240hp Efi v6 2004 no spark

[IComeFromALandDownUnder]

I disconnected at a coil pack connector and hooked the probes up to pins A/B to get the ignition 'pulse'. I then checked pins E/D to check for supply continuity whilst cranking. To make hooking up easier, I used male-male Arduino jumper wires as the male pins slot in nicely to the connectors.

 

[cbatstone]

I had another session Troubleshooting alongside my Mechanic and a Oscilloscope today. I am once again out of ideas of where to look next on this no spark issue, everything seems to test out as good as we can assume it should, with the variable being exactly what we are looking for from the ECU. But the issue remains.

--Observations
-On the Oscilloscope, observed pulses across A/B from the injector connectors while cranking. Checked at the injector harness as well. All seemed consistent, though knowing exactly what we're looking for is unclear. But brief sharp pulses were seen.

-Pin B (Black/Green) with test light, turns off completely while cranking. Might expect this to be dim if periodic ground is being made? Just an observation to report.

-Pin C ground tested good as a ground with the test light.
-Pin D ground tested good as a ground with the test light.
-Pin E with CPS disconnected does not see battery voltage while cranking. With CPS connected, battery voltage is seen when cranking. CPS appears to be sending a signal.

--Outstanding Questions
Are there any other possible inputs that would prevent some function not observed?
What else to check?

From what I read in the manual and can test on, and without a full understanding of exactly what I'm looking for on A/B, I cannot find any point of failure. Still no spark.

 

[IComeFromALandDownUnder]

--Observations
-On the Oscilloscope, observed pulses across A/B from the injector connectors while cranking. Checked at the injector harness as well. All seemed consistent, though knowing exactly what we're looking for is unclear. But brief sharp pulses were seen. - I'd say the CPS/ECM is working correctly. This is what I had when I first investigated (although I had no spark).

-Pin B (Black/Green) with test light, turns off completely while cranking. Might expect this to be dim if periodic ground is being made? Just an observation to report. This is the trigger return GND path to ECM so I suspect it works (during cranking) by a constant feed on the A pin and only completing the GND path when required to fire the coil otherwise they would've used a common GND. Many circuits are designed this way.

-Pin C ground tested good as a ground with the test light.
-Pin D ground tested good as a ground with the test light.
-Pin E with CPS disconnected does not see battery voltage while cranking. With CPS connected, battery voltage is seen when cranking. CPS appears to be sending a signal.

--Outstanding Questions
Are there any other possible inputs that would prevent some function not observed?
What else to check?

If you're getting a pulse then it has to be a grounding issue (famous last words!). Make a separate GND lead and connect it to firstly pin C then pin D whilst still having the other pins connected. I've previously done this by disconnecting the coil connector and using those Arduino wires I've talked about previously. Just be v careful that you don't mis-wire them.

Just looking back at the thread and you say you are getting 9.5v at the coils. I know you had the battery tested but have you tried another one just in case?

 

[cbatstone]

--Observations
-On the Oscilloscope, observed pulses across A/B from the injector connectors while cranking. Checked at the injector harness as well. All seemed consistent, though knowing exactly what we're looking for is unclear. But brief sharp pulses were seen. - I'd say the CPS/ECM is working correctly. This is what I had when I first investigated (although I had no spark).

-Pin B (Black/Green) with test light, turns off completely while cranking. Might expect this to be dim if periodic ground is being made? Just an observation to report. This is the trigger return GND path to ECM so I suspect it works (during cranking) by a constant feed on the A pin and only completing the GND path when required to fire the coil otherwise they would've used a common GND. Many circuits are designed this way.

-Pin C ground tested good as a ground with the test light.
-Pin D ground tested good as a ground with the test light.
-Pin E with CPS disconnected does not see battery voltage while cranking. With CPS connected, battery voltage is seen when cranking. CPS appears to be sending a signal.

--Outstanding Questions
Are there any other possible inputs that would prevent some function not observed?
What else to check?

If you're getting a pulse then it has to be a grounding issue (famous last words!). Make a separate GND lead and connect it to firstly pin C then pin D whilst still having the other pins connected. I've previously done this by disconnecting the coil connector and using those Arduino wires I've talked about previously. Just be v careful that you don't mis-wire them.

Just looking back at the thread and you say you are getting 9.5v at the coils. I know you had the battery tested but have you tried another one just in case?

I had the battery tested/charged by a shop to verify. It's at that voltage while cranking under load, then returns to 12+ when not cranking. I believe this is normal.

Thanks for the ground lead advice. Sounds like I'm headed down a very similar path as you were from where I am in the diagnostics.

 

[cbatstone]

So just to confirm your own resolution, you made up that separate grounding lead, then ground pins C & D, and once you did, you observed spark, likely to all cylinders because the grounds are connected. I should be able to get back to the boat this week.

 

[IComeFromALandDownUnder]

So just to confirm your own resolution, you made up that separate grounding lead, then ground pins C & D, and once you did, you observed spark, likely to all cylinders because the grounds are connected. I should be able to get back to the boat this week.

Correct. As you have a pulse signal across A/B and you don't have a spark on any of the coils then it has to be one of the common feeds. The seperate ground lead will hopefully pinpoint a problem with either C (black) or D (blk/white). I found the easiest way to do this was cross wire at the coil electrical connector and swap in the seperate ground lead to C/D. If that doesn't solve it then try a seperate +12v on pin E.
If it doesn't fix then try 3 seperate test leads for C/D/E simultaneously. It maybe you have more than one wiring failure.