80's FMJ bodies set up for code readers?

53ryder

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Have owned A bodies and a C body. Looking at something in the 80's. Was wondering if 80's FMJ bodies were set up with computers so one could plug in a code reader? I don't know so I thought I'd ask you all!



Glenn
 

Cordoba1

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Have owned A bodies and a C body. Looking at something in the 80's. Was wondering if 80's FMJ bodies were set up with computers so one could plug in a code reader? I don't know so I thought I'd ask you all!



Glenn
Technically, yes -- on some FMJ bodies there is a special diagnostic plug, but this system is miles from the OBD II standards used by modern code readers. Dealerships had the antique code readers back into the 80s, but they are long gone. If you're looking for a modern, computer-controlled engine; the primitive controls (Lean Burn, in this case - look it up) are not what you're looking for.
 

BudW

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Was wondering if 80's FMJ bodies were set up with computers so one could plug in a code reader?
When I first read his question - I thought it could be answered a couple of different ways.
The first thing that came to my mind was fender tag codes (but I was wrong).

There was a limited window when Chrysler had a “diagnostic port” on cars. I think it was ’80 only or maybe ’79 to ’81 only, or something like that.
When I was in a dealership, I didn’t use it much – for the same diagnostic tests could be performed without that port – and sometimes faster (which is why I think that “diagnostic port” went away.
It was a good idea but (IMO) just didn’t work very well in reality.

When the front wheel cars (and pickups) went to fuel injection – they used a small and somewhat hidden diagnostic port – which was a lot more helpful.
A few years later (’96) the OBD2 port came out for all vehicles.

There is no easy way to diagnosis a Lean Burn (Spark Control, or whatever name the air cleaner mounted computer used that year) system.
The best way/fastest way is to have a box of “known good parts” and just start swapping parts out.
Lean Burn is an analog computer and there is just no way to communicate with it. Almost all fuel injection systems made (except for the J-body Imperials which is also analog) use a digital computer.
BudW
 

volare 77

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found this online.... There was one on ebay a while ago IIRC

tester.jpg
 

53ryder

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My question, I believe, is answered. Was just wondering if I picked up a mid to late 80's Dynasty, New Yorker, Lebaron or Town & Country if they had ports to check and see if they were throwing any codes. Sounds for the most part no. That's okay....still going to seek something out! Looking forward to it.


Glenn
 

kkritsilas

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For all intents and purposes, the OBD II type diagnostic port is not on the F, M, or J body platforms. There were diagnostic ports on some of the Lean Burn equipped cars, but they need a specific tester for that system; an OBD II tester will not work. The OBD II port requires a digital computer to put out codes, and there are no digital computers in the power-trains of our cars. I suspect that some of the Electronically Tuned Radios may have a digital computer, but that pretty much covers it.This generation of cars is almost purely mechanical. Diagnostic tools are DVMs, timing lights, tach/dwell meters, and air-fuel ratio meters (at most), combined with some common sense and if present, some background in cars..
 

BudW

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I should also say finding a factory tester – that is still functioning (which both was a problem back in the 80’s) as well as the needed cables – was troublesome. Now days it is very hard to find a tester.

My experience then (and now) still remain the same. Most Lean Burn problems – were not associated with the Lean burn system, but were elsewhere (ie: carburetor, fuel pump, spark plug wires, and so on). The Lean Burn system itself rarely gave any problems, but fingers were always was pointed to it.

Even today, the system rarely gives problems – but when it does, it is still “faster” to have a box of known good parts to diagnosis the system (and a good Factory Service Manual). Now days, replacement parts are becoming hard to find – so generally it "might" be easier to change over to a “non-Lean Burn” system if problem is confirmed to be within that system - in some cases.


On my ’86 5th Ave, the “Electronic Fuel Control System” still operates the ignition system like normal. It is also “trying” to control my computer controlled carburetor – but is having a hard time doing so (because it has a non-computer controlled carburetor on it, currently).
BudW
 

Oldiron440

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Didn't the 80s cars flash codes if you turned the ignition. on, off,on but didn't crank it?
You had to count the number of blinks.
 

80mirada

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Didn't the 80s cars flash codes if you turned the ignition. on, off,on but didn't crank it?
You had to count the number of blinks.

That was OBD 1, Chrysler was the only one that used a key sequence to trigger code flashing. I beleive it was only EFI vehicles.
 

kkritsilas

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MY 1993 Lincoln Mark VIII had a OBD I (not II) port. The only way to get codes read was to bring it to the dealer. The OBD I codes were specific to the car (i.e. the same code from two different models would mean different things). OBD II standardized a lot of the codes, but there are still some codes that are vendor specific, and there are other codes (transmission, ABS, Traction Control, a few others) that haven't been standardized.
 

Oldiron440

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I've got a OBD1 for Ford, I bet it hasn't been used in twenty years.
 

Cordoba1

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Hey BudW: Just out of curiosity, what do you mean by "Analog Computer"? The sensors, sure, produce analog signals, but so do (most) sensors on modern cars. In the case of Lean Burn, the signals are first sent to a sensor circuit and a digital I/O chip for conversion into digital interpretations for the CPU. Lean Burn units have integrated ignition, an I/O chip, a CPU, RAM, ROM, and even a PROM. The video below is VERY insightful into what Lean Burn is actually doing:



1978-Spark-Control-Computers.jpg
 

BudW

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First of all, I know enough about computers to be dangerous (to myself and to any computer I work on - just to get that out of the way).
I’m only repeating what I was told when I worked for Chrysler.

They said something to the effect, that analog works better/faster when performing slide rule calculations or something to that effect.

As computers changed, when they went to Fuel Injection - they tossed the analog aspect out to the curb (I guess).
https://en.wikipedia.org/wiki/Analog_computer
BudW
 

Oldiron440

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Does not matter Bud, we just need to feed info that works.
 

kkritsilas

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The LB/ESC has a microcontroller, which is a very primitive, slow computer, but it is digital. By the looks of the PCB, it looks like a 4 Bit CPU (same as would be found in calculators). It really doesn’t do that much, which, only taking in vacuum, RPM, temperature, and throttke position, and only outputs an ignition pulse. It probably can’t output diagnostic codes.

Modern automotive computers are mostly 32 bit, and must have 50-100X the RAM and Flash storage (equivalent to the ROM/PROM in the above circuit board). For things like adative cruise control, they are probably adding a DSP chip.

All signals from the various sensors are analog. The real world is analog in that it doesn’t change in steps (think temerature, air pressuer, coolant temerature, etc.). The analog signal is converted to digital (by A/D convertirs) so that it can be input into the digital CPU and the software can work with it (same is true for the LB/ESC computer).

Analog computers can be made, and they are in use. But the can not be programmed, and they are for very specific uses, and are not generally used.
 

69-

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@BudW - are you talking about one of those diagnosis testers? It is labeled in German (just a glued on faceplate), but I think you get the idea. Its a ignition tester, and I also have the adapter for the 5pin ignition connector.

By any chance, do you have some wiring schematics of this? It is working (using the self test), except for test 1 (primary coil and ballast resistor) - it fails with signal "short".

I'm going to check the cable first.

_IMG_20210719_205414.jpg


_IMG_20210719_205433.jpg
 

BudW

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That is one of the several factory computers we used. No, I don't think I've ever seen a schematic on one. Cables were treated rough by the different techs and a common problem area.

I've worked on a few PC boards - but, honestly, never looked inside of one of the Chrysler testers.
It does make sense to make a single tester, then slap a different label on it for different languages.
BudW
 
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