[SOLVED] Crank, no start, no spark - absolutely stumped!

H

Hornet99

Greenie N00B Member
Car: 2012 Mazdaspeed 3 2.3L

Issue: No recent changes or accidents, car worked fine one day and next day would not start. Installed new battery and no change - 13.8v measured. For diagnostic tools I have a Cobb AccessPort, OBD II with Forscan, test light, multi-meter and backprobes. No oscilloscope unfortunately.

Fuel: I can hear low pressure fuel pump engaging and smell fuel throughout tests, AccessPort ranges: injector duty cycle 1.3-5%, Injector pulse width 6.90-7.1ms, HPFP desired pressure 1015psi, HPFP actual pressure 925-1313psi

Sensors: I replaced the Crankshaft sensor and verified 20 tooth alignment with TDC. I backprobed the Camshaft sensor and values are as expected. I disconnected the MAF sensor for one test.

Compression: sounds normal, compression tests were performed and good 9 months ago

Fuses/Relays - checked all the obvious ones and they look good

PCM (ECU)
  • There are no codes.
  • I performed a continuity test from 2nd and 3rd coil connector signal wires, through coil pack wiring harness to the PCM connector. Both good, assumed others were as well.
Spark:
  • Inline plug tester shows no spark on any cylinder, pulled plugs and they look normal. Grounded plugs and cranked - no spark
  • Grounds: I inspected and cleaned main ground near battery and chassis ground near HPFP (which is used for ignition coil GND). Measured voltage drop from battery terminal to HPFP chassis ground was 72mV. I also connected a separate wire from this ground to battery negative with no impact. I also performed continuity test between this ground and ignition coil GND. All 4 show 54 ohms of resistance.
  • Ignition Coils all 4 show similar results using multimeter:
    • +B: 12.48v key ON, drops as low as 10.9v on crank
    • Gnd: 70mV key ON, +or- 20mV on crank
    • Signal: 0.33v key ON, on crank most values <0.5v but a few spikes to 2.1v
Right now I'm trying to figure out why the ignition coils are not firing. I'm assuming they are good since it's unlikely they would all go bad at once. Questions:
  1. Is the coil connector GND to chassis ground resistance of 54 ohms an issue? Anything else standout with my ignition coil measurements?
  2. Can anyone think of anything else I should be testing?
I am at a loss of what to check next.

Thanks,
Dave
 
I feel like that resistance between the grounds isn't great but you said you jumped it with another wire so that should rule it out. Any lights on the dash? Did you accidentally trigger the security
 
SOLVED:

That 54ohm value was bothering me, so instead of bypassing the ground near HPFP to battery negative, I bypassed the ignition coil connector ground by back probing that wire directly to the ground near the HPFP. I did this on two ignition coils at the same time and the car started. Not sure if I can repair the ground wire inside the harness or whether I need to buy an whole new ignition harness. Either way I have my answer.

Thanks!
-Dave
 
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