No spark

wookie1wookie1 Member Posts: 116
edited March 2015 in Isuzu
the enging does not have any spark the people we bought it from installed a different PCM no change , new egr, plugs look fairly new and are platinum, battery was bad replaced it, engine cranks over but will not start, the box on top of the plenum is also new, cam sensor is new. any thoughts?


  • wookie1wookie1 Member Posts: 116
    the engine does not have any spark
  • wookie1wookie1 Member Posts: 116
    the engine is a 3.2L DOHC V-6
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaMember Posts: 64,482
    Well here's a basic description of how your ignition system works so that you can approach it more methodically. The PCM was kind of a wild guess and not the most likely culprit. You could have wiring issues here or a bad ICM (Ignition Control Module). A bad CKP generally doesn't cause a non-start (but can cause hard or intermittent starting issues) and will throw a check engine light.

    The powertrain control module (PCM) controls engine ignition through a solid-state switching unit called the ignition control module (ICM). The software in the PCM uses input from several sensors to determine the timing, duration, and strength of the spark.

    The crankshaft position (CKP) sensor sends the PCM a 58X signal related to the exact position of the crankshaft.

    The camshaft position (CMP) sensor sends a signal related to the position of the camshaft.

    The knock sensor tells the PCM if there is any problem with pre-ignition or detonation. This information allows the PCM to retard timing, if necessary.

    Based on these sensor signals, as well as engine load and engine coolant temperature information, the PCM controls the switching function of the ICM by sending it a six 5V signals. As long as the ICM receives the signal, it allows battery voltage to the ignition coil. That voltage allows a magnetic field to build in the coils.

    When the PCM requires each spark plug to fire, it shuts off the 5V signal to the ICM for that plug by grounding it internally. This triggers the transistors in the ICM to switch off the battery voltage to the ignition coil, which causes the field to collapse.

    The lines of magnetic force pass through the secondary portion of the coil as they collapse. As they intersect the coil, they induce high voltage in the secondary ignition circuit which travels toward ground through the spark plug.
  • wookie1wookie1 Member Posts: 116
    I am not familiar with this type ignition system, it looks like electronic spark arrestors on the plugs with a harness connector on each one I pulled one out it has a long I assume plug wire with a spring that sets on the plug, is the box on the plenum the coil?
  • wookie1wookie1 Member Posts: 116
    i worked on vehicles for 45+ years but nthis is greek to me lol
  • wookie1wookie1 Member Posts: 116
    also where would the icm be located?
  • wookie1wookie1 Member Posts: 116
    I just found out what the ICM is it has been replaced with a new one, is the coil harness connected to one source?
  • wookie1wookie1 Member Posts: 116
    I have 3 testers one digital, I have tested the coils they tested good I tested the wiring to the coils the 0ms. tested within specs my next step is to replace the harness to see if it has a broken wire, but my instincts are telling me it's a simple problem not the harness, but I keep thinking about one thing that I learned a long time ago never overlook the obvious I think it's a simple problem I am just overlooking !!!!
  • wookie1wookie1 Member Posts: 116
  • wookie1wookie1 Member Posts: 116
    when I pull the connector from the coil pack on each cylinder there are 3 wires ground. sig. and ref. with the key on I have power at the ref wire but nothing at the sig. wire, the ICM IS NEW, THE CAM SENSOR IS NEW, THE EGR IS NEW THE CRANK SENSOR HAS ALSO BEEN REPLACED is there a relay or some other power box for the ignition? or is it possible the ignition switch itself went bad?
  • wookie1wookie1 Member Posts: 116
    here's a new one, when I checked the ground wire on the cam sensor it tested great but it also tested hot? explain that one if you can!!!
  • wookie1wookie1 Member Posts: 116
    I now have power going to the ignition wires on all coils, now the problem is no pulse I figure cam sensor even though it's new I think it's defective the camshaft has a magnet that connects with the cam sensor every revolution of the cam that's supposed to create the ignition pulse to the coils ssince it doesn't then I believe the cam sensor needs replaced again
  • wookie1wookie1 Member Posts: 116
    I figured out the problem, once we got power to the ignition coils the (no pulse) was simple
    the icm had been replaced with a new one but it was bad the parts store said they do not guarantee electrical parts so we picked one up at a salvage yard started right up ran fine!!!
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