WARNING!!! To all VRO users

[Beernutz]

I've owned my 2001 Johnson 150 since new. Other than the water pump, it hasn't had a screw or bolt turned, and has run perfectly .... until recently. Due to family health problems, it has been used very little over the past 3 years. After a 6-month rest, I ran it. It was dropping a cylinder primarily at low to mid range, but screamed just fine at WOT. The miss got progressively worse.

Suspecting carburetors, I rebuilt all six carb bodies and both throttle bodies. The problem persisted. Human nature made me run it at WOT to try to blow it out. No help. I isolated the miss to #6. After exchanging carb bodies from #2 & #6, swapping spark plug wires, and top and bottom coil packs, it was still #6. I had a similar situation with a '96 Johnson, which turned out to be a failed bottom crank main seal allowing water to intrude and foul the plug. But this time there was no evidence of water on the plug.

I was ready to throw in the towel,when I resorted to this board. I found a post by "Johnalcon" from 7/25/07. Identical problem! After an exhausting diagnostic search, he learned that the fuel pump diaphragm in his VRO pump had perforated. The pump gets its pulse from the #6 crankcase. When the diaphragm springs a leak, raw gas migrates to the pulse side, runs down the pulse tube, thru the pulse limiter, and enters the crankcase. The overly rich fuel charge fouls the #6 plug.

I pulled my VRO pump, disasembled it, and found a leaking diaphragm. I've ordered a new pump, and hopefully it will fix my problem .... OR WILL IT?

That #6 cylinder, with raw gas being intruduced around the carburetor, was probably running at a fuelil ratio in excess of 100:1 at low to mid-range. At WOT, who knows what the ratio was?! This condition could seriously damage or destroy the power head. Seizure and/or thrown rod come to mind, in addition to main seal damage from lack of lubrication. I could be expecting more trouble, like a catastrophic failure, later. Hopefully, I didn't run it too long or too hard in this condition. But .... what if?

My WARNING is due to the insidious nature of this failure. You won't get any alarms, because the oil pump side of the VRO is still operating adequately. The other 5 cylinders are perfectly happy, but #6 is getting trashed!

I'd like to see a response from some of the techs out there. How often is it the #6 (or bottom cylinder of other VRO equipped engines) that throws the rod or seizes?

If anyone experiences a similar misfiring problem, I would advise them to shut it off immediately, and check the VRO pump. The bottom spark plug should also show evidence of running rich (black, sooty plug).

Another reason to not trust the VRO system?

 

[daselbee]

Re: WARNING!!! To all VRO users

I have been talking with a contributor via phone...and he has just experienced what I call the "infamous lean sieze" problem.
He just got his compression testing done...all at 100 psi except #6, which was down at 60.
I immediately wondered about the pulse hose...

Your explanation is VERY informative.
Thanks.

 

[tashasdaddy]

Re: WARNING!!! To all VRO users

1st your 2001 motor does not have a VRO, VRO2 pump, it has an OMS pump, get the terminology correct.

 

[Beernutz]

Re: WARNING!!! To all VRO users

I beg your pardon, Tashasdaddy.

But it does , indeed, have a VRO2 pump. What's an OMS pump?

 

[walleyeboater]

Re: WARNING!!! To all VRO users

I have a '98 115hp ' rude.seized up. 1st mechanic did not mention vro pump. 2nd mechanic said 1st thing is r&r vro pump. I do not know if he meant change it to a different pump, or just change it for another one. My rig does not have oil injection, mix it myself, but still has vro pump as I understand it. Hoping to switch to a '85 GT150hp, if a can swing the funds. fresh rebuild on the GT150- soon as I give him the ok to do it.

 

[jonesg]

Re: WARNING!!! To all VRO users

Theres something about the tendency to try running a poor running outboard at WOT with the hope that it will clear out.

Every time I've tried with a car it throws something, timing chain etc.

 

[Beernutz]

Re: WARNING!!! To all VRO users

I know where you're comin' from, Jonesg. But, we just can't learn. It surely did run good at WOT, though. But, kinda hard to dock her at that speed.

 

[TimmyC]

Re: WARNING!!! To all VRO users

I have had a issue with this, I have a 1990 150 gt. It would idle good, and run good the first and second take off. Then it was like it fouled a plug and it wouldn't get over 3000rpm and sometimes wouldn't even do that. The bulb wouldn't get really hard but would have some good psi on it. So I really didn't think that it was the fuel vro pump.

When the prob started I rebuilt all three carbs,compression was 100 on all 6, new plugs & wires, all 6 coils, a new cdi box, changed the fuel and remixed (I don't use the oil side of the vro pump) and still the problem was there. So I was done messing with it and took it to a local tech.

The first thing he said was the vro pump, and that if you use it only on the fuel side you prob only get acouple of yrs out of the pump. I really didn't believe him cause I am hard headed. Well to make this story short I ordered one today. If this dont fix it I am going to put it on ebay!

 

[kenmyfam]

Re: WARNING!!! To all VRO users

I beg your pardon, Tashasdaddy.

But it does , indeed, have a VRO2 pump. What's an OMS pump?

OMS = Oil Metering System as far as I know.
Did you do a compression check on all 6 cylinders ??
My VRO pump started failing last summer. I changed to a pre-mix pump and mix my own now.

 

[seahorse5]

Re: WARNING!!! To all VRO users

I pulled my VRO pump, disasembled it, and found a leaking diaphragm. I've ordered a new pump, and hopefully it will fix my problem .... OR WILL IT?

For 1998 and later pumps, the factory makes repair kits to replace diaphragms.

That #6 cylinder, with raw gas being intruduced around the carburetor, was probably running at a fuelil ratio in excess of 100:1 at low to mid-range. At WOT, who knows what the ratio was?! This condition could seriously damage or destroy the power head. Seizure and/or thrown rod come to mind, in addition to main seal damage from lack of lubrication. I could be expecting more trouble, like a catastrophic failure, later. Hopefully, I didn't run it too long or too hard in this condition. But .... what if?

My WARNING is due to the insidious nature of this failure. You won't get any alarms, because the oil pump side of the VRO is still operating adequately. The other 5 cylinders are perfectly happy, but #6 is getting trashed!

This fuel leakage from a torn fuel pump diaphragm has been a problem since the late 1950's when pumps replaced pressure tanks. Yamaha has the problem quite often and sometimes with dire consequences to the affected piston.

 

[Beernutz]

Re: WARNING!!! To all VRO users

OMS = Oil Metering System as far as I know.
Did you do a compression check on all 6 cylinders ??
My VRO pump started failing last summer. I changed to a pre-mix pump and mix my own now.

Thanx, Ken. I've been "away" for a couple of years, and wasn't aware of the VRO/OMS controversy. Since my original post, I've read a few others, and it seems there is some sort of an ongoing OMS terminology crusade out there. My appologies to all. My owners manual refers to it as the "oil injection system". My Factory Service Manual says it's a VRO2. And all the parts guys I talked to call it the "4-wire VRO pump". Just for kicks, I called a couple of local dealers, and asked if they had an OMS pump. Both times, I got, "Whassat?". I hate to appear Neanderthal, as the Admiral suggested, but in the interest of confusion relief, I'll bow to conventional wisdom, and call it a VRO pump in public. But, hereafter, on this board it'll be OMS.

Compression is right around 100 on all 6, with a variance of less than 2 psi.

I think that (after spending $400 on a new OMS pump) I'll continue with the oil injection for a couple of years, then change to pre-mix. After all, this OMS pump worked trouble-free for 8 years! That's pretty good service. But it would be a shame to ruin a good motor like that. I could've bought a new diaphragm for 40 bucks, but sprung for the whole OMS pump.

My purpose was to warn people that if they're using the oil injection, they can experience catastropic damage, without ever hearing an alarm .... And to try to outline the symptoms to watch out for. That's all.

 

[kenmyfam]

Re: WARNING!!! To all VRO users

I think it is an excellent post that can relate to any oil injection system. Many will read it and learn from your experiences.

 

[Beernutz]

Re: WARNING!!! To all VRO users

1st your 2001 motor does not have a VRO, VRO2 pump, it has an OMS pump, get the terminology correct.

Oops, pardon me. I inadvertently promoted the Chief to Admiral.

 

[kenmyfam]

Re: WARNING!!! To all VRO users

Oops, pardon me. I inadvertently promoted the Chief to Admiral.

I think you actually demoted the chief !!!!

 

[seahorse5]

Re: WARNING!!! To all VRO users

After an exhausting diagnostic search, he learned that the fuel pump diaphragm in his VRO pump had perforated. The pump gets its pulse from the #6 crankcase. When the diaphragm springs a leak, raw gas migrates to the pulse side, runs down the pulse tube, thru the pulse limiter, and enters the crankcase. The overly rich fuel charge fouls the #6 plug.

That is not quite true. The "VRO"-OMS pump has an air diaphragm that is part of an air motor that powers the fuel pump diaphragm and the oil pump assembly. If it gets a hole in it, the motor runs poorly but no fuel is present on either side of the air diaphragm. The #6 cylinder crankcase pulse only powers the air motor diaphragm and there is no fuel in that area that can get into the crankcase and flood the cylinder like it can with a traditional 2-stroke fuel pump.

The fuel pump chamber is sealed off from the air motor chamber and the center of the fuel pump diaphragm contains 'flapper valves' or check valves, so gasoline normally flows through both sides of the fuel pump diaphragm. Even if it gets a hole in it, the fuel does not go anywhere else and the engine will run poorly due to reduced fuel pressure and flow.

Here is an article and a cut-a-way of the pump assembly and it dispels the myths and explains the internal workings of the "VRO". Most "mechanics" are not familiar with the pump or trained in it's operation but are quick to blame it for almost any engine problem.

http://continuouswave.com/whaler/reference/VRO.html


Yep, the OMS pump is commonly referred to as a VRO because the OMS version was not built until '96 and for the 12 years prior to that it was a VRO.

 

[daselbee]

Re: WARNING!!! To all VRO users

Well now,,,,Seahorse....you just said that the whole premise of this post is not true.
I am now very confused about what to believe.
I just saw a 200 looper with #6 seized....and it made perfect sense to me that raw fuel could dilute the fuel/oil mix thru the pulse hose.

Anyone else please weigh in....

 

[Beernutz]

Re: WARNING!!! To all VRO users

Thanx, Seahorse. But, I beg to differ. I disassembled my OMS pump, and the pulse side of the diaphragm was soaked with fuel. The air motor is actuated by vacuum pulse. If there is a perforation in the diaphragm, that vacuum will suck whatever is on the other side of the diaphragm right through it .... in this case, un-premixed fuel.

Poke a hole in an old diaphragm and reassemble the pump. Reinstall it, except for the pulse line. Put a plastic tube on the pulse fitting of the OMS pump, and suck on the tube after you prime the pump. Then write back and tell me you didn't drink a Molotov Cocktail. That's the stuff that bypasses the carburetor and gets dumped into the #6 crankcase. BTW, I performed this foolish little test before I removed the pump, and still have the taste of gasoline in my mouth. Budweiser won't even touch it!

You're preaching to the choir. You'll note that I used the OMS pump for 8 years without a hitch .... and I'm replacing it with a new one! Sounds like loyalty to me. But it's not right to give people a false sense of security about these things. If they're using the oil injection without premix, they need to be aware of the symptoms that I've tried to describe. At first, it acts just like contamination of the calibration pocket of the throttle body, affecting only the low speed circuit. After I foolishly tried to "clear 'er out" by WOT operation (where it ran perfectly), the malfunction got progressively worse, eventually involving all throttle positions below WOT. Obviously (at least to me), the additional stress of the WOT episode exacerbated the leak. The insulator of the #6 plug was black. The other 5 were chocolate brown. I replaced the plug with a new one, and ran some more tests. By this time, the fuel dumping had become so bad that the new plug never fired. It fouled immediately. When I checked it, it was soaked with gas, but otherwise looked like new.

That's my story .... and I'm sticking to it. If my new OMS pump (actually, I ordered a "4-wire VRO pump", because that's all they had listed) ever shows up, I'll post the results. Right or wrong, I'll let y'all know.

 

[Beernutz]

Re: WARNING!!! To all VRO users

After closer inspection of the disassembled OMS pump, I think I've found what started the entire episode. The seal on the pushrod between the air motor and the fuel pump chamber is torn. This allowed raw fuel to migrate into the air motor. Nevertheless .... same result, same symptoms, and same potential damage to a perfectly good motor. Premix would have avoided this.


So, Seahorse is correct. There "shouldn't" be fuel on either side of the air motor diaphragm. But "The One Horse Shay" doesn't exist .... and Murphy does!

If you're hanging in a life vest, does it matter whether it's a Tiger Shark or a Bull Shark that's circling around you? I've been eyeball-to-eyeball with an 8-10 ft Bull Shark that charged over my transom, and ripped the belly out of a 7 ft Tarpon that I was trying to release under the Bahia Honda Bridge a few years ago. Believe me .... it doesn't make any difference!

 

[daselbee]

Re: WARNING!!! To all VRO users

The air motor is actuated by vacuum pulse. If there is a perforation in the diaphragm, that vacuum will suck whatever is on the other side of the diaphragm right through it .... in this case, un-premixed fuel.

I wonder about that statement.....about the air motor being actuated by the vacuum pulse....
It seems to me that there would be more pressure to activate the air motor if it actuated during the power stroke of the #6 piston. At that point, the reeds are closed, and the crankcase is pressurized. This would provide a strong positive pressure pulse to the pump.

On the other hand, if a vacuum pulse is what activates it, on the compression stroke of #6, it would seem to me to be a weak vacuum, because the reeds are open, the carb throttle plates are open, and plus, there would be a difference in vacuum available to run the pump at idle vs. WOT for instance. High vacuum at idle, and less vacuum at WOT, it would not be constant.

I always thought the pump was actuated by crankcase pressure, not vacuum.
Set me straight, please.

 

[Beernutz]

Re: WARNING!!! To all VRO users

Excellent analysis, daselbee. Perhaps I over-simplified it. The pump appears to operate on both vacuum and pressure, via an internal check valve. I guess I was concentrating on the pulse that I believe was delivering the excess fuel to the crankcase. The 2-stroke engine will produce moments of both during its cycle. Compression will be relieved when the transfer ports open, and as you mentioned, the reed valves will reduce the vacuum. I think it might surprise you to see how much vacuum it takes to open the reed valves, and it only takes a moment of vacuum to operate an air motor. At high RPMs, all the rules change due to the inertia of the air running thru that thing. In my experience, vacuum (atmospheric pressure) is a very powerful force, and much simpler to manage than pressure, which can blow hoses off. So I assumed that was the primary motivating force.

This pump is designed such that the vacuum pulse port is situated near the bottom of the vacuum case. Therefore, even a small amount of fuel accumulating there will travel down the pulse hose and into the crankcase. When I opened my pump, the pressure side of the air motor diaphragm was all but full of fuel, and the vacuum side was soaked. As I mentioned, when I sucked on my plastic tube affixed to the pulse fitting of the pump, it tried to kill me, and it would not hold a vacuum.

It's looking to me that this little seal may be the weak link in this thing, and may very likely be responsible for a large number of the failures that have plagued the reputation of the pump. The inner lip of the seal on the fuel pump side is torn about half-way around, and looks like garden-variety deterioration. Note that TimmyC's tech told him that premixing and using only the fuel pump section tends to shorten the life of the pump. Could the oil be incompatible with the seal material?

If one is using premix, he would only experience a chronic fouling of the #6 (or bottom) plug. If he's using the oil injection like I was, the consequences could be far more dire. Sounds like an easy decision, doesn't it? "I'll trade a new spark plug for a new power head any day." But, I'm a sucker for punishment, so will continue with the oil injection .... now that I think I know what the signs of danger are. Maybe I'm getting the cart before the horse, but like I said, I'll post the results after I install the new pump .... good, bad, or indifferent. And I've made no other changes since removing the pump. I'm so encouraged by Jonalcon's thread beginning on 7/25/07, that I'll even leave the fouled spark plug in the hole. It's worth the time to read it.

How many techs have opened up the pump on a blown engine that was using the oil injection and inspected the pushrod seal for damage. I'm thinking that, if we could all abandon our personal agendas and work together, maybe we could isolate the cause of the failures. Then we could put pressure on the manufacturer to correct it. This could be it.

I'd still like to hear from the techs concerning the frequency of bottom cylinders puking, in comparison to the others in motors that were using the oil injection.