No Spark in Cylinder 2

[UMainePhaze09]

We've been trying to implement the uS in a 2007 Phazer snowmobile for the last few months. We discovered today that we only have spark from the first cylinder and not the second. We are trying to run dual spark, using an M-0 crank wheel and a single-tooth cam wheel. We are sure that the coil and plug both work, and have tested this by switching both to the first cylinder. We are also sure that the power and ground lines are wired correctly to the coil. What could be happening here that would cause this problem? Could I inadvertently change something that would cause the second ignition driver not to fire? Please help!

[24c]

I used "M-0" & I had this problem on my crank cam rig, it would start on IGN1 output, and switch to IGN2 output at high revs. Have you checked your VRsensor outputs using the TachRef.exe program...it's really useful.

You should have set the Advanced Spark Options>Dual Spark Ignitions Options> Dual Spark Options to "Rising Cam Sync with Tach or Wheel"

It should work from this option, my 4+1 set up does,( M=4, N=0, Skip=2, Delay=0 on the rig) Sample from TachRef below , and Al, I got both VRs on this one

GTS_crank_cam_MSpulses_650rpm.jpg (27.98 KiB) Viewed 2069 times

[UMainePhaze09]

We haven't used TachRef.exe, but we've used an oscilloscope and have duplicated the picture posted by Kyle R under another post. We know that we're getting the right signals, have added a diode to the VR+ line to add the necessary offset in the signal as well as a pull-up resistor in the VR2 circuit to create the square wave. We'll try our luck with the "Rising Cam Sync with Tach or Wheel" tomorrow when we get back into the lab. Shouldn't the M-0 settings work though, since they did for Kyle R after adding the necessary items in the circuits?

[24c]

All I know, which is little is I recognised your problem because two days ago I was getting the same thing...Al mentioned something about "Rising Cam Sync..." and when I tried it it worked first time NO issues. I must admit I found the MS manual definitions and the software definitions slightly confusing...as I thought I was a "M-0 wheel" scenario, because I have no missing teeth...but I was using the wrong settings and I had the same fault as you. The only reason I was able to see this was I was using a drill powered rig and I could get past the IGN1 outputs and see IGN 2 working.
I assume there is a tach/sync issue with your set up, because "M-0" doesn't match what is happening, so causing your problem. You could post a datalog .msg , but as it's a two minute job to swap the values, you'll probably be running tomorrow.

PS I don't have any diodes or resistors on my VRs. AFAIK Resistors don't make square waves, but if you aren't getting a signal on the cam, it will just spark IGN1, as I found out when I disconnected the cam sensor VR wire on my test rig.

[UMainePhaze09]

We tried a couple different things this morning that made us more confused than before. When we switched to "Rising Cam with Tach or Wheel" we got one spark in cylinder 2, then nothing after the first spark. We tried changing the cranking trigger to each of the three options, but didn't have much luck there either. We get spark initially with "Rising Cam with Tach or Wheel", and calculated trigger, but we lose tach signals after a few seconds and then lose spark. When we tried the "M-0 Wheel" setting, our tach in Megatune alternated from 0 to around 200 rpm. What could be causing the fluctuation? We shielded the ignition wires from the ECU to the coils to cut down on noise, but it seems like we're still getting noise from somewhere. Any thoughts?

[UMainePhaze09]

To clarify our situation, we are trying to add uS to a 2 cylinder, four-stroke, odd-fire engine. We have an 12-0 wheel on the crank shaft and a single recessed tooth on the camshaft. The circuit for the sensor for the crank wheel has a diode added to it, and the circuit for the sensor on the camshaft has a pull-up resistor added to it. Al has informed us that we should be running the "Falling Cam Sync with Tach/Wheel" not M-0 wheel since we have a cam sync not a crank sync, so we've been trying that. Our signal from the cam sensor drops when the recessed tooth passes so we're using "Falling Cam", and our signal from the crank is what we've interpreted from the manual as rising edge, so our input capture is "Rising Edge".

Could someone explain what cranking trigger changes? We've read the manual, and have tried all three options. We get consistent spark from cylinder 2 with "Calculated", but cylinder 1 sparks only every few camshaft revolutions at most. We get consistent spark from cylinder 1 with "Trigger Return", but nothing from cylinder 2. And "Trigger Rise" doesn't give us anything.

When the cam signal is sent, the crank sensor is between teeth. Cylinder 1 goes TDC halfway between the second and third teeth after the cam signal. Our wheel settings then should be 12 teeth, 0 missing teeth, 12 skip teeth and 2 delay teeth, with a trigger offset of around 15 degrees. Are we interpreting this correctly?

We think that we're close to getting the sled running, but are having trouble understanding the manual. Please help!

[grippo]

Use trigger offset = -15 since Delay = 2 means you start the first tach cycle when the 3rd tooth is detected (Delay = 0 would mean when the first tooth is detected - that is no delay). When the 3rd tooth is detected, you are about 15 deg ATDC, that is the reason for -15 deg. In dual spark mode you want trigger offset to always be negative. Use calculated trigger so you can correlate the advance in MT with the timing light advance. After things work, you could try trigger rise if there is a lot of oscillation during starting, but you should be able to start without it. Do not use trigger return - it is only for special wheels.

If this doesn't work, then the next thing to check is the odd fire setting. If this is wrong it would explain why you only get spark on one output.

[UMainePhaze09]

How do you check the odd-fire setting? We're using the software package from DIYAutotune.com (Megatune 2.25P3) , and the only place I can see where you could set engine type to even or odd-fire is listed under Fuel Set-up/Injector Control at the very bottom, and the box is grayed out. Is there another place to change the odd-fire settings? We'll be checking the -15 trigger offset as soon as we make it to the lab, I was just curious if there was something else we were missing.

[UMainePhaze09]

We changed the trigger offset to -15 and we had consistent spark for slightly longer than before, but we still lose it after a few seconds. We also lose tach at the same time. What could cause our loss of tach? We wrapped our ignition wires with aluminum foil and grounded to the engine block and have tried moving both the uS unit and the serial link away from the other wires with no change.

[grippo]

The parameter I am talking about is called Odd Angle and is in the bottom half of the Advanced Ignition options. This allows you to put in an offset that is needed for odd fire engines. Your loss of tach synch is a totally separate problem that can be caused by random electric noise or by a tooth and sensor mismatch that causes a flat spot between 2 teeth. Rather than looking like a sine wave, it looks like top half of sine, short horizontal (y=0) line and bottom half of the sine wave. You can tell if it looks like this from the scope. What happens is the processor a software and circuitry are designed to find a sharp vertical zero-crossing like from a sine wave. When you put a flat line there it gets confused. There is purposely a small voltage bias there to turn the y= 0 line into a y =+/-0.5 V line so that the vertical zero crossing will be seen consistently at either the beginning or end of the flat line. Sometimes this isn't enough and you have to increase the bias, typically by adding diodes. Many people have gone through this and have described what they did in this forum. It may be time to seek help from the EE dept.