Megasquirt I have a clean RPM,, but no spark at all
03-10-09, 09:24 PM
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I have a clean RPM,, but no spark at all
I am really stupified by this.
I have a MS2 V3, modded with a second VR sensor and pull up resistors on all three of the LEDs. IAC2B is wired for my leading coils ignition signal, IAC1B is my trailing coils ignition signal. I put a scope on these 2 lines and I see a +5 volt square wave when cranking and on my stim. IAC2A is my trailing coil select, and I see a +5 goes high, then low every other trailing fire signal. I think all these signals look good on my scope.
I tried 2 sets of coil packs with exactly the same results. My coil packs are grounded with an extra wire for each pack, I get +12 at the coils + terminal with the plastic cover off. I think with the signals I'm imputing into the ignitors, the coils should spark. I am checking for spark by connecting my spark plug wires to some plugs that are lying on top of my engine. I don't know anybody local with an FC to try and swap out the coils for a test.
This 13B is installed in a Porsche 914. I made my own shielded wireing harness, and I'm 99% sure I scoped out the wires that plug into the connectors at the coils to make sure the signals looked good, and aside from not being as clean with the stim, the signals were all there.
Through megatune, I have data logged some of my cranks,,, and I get an accurate clean RPM trace. In fact all of my sensors look good and noise free,, which is to be expected since there's no Fn spark.
I'm starting to get REALLY frustrated again,, even though I'm so GDFn close. Any suggestions as to why there's no sparky at my coils? Do the coils fire with a -5 volt square wave? do the coils know they're not in an FC? My car is going on year 15 of not running and many iterations.
Any megasquirters out there in Los Angeles area willing to help a rotary bruddah out? I know what color is appreciated the most $green$.
Any help or comments are welcome.
-Rob
I have a MS2 V3, modded with a second VR sensor and pull up resistors on all three of the LEDs. IAC2B is wired for my leading coils ignition signal, IAC1B is my trailing coils ignition signal. I put a scope on these 2 lines and I see a +5 volt square wave when cranking and on my stim. IAC2A is my trailing coil select, and I see a +5 goes high, then low every other trailing fire signal. I think all these signals look good on my scope.
I tried 2 sets of coil packs with exactly the same results. My coil packs are grounded with an extra wire for each pack, I get +12 at the coils + terminal with the plastic cover off. I think with the signals I'm imputing into the ignitors, the coils should spark. I am checking for spark by connecting my spark plug wires to some plugs that are lying on top of my engine. I don't know anybody local with an FC to try and swap out the coils for a test.
This 13B is installed in a Porsche 914. I made my own shielded wireing harness, and I'm 99% sure I scoped out the wires that plug into the connectors at the coils to make sure the signals looked good, and aside from not being as clean with the stim, the signals were all there.
Through megatune, I have data logged some of my cranks,,, and I get an accurate clean RPM trace. In fact all of my sensors look good and noise free,, which is to be expected since there's no Fn spark.
I'm starting to get REALLY frustrated again,, even though I'm so GDFn close. Any suggestions as to why there's no sparky at my coils? Do the coils fire with a -5 volt square wave? do the coils know they're not in an FC? My car is going on year 15 of not running and many iterations.
Any megasquirters out there in Los Angeles area willing to help a rotary bruddah out? I know what color is appreciated the most $green$.
Any help or comments are welcome.
-Rob
03-10-09, 10:38 PM
#2
It sounds like the output signals are correct, so that leads to one of the following:
- a poorly grounded engine
- improperly gapped spark plugs (if they're the strap kind)
- bad spark plug wires
- coils wired improperly
The trailing coil (the one with the 4-pin and 2-pin connectors) should have const 12v (switched by the ignition, MAKE SURE THIS IS STILL 12V WHEN CRANKING!) going to both pins of the two-pin connector. Trailing select should go to the upper right-hand pin of the 4-pin connector (when looking at it with the slot for the tab upward), and trailing ignition should go to the upper left-hand pin.
The leading coil should have the same 12v source from above going to the left-hand pin (with the slot for the tab up), and the leading ignition to the other pin.
- a poorly grounded engine
- improperly gapped spark plugs (if they're the strap kind)
- bad spark plug wires
- coils wired improperly
The trailing coil (the one with the 4-pin and 2-pin connectors) should have const 12v (switched by the ignition, MAKE SURE THIS IS STILL 12V WHEN CRANKING!) going to both pins of the two-pin connector. Trailing select should go to the upper right-hand pin of the 4-pin connector (when looking at it with the slot for the tab upward), and trailing ignition should go to the upper left-hand pin.
The leading coil should have the same 12v source from above going to the left-hand pin (with the slot for the tab up), and the leading ignition to the other pin.
03-11-09, 09:16 AM
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I've made the mistake before of adding the pullup resistors to the wrong side of the LED, then spending hours scratching my head trying to figure out why I don't get spark even though the scope reads correctly. Check your pullup resistors. 
No reason to ground the ignitors though. They ground through their body.
No reason to ground the ignitors though. They ground through their body.
03-12-09, 09:37 PM
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After triple checking my wiring harness and contemplating going fuel only,,,
I think I figured out my mysterious problem. I previously had FUBARd my 2nd VR sensor install,, so I shipped off my unit to a dude from the MS boards who repairs them. He cleaned up my install and sugested some noise reducing mods. I said what the hell,, I've been reading about all my rotary bro's having problems with noise.
I re-scoped my coil signal wires and increased the resolution of the scale,, that's when I realised that my square waves don't go all the way to 5 volts. more like 4.85 volts. I wonder if that's enough voltage to trigger the ignitor, and I wonder if the noise reducing mods are the cause of my lower signal voltage. I contacted the guy who repaired my MS2, and am waiting for some directions on fixing this.
What do you guys think about this voltage thing?
-Rob
I think I figured out my mysterious problem. I previously had FUBARd my 2nd VR sensor install,, so I shipped off my unit to a dude from the MS boards who repairs them. He cleaned up my install and sugested some noise reducing mods. I said what the hell,, I've been reading about all my rotary bro's having problems with noise.
I re-scoped my coil signal wires and increased the resolution of the scale,, that's when I realised that my square waves don't go all the way to 5 volts. more like 4.85 volts. I wonder if that's enough voltage to trigger the ignitor, and I wonder if the noise reducing mods are the cause of my lower signal voltage. I contacted the guy who repaired my MS2, and am waiting for some directions on fixing this.
What do you guys think about this voltage thing?
-Rob
03-13-09, 01:53 PM
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Hi Ken,,
I made sure my pull up resistors are on the correct side of the LEDs, like Aaron Cake suggested.
The repair guy I found on MS boards,, his name is Peter Florence. I believe this guy is a reputable repair-man for the MS units.
Yes it looks like the square wave drops back to zero.
I am sooo close,,, and sooo frustrated. I really want to get this to work. BIG THANKS
I made sure my pull up resistors are on the correct side of the LEDs, like Aaron Cake suggested.
The repair guy I found on MS boards,, his name is Peter Florence. I believe this guy is a reputable repair-man for the MS units.
Yes it looks like the square wave drops back to zero.
I am sooo close,,, and sooo frustrated. I really want to get this to work. BIG THANKS
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03-13-09, 01:54 PM
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Hi Ken,,
I made sure my pull up resistors are on the correct side of the LEDs, like Aaron Cake suggested.
The repair guy I found on MS boards,, his name is Peter Florence. I believe this guy is a reputable repair-man for the MS units.
Yes it looks like the square wave drops back to zero.
I am sooo close,,, and sooo frustrated. I really want to get this to work. BIG THANKS to all who are expending brain power thinking of this.
-Rob
I made sure my pull up resistors are on the correct side of the LEDs, like Aaron Cake suggested.
The repair guy I found on MS boards,, his name is Peter Florence. I believe this guy is a reputable repair-man for the MS units.
Yes it looks like the square wave drops back to zero.
I am sooo close,,, and sooo frustrated. I really want to get this to work. BIG THANKS to all who are expending brain power thinking of this.
-Rob
03-13-09, 05:42 PM
#9
MegaSquirt Mod
Alright, Peter Florance is a good repair guy for MSs... I trust him.
Where did you scope the outputs? Directly at the MS, or at the coils? It might help to scope them on the wire that connects to the coil. It sounds like that's what you did but I just want to confirm.
Ken
Where did you scope the outputs? Directly at the MS, or at the coils? It might help to scope them on the wire that connects to the coil. It sounds like that's what you did but I just want to confirm.
Ken
03-13-09, 07:16 PM
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I put the scope probes on the jim stim output connector while bench testing. and I had the scope probes on the harness side of the connector that connects to the ignitors of the coils, while cranking with the MS2 ecu hooked up,, both signals looked fairly similiar. I have .4 ohms resistance in my ignitor<-->MS2 wires.
-Rob.
-Rob.
03-15-09, 12:44 AM
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MS is grounded to the engine block. and the block has a cable grounding it from the waterpump to the battery.
I was wrong when I earlier stated that the voltage dropped back to 0,, but it's pretty close. I have a couple of pics of the signals. And I was also wrong about the trig voltage coming thru the line. it's 3.78 volts.
-Rob
I was wrong when I earlier stated that the voltage dropped back to 0,, but it's pretty close. I have a couple of pics of the signals. And I was also wrong about the trig voltage coming thru the line. it's 3.78 volts.
-Rob
03-15-09, 08:36 PM
#14
MegaSquirt Mod
That's probably not enough to trigger the coils. I'd say you either have the pullup resistors wrong, or have the wires coming from the LEDs to the ignitors on the wrong legs of the LEDs.
Incidentally, What you're seeing there is about what I see on my scope if I don't have the pullups installed and I watch the square-wave from the negative lead of the LED.
Ken
Incidentally, What you're seeing there is about what I see on my scope if I don't have the pullups installed and I watch the square-wave from the negative lead of the LED.
Ken
03-15-09, 11:36 PM
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That's probably not enough to trigger the coils. I'd say you either have the pullup resistors wrong, or have the wires coming from the LEDs to the ignitors on the wrong legs of the LEDs.
Incidentally, What you're seeing there is about what I see on my scope if I don't have the pullups installed and I watch the square-wave from the negative lead of the LED.
Ken
Incidentally, What you're seeing there is about what I see on my scope if I don't have the pullups installed and I watch the square-wave from the negative lead of the LED.
Ken
I included some pics of my Pull up installs. for the second attempt I installed on the bottom of the board.
What else can cause this low trigger voltage?
-Rob
03-16-09, 01:00 PM
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I was advised by my MS2 repair guy that I might have to change the values of my pull up resistors to increase the trigger voltage. He advised to add another 4.7K resistor in parallel to the one I already have to see if this makes my trigger voltage higher. I plan on trying this tonight when I get home from work.
-Rob
-Rob
03-18-09, 07:59 PM
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Well I added a second resistor in parallel with the current P/U resistor, and I have no change in trigger voltage. Bummer.
Ken,, here are those pics you wanted to see.
-Rob
Ken,, here are those pics you wanted to see.
-Rob
03-20-09, 08:13 PM
#19
MegaSquirt Mod
Have you tried pulling the coils and the MS, and hooking them up to the battery and spinning the CAS by hand?
Just to see if you can get spark that way. Use wires that aren't from your normal harness.
Ken
Just to see if you can get spark that way. Use wires that aren't from your normal harness.
Ken
03-20-09, 08:16 PM
#20
MegaSquirt Mod
It looks like you're using a very old firmware. There are known issues with the old firmware and rotary engines.
I'd suggest using the latest 2.1.0 beta firmware as well. I don't know for sure if that'll fix your problems, but that'll bring you up to what I'm using, which will definitely make it easier for me to help you.
The Firmware sticky thread has a link to the firmware you will want to use (the 3/11/09 one).
Ken
I'd suggest using the latest 2.1.0 beta firmware as well. I don't know for sure if that'll fix your problems, but that'll bring you up to what I'm using, which will definitely make it easier for me to help you.
The Firmware sticky thread has a link to the firmware you will want to use (the 3/11/09 one).
Ken
Last edited by muythaibxr; 03-20-09 at 08:18 PM.
