2007 Mazda 3 crank no start, no spark except occasional single spark event

Looking for some diag help

Car is a 2007 2.0 MT.    I installed a 2.5l fusion motor recently.   First, I tried to start, security light was flashing, no comm with PCM.   Turns out mazda injector/coil plug is interchangeable with another connector, and I had them reversed (stupid mistake, but I assumed Mazda would not make a major wire connector interchangeable, oh well).  It fried the ECU, and popped fuse 69.    Okay.   New ECU, verify all fuses good, program key to new ECU.    Now it cranks but no start...

​​​​​Watched all the videos on ignition coil testing (definitely Have a much better understanding of coils, especially 3 wire function). 

As far as I can tell I got no flashing from test light when cranking connected to coil negative.  - verified +12v, and Gnd at all coils
- test continuity between coil signal wire and ECU, all 4 coils signal pin goes to ECU
I thought I had no spark at all, but very occasionally I would get a single spark event from coil (connected to spark tester) 
I don't have a tool to read a proper wave form, but using a power probe I believe I see some activity on signal wire, but only millivolts, nothing close to 5v.    It almost seems as if the ECU is unable to feed 5v, but I'm not exactly sure what to look for on the signal wire.    

​​​​​​Also I do have 5 v at throttle body, and MAF, and scan tool reads no codes (and I can read accurate live data from TPS, IAT etc, so I know ECU is working).  

Tested crank, and camshaft sensors and I have 12v, Gnd, and some activity on signal wire.   

​​​​​​I was thinking *possibly* the ECU could be missing a sensor ground or 5v reference, but I couldn't find an accurate pinout for this exact ECU, so I can't be certain.   

​​​​​​Any ideas, (or next tests) would be greatly appreciated!   I should get a proper oscilloscope I suppose... 

​​​​ Love the videos!!! Great education, well explained.   I also did read the thread where someone else with a Mazda had a no spark, no start...   But already checked everything there.   

I guess the last thing I'm a little unclear on is where the 5v and ground the ECU sends to the coil comes from....    I can't tell if the ECU is trying, but unable to send signal to coils, or if it's not, or very sporadically getting signal from CAS, so it doesn't know when to fire.    

Any help is appreciated!!!  

Tim


 

Two quick thoughts for now.
1. Something else got cooked with those reversed harness connectors
2. Anti-theft system issue

The occasional spark and signal from the ECM, I wouldn't chase that. I believe that is a symptom of the condition not the cause of the no start. I bet you are missing injector pulse to.

There was a long thread here a while back, I can't find it but this is video is the guy talking about the job.
From what I recall, he needed to remove the harmonic balancer during the swap. Since there is no key on the shaft to align the balancer on the shaft, and since the crank trigger is on the balancer, AND since theres multiple crankshaft locking pins for the balancer alignment, it's very easy to mistime the crank trigger and end up with problems.

Thanks for the reply!

Yes definitely cooked the ECU originally w the backwards connection. No comm w ECU, security light on, no crank. Once I replaced the ECU though, I'm pretty sure anti theft is not an issue, it interrupted cranking when active, and I have a new ECU, and reprogrammed the keys to it.

Is there anything else it could fry aside from ECU? Seemed unlikely it would fry all 4 coils.

I couldn't get a real graph on the injectors, but they are getting power... And my power probe has a injector feature, not sure how reliable it is. It does list a frequency when cranking though.

Don't chase occasional spark, ok.... But I'm wondering what to chase.

This car goes right from ECU to coils for the signal...

Re crankshaft pulley, oh I know! I did that job before recently. No keys at all just friction fit. It also holds the timing sprocket in place.... I don't think it's off timing wise though, because cam timing and compression are good. I'm wondering if the Ford sprocket could cause no spark symptoms though .

Misalignment of the crank trigger will not effect cam timing or compression

Hey, just in case this is helpful for someone....

I replaced the crankshaft pulley, it started immediately and runs great! It was the crank reluctor wheel, turns out the 2 tooth difference (I think) on the Ford wheel causes: no crank no start, and no DTC's at all.

I should have checked the wheel sooner, but I'm a little surprised that caused a complete no start... I remember other vehicles running on 1 sensor alone, in limp mode at least.