MEFI 3 and Code 44

[alldodge]

Don't want to hyjack another's thread but need to discuss code 44 with muc from your comment

Volvo never used the “self spark sensor system test” that MerCruiser used. Also MerCruiser only used this for a very short time on the MEFI 1 ECM. By August 1994 they removed that feature. It was a code 43 that was set. MCM 94-12

alldodge If you were getting a code 44 on a MEFI 3 ------ 93 octane wasn't your problem.

This is why serial number can be so important. Not only is there a difference between Volvo and MerCruiser in what program is in the ECM. There is also a difference between MEFI 1-2-3-4-4a-4b

Current motor in my Formula is a 500+ HP custom built motor. When it was being tuned in the boat with AFR meter and laptop it would throw a code 44 at times. Codes for MEFI 3 which I can find do show 44 as cannot detect knock activity.

If I always used 89 to 91 octane there was no code 44. When I disabled 44 (using MEFIBurn) I can run 93 and not have an issue or loss in power.

 

[muc]

Didn't see a question and not sure how much I am able to help with this because I only worked on stock EFI engines.I learned early on that the saying "if you want your boat to go faster --- buy a faster boat" was almost always in the best interest of the customer.
We are told in school that all MCM and MIE engines built after 1994 will run on premium fuel with out problems. But to not recommend premium to customers because it's a waste of money and can cause carbon to build up faster. These days if you want to avoid alcohol in the fuel, 93 is all that's available.

I don't know why you're experiencing the symptoms that you are.
Is it possible that when you rebuilt the engine something was changed that required a different knock sensor to be installed? Or maybe it's not making a proper connection to the block? The auto guys and the MerCruiser manual really push using a torque wrench when installing, although I have installed more then a few just by guessing at the torque and not had a problem.

I'm sure you have seen this in the manual.

IMPORTANT: If installing a new knock sensor, be sure to replace it with an identical part. Knock sensors are very sensitive and designed for each specific application. IMPORTANT: In the following step, it is very important that the knock sensor be torqued to the precise specification. Incorrect torquing will result in unsatisfactory performance. DO NOT use sealer on threads. 1. Install knock sensor in engine block. Torque to 12-16 lb-ft

My experience with code 44 on a MCM MEFI 3 has been the wire fell off the sensor, the wire got cut and rarely a bad sensor.

Did you have the engine balanced when you rebuilt it? Maybe that might change something?

MerCruiser's words are "A Code will be set only if the ECM does not see any activity on the KS signal circuit(s).".
I would think that it would take more than octane to get to no activity.

 

[alldodge]

Yes I know about the statement, a torque wrench was used and also installed a new sensor on build.

Motor was built and tuned by Eddie Young, so the internals were built correctly

Eddie was on the boat when it started showing up during tuning.

MerCruiser's words are "A Code will be set only if the ECM does not see any activity on the KS signal circuit(s).".

Agree, only way to get activity from a knock sensor is to have the crystal modulate at a frequency and produce output.

Your saying that the 3 does not test the sensor and from my research says it does. Code 44 was discontinued later. Guess we will just have to agree to disagree