Starboard engine won’t fire

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05-28-2021 | 07:28 AM

Steve513

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Starboard engine won’t fire

I have a Cobalt 343 with twin 496 HO’s. Last fall I damaged a push rod on my starboard engine, still started and idled fine when we pulled it out to have it rebuilt. Just had the engine reinstalled last week and in won’t start, just cranks with a poor fire about every 20th revolution, or so. We’ve swapped the crank sensor, cam sensor and pcm with the running port engine and still have the same response and we have great fuel pressure. Any thoughts?

*also, I’m told the left vs right engine pcm’s might be different?

-Any help would be appreciated...
-Currently no active faults are shown while connected to mercury diagnostics...

Last edited by Steve513; 05-28-2021 at 07:33 AM.

05-28-2021 | 08:02 AM

Barnacle Bill

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Timing?

05-28-2021 | 08:38 AM

AllDodge

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From: KY

What's the motor serial number?

Reason for the rebuild?

When key is turned ON, does the fuel pump run?
Do you hear it beep?

When cranking can you see the Tach show 300 rpm or so?

05-28-2021 | 10:01 AM

Steve513

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Quote:

Originally Posted by AllDodge

What's the motor serial number?

Reason for the rebuild?

When key is turned ON, does the fuel pump run?
Do you hear it beep?

When cranking can you see the Tach show 300 rpm or so?

Damaged push rod

Yes - and I have >40 psi of fuel pressure when turning key to on position

Yes, we have rpm

05-28-2021 | 10:20 AM

AllDodge

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From: KY

Something is not making connection
RPM shows so CPS is connected
Fuel pump turns ON so MPR and FPR is working

Coil harness to engine harness
Injector harness to engine harness

Fuse to fuel injector harness

From manual 33

Quote:

The normal resistance values for these sensors at 21 degrees C (70 degrees F) are:
 Camshaft Position Sensor - A to B 24.04 mohms and B to C 24.05 mohms
 Crankshaft Position Sensor - A to B 23.2 mohms and B to C 23.21 mohms.

With software prior to level 091, a malfunction of the crankshaft position sensor or the
camshaft position sensor will not set a fault.With level 091 software, if the camshaft position
sensor is bad and does not send a signal to the PCM, the engine will backfire and not start.