1980 stock ignition puzzle
02-15-14, 05:53 PM
#1
1980 stock ignition puzzle
Any of you folks who have long experience with the stock 80 ignition, I could use to kick an issue around with you.
[Please, no suggestions to swap/upgrade to a different system (FB, DLID***, etc); I know those options but am not looking to pursue them at this time.]
I was checking my timing today, preparatory to getting my bi-annual smog check.
Car runs and idles well, steady idle at 800 RPM. Listening closely reveals a minor periodic stumble, just serious enough to slightly shake the engine.
Lead timing is rock solid, dead on the mark, and steady.
Trailing timing is firing on the lead timing mark about 80% of the time. I can see the timing mark jump back and forth (it changes color as I have the marks painted different colors.
Trailing firing is either exactly on the lead mark, or exactly on the trail mark.
System is completely stock - I have some Blaster coils I plan to try out but have not installed yet - and is in very good general repair.
I noticed this issue last time I was tuning the car (before last smog check) but it was much less frequent. Roughly 1 wrong-timed firing every second or so. I passed that smog check but numbers were not quite as clean as in the past, so I'm concerned this issue might give me grief this time around. I'd like to clear it up!
Things checked so far:
Pickup coils ohm out properly, no shorts between the leads, shields of the cables are solid, no frayed insulation, nothing seems to be grounding out. Connectors seem clean and tight. Coil gaps in tolerance.
Plug wires are in fine shape; cross-fire on the high-voltage wires doesn't seem to be a candidate. Cap and rotor are brand new & OEM, as are plugs - installed today.
Ignitor control box ground seems solid. Wiring seems correct and is unchanged for last two years.
Resources available:
I have a clean spare dizzy with a good-condition pickup coil in it. Not beautiful, but it should be reasonably functional. It's spare because it has more shaft end-play than the currently-installed dizzy.
I have a spare ignitor control box that tested good the last time I used it in 2009. It's not 'pretty,' but it should still be operable.
I have spare J-105's, though I can't convince myself that a failing ignitor itself could cause this precise issue, where it's firing most of the time on the wrong signal.
Multimeter(S), timing light, ancient but functional 60MHz oscilloscope, fair kit of electrical/electronic tools.
Thinking so far:
The 80 ignition design was prone to signal crosstalk issues; that's why it was done away with & the J109's-on-the-dizzy design came out - - no need for the tiny pickup signal to go through 3 feet of cabling & an amplifier. Mine hasn't been a problem until now, though, and it's only a "problem" in that it might cause a smog-test fail.
If it's not a breakdown in the pickup coil cabling, then the smart money would be on the ignitor control box, seems to me.
There's a small chance that the condenser on the dizzy itself may be failing, but that would seem far more likely to cause mis-triggers off-time than this odd substitution of signals. I do not see any leading misfires, only the trailing-at-leading-time described.
Theories and suggestions welcome. One thing I don't have is an abundance of free time, so I'm trying to make my available hours count. The other thing I don't have is the option to modify away from stock configuration.
[Please, no suggestions to swap/upgrade to a different system (FB, DLID***, etc); I know those options but am not looking to pursue them at this time.]
I was checking my timing today, preparatory to getting my bi-annual smog check.
Car runs and idles well, steady idle at 800 RPM. Listening closely reveals a minor periodic stumble, just serious enough to slightly shake the engine.
Lead timing is rock solid, dead on the mark, and steady.
Trailing timing is firing on the lead timing mark about 80% of the time. I can see the timing mark jump back and forth (it changes color as I have the marks painted different colors.
Trailing firing is either exactly on the lead mark, or exactly on the trail mark.
System is completely stock - I have some Blaster coils I plan to try out but have not installed yet - and is in very good general repair.
I noticed this issue last time I was tuning the car (before last smog check) but it was much less frequent. Roughly 1 wrong-timed firing every second or so. I passed that smog check but numbers were not quite as clean as in the past, so I'm concerned this issue might give me grief this time around. I'd like to clear it up!
Things checked so far:
Pickup coils ohm out properly, no shorts between the leads, shields of the cables are solid, no frayed insulation, nothing seems to be grounding out. Connectors seem clean and tight. Coil gaps in tolerance.
Plug wires are in fine shape; cross-fire on the high-voltage wires doesn't seem to be a candidate. Cap and rotor are brand new & OEM, as are plugs - installed today.
Ignitor control box ground seems solid. Wiring seems correct and is unchanged for last two years.
Resources available:
I have a clean spare dizzy with a good-condition pickup coil in it. Not beautiful, but it should be reasonably functional. It's spare because it has more shaft end-play than the currently-installed dizzy.
I have a spare ignitor control box that tested good the last time I used it in 2009. It's not 'pretty,' but it should still be operable.
I have spare J-105's, though I can't convince myself that a failing ignitor itself could cause this precise issue, where it's firing most of the time on the wrong signal.
Multimeter(S), timing light, ancient but functional 60MHz oscilloscope, fair kit of electrical/electronic tools.
Thinking so far:
The 80 ignition design was prone to signal crosstalk issues; that's why it was done away with & the J109's-on-the-dizzy design came out - - no need for the tiny pickup signal to go through 3 feet of cabling & an amplifier. Mine hasn't been a problem until now, though, and it's only a "problem" in that it might cause a smog-test fail.
If it's not a breakdown in the pickup coil cabling, then the smart money would be on the ignitor control box, seems to me.
There's a small chance that the condenser on the dizzy itself may be failing, but that would seem far more likely to cause mis-triggers off-time than this odd substitution of signals. I do not see any leading misfires, only the trailing-at-leading-time described.
Theories and suggestions welcome. One thing I don't have is an abundance of free time, so I'm trying to make my available hours count. The other thing I don't have is the option to modify away from stock configuration.
02-15-14, 09:37 PM
#2
I inspected my spare ignitor box, and it looked solid, so I swapped it in.
Problem appears to be gone, so either it's the box, or some loose connection got corrected during the swap.
Now, to figure out what's wrong with the box & see if it can be repaired - not a lot of them floating around.
Problem appears to be gone, so either it's the box, or some loose connection got corrected during the swap.
Now, to figure out what's wrong with the box & see if it can be repaired - not a lot of them floating around.
02-17-14, 09:56 AM
#4
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i wonder how the amp part of the circuit works? it seems like its probably a loose/bad connection, but the part where the signal gets manipulated might be a good choice too
02-17-14, 12:48 PM
#6
I took the currently-installed unit apart before putting it in to make sure it looked OK, and took detailed pictures.
If I can find the time (hah), I'm going to try to reverse-engineer the circuitry & see if it's possible to build a replacement using modern components. It's not horrendously complex, but there are two unusual modules inside that I've been unable to ID thus far. The rest is pretty generic resistors, transistors, and diodes, though 35 years outdated and in some cases the component ratings aren't obvious. No capacitive parts at all.
For now, the ugly-but-serviceable backup box seems to be working 100%. This was actually my original, swapped out maybe 10 years back when I cleaned and polished my then-spare unit during my first engine-bay restore.
This particular dizzy I refurbed only a year or so back; end-play is well within spec.
02-17-14, 07:42 PM
#7
Took about a 40-mile drive today, over varied terrain. Car is clearly running better, idle is butter-smooth, and the stutter/miss is totally gone. Only change was the ICU swap.
Old box is ready for cautious dissection. No initial visible faults like bad connections or the like.
May be a while before more can be done - two very busy work weeks on tap starting tomorrow.
Video (click to play): This is what it used to sound like - - never could get it to go away completely:
This is what it sounds like now (ignore the buzzing arc noise, the camera is real sensitive to my ignition)
Old box is ready for cautious dissection. No initial visible faults like bad connections or the like.
May be a while before more can be done - two very busy work weeks on tap starting tomorrow.
Video (click to play): This is what it used to sound like - - never could get it to go away completely:
This is what it sounds like now (ignore the buzzing arc noise, the camera is real sensitive to my ignition)
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02-18-14, 07:09 PM
#8
Waffles - hmmm good
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Mine did this for years before it finally failed. I just ignored it since it otherwise ran fine and
chalked it up to the old design.
I've never dissected mine to determine what killed it. If I had time it would be fun project.
chalked it up to the old design.
I've never dissected mine to determine what killed it. If I had time it would be fun project.
02-21-14, 10:07 AM
#9
I don't have 'time,' really - - but I've always had a hard time walking away from a puzzle until I understand it.
I'm currently extracting the schematic of the ICU & chasing component specs; not simple for 35-year-old Japanese electronics. making headway, though. Had to grab some very old textbooks off the shelf a couple times already as I've forgotten a lot of what I once knew about discrete transistor circuit designs.
I'm currently extracting the schematic of the ICU & chasing component specs; not simple for 35-year-old Japanese electronics. making headway, though. Had to grab some very old textbooks off the shelf a couple times already as I've forgotten a lot of what I once knew about discrete transistor circuit designs.
03-02-14, 02:57 PM
#11
I think I've got the schematic correct, now, and am working out the voltages and current flows.
This ICU box does absolutely nothing to amplify the pickup signals. The J-105's are the only signal amplifiers In the circuit.
It has two primary functions:
1) Shutting down the trailing ignition during warm-up and short accelerations up to around 3300 RPM (except in 4th or 5th gear), under control of the ECU.
2) Retarding the leading ignition around 10 degrees in a *VERY* creative way during the first two minutes of full-choke operation, post-start - - unless revs rise above about 4600. Also unless in 4th/5th.
The box controls voltage to the B terminal on the trailing ignitor, and it controls the pickup coil used to trigger the leading ignitor. But it does not amplify the pickup signals at all - - they go straight in and out through a pair of reed relays that do nothing but switch the signal.
All the electronic components on the PC board are used to regulated voltage used for the reed relays, and to clamp and amplify the control signals coming from the ECU for switching.
I'll do a complete write-up on it when I have the schematic written in something other than hen-scratch.
I haven't located the cause of failure for certain yet, but I can see a couple things that could cause the Lead trigger signal to show up on the Trail ignitor when it's not supposed to. Just a matter of figuring out which it might have been.
So long as replacement parts can be ID'd (and I have about 70% ID'd thus far) these are pretty repairable units.
This ICU box does absolutely nothing to amplify the pickup signals. The J-105's are the only signal amplifiers In the circuit.
It has two primary functions:
1) Shutting down the trailing ignition during warm-up and short accelerations up to around 3300 RPM (except in 4th or 5th gear), under control of the ECU.
2) Retarding the leading ignition around 10 degrees in a *VERY* creative way during the first two minutes of full-choke operation, post-start - - unless revs rise above about 4600. Also unless in 4th/5th.
The box controls voltage to the B terminal on the trailing ignitor, and it controls the pickup coil used to trigger the leading ignitor. But it does not amplify the pickup signals at all - - they go straight in and out through a pair of reed relays that do nothing but switch the signal.
All the electronic components on the PC board are used to regulated voltage used for the reed relays, and to clamp and amplify the control signals coming from the ECU for switching.
I'll do a complete write-up on it when I have the schematic written in something other than hen-scratch.
I haven't located the cause of failure for certain yet, but I can see a couple things that could cause the Lead trigger signal to show up on the Trail ignitor when it's not supposed to. Just a matter of figuring out which it might have been.
So long as replacement parts can be ID'd (and I have about 70% ID'd thus far) these are pretty repairable units.
03-02-14, 05:09 PM
#12
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wow neat. who knew it did anything other than hold the ignitors? well and the leading cut thing
03-03-14, 08:28 AM
#13
Waffles - hmmm good
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Great work. I knew the 4th and 5th speed switches on the tranny affected the cutting off of the
trailing. I didn't know about the 2 issue where the timings gets messed with.
So if your in 4th or 5th gear it basically does nothing.
trailing. I didn't know about the 2 issue where the timings gets messed with.
So if your in 4th or 5th gear it basically does nothing.
03-03-14, 10:20 AM
#14
The "Top Switch" and "Overdrive Switch" on the trans are normally closed and wired in series.
One signal from the ECU that suppresses the Trailing ignition passes through them.
Still working on one section of the schematic that governs the inter-relation of the "L" (lead-only) and "LR" (lead retard) signals. not quite sure if they are "OR"ed going into this one transistor or not. Have to calculate some base currents to be sure.
ONLY place in the entire FSM and schematics those two signals are referred to is in the section on testing the "Ignitor, which the factory docs seem to have trouble deciding if that means the whole assembly (ICU box plus J-105's) or just the J-105's. The ICU box just gets kind of ignored in a lot of the docs, frankly.
Found a reference in the 1981 "Product Highlights" document that mentions elimination of the L and LR relays in the FBs. Those would appear to be the two reed relays inside the ICU.
Never seen a copy of the 1980 Highlights document - would probably answer some questions.
One signal from the ECU that suppresses the Trailing ignition passes through them.
Still working on one section of the schematic that governs the inter-relation of the "L" (lead-only) and "LR" (lead retard) signals. not quite sure if they are "OR"ed going into this one transistor or not. Have to calculate some base currents to be sure.
ONLY place in the entire FSM and schematics those two signals are referred to is in the section on testing the "Ignitor, which the factory docs seem to have trouble deciding if that means the whole assembly (ICU box plus J-105's) or just the J-105's. The ICU box just gets kind of ignored in a lot of the docs, frankly.
Found a reference in the 1981 "Product Highlights" document that mentions elimination of the L and LR relays in the FBs. Those would appear to be the two reed relays inside the ICU.
Never seen a copy of the 1980 Highlights document - would probably answer some questions.
03-03-14, 08:19 PM
#15
SO, it looks like function of the ICU is this:
Normal:....................Trailing Ignitor "B" pin powered, Lead Ignitor Sig + comes from Lead pickup coil
"L" signal +12V:........Trailing Ignitor "B" depowered, Lead Ignitor Sig + comes from Lead pickup coil. On an SA, this happens during cold start and when accelerating. up to about 3300 RPM, except when in 4th/5th gear.
"LR" signal +12V:.......Trailing Ignitor "B" depowered, Lead Ignitor Sig + comes from Trailing pickup coil, & Trail vac advance disabled (by ECU signal to the Vac Control Solenoid). End result is Lead timing is retarded ~10 degrees & follows mech advance curve below 4600 rpm. This basically is supposed to happen only for ~ 2 minutes after a full-choke cold start.
If L and LR are both active, result should be the same as LR only.
The L signal comes from pin R of the ECU, and the LR signal from pin O, but L can be blocked by some gear sensing switches on the transmission (Top switch, OD switch) and both are sensitive to RPM via the ECU's control - ECU picks up RPM signal on pin A.
The functions are described somewhat on page 1A:18 of the FSM, in figure 1A-70, but you have to chase around three references to actually find out which pin letter corresponds to which wire in the wiring diagram... because the EU pin numbers aren't on the wiring diagram. (Well, they are on mine, now!) And nowhere I can find the actual function just laid out & explained.
The L and LR terminology only appears in the FSM on page 5:15, in section 5-F-1 ("Checking Ignitor")
Attached is a rough draft of the ICU schematic; I still have a final check and some voltages to define, and I want to augment it with notes on the signals, and the wiring and connector info for the Ignitors and the ICU/Pickup cable, all of which is missing from the factory wiring diagram.
Then, I can try to figure out what's wrong with mine.
Normal:....................Trailing Ignitor "B" pin powered, Lead Ignitor Sig + comes from Lead pickup coil
"L" signal +12V:........Trailing Ignitor "B" depowered, Lead Ignitor Sig + comes from Lead pickup coil. On an SA, this happens during cold start and when accelerating. up to about 3300 RPM, except when in 4th/5th gear.
"LR" signal +12V:.......Trailing Ignitor "B" depowered, Lead Ignitor Sig + comes from Trailing pickup coil, & Trail vac advance disabled (by ECU signal to the Vac Control Solenoid). End result is Lead timing is retarded ~10 degrees & follows mech advance curve below 4600 rpm. This basically is supposed to happen only for ~ 2 minutes after a full-choke cold start.
If L and LR are both active, result should be the same as LR only.
The L signal comes from pin R of the ECU, and the LR signal from pin O, but L can be blocked by some gear sensing switches on the transmission (Top switch, OD switch) and both are sensitive to RPM via the ECU's control - ECU picks up RPM signal on pin A.
The functions are described somewhat on page 1A:18 of the FSM, in figure 1A-70, but you have to chase around three references to actually find out which pin letter corresponds to which wire in the wiring diagram... because the EU pin numbers aren't on the wiring diagram. (Well, they are on mine, now!) And nowhere I can find the actual function just laid out & explained.
The L and LR terminology only appears in the FSM on page 5:15, in section 5-F-1 ("Checking Ignitor")
Attached is a rough draft of the ICU schematic; I still have a final check and some voltages to define, and I want to augment it with notes on the signals, and the wiring and connector info for the Ignitors and the ICU/Pickup cable, all of which is missing from the factory wiring diagram.
Then, I can try to figure out what's wrong with mine.
03-06-14, 10:08 AM
#16
Started o-scope testing last night. Probably should fake up something to spin my spare dizzy at a constant speed to make things easier. Right now, I'm using a piece of string to turn it while making observations, but that only gets me a couple seconds of operation for each "pull,"& speed is hard to keep constant.
Drill press might be the right choice, but I'd hate to have an 'accident' on something with that much torque.
Drill press might be the right choice, but I'd hate to have an 'accident' on something with that much torque.
03-06-14, 05:06 PM
#18
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*notice please i have made two errors, the first is that i thought we had this book on Foxed, and second i didn't know i owned it
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