89 Merc Laser 220 XRi - fouling or over-oiling

[gmacrae]

Hi Guys. I posted a thread here a while back to help pinpoint this engines issues. The result of that batch of work was replacing the trigger coils, which at least has it firing all cylinders reliably now.

But it turns out that was only half the problem. It still will foul the plugs badly and run like s**t whenever I try to putt around slowly (close to shore or picking up wakeboarder etc). If im able to take it for a good run for 5-10 mins to heat it up and clear the plugs it will eventually run well again ...until i back off the throttle again. When it does play up, it will even struggle to free-rev over say 1500-2000rpm sometimes and will pump out oil smoke like nothing else. To me, it seemed like the thing was just pumping too much oil into the mixture, but aparently this isnt really possible, and i dont know jack about 2 strokes.

I've talked to a guy locally that said he suspects an issue with the "recirculation system" ...maybe a stuck check valve or something, so that its basically overfueling constantly and pooling up in the crankcase - he seems to think this is common with these engines. I would've thought that that would result in a blacker smoke than the white/blue smoke im getting.

Another idea of his was to check the tps setting. The merc manual he had said to check it with a test harness to see output voltages but of course i dont have one of these, neither does he. Can i check resistance with the sensor unplugged? Can anyone help me out with the specs i should be looking for?

Thanks for any help you can give me, much appreciated

Gene

 

[Chris1956]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Gene, I think the first check should be the fuel pump diaghram and oil pump linkage. You should get a manual. If the fuel pump diaghram leaks, you will get raw fuel into the crankcase.

Make sure the oil pump is synchronized to the throttle.

After that you can inspect the recirculation system. The procedure is in the manual.

 

[Faztbullet]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

That engine does not have a bleed system like a carb engine has. The EFI bleed system sends all the unburnt fuel back to VST tank to be recycled. This is controled by a shut off valve and filter. If the filter is stopped up it will cause engine to load up and hesitate.Also a bad engine temp sensor will make it run rich as ECU sees engine as cold. A overpressurized oil tank will also make engine run rich as it forces oil thru check valve into VST tank. A TPI will make it run rich but more toward top end than idle.

 

[gmacrae]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Great replies guys, thanks very much.

I checked and reset the TPI, so no worries there

The fuel pump diaphram is ok (tested by squeezing the prime bulb).

Throttle does appear to be linked to oil pump.

There was a little inline filter in a small line that goes back into the top of the VST tank that had quite a bit of gunk in it, i just removed the filter to test, didnt make a difference, will replace the filter.

One thing worth mentioning is the oil i get dripping out of the top oil tank from a line that goes down to a brass "T" ...is this a pressure relief of some sort? It drips oil out of there regularly, enough to make a bit of a mess on the engine anyway - does this indicate too much oil pressure?

Thanks again guys

Gene

 

[Faztbullet]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Symptoms of overpressurized tank. Remove the crankcase fitting supplying air to oil tank and redrill the small hole in center of disk to .040. This is what bleeds air pressure when engine is not running. Over pressure will force oil thru pump and into VST tank causing a over rich mixture. Install the bleed filter as it keeps trash from entering VST tank and fuel system!!

 

[gmacrae]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Hi AGAIN guys... I'm still trying to troubleshoot this engine.

I haven't had a chance to check the last suggestion yet (thanks Faztbullet). I didnt get a chance to check back to this thread then the iboats forums disappeared?

Anyway, i'll look at that tomorrow. One thing though, the engine usually starts up cold and idles well, after a bit of running/warming up is when the problems arise. Would a plugged up crankcase supply line cause this or would it constantly run like crap? One thing i've noticed though is that the main oil tank does hold pressure even a week or so after the engine was last run... is this normal?

I also just replaced the plugs (in case) and took the boat for a run. This time I used NGK BU8H (cheaper, used BUZ8H supressor plugs last time). The boat ran worse than ever on these new plugs, couldn't even get my tiny ski boat on a plane! Would free rev up to about 2500rpm only but VERY boggy and flat, enough white/blue smoke to make a bit of a scene

For anyone looking on thinking the engine could just be shot, the engine is physically in good health (was rebuilt about 2 years ago). Compression tested recently. Every once in a while when the fuel/spark behaves, it goes like a rocket, just as it should.

I'm going to check Faztbullet's suggestion tomorrow, just providing some more info for possible long distance diagnosis incase anyone else can chime in. I'll report back tomorrow with what that air line shows up.

Thanks again, and any other input is much appreciated

Gene

 

[Faztbullet]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

The oil tank should have no pressure it after it has set overnight...

 

[gmacrae]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

This is the big air line that plumb's into the block thru a big flow restrictor fitting thing (15/16 - 24mm hex), near the fuel filter, right?... I got that sucker off, and can definitely see light thru the flow restrictor disc/plate, but its a VERY small hole, more like a tiny pin hole than 40thou/1mm.

Will changing the size of it that much cause any issues? I'm keen to give it a go, just want to check that's what you would expect to see before i get out the drill

 

[Dukedog]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Check tha regulator (fuel pressure) also. It can make tha motor act pretty stupid too...........

 

[gmacrae]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

We've checked the FPR, pressure is in spec

 

[gmacrae]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

OK I drilled the 1mm hole in the crankcase air restrictor fitting, will try to get the boat out tomorrow to test this. Im going to try running different levels in the main oil tank - it was worst last time out with a very full oil tank, so i'll try it half full. Ill also check to see if the trim/tilt affects how it runs (i've seen this mentioned here with similar problems).

Is someone able to clarify what this brass T-piece is on the oil supply line to the top tank?

It drips oil slowly so i put a short hose on it to route the drips straight to the bottom of the engine cover so it doesn't make such a mess. Is this thing supposed to be there? Seems weird to me

Thanks guys

Gene

 

[gmacrae]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Happy new year!

OK, here's the latest installment in this ongoing saga

I tried Faztbullet's suggestion and drilled out 1mm/40thou hole in the restrictor in the block that pressurizes the oil tank. Afterwards, I took the boat out for a spin, started rough but cleared quickly just idling around near the jetty, took off out around the lake, idling, slow, fast, on, off etc, it was running the best it has since I've owned it, perfect! I tried to get it to misbehave but it was running crisp and clean, awesome! Pulled the boat in and parked it up...................................... BUT... a week later we took the boat out again and it was up to its same old tricks.

This time though i was armed with more info from reading similar posts to mine. I checked to see if the trim/tilt had anything to do with how it ran... IT DOES!

With the motor up, it idles nicely and will seem to idle away happily all day, when i drop the motor to take off it starts running as described above, missing, coughing, smoking etc.

Does anyone have any more things i should look at? Im thinking some kind of problem with the vapor separator tank? Fuel line maybe?

Thanks again guys, any time you're willing to spend helping me out is really appreciated.

Gene

 

[Dukedog]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Tha "T" in tha picture needs ta be replaced. Its a pressure releif valve. Shouldn't leak at all especially if ya drilled tha other fitting out like FB said. Think it should hold 'bout 4 lbs before releasing. Change tha little white one-way in-line filter in tha bleed system. Check tha rest of tha bleed system (lines and fittings). What's tha TPI setting at idle? Idle timing been fooled with? Double check tha stator and switch boxes as soon as it starts actin' up if possible.............

 

[gmacrae]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Hey Dukedog, thanks for the reply;

Tha "T" in tha picture needs ta be replaced. Its a pressure releif valve. Shouldn't leak at all especially if ya drilled tha other fitting out like FB said. Think it should hold 'bout 4 lbs before releasing.

I must say, i havent noticed the "T" pressure relief valve leaking lately, will check again though.

Change tha little white one-way in-line filter in tha bleed system.

I replaced this filter just recently, but ran the boat for a little while with it off - possible some crap made its way to the VST to cause these issues?

Check tha rest of tha bleed system (lines and fittings).

I'd love to check this all out but dont know the procedure to follow, i've got a manual for a *similar* injected merc here but it seems like you need special merc tools to carry out most of the tests - is anyone able to point me to a test procedure you can do with standard tools?

What's tha TPI setting at idle? Idle timing been fooled with?

TPI setting... well, i did set the TPI according to some specs i found a while back (using multimeter/resistance - dont have merc test tool - again). Are there some TPI/TPS specs around here that I can use to check it again? I think the idle adjust screw has been tweaked since i set the TPI last time to bring the idle up a bit - didn't think this could affect too much tho?

Double check tha stator and switch boxes as soon as it starts actin' up if possible.............

The switch boxes were the first thing a friend of mine checked out a while back (apprentice yamaha marine tech). According to his testing, they're working fine, though he did spot the faulty trigger coils (2 sparks weren't firing down low), replaced them.

 

[j_martin]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

You asked for my comment. I own a carbed V6, so I haven't been watching this thread.

I assume that there is a variable rate oil pump linked to the throttle linkage. In the book there is a setting for that linkage, usually lining up a mark at closed throttle.

1. It may be possible for the linkage on the pump to be installed wrong, invalidating the setup mark.

2. It might be possible that something is wrong with the VRO valving within the oil pump.

3. Even when they are nominal, sometimes we have to turn the turnbuckle on the linkage one turn toward lean from the base setting to get a decent idle mix.

Sooner or later someone is going to recommend you tear the oiler off and pre-mix. That works if you only use two speeds, WOT and off.

The T fitting is a valve that allows air to enter if the suction at that point exceeds 2 psi. That way, if the oil line to the deck tank gets pinched off, you have about a half hour of oil in the engine reserve tank, and allowing the air to enter allows the oil to be pumped out. It shouldn't leak, but they often do, and that is not part of this problem.

hope it helps
John

 

[Dukedog]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Tha bleed system is simple if ya don't mind a little bit of a bad taste. You SHOULD NOT be able to blow through any of tha lines or fittings but you should be able ta suck fuel/air out. Its a one way system. Don't confuse tha two hoses that go to tha center mains and tha one that goes bottom ta top with tha bleed system. Make sure you can blow THROUGH tha fittin' on tha VST that tha bleed lines attach to after tha little filter. Dought this is tha problem but is worth checkin'...........

TPI. Idle should be .20 ta .30 vdc. higher tha number tha fatter tha mix. WOT is not that critical. Be sure ta disconnect tha wires on tha sensor on tha port head............

I am refering to tha idle "timing" adjustment. Not tha linkage adjustment...........

 

[gmacrae]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

Cheers for checking my thread out John, and again Dukedog

Today i checked all 6 of the bleed vac fittings in the block, all flow out from the block and not in. The line from these into the top of the VST flows into the VST (very slowly) but not out. I guess its normal for this to be hard to blow into?

I also found some small holes in the vac lines of the bleed system so i replaced all the lines (merc hose, fuel compatible). Dunno if these holes could cause my problems but I'll try it in the next couple of days.

The oil pump linkage hasn't been touched since the engine was last running well. I checked though, and the marks line up nicely at idle and WOT. I guess if the pump itself was playing up, the problem would be more consistent?

I'll check the TPI again tomorrow hopefully. I mainly want to make sure its feedback is smooth with throttle position, we'll see. I'll post up any updates.

Cheers

Gene

 

[j_martin]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

I also just replaced the plugs (in case) and took the boat for a run. This time I used NGK BU8H (cheaper, used BUZ8H supressor plugs last time). The boat ran worse than ever on these new plugs, couldn't even get my tiny ski boat on a plane! Would free rev up to about 2500rpm only but VERY boggy and flat, enough white/blue smoke to make a bit of a scene

This reaction is exactly what would be expected. The reason that resistor plugs are used is to prevent radio frequency interference with the computer.

That said, any spark jumping somewhere could cause such interference. Also, grounds are critical on this engine. Check the cleanliness and tightness of all ground screws, and also the integrity of the crimp on the ground connectors.

As I look back over the thread, it appears that the engine idles well, but smokes and runs rough (misses) when it's in gear. The smoke would be normal if it's missing, and is from unburned fuel/oil partially burning in the exhaust system and not from too much oil. That said, what makes it miss when it's warm?
You need compression, spark, and fuel to fire. One is weak or missing under the circumstances of the failure.
1. Check compression when the engine is warm and mis-behaving. Either it's good, or you have intermittently sticking rings.

2. When it's in the hit and miss mode, put a timing light on the spark plug wires one at a time and see if you can determine which is missing. If you find one missing, swap coils around to try to move the problem. If you can't, it's in the switchboxes, stator, or trigger. Any pattern of failure you come up with would help to isolate the faulty part. Sorry folks at the dock, yer gonna have to eat my smoke while I figure this thing out. If this were mine, I'd also put an oscilloscope on the primary coil wires one at a time. It will show a misfire, but also if the plug is firing into a cylinder that doesn't respond. Normal compression will suppress the voltage at firing time. A dead cylinder will have a higher voltage. You might be able to discern that fact with a DVA also. In this case, high is bad.

3. Last is marginal fuel delivery. If all else fails, send the injectors out to be cleaned and flow tested. Some consider that an annual maintenance item anyway, especially if they have a lot of expensive parts in their engine. Item 1 and 3 could be related as low fuel flow will damage a piston. Before you do this, you should do a WOT-kill sequence on it and then inspect the piston tops through the spark plug holes. They should all have the same pattern of wetness. A dry clean cylinder would be under fueled.

Another item that affects idle much more than anything else is the reeds. Getting to them is somewhat time consuming, but well within the realm of the shade tree mechanic.

hope it helps
John

 

[gmacrae]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

This reaction is exactly what would be expected. The reason that resistor plugs are used is to prevent radio frequency interference with the computer.

Great. I questioned the guy at the local merc workshop when i got the plugs, he said they'd be fine.

That said, any spark jumping somewhere could cause such interference. Also, grounds are critical on this engine. Check the cleanliness and tightness of all ground screws, and also the integrity of the crimp on the ground connectors.

Will definitely do this. I'm hoping this is where the problem lies, a few of the connectors do look past their use-by. I'll replace wires and connectors and scuff up contact points.

As I look back over the thread, it appears that the engine idles well, but smokes and runs rough (misses) when it's in gear. The smoke would be normal if it's missing, and is from unburned fuel/oil partially burning in the exhaust system and not from too much oil. That said, what makes it miss when it's warm?
You need compression, spark, and fuel to fire. One is weak or missing under the circumstances of the failure.
1. Check compression when the engine is warm and mis-behaving. Either it's good, or you have intermittently sticking rings.

The compression has been checked and came up perfect. Didn't think of an intermittent sticking ring tho, ill try take the compression tester with me next time on the lake.

2. When it's in the hit and miss mode, put a timing light on the spark plug wires one at a time and see if you can determine which is missing. If you find one missing, swap coils around to try to move the problem. If you can't, it's in the switchboxes, stator, or trigger. Any pattern of failure you come up with would help to isolate the faulty part. Sorry folks at the dock, yer gonna have to eat my smoke while I figure this thing out. If this were mine, I'd also put an oscilloscope on the primary coil wires one at a time. It will show a misfire, but also if the plug is firing into a cylinder that doesn't respond. Normal compression will suppress the voltage at firing time. A dead cylinder will have a higher voltage. You might be able to discern that fact with a DVA also. In this case, high is bad.

This was done at first, one or two pots were showing high voltage... i think it was put down to plugs being fouled because the compressions were good... cant quite remember. Ill go back to this if i dont get anywhere checking ground connections and TPI.

3. Last is marginal fuel delivery. If all else fails, send the injectors out to be cleaned and flow tested. Some consider that an annual maintenance item anyway, especially if they have a lot of expensive parts in their engine. Item 1 and 3 could be related as low fuel flow will damage a piston. Before you do this, you should do a WOT-kill sequence on it and then inspect the piston tops through the spark plug holes. They should all have the same pattern of wetness. A dry clean cylinder would be under fueled.

I had the injectors ultrasonically cleaned a few months ago, he said they were already flowing quite evenly. I replaced the injector o-rings while they were out but didnt to a couple of other o-rings on the fuel rail, wonder if i should pull it all back out and do the lot?

Another item that affects idle much more than anything else is the reeds. Getting to them is somewhat time consuming, but well within the realm of the shade tree mechanic.

hope it helps
John

The reeds haven't done much work at all. They were replaced when the engine was rebuilt before the last owner bought it. The last owner used it for about 6 months then moved to australia, left the boat with his parents. After a year sitting in the garage he decided to sell it. I talked to the guy that built the engine before i bought the boat (big merc dealer/workshop). He's an old pro and has been real helpful on the phone but he's 5 hours drive away, i'd take the boat to him if i could.

Are there any other reasons the fuel/oil system could be affected by tilting the motor? I've seen someone mention water in exhaust ports, didnt quite get what they meant but is it a possibility?

Well you've given me some things to look at anyway, im off out to the shed to get stuck in - let ya know how i get on

Gene

 

[j_martin]

Re: 89 Merc Laser 220 XRi - fouling or over-oiling

This was done at first, one or two pots were showing high voltage... i think it was put down to plugs being fouled because the compressions were good... cant quite remember. Ill go back to this if i dont get anywhere checking ground connections and TPI.

High voltage simply means it isn't firing. It could be compression, or some other reason. The interesting thing about a 2 cycle is that bad reeds will not show up as low compression, but they will prevent a fresh charge from flowing into the cylinder, and cause a misfire that way. A fouled plug shows low voltage and on a scope extended rise times.

If the reeds were replaced, and the cages were not lapped, that could be yer problem. Keep this possibility in reserve.

Great. I questioned the guy at the local merc workshop when i got the plugs, he said they'd be fine.

I think at this point yer knowledge is surpassing his. The noise suppression bit is common knowledge.

hope it helps
John