Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

[muc]

Didn't know you were on the other side of the pond!
I have NO idea how this might affect anything.
The only thing I know about prepping a boat for Europe is from many years ago having to install a special transformer for shore power on a boat heading there. That was back in the Days of MEFI so you might want to call Merc if there is anything about the PCM 112.
CONSUMER SUPPORT for North America is,
Mercury Outboards / MerCruiser / MotorGuide
Phone: 920-929-5040
Maybe they can advise?

 

[Captain of the Double G's]

timing, and that 32f reading still bothers me, if u are not using that system install it. In the meantime replace the TMAP again. Gut feeling and you still do not have a HZ reading.
Now I can solve your problem completely. " I should have had a V8 " old school chevy ( small block , pick any but 305 with a 2 barrel rochester carb, we are done.

 

[muc]

Thats correct. Not sure what's the logic of this PCM. Speed and density controlled. There is no IAC just throttle drive by wire. Guessing that PCM calculates air density from vacuum and temperature (TMAP sensor) and adjusts injector pulses to keep stichometrtic ratio. How does the RPM stay steady at idle with low vacuum IDK maybe controlled with timing?
Reason I want to pull the intake is to check valve lifters. But that after few more checks before that.

I really don't think you have a problem with lifters or cam timing. Your fuel trims look too good. But if I had some good O2 numbers I could be more sure.

Also with the electrical problem you have, all bets are off on these numbers.

The PCM Diagnostic manual gives a little info on how all this works. Like I said it uses many different "tables" to adjust all this stuff. Unfortunately all these manuals are written for a Mercury trained tech. So I'm guessing it might be pretty hard for the normal person to understand. Good Techs spend a lot of time learning this stuff.

 

[muc]

timing

Spark advance looks pretty good to me. But once again --- low cranking volts could affect this.
Did you mean ° degrees or % percent?
What sensor are you thinking of?

But that does bring up a somewhat exotic possibility. I've never seen it, but in class the instructor does bring up the possibility of the RELUCTOR WHEEL slipping on the crankshaft. I've never had a 4.5 apart so I'm not sure if this engine is keyed (can't slip) or pressed (can slip)

 

[Captain of the Double G's]

Degrees

 

[nola mike]

Yes I did remove oil cap - no smoke there.

Did not check timing old fashion but will it work if PCM controls timing and shows already -3 deg at idle?

Broken valve spring - don't think so compression 180psi each cylinder.

I will definitely remove intake and check valve springs and clean hydraulic lifters, gaskets etc, but that after summer. I've got still two weeks in marina and then will take boat on trailer.

Exhaust checked no restrictions.

14.7V but all sensors getting correct 5V.

I know that PCM can double injector pulse time if vaccum is incorrect - see once more attached ECM555 logic. I believe PCM112 works similar way.
Vaccum is way off at idle and I hope I will find the reason.

That doesn't explain your fuel consumption. Your vacuum looks ballpark once you get off idle. And unless you have the specs, you're just guessing that it remains off throughout the rpm range.

 

[muc]

Degrees

This engine adjusts timing for each cylinder separately. And like I said #s look normal. You wouldn't check timing with a timing light. You use a dial indicator and it's a really big pain in the azz. It's not ajustable.

 

[nola mike]

Spark advance looks pretty good to me. But once again --- low cranking volts could affect this.
Did you mean ° degrees or % percent?
What sensor are you thinking of?

But that does bring up a somewhat exotic possibility. I've never seen it, but in class the instructor does bring up the possibility of the RELUCTOR WHEEL slipping on the crankshaft. I've never had a 4.5 apart so I'm not sure if this engine is keyed (can't slip) or pressed (can slip)

I don't suppose there's a cam position sensor on this?

 

[muc]

I don't suppose there's a cam position sensor on this?

Nope, not needed with this system, just like no knock sensors.
Only used on the new stuff that has VVT - variable valve timing.

 

[muc]

That doesn't explain your fuel consumption. Your vacuum looks ballpark once you get off idle. And unless you have the specs, you're just guessing that it remains off throughout the rpm range.

What do you see wrong with fuel consumption? It's tracking with MAP, Demand and RPMs
O.P. has never stayed stable on the throttle long enough to get into ARO (advanced range optimization) where they will get best fuel burn. This is one off the things Diacom doesn't display like G3 does.

 

[nola mike]

What do you see wrong with fuel consumption? It's tracking with MAP, Demand and RPMs
O.P. has never stayed stable on the throttle long enough to get into ARO (advanced range optimization) where they will get best fuel burn. This is one off the things Diacom doesn't display like G3 does.

I don't... He was saying he thinks he has increase fuel consumption because of his vacuum being low (and posted a table). I didn't think that was his problem

 

[nola mike]

Nope, not needed with this system, just like no knock sensors.
Only used on the new stuff that has VVT - variable valve timing.

You'd be able to tell if the reluctor on the crank slipped...