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Should i run EFI dry

B

boebs

Member
Hi All

Have a XRI 220hp Mer

Hi All

Have a XRI 220hp Merc that i have removed the oil injection from. My question is after the weekends boating should i run it dry (would only use it again about two to three weeks later)?
thanks
Bruce
 
"Bruce, it's not normally

"Bruce, it's not normally advisable to remove the oil injection from an fuel injected motor. The injectors were not designed to handle mixed gas.

But that's a mute point now.

Normally, you would not run an EFI out of gas because the oil is injected into the intake and that would cause excess oil to the cylinders (with no gas) which would cause a hard start next time out.

In your case I don't think it matters either way. I suspect that the lifespan of your injectors is already very short. They are probably going to gum up on you no matter what you do.

To try and save them as long as possible you should not run standard 2 stroke oil. A fully synthetic or oil designed for Direct Injected motors (ya the stuff that's over 30 bucks a gallon) is probably what you should be running.

Is there any particular reason the oil injection was removed? It's kinda a "must have" system for that particular motor - only carburated motors should run mixed gas..."
 
"Good point, Graham, for diese

"Good point, Graham, for diesel injectors lock up pretty quickly if someone uses gas instead of diesel (and my son-in-law can attest. The repair bill for his Daddy's Mercedes ran into many figures!)

Jeff"
 
"It may seem expensive at firs

"It may seem expensive at first to replace/repair an oil injection pump (or whole system), but in the end the cost of new injectors and possibly a fuel rail will quickly add up to far more..."
 
"Thanks Graham & Jeff,

"Thanks Graham & Jeff,

My goodness but you have painted a horrible picture here. I was advised by a couple of people that the oil pump was driven by a PLASTIC GEAR on this model and that it could strip at any time without any warning. This would then lead to me driving the boat without any oil being injected into the system thus Cooking the entire motor. I was advised that as a preventative measure it was safer to remove the injection system and premix the fuel myself. I was also told that once this motor runs without oil it is basically toast. So what are my alternatives\options here now ? Do i run it with the fully synthetic oil and hope for the best, or reinstall the oil injection and hope like hell it keeps pumping??
Thanks
Bruce"
 
"Had that same question asked

"Had that same question asked of me last night in my CG Aux boating class. Man just bought a 1999 Merc 115 and has no history on the motor. He's worried that the oil injection system might not work and...poof!

I advised him to run BOTH--premix the gas at 100:1 ratio, and keep the oil tank full. Also, keep his eye on the oil level in that tank, to see if it's being consumed.

I know--it might smoke a bit, but that's "good" smoke; burnt piston smoke is the bad kind!

Jeff"
 
"Absolutely the correct advice

"Absolutely the correct advice.

I'm not sure where the big doubts came about the oil injection.

Yes, the auto-blend system was a nightmare.

But OMC VRO2 which has been on motors now for over 20 years and Merc's gear driven system just don't fail anywhere near how often they get blamed.

You hear, my oil injection failed and toasted my number 2 cylinder - naaaaa, wrong, if the oil injection failed "all" the cylinders would be toast - you had a dirty carb etc etc.

Mixed gas motors toast cylinders all the time, and overheat, and fry ignitions - and none of that has anything to do with an oil pump or lack of one.

If you have a carb'd motor and will sleep better at night disconnecting the oil injection, go for it - but and EFI and a DFI is a different beast. The EFI is not advisable and a DFI just can't run mixed gas.

Hmmm, you never hear about a 4 stroke owner ripping out the oil pump and trying to figure another way to oil the system?????

What, we can trust a 4 stroke oil pump (from the same builder) without question, but somehow think the minute we run the oil pump on our 2 stroke it's going to blow up????"
 
"So Graham,
Is what you sayin

"So Graham,
Is what you saying, if i can find all the bits and pieces put it all back, and make sure all is 100% and monitor oil consumption very closely???
Or could the injectors be toast already. It still goes like a beast
biggrin.gif
"
 
"Personally, I would really tr

"Personally, I would really try and restore the Oil injection - it is a good system.

Yes, has plastic (or maybe nylon) gears. Yes, there is a guy or two out there that had one strip and had a problem, but there are thousands of these out there - it's just not a "chronic" problem.

And why did the gear strip? Maybe the pump seized and that stopped the shaft, stripping the gear - was that the gears fault, or a poor storage practice on the part of the owner - a pump with no oil in it is going to come to a grinding halt like anything else.

So yes, I would put it back together and hope that the injectors will be fine - if not, they will go at some point alot sooner than they should.

And yes, definately monitor the oil consumption.

And is my advice all "in theory", no, I have a 1986 140 horse OMC, and yes, it's VRO pump is still very much attached. I had the opportunity to scrap the VRO - it developed a leak, but no, even though it's a carb motor, I replaced the pump.

When it comes out of winter storage, I put a mark on the oil tank and run 100:1 mixed gas until I see that the oil has moved.

She is now 23 years old and no blow ups yet, although I do think I will tear her down and hone the cylinders and give her new rings (at least) - I want it to last for at least another 20 years now (have you seen the cost of a new motor)
"
 
"seems to me that an EFI engin

"seems to me that an EFI engine with injectors would run fine on mixed gas, because it is mixing oil with gas at the fuel pump and that dont hurt the injectors. right or wrong??"
 
"No, it mixes the oil/gas and

"No, it mixes the oil/gas and air at the intake.

The oil is directly injected, just in front of the reeds. The (gas) injectors spray their gas directly into the intake or fuel rails (depending on design), so it's always straight gas going through the injectors.."
 
"Graham,
are you saying that

"Graham,
are you saying that the gas is injected above the piston, so to speak, like a 4 stroke diesel, and therefore if premix was used, would only provide cylinder lubrication and none to the crankcase, as it's not passing thru the "bottom end" first?"
 
"No, not in a (standard&#4

"No, not in a (standard) 2 stroke EFI.

There are now 2 different injected 2 strokes out there.

The (traditional - for lack of a better word) where the carbs have simply been replaced with either a throttle body or a fuel rail - both of which feed an air plenum (or intake, or vapour separating tank VST) which then feed through the reeds into the lower crank case.

In those designs the oil is "injected" at the plenum and then the gas, oil and air mix is sucked through the reeds. So at the gas injector it's pure gas - the mix occurs later.

In the Direct Injected models (Merc Opti's, OMC Etec's, Yami's HPDI and Tohatsu's TLDI models) There is a (two stage) gas injection system.

Those use a fuel rail/air rail and two injectors for each cylinder. The first is a traditional gas injector which gets the gas into the fuel rail. Compressed air (from the air rail) then injects the straight gas through a second injector (the direct injector) directly into the head of the cylinder.

On the DFI's, the oil, is likewise injected into the plenum (or intake or VST - choose your term) and an air/oil mix is sucked through the reeds into the lower crankcase.

Regardless of which technology is in place, the gas running through the gas injectors is not mixed with oil...

The only models that mix the gas/oil at (or near) the fuel pump are oil injected "carb" models."
 
"Sorry Greg,

To answer your

"Sorry Greg,

To answer your question more directly -

If it's a DFI model, then yes, the same as the diesel you mention. Disconnecting the oil injection on a DFI and running mixed gas will cause the engine to seize in very short order - no oil anywhere except the cylinder head.

And on a (regular) EFI 2 stroke, mix can be run but will eventually kill the injectors.

So basically, with any injected 2 stroke, it is not wise to disconnect the gas and "run it out" because the oil keeps pumping and will cause a hard start next time out by flooding the reeds/lower crankcase with oil...

That also applies to carb models with variable oilers - likewise the oil will continue to flow to the fuel pump after the gas is cut off and will flood the carbs with oil."
 
Don't run dry or keep brea

Don't run dry or keep breaking fuel pumps.


Plastic gear problem was the coupler.That pump had problems in the '80s. That was fixed. The coupler had problems in the '90s. They took it down .010" It squeaks in the block mostly due to alcohol swelling it. A hard spot in the pump will cause this. That should get replaced if you are doing the gears. 2.xL gear in the middle if the crank adds to the problem.
 
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