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Old 11-29-2020, 07:07 PM   #1
Bluebieru
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Member#: 520461
Join Date: Nov 2020
Location: Toronto
Vehicle:
2004 WRX
Silver

Question No Spark on 2 Cylinders?

so I've got a 2004 wrx with a jdm ej205 single AVCS, and V7 ECU swapped in. The problem im having is im getting no spark in cylinders 3 and 4 (both rear cylinders with the black coil pack connectors).

Heres what I've onfirmed:
1. All 4 coil pack connectors are getting 12V
2. All connector grounds have perfect continuity
3. Using all coil pack on all connectors gives the same result
4. All connectors wires have continuity to the ECU (no shorts with any other pins)

What I cant confirm:
1. Voltage across any 4 signal wires while cranking (to jumpy for my multimeter)
2. Whether or not the ecu is fried
3. Cant confirm Voltages from crank or cam sensors

Also my crank sprocket looks like this, I belive its the correct one for JDM ECUs
Ive been trying to get this car to start for almost 3 weeks but ive hit a wall now. Any advice is welcome, thanks
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Old 11-30-2020, 07:15 AM   #2
Cougar4
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In your picture you can see the reluctor cog with the numerous tabs on it behind the belt. Check all those tabs and make sure none of them are broken off the cog. That is what generates the sensor pulses seen by the ECU for the crank position.
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Old 11-30-2020, 08:26 PM   #3
Bluebieru
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I spun the engine by hand and all the teeth are still intact
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Old 12-01-2020, 01:05 PM   #4
Bluebieru
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Is there a chance of it being a faulty ecu, and is there a way to check for that?
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Old 12-01-2020, 01:53 PM   #5
Cougar4
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If all the teeth are intact then we have to assume the proper input signal to the ECU is good. You would need a scope to verify the signal waveform. You stated that swapping the coils makes no difference and power and ground to the coils is good. That seems to indicate that the ECU has a problem and you will need to swap it out to see if that works.
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Old 12-02-2020, 09:10 PM   #6
Bluebieru
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Ok ill have to find someone local with a jdm ecu I can use to check.

In the mean time, just out of curiosity would a faulty crank sensor, cam sensor, or either rear avcs cam sensor, could spark in some cylinders and not others?
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Old 12-02-2020, 11:17 PM   #7
Cougar4
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If one coil is working then the other one should work also.

I have another thought. I think your engine has a wasted spark design for the ignition. Have you tried replacing the plug wires on the faulty side. Perhaps one of them is bad.
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Old 12-03-2020, 10:14 PM   #8
Bluebieru
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I looked into it and this engine isnt wasted spark just stright up coil on plug. But I did check the the wires in the engine harnes, with a multimeter. Both the working and not working connectors are showing 0 ohms between their respected power ground and signal wires. no resistance and no path to ground means a non broken wire right? I cant really switch around the wires because that would involve cutting up the harness, which with my luck will cause more problems than it fixes.

Also I got no luck with a second jdm ecu. Noone i know local has 1 for me to test and the only similar ecu on ebay is $600 which is waaay out of my budget.

Any other suggestions? thanks btw cougar you've been real helpful
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