JBoat

I am having an issue with a 496 where the power seems to be up and down. I’ll start it up and it’s fine. Then the next time I starts it will get up and go but at like half steam. After checking fuel and harness connections I decided I would need more help finding my issue. I ordered the Rinda / Merc scan tool in hopes to pick up a code and I am now having a hard time getting that to connect. It will hook up and read the first 3 menus and even detect that I have a MEFI 4 computer but when it get to the scan menu it errors out. I just get “***error*** check connections “. I did check connections and try it with the engine off, engine on, every way I could think to try it and am not have any luck. Anyone see this message before and have any idea what I could look for next? Does it sound like a computer issue?

Also the scanner is working as I tried 2 motors in my buddies boat right after and they both picked right up. I would be greatful for any advise as the boats in the water on a hoist right now so I have limited option to figure things out here

FIXX

iTrader: (2)

usually its a ground or power issue,,try your friends again..if it works fine then i would check for a power loss to the plug or a ground loss..

JBoat

Not sure if it matters but I forgot to mention the 10 pin connection for the scanner has a jumper wire onto the cap. My friend thinks this is because I have a custom ECM curve. Would this wire need to be removed to get a proper scan? The wire it jumps to is a open spot in the connection for the scanner so it should not even connect. Unfortunitly Im in NY and the motor was built 7 yrs ago in MI so I am having a tuff time with asking the builder.

BUP

iTrader: (9)

what motor do U have ? Mercruiser never used MEFI 4 in a 496 unless U have a bored and stroked 454 CID MPI that was programed using MEFI 4 inwhich maybe the engine builder of the motor used it. If U have the Mercruiser 8.1 / 496 this has PCM 555 computer controler. Your software then might not be the current version for the PCM 555.

If this is a Volvo motor then that uses a E-Controls computer controler. Just posting because I'm not clear what exactly you have nor if this even is a Mercruiser. Wellcraft used alot of Volvo motor packages thru out the 90's till they stop making rec boats permanently.

JBoat

BUP its a custom built 496. Its a Tyler Crocket motor. The plug is the older style and the scanner connects just far enough to figure out its a MEFI 4. The boat had a 454 from the factory so my guess is that computer was used an remapped to fit the origonal wiring harness

4bus

iTrader: (4)

He has a Tyler Crocket 496 bastard child Looks just like a 496ho from merc, cover and all. And it is a true 2001 496 Ho engine with all the crazy sensors and no distributor, not a punched out 454. Has crossover cooling and SM exhaust as well.

Not sure why it has the mefi 4 or how tyler even pulled it off, Jay I think a call to Tyler is your only solution.

Did you check for broken ground wires on the back side of the engine?

BUP

iTrader: (9)

oh then it might be a custom calibration by the builder. I would call him and find out what exactly U have and how to diagnosis it or what version software would work with Diacom / Rinda. Also you could call Ed Rinda to hopefully get some answers as some help to read / scan this motor. IMO U might have a custom recalibrated MEFI 4 b.

Aslo make sure U have good grounds and the computer itself did not loose its ground.

Raylar

Call Tyler, he tell you what the engine has. I know back a few years ago he did some 496 conversions with 496's that had re-rigged with Mefi4 conversion harnesses and ECM's from Arizona speed & Marine, you might have one of those and the ECM software was custom and the Rinda should still read it through a standard diagnostic connector on the harness.

Best Regards,
Ray @ Raylar

JBoat

Thanks for all of the feedback, it great to have a place like this for some guidance. I spoke to Tyler and he said the ECM is locked, I had to mail it out to him so he can open it up to be read on a scan tool. He has some master machine of some thing to that effect. Shortly after I got the ECM out and on the way I realized I had a plug wire split right in the middle (core showing). I am hopeful this is what has been ailing me and started all of this mess.

Raylar - Some how I had just ordered a set of your 496 silicone plugs wires last week, I am the guy in Cicero NY. Not sure how that worked out as such good timing, I intended to change them anyway just did know how bad I needed one. Glad I had a set on the way. Now just waiting for my ECM back from Crockett and can give it a go for the weekend hopefully.

4bus

iTrader: (4)

Edit - my friend 4bus found the bad plug wire while he was removing my ecu for me