Naughty Kitty

Unfortunately I'm dealing with a recurring problem with one of two 496 HOs installed in my boat that I can't find a smoking gun. At 225 hours, cylinder #1 of the starboard motor burned the edge of the piston. Had the motor rebuild (builder said he tested the injectors), then I had a marine tech ride with me plugged in to the PCM with a Diacom unit to watch the engine vitals (reports attached). After finding nothing wrong, I chalked the problem up to bad gas (each motor has it's own tank).

Port Motor Report (still running awesome with 450 hours)
Starboard Motor Report (failed twice)

Fast forward another 225 hours and the same problem happens again (not sure which jug yet) to the starboard motor. I got a great deal on two new First Mate long blocks, so opted to just do both motors as the port motor was now at 450 hours anyway. I pulled all (16) injectors (which after removing them was easy to see the original rebuilder lied to me as the paint was still bonding the connector to the injector) and sent them to Mr Injector to be flow tested and rebuilt. His report showed only a 3% decrease in output from injector to injector so here i am again without the smoking gun.

What am I missing (besides a stack of Benjamins for buying a 496 to begin with)? I remember a few years back when Ray was active in the 496 topics, he stated the 3/8 ID fuel lines builders use on these motors is a source of problems, any one else have suggestions or experience with this?

14 apache

iTrader: (1)

maybe pick up tube sucking air a cracked.

HALLETT FAN

Not a lot to go on as to why you're burning pistons ...what is odd is the negative timing data , I would somehow hook up a 02 sensor
and monitor air - fuel ratio at various throttle positions , also see if you can get a lap top and monitor injector pulse - width .

BUP

iTrader: (9)

Internal fuel rail corrosion and leads to fuel injectors contamination that causes restrictions in which causes lean conditions. yoiur full injectors need to be flow tested and most likely new fuel rails or at least checked very closely.

BUP

iTrader: (9)

I do fuel injector flow testing and cleaning. I am working on HO 496 that has this same exact problem with fuel rail corrosion and really bad injectors. If anyone can post pics for me I will be gladly to show what the fuel injectors look like internally.

BUP

iTrader: (9)

I opened up your scan reports just now and took a quick look at them.. they were with 225 / 226 hours on them back in 2008. You do not have a current scan ?

back then the port engine had a about 6 faults or more. you have crank and cam sensor faults, low voltage, both exhaust manifold temps, Overspeed,, low block pressure, guardian mode for almost 1700 seconds in which is a lot.

Did you get all that fixed as you state the motor has 450 hours and runs good ? surely it could not have been running good back then when the scan took place.

A current scan of your both motors might pin point something better than a scan 7 years ago with half the hours on them.. Just saying.

Naughty Kitty

Thanks for the suggestions thus far.

The scans posted followed my original failure, nothing since then as the new motors are not completely installed yet. I did pull the rails and have the injectors all cleaned, rebuilt and tested by Mr Injector, however the flow testing prior to beginning the work showed it was unlikely this was the source of failure as all injectors performed within 3% of rating. Also related to the fuel rail, internally there is no corrosion and looked smooth and clean.

the faults I was told are normal, as the waters we boat on eat sea water pumps...so its not uncommon to see faults logged related to water supply. The low block pressure I didn't notice before...what system does that relate to?

I am leaning (no phun intended), toward a problem on the suction side (too small of a supply hose or air leak in tank siphon) as Ray mentioned this in a previous post about the 496.

Keith Atlanta

All this "stuff" can be had from CP Performance and eBay relatively cheap. Start at the tank and confirm everything is acceptable.

For what its worth, I replaced most of this stuff already. Upon rebuilds, I replaced the tank pickup with 1/2 inch (CP Performance), all new injectors (eBay), swapped out the fuel rails for new ones (eBay), last, i upgraded the fuel pump and piece of crap regulator to Aeromotive.

Have you analyzed your fuel water separator? Tear them down and see whats in them with an oil filter cut off tool. Maybe you have a tank issue with debris?

Naughty Kitty

hey KA, I'm comfortable with the injectors and fuel rail now, but the fuel pump and regulator, along with the tank/supply lines are all unknown right now. I would think the smartcraft system would shut the motor down to guardian if supply pressure was too low? Can you provide me the details of your pump and regulator you upgraded to? Also, are you still using the inline filter between the tank and the water separator filter?

BUP

iTrader: (9)

There is fuel tests that can be done both at the sametime to see if you have a suction side restriction or air and of course proper fuel pressure tests thru out the rpms.

You want to check fuel for restrictions or air leaks with a vacuum gauge and a clear fuel line hose coming out of the gas tank hooked right after your metal canister inline fuel filter, Tee in your vacuum gauge into that clear fuel line right after the inline fuel filter.

U are looking for a very solid fuel flow thru your clear fuel line and no more (MAX) of 2 hg inches of vacuum. anything under 2 hg inches the better and of course the solid fuel flow going thru your clear fuel line. You are looking for air bubbles, if present you have a problem either with a restriction and or air leak. plus looking for any vacuum reading that is over 2 hg inches, I really like 1 hg inches or under if all possible for fuel vacuum reading testing.

The next testing is with the fuel pressure gauge to make sure you have the proper spec on that side of it as well.

The clear fuel line is for testing purposes only. Just to be clear on my end.