Diagnosing The Chrysler Electronic Ignition System

okay what i want to talk about here is diagnosing the chrysler electronic ignition system debuted on all engines 1976 uh through 1991 in the marine world uh started out in the automotive world i believe 1971 and a 340 engine uh in a plymouth duster dodge dart something like that california emissions uh engine so and the purpose of the electronic module uh is is dwell uh one thing with point ignition you don't have the same dwell every time where from the points uh obviously the dwell changes as the rubbing block uh wears down the the points get uh closed up more uh that's gonna increase the dwell so um the purpose of the constant dwell is for federal emissions you know at the spark is the same every time in theory so that's why this stuff was introduced uh it is a hotter spark as well so on the on the components here you have the ignition coil which is just a normal one and a half ohm coil so if i disconnect the two wires on the coil and take my ohm meter it's approximately one and a half ohms you know 1.3 to 1.6 depends on the temperature of the coil on the quality of coil and so forth um but it's an externally resistant coil you have the ballast resistor which i just stuck one here because it's easy out see how hot that is because i got the key on that's supposed to do that okay so um this ballast resistor is a dual type okay one resist one this top part here is for the ignition coil that's a one and a half ohm i believe and the 5 ohm one on the bottom is for the ignition module and that is a auxiliary ballast the engine will run with that circuit bad so it is an auxiliary circuit for the five pin module a four pin module will completely bypass that circuit anyway which is totally interchangeable so a five pin module is an lx101 in standard excuse me an lx100 and an lx101 is a four pin if i'm not mistaken off top of my head so um and this is the electronic control unit he's the guy that's taking the pickup coil which i'm gonna get to here next which is this connector which is the two wires coming out of the distributor so see right there it's coming out of the distributor he's generating the ac voltage required to trigger this transistor okay so um that's basically a crash course how it works now the tools we need are very simple at least in my opinion a meter it could be a harbor freight meter it doesn't have to be this fluke fancy dancing 78 or 88 or whatever you've got but a harbor freight dvom will work great an old-school test light with an actual light bulb in it um not a fancy snap-on high dollar led uh with the red light green light tells you if it's a ground or red obviously if it's a hot that won't work that doesn't flow any current we need an old-school test light okay with a bulb that bulb draws about 250 200 milliamps something like that we can flow current we're going to use that to trigger that transistor those fancy test lights won't do that and an actual adjustable spark tester or an st 125 if you're old school guy st 125 means 25 000 volts it takes to crack the gap so what i like about and again these are lyle numbers here 28 400 for the test uh the test light and the 50850 for the adjustable spark tester so the reason you use a spark tester and not a spark plug laying against a manifold or carburetor or whatever is the spark tester will stress the coil this coil even though this is 1970 whatever design okay needs to crack at least 20 000 volts minimum if it cannot crack 20 000 volts it's junk okay or there's a problem someplace so uh even though normal firing voltage if everything's correct plug gap wires and so forth rotor air gap in the distributor uh distributor contacts that sort of thing is eight to twelve thousand volts that's where you're at idle uh revved up under power somewhere in the timing of advance so sometimes the kv goes down but in that neighborhood when you start getting 15 000 volts more than that you've got an open in the secondary circuit you know junk wire rotor air gaps crappy something like that but for the sake of testing when we have a no start concern okay or or a hard start i want to know the kv okay and when i come back i'm going to have this tester set up on the coil wire and i'm going to show you how to diagnose this system or this system with these tools okay i've got my spark tester connected in line here i just disconnected the coil wire out of the cap connected my spark tester here to a known good ground okay and i don't know if i can show you this i've adjusted to just over 20 kv so it's probably 2122 kv obviously the wider this gap the more kv it's going to take to crack this gap electricity is lazy it's going to take the least path of resistance so i'm forcing this spark to crack this this space here okay and that's very important so like i said you know don't use a spark plug you know i'm not that little 30 000 scap through there it doesn't take a lot of current and a lot of voltage to crack that gap so this is how you check for spark this is the only way to do it right i don't care if you're working on a 96 pontiac grand am or you're working on this chrysler or you're working on a 2021 ford mustang this is the correct way you've got to stress it so with that said uh what i'm gonna do is let's look at the voltages at the ignition module first so if we have a no start concern this would be the first thing i would do i've got the battery i've got my key on here with my jumper wire so um and i'm gonna take my meter all right now i got the module disconnected all right so i've got some wire colors here i've got green and i've got this um uh blue here okay blue is my normal feed from the ignition switch if i follow the blue back see how piggybacks this is the 12 volt side of my resistor okay the purple is what's coming from the ignition switch comes into here and you see i got a little black jumper to this side okay so my blue is is my 12 volt feed that does not go through the resistor so i'll take my meter here and i'll verify sorry doing this one-handed and my battery's kind of half dead here but i got 12.38 on the blue circuit okay the next circuit is the green one okay that is the auxiliary ballast okay now if you understand how a ballast resistor works um that voltage is going to be 12 volts okay it's going to be battery voltage i'm going to prick it see how it's 12.38 the reason that is is because i'm not flowing any current so when i'm not flowing any current open circuit voltage the voltages are going to be the same on both sides of the resistor okay so as soon as i plug that in that voltage is going to drop okay and i'll demonstrate that that's how balanced resistors work it has to flow current to create heat the heat creates resistance which lowers the voltage the reason the resistor is in the circuit is primarily for the ignition coil okay at low speed i don't need a lot of current i'm at idle you know 5 6 700 rpm i don't need full bore voltage so when that reluctor is slowing down or if it's a point system the points are closing slower that means the dwell is longer it's going to create more heat and cut the current to the coil when i rev the engine up everything's happening faster and there's less time for that magnetic field to collapse that this thing will cool down and the voltage will increase okay and the current uh will also increase okay so again i will i've checked power here this thing grounds when it mounts okay um so one thing you could do too is just take your meter and i should have zero volts here or touch the case if i have power here and i'm touching the case and i have voltage here i have a background okay open circuit voltage is going to be power on this case so again i don't have it plugged in but you see it's zero so what i'm going to do to demonstrate same thing with the coil the coil's excuse me because i don't have the um i don't have the module connected so right here is the positive side of the coil okay so i've got 12 volts sitting there okay it did not decrease i'm gonna have 12 volts on both sides okay so i got uh take my word for it see i'm going to both sides of the coil the reason that is is the coil's got continuity which it should okay that's a good sign now as soon as i plug this module in this is gonna drop i'm just gonna plug it in i'm not even gonna put the phillips screw in i plugged it in boom now i'm dropping across this resistor i'm going to go to the positive side of the coil here and look what i've got oops just a little over 5 volts okay i've got 5 volts there because i plugged it in we are flowing current through this coil because it is going through the module it's waiting it's pulling it down okay so excuse me that's a good sign that the module can do something because as soon as i plug this in that voltage should immediately drop so if i plug my module in and that doesn't drop something's going off my modular circuitry now that i've got a load let's check the ground here all right and i've got you know one tenth of a volt there so nothing all right i just disconnected zero if if i had a background i would show voltage there okay because i've got 12 volts going into the module battery voltage has to return to where it came from so it's got to go back to ground so if this thing's got power we have a background all right the next step in the diagnosis if all that checks out just like we did okay is this wire right here this is coming from the ignition harness this is coming right from the ignition module let's take our volt meter and let's connect across these two terminals all right so i'm going to take my ground doesn't matter pick your favorite one in this particular test we'll shove our thing in here all right and excuse me and here's my red okay the ignition module is going to put half a volt on the gray wire okay see i've got a good connection here about 0.53 volts that's correct the module puts the voltage on the line if i don't have half a volt there with the key on excuse me something's wrong with the module okay or connection or whatever excuse me so that is very important the next thing i'm going to do is i'm going to disconnect this all right okay i'm back i got my spark tester connected and where i left off was this gray wire okay i talked about how the brown and the gray brown is technically ground through the module and gray is what has the half a volt so every time i take that half a volt and pull it to ground i'm going to get spark through my tesla you can't do this with a jumper wire but you should do it with a test light so it limits the current so i'm going to take my test light and i'm going to touch the gray wire and watch what happens to the spark tester when i do this [Music] i'm just sitting there and touching and dancing it just like the reelector going around so i'm cracking 20 kv here all day we can make this a fireworks show fourth of july okay [Music] all right like i said i should be able to do that all day long i mean we can play games for this all day all right now that tells me the ignition module is good and everything now if i wouldn't have got sparked there then i probably would have checked my coil wire or something like that assuming that i've already tested the resistance of my coil with the wires disconnected i like to say approximately one and a half ohms uh if that that one to work then i would have changed the module okay now if i have spark there but i connect this pickup coil up and i still don't have spark then the next thing we need to do is we need to check the pickup coil now there's two tests for the pickup coil the first test i would do is an ohmic test let's make sure that there's continuity through that magnet all right and what we're going to do is we're going to take our handy dandy meter and we're going to connect our meter in the pickup coil wires and again doesn't matter whatever your favorite color is it's an ac device it doesn't enter excuse me what wire is what and i'm going to put that in there i'm going to change my meter to ohms excuse me again all right and i should have somewhere between 200 and 500 ohms that's what i'm looking for all right i've got 292 right across those two terminals all right that's what we want to see something like that now the next thing we want to do is we want to flip our meter to ac well i'm going to leave it i'm going to leave it make sure i'm connected good here [Music] all right all right i'm at 292. i'm trans-free here and i'm going to flip my meter to a c voltage okay all right ac right here a little squiggly i'm going to crank this engine over okay obviously it's not going to start because the coil wire stuff's not in and i don't have the pickup in connected this thing with normal cranking speed you know 150 176 rpm something like that depending on your battery the weight of the oil the temperature of the engine this is going to vary but i want to see at least 200 millivolts cranking that's point two and whatever minimum so i'm gonna take my wire and i'm going to crank this guy over okay and let's see what we got [Laughter] there you go i got 200 millivolts cranking that's great that's enough to trigger that transistor there's nothing wrong with that pickup the air gap's good the coil wire and that pickup assembly is good there's no further testing there's no reason to take the cap off there's no no sense screwing around with anything that's what we're looking for the last bit of circuit i'm going to get into is going to be the bypass circuit so during cranking you saw how low the voltage is of the coil during cranking um the voltage is going to get really really low if it's 5 volts sitting there with the key on cranking it over it's going to be 2 3 volts not enough maybe less so there's a bypass circuit the bypass circuit is right here see these two purple wires purple the white tracer not this one the white one is the crank circuit coming from the neutral safety switch but this guy right here the eye wire as it's called okay the eye wire puts full 12 volts to the ignition module okay excuse me to the ignition coil all right that's its whole purpose in life so we bypass the ballast resistor for cranking and put cranking voltage there rolling the engine over i should have about nine and a half volts there or something like that okay that's very important so um and that's what that circuit's for so you can test it with a meter like i say whatever voltage you have at your battery should be very close so if i take my meter and go across my battery i should have very similar i'll have probably a little bit less for a little bit of voltage drop but i should have that the only other thing to take in consideration when diagnosing systems is there's a lot of connections some of them are unnecessary in my opinion you know right here this little two-wire guy this is actually the pickup so when you guys are having intermittent problems you know stalling quitting you've changed all the parts stuff's still not right you need to look at these connections take them apart make sure they're clean make sure they're tight make sure everything's good okay like i say this two-wire plug is the same plug as here all right i don't know why they did this i beats me all right this here you go like this connection here for the ignition this is your main ignition feed to the whole operation this is feeding the coil and the module if this little spade terminal is green nasty crappy gonna have problems okay the other thing we got here is is this one here this one goes to the coil leaves the module and goes right to the coil check that connection okay this one right here is going to the negative side of the coil and i did not talk about this circuit yet i covered every circuit except this um and the black with the white tracer is going to the negative side of the coil this is the trigger signal but it's got a little bullet connector right here that could be crappy rusty krody whatever so don't forget to check all these connections behind this box you know i see lots of trouble with that so in review these two wires are the pickup coil the blue is my 12 volt feed all the time uh from my ignition switch all right my green is my auxiliary ballast not that important it'll run with this circuit out um but it should be checked just to be sure um and that's it grounds when it mounts so i hope this uh shed some light on how to diagnose this system it was a very good system i know it gets a bad rap online i know it's old you know i mean you got to remember this stuff was designed in the late 60s i mean it debuted in 1971 and like i said the marine engines used it all the way to the end until 91 most of the cars got out of this system you know the lean burn days because this module was incorporated into the uh they're into the uh the computer on the carburetor around excuse me on the air cleaner the pickup in that was still the same but this module was basically inside the computer and then later years um you know like i say these totally disappeared but in the marine engines they use them for quite a while so everything i just discussed you could diagnose on a chrysler car i mean you got a 73 uh polaris or something like that it's the same thing you know um so all this stuff applies so i hope i hope you learned something if you got any questions whatever don't hesitate to comment and happy boating

Channel: Lakeland Auto & Marine

Views: 51,110

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Id: tVja7UctgIw

Length: 19min 48sec (1188 seconds)

Published: Sat Oct 02 2021