Mercury EFI problem

[aussiejake]

I thought I had this fixed with a new MAP sensor but the problem happened again today on a cold morning (7 degrees C )

This is a 2006 mercury 150HP EFI 2stroke. Coils are battery driven (no stators etc)

1.The number 2 cylinder will foul the spark plug by what looks like the port bank running too rich.

2. The spark plug will fire again on idle once temps are back up to 62 C

3. The spark plug will foul again once I start to get up on the plane.

4. If I put another spark plug in the no.2 cylinder once the other one has fouled it will foul the new plug

5. If I put a hot plug out of another cylinder into No.2 it will fire and run perfect unless I go up to high rpm (4000 plus) and drop back to around 3300rpm. It fouls when I vary the rpm range.

I have changed coils, leads, MAP, new plugs, thermostats ...and I am lost at now what to do. Compression is perfect, all other cylinders are burn perfect, but this number 2 (top port) is doing my head in.
Reeds are perfect
Injectors have been checked and all perfect
The motor only has 180 hrs on it.

I do not understand why when I put a hot plug (hot from running) from another cylinder into No.2 the motor will then run perfect until I let it cool or vary the rpm too much.

Im thinking now air temp sensor but dont want to keep throwing money into spare parts. Im thinking this air sensr because the No.2 cylinder is the coldest cylinder and would possibly be the first to foul?
Symptoms are very much like a MAP but I have already replaced it....and also I dont have the problem as much or at all through the summer warmer days.

If anyone can lead me in the right direction I owe them a lot of beer

Sorry about the long post but I am now completely lost.

 

[sxmerc]

Re: Mercury EFI problem

Is the engine coming up to proper running temp? Both banks? I wonder if the #2 plug is fouling out as maybe the port bank is not warming up completely and cold fouling the plug? Maybe the port thermostat is stuck open? My two cents.

 

[aussiejake]

Re: Mercury EFI problem

Thank you for the reply sxmerc but both banks come up to 64 degrees C on idle, I have checked this with a DDT.
The temperature does drop very quickly once I throttle up which I believe is due to the poppet opening. In the cold mornings SmartCraft will read 27 degrees C while cruising on 3500rpm. I assume this is OK?

Ive just gone through all my harness connections again and cleaned out a lot of dielectric grease. No.2 coil connection was full of the stuff....dont know if this would cause a problem but Im clutching a straws at the moment.

It is a very odd problem and being so erratic it is very hard to pinpoint.

Jake

 

[Faztbullet]

Re: Mercury EFI problem

I am leaning toward a sticky injector or weak coil, I have seen coils get weak and not fire under compression. These are several items I would do if in my shop:
1) check connector at coil to see if pins bent
2) make sure plugs are correct
3) swap coil to # 1 cylinder and see if problem follows
and if that didnt help pull and have injectors cleaned(Brucatto) or replaced

 

[aussiejake]

Re: Mercury EFI problem

Thanks Faztbullet but I have done the injectors and swapped around coils.

Plugs are NGK BPZ8HS-10 which are recommended for this motor.
Im thinking about running hotter plugs???

Im checking the harness this morning and removing all the dieletric grease in No.2 coil connection (harness) I know this is clutching at straws but I am really at a loss.

Would the air intake sensor & MAP mostly affect the port bank of cylinders or would it be all cylinders.

Any other advice would be greatly appreciated.

cheers
Jake

 

[aussiejake]

Re: Mercury EFI problem

I bought a can of MAP sensor cleaner and sprayed the crap out of the MAP.
Fired up the motor and it seems to be fine for now
Hopefully the oil build up in the sensor caused the problem.