It's an '81 Dodge D150 Pickup with the Lean Burn computer (ECU).

I'm looking for the Ground point for the ECU.

The Wiring diagram shows a ground from the ECU and the Charge Air Temp Sensor (CATS) spliced together and grounded at a single point and that this ground is separate from any other grounds on the truck. Of course the ground wires from the ECU and CATS disappear into the harness and I have no idea where the ground emerges, i.e. is it attached to the engine block, the body/chassis or does it travel back the (-) battery terminal?

I know this is a bit of a long shot that someone would know, but the truck is outside, and it started raining out, chasing me indoors, so I though I would give it a shot and see if someone knows, before I start slicing open the harness to trace the wires.

Here is the background problem:

It starts and runs fine, but then completely cuts out, like the key is shut off and then on. I put a meter on the coil (+) terminal** and the power to the coil is steady during the cut outs. I then put a timing light on the plug leads, and sure enough, the spark is cutting out. I found a bad wire end connector to the coil (-) terminal, which I replaced, and checked the continuity of the wire from the ECU to the coil, but it checked good. The next thing to check is the ECU ground (kind of hard for the ECU to control the path to ground to fire the plugs if the ground itself is bad).
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My "Other" Slant Six is an M30 in an '87 BMW 635 with a Bosch ECU. In these ECU's you can get solder joints for the power transistor controlling the coil that crack and become intermittent. Simply reflow the solder on the joints and they are good to go for another 200,000 miles. Has anyone done this on the Dodge Spark Computer?
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**I was hoping for something easy, like a bad/intermittent splice in the power supply wiring or a faulty ignition switch, but no such luck. Now that I think about it I need to check the power to the ECU also, but it comes from the same splice as the coil so I doubt it is a problem (famous last words, I need to check it anyway).

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'81 D150 with "Lean Burn"

If for whatever reason you're bound and determined to keep the Lean Burn system, this outfit can probably supply a rebuilt module or rebuild yours. The troublesome lean burn equipment can easily be removed and a conventional ignition system installed. Save yourself a lot of hassle and get a new distributor, not a cruddy "remanufactured" or worn-out used one. Source info (and other info you need to do a nice ignition upgrade away from Lean Burn) is in the HEI upgradethread.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

hello danno and other fellow sages- i guess this might be as good a place to ask my question as any,which some may think dumb. have heard many ponderous criticisms of the lean burn computer system in some slant sixes. never had one . also heard its easy and desirable to dump it out and replace it with the regular ecu system. seems they were on 81 models and maybe a few years after that. saw a few on the side of the aircleaner housing. what exactly was bad about this system, just didnt work, unpredictable crapouts on I 95 at 2am, driveability problems and mysteries, easy for shyster repair shops/dealers to make a home run, etc. concerned b/c i have found it necessary to broaden my search for a f body sl6 stickshift model to m bodies and j bodies some of which have this lean burn computer. surprised how the market has changed in the last 3 years. despite using various sources, has been tough trying to find a vehicle like this to replace my wrecked volare sw. so as we used to say in jersey , sages, whats the story (lean burn system)? thanks tons bob f

First year of Lean Burn (on some models) was '76. Under various names such as "ESA" it was used from then until the end of carbureted Mopars.
Yes (with accompanying poor gas mileage)

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Lets see, you're suggesting either spending hundreds of dollars, plus the down time to send the Lean Burn out to have it rebuilt, or spending hundreds of dollars on new parts for a replacement ignition system or alternatively spending weeks of chasing all over hells-half-acre combing yards looking for used parts ......

Versus

Spending 20 minuets checking the grounds, power and wiring to the ECU first, to make sure it is actually broken? And if the ECU is the problem, spending an hour reflowing the solder joints that may fix it?

Come on Dan, you're better than that!

I'm not "bound and determined" to keep the lean burn system, but I'm not afraid of it either. I'm simply following the path of least resistance (read: least money ). I simply asked where the ground to the ignition system was located, it doesn't matter if it is a HEI or lean burn, I'm still going to check the ground to the ignition system when it gets intermittent, funky like the power is being cut off.

If the ECU is bad I'm certainly not going to buy a rebuilt unit when for similar money it can be replaced with a HEI, I've already been looking at the links before I posted, in case it is a bad ECU, it is a great write-up.

Which brings me back to the question: Does anybody know where the ignition system ground is?? It is still drizzling here, it would be nice not to have to slice open the harness to trace the wires when it lets up.
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I've had the truck for about 8 years now and although it started as a weekend, trips to the Home store/dump, beater utility vehicle, I drive it about 70/75 % of the time now to keep the milage down on my "Other" Slant Six, the '87 635, and have had almost no problems with the lean burn system itself. The one time it stalled in the first year of ownership, I found the plugs to the ECU full of oil, crud and corrosion. A good cleaning and a new valve cover gasket to stop the massive external lubrication program going on, and 7 years later the truck has never failed to start or run because of ignition problems, this is the first time. So I would hardly call the lean burn "troublesome" in my particular case.

But that may be the case because my lean burn is the early version, it only has 2 sensors, temp switches actually, one for the intake air and the other for the water temp. It has no fueling control or feed back ( no O2 sensor), or throttle position sensor. It is little more than one step above a straight electronic ignition module with a couple of choices of ignition maps calculated on the basis of temp and vacuum (load).

Thats not to say the truck hasn't run like crap in the past, but nearly every problem can be traced back to a #@&%@ PO's bungled attempts at repairs or "improvements". He has striped off nearly everything that even remotely might be considered a pollution device, including the automatic choke!! And on top of that, the engine appears to be from the mid '70's, swapped into the '81 truck. I thought of replacing the lean burn when I first got the truck, but didn't have enough information (hadn't found this site yet), but after straightening a few of the PO's bungles out (Distributor installed one tooth off, wrong coil, etc.), the ignition ran good enough I didn't need to. It has had other problems that I have been massaging out as time, inclination and necessity allow and it just gets better and better.

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'81 D150 with "Lean Burn"

I'm not sure but I would guess its the ground terminal just to the passenger of the firewall bulkhead. That was the only ground under the hood I found while I was simplifying my engine compartment.
good luck

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85 d-100 HEI 2BBl
06 Toyota Corrola

Not really, no, especially not that last part that you seem to have guessed, assumed, and/or made up, but y'know what they say: every silver lining has a cloud. You're pretty much on your own finding the grounds you're after; that level of info was not published. I will wish you the best of luck getting your truck running right and leave you to it.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

In case you do want to be rid of the lean burn I wanted to let you know I built my HEI system from used parts for less than $40 and have been running it about 2 years now. Even have a little You Tube video of the car running and me explaining. http://www.youtube.com/watch?v=sV1BhSPyySE

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Joshua

Hello everyone I have been lurking here for a while and thought I might be able to help with this question.

Unfortunately, I don't have a 1981 Truck FSM. However my 1982 manual indicates the ground location as a eyelet bolted to the engine. It has no locating information beyond that. My 1981 Car FSM indicates the ground at the Choke Control Unit mounting bolt.

Hope this helps.[/quote]

Unsolicited testimonial form the past & current thought:

Spring of 1976 my bride to be purchased a 1976 Chrysler Cordoba. Ricardo M. convinced her that car would be the perfect perch for her back side, me, I was bewitched by the latest engine management development since vacuum advance; Lean Burn. The fact that that year it was only available on a big block 400 ci., 4 barrel equipped engine only enhanced my interest in technology that spring.

Keep in mind that this was just a few years before the second oil embargo when mid sized cars became full sized, and compacts became mid sized, and than front wheel drive swept Detroit. But, I’m getting ahead of my self. Back to the analog computer controlled spark & fuel mixture device that Chrysler put into production several years before GM, or Ford’s examples hit the road in mass.

If memory serves me correct, several conditions were monitored by the spark control being: coolant, & ambient air temperature; timing; throttle position; and throttle input (that is to say is the car cruising with few throttle position changes, or the car being hot dogged).

All this information was crunched slowly by today’s standards, and the air fuel mixture was adjusted from the rich side of stoichiometric to 19.0:1, hence the Lean Burn handle.

Long story short, this Cordoba performed flawlessly for 86,000 miles until we sold it and the 1982 LeBaron Convertible took up residence in our gagrge. It was possible to trick the computer during very cold weather, 0 and below, before fully warmed up it would run lean during a hard acceleration causing a bog and a pop through the carburetor. Also during long steady cruising a sudden throttle change for a pass would result in a slow response to accelerate. This condition could be over come by tricking the computer by several large quick throttle movements dialing back the air fuel mixture before a passing maneuver took place.

Unlike the car of today, pre 1980 vehicles had vastly different personalities & driving quirks that most people would not put up with today as most are used to kitchen appliance monotony in their mass-market rides.

I realize that some 35 years down the road the electronics living under the hood are most likely not up to factory fresh specs. And, if they were, don’t come close to the speed of crunching data that today’s controls posses, most likely leading some to believe these old controllers aren’t working correctly. Additionally, when this technology came on the seen, there was a considerable lag time for the technicians to become computer savvy, and comfortable with its complexity. That trusty test light suddenly wasen’t cutting it any longer. Many, meny wasted trips & dollars were experienced by owners because the service team did not under stand how these systems worked, and willie-nilliy played the part swap game.

No one here thinks twice about pulling a head for a needed valve job to bring an engine up to snuff, so why wouldn’t one want the same refreshing of the electrical controls afford those iron parts?

Those of us that desire to keep their cars in original condition, and appreciate a technical mid step in the march to today’s fuel injected micro managed complex rides should be encouraged to do so.
Just my $0.02

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Just ditch the Lean Burn. Keep in mind that putting the older electronic ignition in, with a suitable carb, was actually a documented Chrysler fix for the Lean Burn (where the law allowed).

Ever notice what the value of used electronics is? Pretty much nothing. Same goes for a TTL & power transistor based ECU on an old Chrysler product.

Cold solder joints are probably not issue--failed components probably ARE the issue. The engine enviroment is an awfully harsh place for electronics to reside. Besides, once you start waving a soldering iron around those solder joints you might just cause more problems--and one hopes it isn't an AC waveform puking Weller you were planning on using. That will kill things for certain.

Some parts just are not economical to repair. When was the last time you rebuilt a battery? I remember as a kid that there was a shop that did just that. I imagine the workers there died about a month after they started! I can only imagine the health "benefits" associated with melting lead and playing with sulfuric acid on a daily basis...

What IS amazing about the Lean Burn is sometimes how it even works at all. Mice ate most of the wiring in mine and the Slant still started and run, albeit poorly.

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Slanted D150

It finally quit raining, yea !!

• Time spent waiting for the rain to quit ........ 48 Hours
  
  Time spent finding and fixing the problem ........ 40 Minutes
  
  Cash spent to fix the problem ........ $0.00 dollars ........ Priceless !!
  

Thanks for all of the replies!

I did find the ECU ground and I didn't have to slice open the harness to do it. It is screwed to the firewall right next to the bulkhead wiring through block in the firewall on the driver's side (it is a bit hidden by the wires).

Well, all of the grounds tested good, the power to the coil and the ECU tested good and I was about to pull the ECU and take it inside, but I figured since I had the meter out. I might as well test the resistance of the ignition coil and the dizzy pickup coils first (dual coil setup).

Checked the "start" pickup coil, got 314 ohms and then checked the "run" pickup coil - no reading. Humm ..... scratch the probes to get better contact, still no reading, What the ...... !?? If the coil is open, it shouldn't run at all, right? (I'm not sure how the ECU handles that).

Peer into the female half of the plug and I can't even make out that there is a metal plug in there, it is so gunked up with crud. Break out the emery and contact cleaner, clean it and try it again and I get 315 ohms. Make sure the pin barrels are pinched together and plug it back together and it is back to purring like a kitten! Actually, it is idling better then before, it always had a tiny, occasional intermittent vibration or miss that is now gone.

That just reinforces my mantra of "Do the Cheap, Simple Stuff First"!

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'81 D150 with "Lean Burn"

cw6er:
Sarcasm Corner:

Oh crap! That is too bad. You could have had a whole bunch of new parts under your hood, now your stuck with the crappy Lean Burn stuff…

I feel your pain, man. And, you spend no bucks? Bummer Dude…

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Bad Billy; evil twin:
Sorry about that unsolicited comment from my ironic, negative twin brother, the bad Billy. That creep sometimes logs in here as me while I’m in the kitchen getting a coffee refill…

Cw6er, I’m pleased to here that one more Lean Burn has been saved. Kind-ah cool to walk around a car show and see an original ignition set-up, and not a great big red box bolted to a fender. When that system first came to be, I had the same excitement that folks seam to now have over all that Apple i stuff. We went to the moon in 69’, and seven short years later computers were running cars…

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

The worst part was I didn't have an excuse to buy even 1 new tool ... Oh the horror!!
Car Show! This wont be at a car show unless they have a "Worst in Category" or a "Why Is This Thing Still Running?" prize, LOL.

Actually this wasn't a case of saving a Lean Burn system, this problem could have happened on a HEI system also. It is about systematic, organized troubleshooting instead of condemning the usual suspects out of hand and throwing money and parts at it.

I've been thinking about converting it to HEI for some time now but haven't done so because I really don't believe it would be much help if I left this ratty, jury rigged, lean burn Carb the PO left on there. He stripped everything off of it! I need to replace the carb when I do the conversion.

As to Looking original for a car show, I was looking at that and I think I would use the existing lean burn pick-up coil wiring to the new Dizzy (plug looks like it will fit) and gut the Lean burn box and mount the module and relay in the original box on the air cleaner.

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'81 D150 with "Lean Burn"