2014 F250xa No Spark Cylinder 1 and 6

[grouper249]

2014 F250xa
6p2 X 1040034 A

Have a no spark condition on cylinders #1 and #6. This was confirmed via YDS stationary test with spark tester. Have continuity to ECM and fuse box on both cylinders. Intake pressure matches Atmospheric pressure on Key On engine off, pulsor coil is new, battery voltage is 12.41 (key on engine off) and when running 13.95. Also borrowed a friends ECM (same motor) with no change. Rather than throwing parts at it, hoping you experts can help guide me to next steps.

[fairdeal]

Did you happen to save a recent YDS "dump" showing the "Engine Monitor" fields?

There is one called "Shift cut-off switch"
I am wondering if that shows OFF or ON

[grouper249]

Looking at it now and shift cut off switch is OFF. Also, it’s only cylinder #1 that’s not firing through YDS stationary test

[ausnoelm]

If it’s only one cylinder (not two like you said) chances are a wiring inspection and/or a coil swap is in order.

[grouper249]

Did perform a coil swap and the problem did not follow. I did successfully confirm continuity from #1 coil connector to both ECM and fuse box. I also tried wiggling the coil connector and repeat stationary test on #1 with no luck. Anyone know if the cam position sensors could be a cause? That and the knock sensor are the few sensors I haven’t tested yet

[grouper249]

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[grouper249]

Also failed to mention I do have 12vlt at #1 coil connector when key on engine off.

[boscoe99]

Also failed to mention I do have 12vlt at #1 coil connector when key on engine off.

And continuity on the other two wires that go to each ignition coil? One to ground and one to the ECU.

[boscoe99]

Have you thought of triggering each coil/plug on your work bench?

[fairdeal]

That one - and only one - will not fire even with the YDS static test
and you've swapped ECM, swapped coil to no avail

seems to me that must indicate a wire/connector fault;
there are 3 wires, 6 terminal ends

Tangentially,
I would like to know exactly how the ECM triggers the coil:
does it supply power? or ground?
and is that normally on, off to fire? or normally off, on to fire ?

[boscoe99]

One side of the primary coil is supplied with battery voltage.

The other side of the primary coil is grounded but through a coil driver.

The ECU tells the coil driver when to disconnect the ground to the primary coil. At which time the spark plug fires.

A crafty person should be able to power and ground the coil with a spark plug installed. Plug also being grounded. When the ground to the coil is removed the plug should spark.

[boscoe99]

[fairdeal]

The other side of the primary coil is grounded but through a coil driver.

The ECU tells the coil driver when to disconnect the ground to the primary coil. At which time the spark plug fires.

Yes, but its the detail of "tells the coil driver" I'm wondering about.

Your drawing - if I'm understanding correctly -
shows it done with a 5V+ control signal
originating within the ECM

(so the ECM is switching a current that it supplies,
not, as in some other applications, switching the "ground" for the familiar red/yellow 12V)

is that right?

[grouper249]

Thank you all for the responses. It's starting to piece together in my brain. Is the Coil Driver physically located on the Coil itself? Are their specific "upstream" sensors that would/could impact the ECU signal to the Coil Driver? Is the best way to confirm coil driver function via the "crafty person" bench test?

[boscoe99]

Yes, but its the detail of "tells the coil driver" I'm wondering about.

Your drawing - if I'm understanding correctly -
shows it done with a 5V+ control signal
originating within the ECM

(so the ECM is switching a current that it supplies,
not, as in some other applications, switching the "ground" for the familiar red/yellow 12V)

is that right?

I like to think of a driver as a relay. A relay that is being switched on and off by the ECU. To open and close the primary ignition coil ground path.

5 volts from the ECU in the example above. To the driver/relay. Not switching a ground as is in the modus operandi of many Yamaha components.

Wish that I had a motor with a coil on plug ignition system. I might use my Oscope tablet to try and view the electrical signal from the ECU to the coil on plug.