2011 New 3.0 MFI with no spark mystery

[Doubletrouble 1965]

I am restoring a 22 ft Grew runabout. The original engines (3.0 Mercruiser 1965) were replaced
with new Mercruiser 3.0 mfi units in 2011. These engines were never used as the restoration
was ongoing. The port engine started and ran immediately. The starboard engine has resisted
all attempts to achieve a spark.
To date we have swapped components from one engine to the other without success.
Including:
Wiring harness to helm
Engine wiring harness
ECU
Distributor
Fuses and neutral switches
Something is telling the ECU not to provide the spark.
Any suggestions to solve this mystery
Thanks

 

[alldodge]

Do you have 12V when key is ON at the coil?
Edit: your saying mFi but do you mean mPi?
Also this is a EC or CAT motor right?

 

[Doubletrouble 1965]

Do you have 12V when key is ON at the coil?
Edit: your saying mFi but do you mean mPi?
Also this is a EC or CAT motor right?

Yes 12v at coil.
Sorry I did mean MPI (EC)
The tach on the starboard engine, the one that has no spark does not
register when engine is cranked.

 

[alldodge]

Being a 3.0 it would have the Delco EST distributor and how it works is pretty simple. Having swapped the distributor with the other motor and no spark I'm scratching my head like you are.

The EST is all self contained and the port works. Move the port dizzy, coil and dizzy harness and it doesn't work on starboard. It has 12V with key ON, and unless the 12V is dropping out when starting then only thing left is the tachometer.

Disconnect the gray wire on the back of the tach and see if that works

 

[QBhoy]

Sound silly and obvious...but is the battery good ? Try jump leads from the other engine battery and see what happens. Said it a few times about larger mpi engines...may be the same with these wee 3.0. The cranking takes enough load to stop the engine wanting to fire at all. Seen it loads on the larger mpi and gxi. Good to rule it out at least.

 

[Fun Times]

Engine wiring harness
Fuses and neutral switches
Something is telling the ECU not to provide the spark.

When you mention neutral switch, is that up at the helm shifter or back on the engine? Such as item # 19 for the engine side, https://www.mercruiserparts.com/bam/subassembly/30916/13809/210
If item 19 is out of adjustment via the shift cable/s, it would keep the system from sparking.

Also did you happen to swap over wire harness item # 19 that runs between the "Coil and Distributor" and Ignition Components
That wire harness could fail creating no spark and signal to RPM gauge.

 

[Scott06]

I like the comment on disconnecting the tach, look at the shift interrupt as well (Im assuming alpha drives ?) . Also maybe take the distributor cap off and crank it to verify the distributor does spin on the off chance the cam or geardrive is messed up.

 

[Doubletrouble 1965]

I like the comment on disconnecting the tach, look at the shift interrupt as well (Im assuming alpha drives ?) . Also maybe take the distributor cap off and crank it to verify the distributor does spin on the off chance the cam or geardrive is messed up.

Many thanks for your replies and suggestions.
To answer questions
We tested the interrupt switch at the motor.
The battery is new and tested.
Disconnected the tach with no result.
After referring to the workshop manual we can confirm that after switching
on the ignition the warning buzzer sounds for 60 seconds then pauses then
gives a short buzz. The manual says this indicates a OBD problem. No kidding!
As we have swapped the ECU I can only conclude that the problem is on the engine.
I have no scanning tool but would consider getting one if I thought it would
find the fault. I would appreciate any suggestions or recommendations.
In addition to no spark it looks like the FI is not being activated either when
we try to start the engine.
We are now swapping the entire distributor assembly to see if that does anything. Previously we only swapped the module and cap/wires.

 

[alldodge]

FI is not being activated either

Can you give more info on what Fl is?

now swapping the entire distributor assembly

There is also a coil inside the distributor

 

[Fun Times]

Previously we only swapped the module and cap/wires.

If this swap starts the engine then the issue may be item number 6 though typically a failed pickup coil doesn't set off a warning horn fault code that I recall, https://www.mercruiserparts.com/bam/subassembly/30916/13809/50

Search online testing gm pickup coil for many ways including how to videos, https://easyautodiagnostics.com/gm/4.3L-5.0L-5.7L/distributor-mounted-icm-tests-6

If you haven't yet, first try harness # 19.

Be aware that you may need the marine scan tool to reset ignition timing properly from removing the distributor assembly.

Maybe try to find someone local with a scan tool to see what's happening or even try locating a Mercruiser Smart Craft gauge as some may help give you some indication of where to start.

Testing The Obd-M Malfunction Indicator Lamp (Mil); Guardian Strategy; Audio Warning System-3.0 Tks; Testing The Audio Warning System - Mercury/Mariner 3.0 MPI ECT Manual [Page 43]

Mercury/Mariner 3.0 MPI ECT Manual Online: testing the obd-m malfunction indicator lamp (mil), Guardian Strategy, Audio Warning System-3.0 Tks, Testing The Audio Warning System. 1. Turn The Ignition Switch To The On Position Without Cranking The Engine. 2. The Service Engine Icon And...

www.manualslib.com

 

[Doubletrouble 1965]

If this swap starts the engine then the issue may be item number 6 though typically a failed pickup coil doesn't set off a warning horn fault code that I recall, https://www.mercruiserparts.com/bam/subassembly/30916/13809/50

Search online testing gm pickup coil for many ways including how to videos, https://easyautodiagnostics.com/gm/4.3L-5.0L-5.7L/distributor-mounted-icm-tests-6

If you haven't yet, first try harness # 19.

Be aware that you may need the marine scan tool to reset ignition timing properly from removing the distributor assembly.

Maybe try to find someone local with a scan tool to see what's happening or even try locating a Mercruiser Smart Craft gauge as some may help give you some indication of where to start.

Testing The Obd-M Malfunction Indicator Lamp (Mil); Guardian Strategy; Audio Warning System-3.0 Tks; Testing The Audio Warning System - Mercury/Mariner 3.0 MPI ECT Manual [Page 43]

Mercury/Mariner 3.0 MPI ECT Manual Online: testing the obd-m malfunction indicator lamp (mil), Guardian Strategy, Audio Warning System-3.0 Tks, Testing The Audio Warning System. 1. Turn The Ignition Switch To The On Position Without Cranking The Engine. 2. The Service Engine Icon And...

www.manualslib.com

Progress! Mystery solved I think

While we were swapping the distributors we noticed that the module in the
Starboard engine was not grounding with the block. We made a supplementary ground and presto everything worked, tach, FI (fuel injectors), ignition spark. We have now to hook up a temporary fuel supply
and see if we achieve internal combustion.
I am hopeful that we have solved our mystery but I must say that the original
ground for this module is not a good design and I think I will add a separate
ground on the Port engine as well.
I will report back when we try the engine.