Bleed questions

[gmacrae]

Hi guys. I'm again tackling the long standing issue (minor really) of my old Merc Laser 220 EFI that runs great when you have your foot down, but starts to overfuel, splutter and smoke up when you're going slow (learner wakeboarders etc)...

My latest idea is to have another look at the bleed system, thinking it might not be doing its job and the crankcase and/or manifold is gradually pooling fuel.

So I started looking around at diagrams and one mentioned that the top of the VST is supposed to have a hose back to the intake manifold (assume to introduce vacuum to the VST to help the bleed system scavenge fuel?), but mine doesn't. I couldn't find any diagrams making this clear. This line wasn't hooked up when I got this motor, so I assumed it was some kinda overflow, and sent it out the back of the motor by the pisser).

The nipple on the manifold that it might connect to is blanked off - no problem to drill it out if need be and connect this up. I'm just worried putting vacuum into the VST might have an effect on the EFI pump - starve it or something and blow the motor...



What say you, S&F Merc Gurus?

Cheers!

[rock]

I don't have a 2.4 efi unit around but the older 2.5 vst has two outlets in the same area one of which goes to the wisker valve and the other plugs into the back side of the manifold so my guess is your guess is correct. Good luck.

Rock

[gmacrae]

Thanks Rock, yea no whisker valve on my motor either. Will give this one a vacuum source and see how I go.

[billybob]

That may be normal on this motor, merc. changes stuff like that, alot. If I were working on this, first thing I would try. Run on flush, unhook temp. sensor on top of port head, & listen for sound or RPM change. if no change, that tells me that, either temp. sensor, or enrichment circuit in ECM is bad, stuck in enrichment. then before hooking wires back up, check TPI it must read .250 volt. with temp. wires unhooked.

[gmacrae]

That may be normal on this motor, merc. changes stuff like that, alot. If I were working on this, first thing I would try. Run on flush, unhook temp. sensor on top of port head, & listen for sound or RPM change. if no change, that tells me that, either temp. sensor, or enrichment circuit in ECM is bad, stuck in enrichment. then before hooking wires back up, check TPI it must read .250 volt. with temp. wires unhooked.

Thanks man, I've been thru the temp sensor and TPS checking things lots though (this has been going on for years). The head temp sensor is removed, with a resistor in it to tell the ECM it's always hot (i forget the ohm). I wanted to remove that variable, and it's always started really well cold (unbelievably well for an old motor). The motor does definitely richen when i unplug that resistor (or the sensor), as evident by the TPS voltage.

Currently the TPS is set quite lean (i think about .08v with temp resistor unplugged). Don't worry tho, timing is @ 21 WOT, and always 98ron gas.

I also have noticed that the bleed system doesn't seem to move much (yellow tygon tubing). So figured i'd investigate here next - will see if any checkvalves are faulty next.

Do you think introducing a vacuum to the VST could cause any problems? I can see it assisting the bleed system, also the pulse/lift pump, but stressing the EFI pump (which is new).

[ironhead stv]

check fuel pressure regulator

[gmacrae]

check fuel pressure regulator

Yeah cheers, will be doing that next I think

I've found a blocked check valve in the bottom of the intake manifold (the ones that feed back to the side of the block by 5 and 6). Its little spring has disintegrated, wasn't flowing either way

Can anyone help me identify this part number? I've searched thru manuals but can't find it listed as part of the bleed system and intake manifold pages don't show them

Cheers guys

[gmacrae]

or is anyone able to tell me the size (press-in diameter from some verniers) of the straight fitting bleed valves that fit into the reed cages (part 21-42698)? This one I pulled out is measuring 6.95mm

I'll use some of these if I can't find any like the original 90 degree ones (if they fit the holes)

[gmacrae]

Ok, I pulled one of the reed cage checkvalves out of my motor, and its slightly less than 6.5mm - so not an option to use them instead.

Can anyone tell me if these checkvalves on the bottom of the manifold are even necessary for keeping the motor running clean? I've since seen a couple of very similar motors that don't even have them (one was a 2.5 150 XRI). Here's a pic of mine, one in place right at the bottom of the manifold, and one removed:


Cheers!

[texasvector]

http://www.boats.net/parts/search/Me...IGN/parts.html

not sure if they are on here....doesnt look like bottom 2 you are referring to?

its not #5?

http://www.boats.net/parts/search/Me...%29/parts.html

or would #5 in above ^^^work?

[gmacrae]

http://www.boats.net/parts/search/Me...IGN/parts.html

not sure if they are on here....doesnt look like bottom 2 you are referring to?

its not #5?

http://www.boats.net/parts/search/Me...%29/parts.html

or would #5 in above ^^^work?

Thanks man, but na these valves aren't in either diagram, but the hoses that go to them ARE in that first diagram, and are cut off (green circles in my pic above) - frustrating huh! I pulled the 42698 (#5) checkvalve out of my motor and it's too small to press in to replace these two.

[texasvector]

i saw green circles but couldnt find that exact location shown in any diagram(with part #)....figured maybe theyre interchangable with one of the other fittings.....just which one?

i say **** it....long as it doesnt feed a main bearing

[gmacrae]

i saw green circles but couldnt find that exact location shown in any diagram(with part #)....figured maybe theyre interchangable with one of the other fittings.....just which one?

i say **** it....long as it doesnt feed a main bearing

Na, you can see exactly where they go in this pic, straight from the manifold to the side of cyl 5 and 6. Is it really a good idea to be dumping excess fuel into those transfer ports tho?? hmmm..... anyway cyl 1,2,3,4 fittings are all capped like the diagrams. I imagine fuel does puddle up at the bottom of the manifold is the only thing - would be good to make sure these were draining into the VST somehow but I guess I'll just cap em for now