, but I have a theory why they might not have. Emissions regulations were easier on trucks than cars at the time I believe, and so the trucks may not have gotten feedback carbs, w/ is what used the O2.
 
#19 ·
All I remember was the mid 80s 318s having the special heads (swirled) for the diplomats and police cruisers with O2. Other then that the only others were horizons aspens Omni and K cars in general. I am sure there are more but I have yet to see a truck from 85-87 that had an O2 sensor.
 
#21 ·
Air Charge Sensor?

So you are saying that only the 6cyl models received the air charge sensor? That's good news if true as it means I don't have to do anything.

It sounds like there were a bunch of different versions of the lean burn system outfitted to these 80's vehicles. I bet it was a gigantic headache for Chrysler mechanics back then..
 
#22 ·
DiverDwnPowrRam said:
Well usually you are right Chump but unfortunatly you are wrong in this case. I owned an 85 LWB 318 no O2 sensor. I traded this for the 86 3/4 LWB 360 I still own...no O2 sensor. Both also did not have computers (in the sense of the 10 pin modules) but both did have the dual modified ECU on the driver fender. Not trying to be a smartass but I own two trucks on these years and you can see my engine rebuild on another thread...I like mild over stock but I retain the stock look for restoration.
Well, like the factory information says in my post, "some" have "some" of the sensors.
Also just owning a truck that has not been equipped with something does not mean it wasnt availble or required, have to keep an open mind with the emissions system of yesteryear. I have a 77 W200 that I bought brand new with a 440 and it is different than other trucks but they were equipped based on sales destination.
None of us have seen all the options available for these trucks but they are listed in the factory parts books and the factory service manuals. Remember that these systems are also used on the Dakota and Van that have different GVW specs. Also California and High Altitude vehicles were different. It depeneded on what Zone the truck was ordered for also. You could get 2 differently configured trucks that were ordered from dealers that were just across the street from each other. Remember that a true feedback carb has to have something to feedback from? Most times people think they have a feedback carb just because they see a wire going to it, not so.

Here's a non-inclusive list of emissions configurations for the 86-87 Truck years. I havnt seen all these.

EGR SYSTEMS AND HOSE HARNESSES
EGR SYSTEM 2.2L ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-825
EGR HOSE HARNESS 2.2L ENGINE - EXC. CANADA N BODY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-850
EGR HOSE HARNESS 2.2L ENGINE - CANADA N BODY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-875
EGR SYSTEM 225 ENGINE - EXC. CANADA B1,2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-900
EGR HOSE HARNESS 225 ENGINE - FEDERAL AND HIGH ALT. B1,2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-1000
EGR HOSE HARNESS 225 ENGINE - CALIF. B1,2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-1100
EGR SYSTEM 225 ENGINE - CANADA B1,2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-1200
EGR HOSE HARNESS 225 ENGINE - CANADA B1,2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-1300
EGR SYSTEM 225 ENGINE - EXC. CANADA D1,2,5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-1400
EGR HOSE HARNESS 225 ENGINE - FEDERAL AND HIGH ALT. D1,2,5 . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-1500
EGR HOSE HARNESS 225 ENGINE - CALIF. D1,2,5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-1600
EGR SYSTEM 225 ENGINE - CANADA D1,2,5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-1700
EGR HOSE HARNESS 225 ENGINE - CANADA D1,2,5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-1800
EGR SYSTEM 3.9L ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-1815
EGR HOSE HARNESS 3.9L ENGINE - FEDERAL AND CALIF. N BODY . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-1830
EGR HOSE HARNESS 3.9L ENGINE - HIGH ALTITUDE N BODY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-1845
EGR STSYEM 318 ENGINE - CANADA W/MAN. TRANS. OR FEDERAL B BODY . . . . . . . . . . . . . . . . . . . . Fig. 25-1900
EGR HOSE HARNESS 318 ENGINE - FEDERAL AND CANADA - MAN TRANS. B BODY . . . . . . . . . . . . . . Fig. 25-2000
EGR HOSE HARNESS 318 ENGINE - FEDERAL AND CANADA - MAN TRANS. B BODY . . . . . . . . . . . . . . Fig. 25-2000
EGR HOSE HARNESS 318 ENGINE - FEDERAL - AUTO. TRANS. B BODY . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-2100
EGR SYSTEM 318 ENGINE - CALIF. AND HIGH ALT. B BODY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-2200
EGR HOSE HARNESS 318 ENGINE - CALIF. W/MAN. TRANS. AND HIGH ALT. B BODY - UP TO 10-24-85 Fig. 25-2300
EGR HOSE HARNESS 318 ENGINE - CALIF. W/MAN. TRANS. AND HIGH ALT. B BODY - AFTER 10-24-85 Fig. 25-2325
EGR HOSE HARNESS 318 ENGINE - CALIF. - AUTO. TRANS. B BODY . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-2400
EGR SYSTEM 318 ENGINE - CANADA W/MAN. TRANS. OR FEDERAL D BODY . . . . . . . . . . . . . . . . . . . . Fig. 25-2500
EGR HOSE HARNESS 318 ENGINE - FEDERAL AND CANADA - MAN. TRANS. D BODY . . . . . . . . . . . . . . Fig. 25-2600
EGR HOSE HARNESS 318 ENGINE - FEDERAL - AUTO. TRANS. D BODY . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-2700
EGR SYSTEM 318 ENGINE - CALIF. AND HIGH ALT. D BODY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-2800
EGR HOSE HARNESS 318 ENGINE - CALIF. W/MAN. TRANS. AND HIGH ALT. D BODY - UP TO 10-24-85 Fig. 25-2900
EGR HOSE HARNESS 318 ENGINE - CALIF. W/MAN. TRANS. AND HIGH ALT. D BODY - AFTER 10-24-85 Fig. 25-2925
EGR HOSE HARNESS 318 ENGINE - CALIF. - AUTO. TRANS. D BODY . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-3000
EGR SYSTEM 318 ENGINE - CANADA - AUTO. TRANS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-3100
EGR HOSE HARNESS 318 ENGINE - CANADA - AUTO. TRANS. B BODY . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-3200
EGR HOSE HARNESS 318 ENGINE - CANADA - AUTO. TRANS. D BODY . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-3300
EGR SYSTEM 360 ENGINE - FEDERAL AND HIGH ALT. B BODY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-3400
EGR HOSE HARNESS 360 ENGINE - FEDERAL B BODY - 1986 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-3500
EGR HOSE HARNESS 360 ENGINE - HIGH ALT. B BODY - 1986 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-3600
EGR HOSE HARNESS 360 ENGINE - FEDERAL AND HIGH ALT. B BODY - 1987 . . . . . . . . . . . . . . . . . . . . Fig. 25-3625
EGR SYSTEM 360 ENGINE - FEDERAL AND HIGH ALT. D BODY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-3700
EGR HOSE HARNESS 360 ENGINE - HIGH ALT. W/MAN. TRANS. OR FEDERAL D BODY - 1986 . . . . . . . Fig. 25-3800
EGR HOSE HARNESS 360 ENGINE - HIGH ALT. - AUTO. TRANS. D BODY - 1986 . . . . . . . . . . . . . . . . . . . Fig. 25-3900
EGR HOSE HARNESS 360 ENGINE - FEDERAL AND HIGH ALT. D BODY - 1987 . . . . . . . . . . . . . . . . . . . . Fig. 25-3925
EGR SYSTEM 360 ENGINE - CALIF. AND CANADA - 1986 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-4000
EGR HOSE HARNESS 360 ENGINE - CALIF. - 1986 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-4100
EGR HOSE HARNESS 360 ENGINE - CANADA - 1986 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-4200
EGR SYSTEM 360 ENGINE - CALIF. - 1987 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-4210
EGR HOSE HARNESS 360 ENGINE - CALIF. - 1987 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-4220
EGR SYSTEM 360 ENGINE - CANADA - 1987 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-4230
EGR HOSE HARNESS 360 ENGINE - CANADA - 1987 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-4240
EGR SYSTEM 360 ENGINE OVER 8500 LBS. GVW B,D,T MODEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fig. 25-4300
EGR HOSE HARNESS 360 ENGINE OVER 8500 LBS. GVW B,D,T MODEL - UP TO 12-16-85 . . . . . . . . . . . Fig. 25-4400
EGR HOSE HARNESS 360 ENGINE OVER 8500 LBS. GVW B,D,T MODEL - AFTER 12-16-85 (1986) . . . . . Fig. 25-4410
EGR HOSE HARNESS 360 ENGINE OVER 8500 LBS. GVW B,D,T MODEL - 1987 . . . . . . . . . . . . . . . . . . . Fig. 25

Engine Wiring Harnesses
Notice the options.

4362 483 1 WIRING, Eng. 318 Eng. 60-114, Amp., E.S.A., 1986
4362 486 1 318 Eng. 60 Amp. Calif. w/ESA, 1986
4362 339 1 318 Eng.-114 Amp. w/ECU, 1986
4362 074 1 318 Eng.-114 Amp. w/E.C.U., 1986
4362 078 1 318 Eng. 60 Amp. w/E.C.U..1986
4362 490 1 360 Eng.-114 Amp. E.C.U., 1986
4362 484 1 360 Eng. 60 Amp. w/ECU, Light Cyc. 1986
4163 127 1 318,360 Eng.- 60 Amp. Calif. 1986
4362 485 1 318,360 Eng.- 60 Amp. w/ECU, Canada 1986
4163 128 1 318,360 Eng.-114 Amp, Calif.
4362 070 1 360 Eng.- 114 Amp. 4 BBL. w/ECU, 1986, w/Dual Pick-Up
4362 564 1 318 Eng. 50/120 Amp. E.S.A. 1987
4362 396 1 318 Eng. 78 Amp. E.C.U., 1987
4362 387 1 318 Eng. 78 Amp. w/E.S.A. 1987
4362 392 1 318 Eng. 78 Amp. w/E.S.A. Calif. 1987
4362 566 1 360 Eng. 78 Amp. w/ECU, 1987, Calif.
4362 569 1 360 ENG. 50/120 Amp. E.C.U. 1987
4362 388 1 360 Eng. 78 Amp. E.C.U. 1987
4362 567 1 360 Eng. 50/120 Amp. w/ecu, 1987, Single Pick-Up
4362 389 1 360 Eng. 50/120 Amp. E.C.U. 1987, Dual Pick-Up
4362 551 SNOW FITER
 
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