496mag no start issue.

[Mercafe31]

I have a 2006 496 mag (ser. No. ow618...) with DTS, bravo 3 and 555 ECM. Roughly 500hrs.
Had an issue last year with the cool fuel 3, which I replaced that turned out to be multi layered. (Bad fuel- so I drained tank, replaced fresh but in April and all ethanol free). Replaced fuel tank pick up tube and everything was running perfect. Along the way, I replaced all spark plugs, spark plug wires, MAT and MAP sensors. Unrelated but exhaust manifolds are 3 years old and alternator is 1 year old. I had some minor surgery and didn't get to the marina to start the boat for a few months. Tried starting it and no good. It made an attempt ran rough and died. Now it will crank but won't start. No codes on my Rhinda diagnostic tool. (Had a 5v fault in sensor power 2 and found a bad connector to the trim indicator, repaired but still loses 5v when plugged in. The book indicates this fault won't cause no start. ) I have 35psi on the fuel rail, the fuel pump relays cycle, 1 short beep on "key on" and i hear a relay click, after fuel pumps cycle. I see rpms register, as it cranks. Swapping cam sensors made no change. Port motor next to it runs fine. I'm pulling my hair out on this one, any suggestions would be appreciated. Thanks

 

[tpenfield]

Welcome to iBoats . . .

Aren't these hi-tech engines fun ???

I would remedy the 5v fault even though the manual (?) may indicate that the engine would start. Maybe the engine will crank, but not actually start.

Do you have the Rinda scanner or the Rinda Diacom PC Software? Got any screen shots of the scanner/PC to share?

I assume that the port engine comes up clean on the Rinda

Maybe some of our experts . . . @muc, @Fun Times, @alldodge (or others) can weigh in on the issue or any next steps.

 

[alldodge]

Fuel pressure should be 39 psi but at 35 it should start.
Does fuel pressure stay up when the pump stops or does it drop?

Use a spark gap tester and check for spark

 

[curtster122]

Are you getting spark?

 

[Scott Danforth]

what do the contents of the fuel filter look like.

Fresh fuel to you in April is now 7 months old. Also, wouldnt be the first time contaminates would be pumped into the system when fueling.

check for spark

check your injectors for proper spraying. plenty of 8.1's requiring injector cleaning on iboats in the past 4 months

 

[Fun Times]

No codes on my Rhinda diagnostic tool. (Had a 5v fault in sensor power 2 and found a bad connector to the trim indicator, repaired but still loses 5v when plugged in. The book indicates this fault won't cause no start. )

If you haven't yet, Try unplugging the trim connector, see if you get your 5 volts back and then see if the engine will start.

Also just to be sure, maybe try checking/asking around to see if maybe either your or other boats in the area may have been struck by lightning recently.

 

[Mercafe31]

Welcome to iBoats . . .

Aren't these hi-tech engines fun ???

I would remedy the 5v fault even though the manual (?) may indicate that the engine would start. Maybe the engine will crank, but not actually start.

Do you have the Rinda scanner or the Rinda Diacom PC Software? Got any screen shots of the scanner/PC to share?

I assume that the port engine comes up clean on the Rinda

Maybe some of our experts . . . @muc, @Fun Times, @alldodge (or others) can weigh in on the issue or any next steps.

 

[Mercafe31]

Thanks for all the replies. I have the Rhinda pro diagnostic tool. My mechanic came to look at it today with the CDI computer type scanner. What he found was the MAP sensor, which is a Delphi (not mercury) is throwing off the 555 ECM. We swapped it out but still no start. Confirmed spark too. He's leaning towards the Cam sensor, as the issue, because the scanner is not picking up spark advance. So when the starter is cranking the spark advance stays at 0 degrees. His comment was like it's attempting to start but the computer is acting like it's not cranking. The computer was also showing numerous TPS errors. I'm buying a new MAP and CBS sensor. Crossing my fingers. Hoping I don't wind up needing a new throttle body.

 

[Mercafe31]

Fuel pressure should be 39 psi but at 35 it should start.
Does fuel pressure stay up when the pump stops or does it drop?

Use a spark gap tester and check for spark

Fuel pressure shoots up to 39 at key on drops after a bit to 35. After a few days of sitting it drops to 22. Spark is good and confirmed.

 

[Mercafe31]

Love em! Grrr

 

[Mercafe31]

what do the contents of the fuel filter look like.

Fresh fuel to you in April is now 7 months old. Also, wouldnt be the first time contaminates would be pumped into the system when fueling.

check for spark

check your injectors for proper spraying. plenty of 8.1's requiring injector cleaning on iboats in the past 4 months

Fuel injector condition is still on the suspect list. I have new cool fuel 3 and the old fuel regulator was clean so I'm hoping there no paint in there. I did clean out the fuel line when I changed out CF3 but didn't clean rail or injectors.

 

[Mercafe31]

Fuel injector condition is still on the suspect list. I have new cool fuel 3 and the old fuel regulator was clean so I'm hoping there no paint in there. I did clean out the fuel line when I changed out CF3 but didn't clean rail or injectors.

Still need to look at filters will check tomorrow, weather permitting and advise.

 

[Fun Times]

If you are throwing a bunch of codes consistently after clearing them then usually a bit more often than not that’s more of an bad ground type connection somewhere than actual bad parts… Or maybe you have a bad internal PCM component issue… You have 2 engine’s? If yes and you go this route, Usually it’s better to put a thought to be bad PCM on a known running engine vs good PCM on a bad running engine in case somethings wrong with the bad engine burning PCM’s.

Your fuel psi should be around 40-42ish psi so you should be okay with your numbers.

 

[tpenfield]

Did replacing the MAP sensor remedy the 5v #2 Voltage Source issue? sometimes the mechanics are at their wits end trying to fix the 'hi-tech' engines.

I assume that you have the service manual for the engines? Maybe review the 'cranks but does not start' troubleshooting guide to see if it correlates to anything you have found.

I'm not sure about the spark advance comment, generally the PCM does not do its complete magic until the engine reaches 300 RPM. Cranking would be about 200 RPM.

FWIW - the engines are GM big blocks, so you will find a fair number of GM/Delphi/AC/Delco parts, particularly the sensors.

I agree w/ @Fun Times . . . best not to swap PCM's . . . just use the 'good' engine for PCM data value comparisons. Often that helps ID the root cause. Otherwise, it is the 'parts cannon', not knowing what actually fixes it.

You have spark, but perhaps no fuel . . . . . . so maybe the PCM is not telling the injectors to fire

 

[alldodge]

Your fuel psi should be around 40-42ish psi so you should be okay with your numbers.

Recorded this from one of MUC post

2002 or 2003 or 2004 it will fall under these engine serial ranges 0M025000 thru 0W059999 and fuel pressure for Gen II should be at 43 PSI. Fuel pressure regulator part number 861126A1

Gen III module should be 39 PSI at idle and 43 PSI at WOT. Test pump pressure high level by removing vacuum line off regulator.

Looks like your fuel pressure is good
With no 5V the ECM doesn't know much. One thing is if there is a bad sensor the motor would start, but if there is low 5V then all the sensors are feeding bad info and the motor won't start

 

[paulswagelock]

Have you tried the simple test - remove the filter screen from the air inlet and spray carb cleaner or fuel into the inlet. See if it starts. Yes - fuel issue. No - spark issue. Gets you headed down the right path.
when my 496 had a no start, this quick test pointed me to fuel issue and a faulty CF3 module.

 

[Mercafe31]

Wasn't able to get down to the boat today. Rained out in SC today. New sensors will be in Friday- Saturday.

 

[QBhoy]

Hi. Before going too deep into things…I would 100% try starting it with jumper leads from the other running engine’s battery. These things won’t fire if the battery is anything but brilliant. Cranking takes that much load from a weak battery, that it won’t have enough left to actually fire the ignition system and all its ecu related items. Worth a try for sure. Caught me out years ago. Dismissed the idea of the battery, just because it seemed to crank over healthy enough. The mpi engines just need a superb battery or they won’t even try and fire.

 

[wjs1820]

So it took a month to get a Sierra MAP sensor, the Merc ones are still on back order. I replaced the battery after my battery tester showed 52%. (I had 13v but only 1/2 the CCA). It will start on starter fluid but won't continue to run on starting fuel. I confirmed fuel injector pulse with a noid light. So fuel supply is high on the suspect list. I opened my fuel filter and found it almost dry but still had fuel pressure on the rail. I disconnected my gage and reconnected, now it reads 0. I'm going to try to prime the cool fuel again and attempt to get it running on a portable tank to see if I can focus the issue. I'll update again after the weekend. Thanks for the replies.

 

[alldodge]

Have you tried bleeding the fuel rail?