First Car 75 Duster
Member
Ok so I know the wires go from the ignition control to my distributor but I need to know what their specific "job" is. I think one is a crank signal but I need to be sure.
Ignition Control to Distributor
- Thread starter First Car 75 Duster
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67Dart273
Well-Known Member
Mopar ignition is complicated by the fact that older modules are "5 pin" and you cannot tell by looking because some newer replacement 4 pin modules still have the 5th pin--just not connected
Five pin modules MUST have a 4 pin ballast, but newer 4 pin modules can use either 2 or 4 pin--it's just that the second resistor is then not used
From MyMopar here are the simplified diagrams for 4 pin/ 5 pin boxes:
Simplified Ignition System Diagram – MyMopar
The reason there is a labled "new wire" is that these are geared towards conversion of older points cars. What is missing is the IGN2 ballast bypass circuit for start, which goes to the coil+ side of the ballast. NOTICE the path through the ballast to the coil, this is the SAME for either points cars, 4 pin modules/ 2 pin ballast, or 5 pin modules/ 4 pin ballast.
The difference is the 5 pin module is supplied voltage through the second resistor, molded into the same package in the 4 pin resistor
Here is yet another diagram from the same website
https://www.mymopar.com/downloads/Dual_Ballast_5pin.pdf
Five pin modules MUST have a 4 pin ballast, but newer 4 pin modules can use either 2 or 4 pin--it's just that the second resistor is then not used
From MyMopar here are the simplified diagrams for 4 pin/ 5 pin boxes:
Simplified Ignition System Diagram – MyMopar
The reason there is a labled "new wire" is that these are geared towards conversion of older points cars. What is missing is the IGN2 ballast bypass circuit for start, which goes to the coil+ side of the ballast. NOTICE the path through the ballast to the coil, this is the SAME for either points cars, 4 pin modules/ 2 pin ballast, or 5 pin modules/ 4 pin ballast.
The difference is the 5 pin module is supplied voltage through the second resistor, molded into the same package in the 4 pin resistor
Here is yet another diagram from the same website
https://www.mymopar.com/downloads/Dual_Ballast_5pin.pdf
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Here is a peek at the Electronic Ignition layout on my engine run stand.
(it's what's on the aluminum plate.)
(it's what's on the aluminum plate.)
First Car 75 Duster
Member
Ok, that I understand. But what I am interested in has nothing to do with the resistor or the ignition control module/ECU. I need to know what the two wires that go from a stock ignition control module/ECU to a stock distributor do.
First Car 75 Duster
Member
Maybe a different question. What are each of the wires for, on a 5 pin module? Specifically the two that go from the module to the distributor.
They go to the pickup in the distributor.
First Car 75 Duster
Member
I know but what are each of the two for. What do both wires do?
Inside the dist is a coil of wire wrapped around a pole piece that has a small air gap, coil will measure about 150-400 ohms, depending on brand. Called the pick up coil. This is mounted on the plate where the points used to be, it does not move.
On the rotating shaft is the reluctor, which has tips or projections that sweep past the above air gap, distance from the tip is reqd to be an air gap of 0.008" to generate the correct signal strength. Number of rel tips matches the number of cyls.
The movement of the rel tip generates a small AC voltage, a sine wave, that will be millivolts in amplitude at low engine speeds but will increase to a few volts at higher engine rpms. This creates the signal to the box that says 'I want the spark NOW'.
The two wires coming out of the dist are the wires from the p/up coil.
On the rotating shaft is the reluctor, which has tips or projections that sweep past the above air gap, distance from the tip is reqd to be an air gap of 0.008" to generate the correct signal strength. Number of rel tips matches the number of cyls.
The movement of the rel tip generates a small AC voltage, a sine wave, that will be millivolts in amplitude at low engine speeds but will increase to a few volts at higher engine rpms. This creates the signal to the box that says 'I want the spark NOW'.
The two wires coming out of the dist are the wires from the p/up coil.
First Car 75 Duster
Member
Fantastic. Now I just need to know what wire is the one that sends the signal
Phreakish
Well-Known Member
Both. The reluctor wheel induces a current into the pickup coil. The two wires come from the pickup. There isn't a dedicated role for each wire, neither is a positive or ground, both wires are needed in order to "read" the signal.
Kendog 170
Let the boy go !
It's my understanding that the engine will run either way but if it's wrong, your timing will jump all over the place with a time light. If that's the case which them around or your engine will have a miss when accelerating.
Dave999
Well-Known Member
its an AC signal.
the current flows for a short period in both directions in both wires. it crosses 0V (not flowing in either direction) in the middle of its wave form and at some small voltage above 0v in the positive direction it triggers the igntion module. the picture below shows why getting those two wires the wrong way round can cause timing drift. it should trigger off the upswing above 0v not on the down swing below 0v
This is the reason for the mopar specific male/female dual bullet connector, stops you getting this part back to front.
its not an on off or 0, 1 type digital signal on a single wire that can be measured above the modules case ground, as you get on some modern instrumentation or devices. or just a voltage above ground like out the back of an AF guage (both assume 0V is case ground) The coil in the dizzy is held at what the module thinks is ground, and the movement of the iron reluctor star on the distributer armature, past a magnetic pole, with a coil around it connected to both wires, causes a current to swing south of 0v and then north of it triggering the module to switch off the coil....
its very very analogue.
Dave
the current flows for a short period in both directions in both wires. it crosses 0V (not flowing in either direction) in the middle of its wave form and at some small voltage above 0v in the positive direction it triggers the igntion module. the picture below shows why getting those two wires the wrong way round can cause timing drift. it should trigger off the upswing above 0v not on the down swing below 0v
This is the reason for the mopar specific male/female dual bullet connector, stops you getting this part back to front.
its not an on off or 0, 1 type digital signal on a single wire that can be measured above the modules case ground, as you get on some modern instrumentation or devices. or just a voltage above ground like out the back of an AF guage (both assume 0V is case ground) The coil in the dizzy is held at what the module thinks is ground, and the movement of the iron reluctor star on the distributer armature, past a magnetic pole, with a coil around it connected to both wires, causes a current to swing south of 0v and then north of it triggering the module to switch off the coil....
its very very analogue.
Dave
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Wow great explinations.
Charrlie_S
Well-Known Member
Think of those wires like a lamp. It needs both wires to plug into the outlet for the lamp to light.
KitCarlson
Well-Known Member
Signal is better described by voltage not current. Signal voltage is proportional to RPM. Reluctor swinging past magnet biased pickup coil, generates EMF voltage related to change in flux over time.
Current is that voltage divided by load impedance. That load, is circuit that turns ignition transistor off, for spark event.
Current is that voltage divided by load impedance. That load, is circuit that turns ignition transistor off, for spark event.
Owen 340+6
Bang em till it breaks
You guys are all incredible. I love when people make me realize how stupid I Truley am!!! Thank you all for this knowledge
67Dart273
Well-Known Member
Geezus Christ, I guess tellin you how it connects is not enough
The Mopar distributor has a magnet and pickup coil and generates positive and negative spike pulses. One or the other (I don't remember which) triggers the box which interrupts coil current juswt like when breaker points open.
S'why I hang out here. lol
I saw a schematic once on the electronics inside the boxes.
One of the wires in question was grounded in the box the other went to transistor or the like.
That lead me to wonder if you could trigger the electronic box by momentarily grounding the un grounded of the two leads?
Here is the schematic I was referring to.
It came from this site
Whats in the orange box ?
If you look at the D post it goes to ground.
And with the diode on the C pin only a path to ground can be made by the pickup coil.
I can only assume the author knows what he is talking about.
One of the wires in question was grounded in the box the other went to transistor or the like.
That lead me to wonder if you could trigger the electronic box by momentarily grounding the un grounded of the two leads?
Here is the schematic I was referring to.
It came from this site
Whats in the orange box ?
If you look at the D post it goes to ground.
And with the diode on the C pin only a path to ground can be made by the pickup coil.
I can only assume the author knows what he is talking about.
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Dave999
Well-Known Member
Yeah the pickup coil will have 1 end connected to a ground that is chosen as ground by the module. it may be slightly above chassis ground to avoid interfernace from the regulator igntion or diodes switching in the alternator.
it acts as the 0 line in the diagram i posted
signal plunges lower than this ground and then swings higher than this ground.
better called 0 volts as i don't know if its the same as chassis ground.
so that the module can tell when it is positive enough to be considerd trigger voltage. it needs a 0V in order to act as a comparison to what it sees from the pickup which will be lower than 0 v then higher than 0v. as a metal tooth approaches and then retreats from the pickup.
transistors and similar are just an electronic switch. or think of it like a Tap in a pipe. middle pin is the switch or tap handle and depending on type the transistor switches a flow of current through the other two pins on or off
most switches you just flip a lever with a transistor you apply 0.6V or more to the middle pin and it switches on or off....depending on type.... i.e the middle pin is the tap handle on the pipe between bottom pin and top pin. transistor is basicaly two diodes back to back with their annodes or cathodes joined. you can check em with your multi meter.
you should see high resistance between middle pin and top pin with the leads 1 way and low resistance the other. the situation should be mirrror image for the middle and bottom pin with the trsnsistor on the bench. low resisistance setting please do not blast it with 15 volts.
NPN transistor will do exact oposite of a PNP transistor hence my talk of OFF or ON
so in the module i would imagine a small transistor and potential divider as part of the trigger circuit used to switch on or off the big power transistor that controls coil current. keep the sensitive low amp stuff away from the big amps.
like controling your headlamps with a relay to save your hedlamp switch.
The switching voltage + bias voltage that is at the middle of the potential divider set by the two resistor sizes will be enough to trigger the small trigger circuit transistor to switch a voltage on that is more than the switch on/of volts into the middle pin of the BIG transistor which controls the coil.
i'll have a look at the schematic later so at the mo. this is just a basic guess.
the real circuit will have lots of control and compenstation parts to take into account frequency, heat, variation in pickup coil, and depleating magetism in the pickup etc.
the forerunner to the transistor was the Valve (europe) or Tube (in USA speak) hence the tap anaology which is totally wrong in electrical terms but works well for understanding is going on.
a triode tube would be used in the old days where we use to a basic transistor today. the russians used tubes in weapons systems fighter jets and space flight until the early 2000s. tubes are not killed by the electro magentic storm caused by a nuclear blast, transistors and chips are.
Or indeed as many have found out, killed by a faulty alternator.
Dave
it acts as the 0 line in the diagram i posted
signal plunges lower than this ground and then swings higher than this ground.
better called 0 volts as i don't know if its the same as chassis ground.
so that the module can tell when it is positive enough to be considerd trigger voltage. it needs a 0V in order to act as a comparison to what it sees from the pickup which will be lower than 0 v then higher than 0v. as a metal tooth approaches and then retreats from the pickup.
transistors and similar are just an electronic switch. or think of it like a Tap in a pipe. middle pin is the switch or tap handle and depending on type the transistor switches a flow of current through the other two pins on or off
most switches you just flip a lever with a transistor you apply 0.6V or more to the middle pin and it switches on or off....depending on type.... i.e the middle pin is the tap handle on the pipe between bottom pin and top pin. transistor is basicaly two diodes back to back with their annodes or cathodes joined. you can check em with your multi meter.
you should see high resistance between middle pin and top pin with the leads 1 way and low resistance the other. the situation should be mirrror image for the middle and bottom pin with the trsnsistor on the bench. low resisistance setting please do not blast it with 15 volts.
NPN transistor will do exact oposite of a PNP transistor hence my talk of OFF or ON
so in the module i would imagine a small transistor and potential divider as part of the trigger circuit used to switch on or off the big power transistor that controls coil current. keep the sensitive low amp stuff away from the big amps.
like controling your headlamps with a relay to save your hedlamp switch.
The switching voltage + bias voltage that is at the middle of the potential divider set by the two resistor sizes will be enough to trigger the small trigger circuit transistor to switch a voltage on that is more than the switch on/of volts into the middle pin of the BIG transistor which controls the coil.
i'll have a look at the schematic later so at the mo. this is just a basic guess.
the real circuit will have lots of control and compenstation parts to take into account frequency, heat, variation in pickup coil, and depleating magetism in the pickup etc.
the forerunner to the transistor was the Valve (europe) or Tube (in USA speak) hence the tap anaology which is totally wrong in electrical terms but works well for understanding is going on.
a triode tube would be used in the old days where we use to a basic transistor today. the russians used tubes in weapons systems fighter jets and space flight until the early 2000s. tubes are not killed by the electro magentic storm caused by a nuclear blast, transistors and chips are.
Or indeed as many have found out, killed by a faulty alternator.
Dave
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Kendog 170
Let the boy go !
The ground is controlled thru the ECU that is why it's important to ground your ECU your chassis.Some add a ground wire to one of the mounting bolts.
I am not so sure one leg of the p/up coil is grounded. If this was the case, the grd wire could be grounded internally in the p/up, & only one p/up wire reqd to connect to the ECU. A saving in money. Grounding through the dist body is not a problem, the GM HEI grounds the coil through the dist body, & a far higher current than the p/up generates.
I added a ground wire to mine. Used the same bolt in the firewall the factory ground bolts to off one of the bellhousing bolts.
Although the back plate of the GM HEI module is grounded to the distributor (or mounting plate).
Same with the Mopar brain boxes, their steel casings must be grounded or it will not run. (hang one in mid air with the wires attached and try and start the engine, it's a no go.)
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