Faulty check valves on oil injection system causing smoke?

[hkeiner]

I have a 1996 150 HP Mercury OB (serial OG397853). It starts fine when cold, runs well at WOT, and idles well (without smoke) when I slow down to low speed or neutral after running at WOT. However, the motor does not like to start again in neutral when the engine has been turned off for a few minutes (or more) when the engine is warm. Here are the symptoms I have identified:

1) It won't start in neutral and seems to be either flooded or overloaded with oil.

2) I have to advance the throttle lever to medium/low throttle (with side button pushed in so it does not go into gear) for it to start

3) I have to keep it running at medium/low throttle until the gas/oil burns off (say for 15-30 seconds) with a lot of smoke .

4) The engine dies if I pull the throttle back to idle position and I didn't wait until the heavy smoke stops coming out of the exhaust at medum/low throttle.

5) All six spark plugs are equally very oily when I remove them.

6) There is an accumulation of oil at the bottom of the cowel below the carbs, as if oil runs out of the carb barrels when the engine is tilted forward.

7) None of the gas or oil hoses appear to be leaking.

8 ) The bottom of all six carb barrels are oily with some of them having an accumulation of oil on them

I have read some old posts suggesting that excess oil may being forced into the carbs (after the engine is turned off) if the pressure in the oil injection system is not automatically relieved due to a faulty check valve. It was not clear, however, how to fix this problem or which check valve may be the culprit. Based upon the system diagrams for my motor, there appears to be three check valves in the fuel/oil injection system. None of these, however, are described as being for the purpose of relieving the oil injection system's pressure. The three check valves are described as having the following purposes:

A) One 2psi check valve avoids a vacuum in the top reservoir if oil flow to the reservoir is obstructed.

B) The second 2psi check valve is to avoid fuel being forced into the oil lines.

C) The third check valve regulates the crankcase pressure going to the remote oil tank.

Any thoughts on this? Should I just replace all three check valves and see what happens? I would like to avoid spending the money to get the carbs rebuilt until I have tried some easier/less expensive/more likely solutions myself.

 

[Silvertip]

Re: Faulty check valves on oil injection system causing smoke?

If the float in one or more of the carbs is not sealing, fuel (and oil mixture) can run out the throat of the carb when the engine is tilted up. It can also tend to flood the engine at slow/idle speeds. If you think the oil system is ok, I'd rebuild the carbs to eliminate them as the cause (especially if it has not been done recently or at all).

 

[gss036]

Re: Faulty check valves on oil injection system causing smoke?

I would be leaning towards the carbs also, but you need to determine if the check valves are working.
The one under cowling on the front of the engine will allow oil to leak into the cowling if now working properly. There is a short piece of tubing (at least on mine) that is open. Place a small clear plastic water bottle under the end of tubing to see if oil is collecting. Drill a small hole in the cap of the bottle so the hose has tight fit and will stay put.
After you shut the engine off, wait about 5 minutes and then loosen the cap on the oil tank(same tank as above)and see if oil will run out of the loose cap, is so, then the 2 psi check valve which controls the pressure is not relieving properly and allowing oil to forced into the oil pump and into the carbs. (the pressure is supposed to relieve) In reality, the floats should prevent that, but that would account for all the oil in the carbs and the flooding and oily plugs. Also take a look at the 3 gal oil tank on the boat to see if it is bulging from over pressurizing. Just some thoughts about the system and maybe a simplier fix than carb rebuilds.

 

[hkeiner]

Re: Faulty check valves on oil injection system causing smoke?

After you shut the engine off, wait about 5 minutes and then loosen the cap on the oil tank(same tank as above)and see if oil will run out of the loose cap, is so, then the 2 psi check valve which controls the pressure is not relieving properly and allowing oil to forced into the oil pump and into the carbs. (the pressure is supposed to relieve) In reality, the floats should prevent that, but that would account for all the oil in the carbs and the flooding and oily plugs. Also take a look at the 3 gal oil tank on the boat to see if it is bulging from over pressurizing. Just some thoughts about the system and maybe a simplier fix than carb rebuilds.

Gary,

Thanks for the reply. Yes, I do want to make sure that the oil injection system is not over pressurizing before getting the carbs rebuilt. I'll check for over pressurization by seeing whether there is any residual pressure in the reservoir tank (under cowling) 5 minutes after turning off the engine and whether the remote 3 gallon tank shows signs of any overpressurization .

It is not yet clear to me which defective check valve could be the culprit, if over pressurization is occuring. The 2 psi check valve I believe you are refering to functions to prevent a VACUUM in the reserve tank and not to relieve POSITIVE PRESSURE from the reserve tank (I labeled as valve A for identification purposes). I interpret that to mean that the check valve, if working properly, would let air IN to the sytem (if the vacuum exceeds 2 psi) and would never let air OUT of the system at any time. Also, this valve is connected to the oil line and there is no air on the system side of the check valve to be released. If this valve is not working properly (i.e., it did not allow air to enter the system if vacuum exceeds 2 psi), the valve would allow a VACUUM to occur in the reserve tank rather than an overpressurization situation. Have I got this right or are your refering to check valve B, check valve C, or another valve that I have not yet identified?

I really appreciate the advice and information that I get on this forum. It adds to what I have learned by reading the three service manuals I have already bought (Mercury's, Seloc's, and a third on CD). All three vary somewhat but none of them, however, discuss OVER pressurization problems or how over pressurization is regulated. While I am familiar with working on car engines, this 2 stroke Mercury outboard is new to me and I have a lot to learn about troubleshooting problems. I figure knowing exactly how the oil injection system works, pariculary in the area of controlling the pressure in the system, is a good way to improve my troubleshooting expertise and solving my problem.

Thanks again for any clarification on how a defective check valve could cause overpressurization and which one it would be.

Description of check valves (per service manuals and other sources):

A) If oil flow to reservoir is obstructed and injection pump continues to pump oil, the 2-PSI valve will open to allow air to enter reservoir to prevent a vacuum.

B) This valve prevents gasoline from being forced into the oil lines.

C) Crankcase pressure with one way check valve.

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

 

[gss036]

Re: Faulty check valves on oil injection system causing smoke?

It my understanding that the "Crankcase pressure 1 way check valve" controls the pressure in both the oil tanks.
#5 prevents vaccum, but may also leak oil of of the vent hose.( I just had to replace mine this year as my cowling was getting oil all over) That is why I told you about the water bottle for checking to see if oil was coming out.
You may want to check all the small oil hoses shown in the diagram for the oil injection system. Make sure they are soft/(not brittle) and plyable. If one of them fails, you will cook the engine as the alarm system does not monitor oil at the point. It monitors the on board tank for low oil and the oil pump for rotation.

 

[hkeiner]

Re: Faulty check valves on oil injection system causing smoke?

Gary,

Thanks for the additional clarification. If I understand your comments correctly, over pressurization of the oil injection system or persistant pressurization of the system after motor shutdown could be caused by a defective check valve part number #21-878105 (Refr #14 on the Mercury Parts List), and replacement of this check valve would be in order. The other check valves in the system, if they were to be defective, would NOT be likely causes of over pressurization or persistent pressurization of the system. Have I got that right?

Further, I will monitor the #5 check valve to see if it is leaking oil into the cowling. Perhaps I have two defective check valves at the same time. All of the oil injection system hoses look OK and do not appear to be leaking.

Thanks again,

Hal

Parts List:

http://i27.photobucket.com/albums/c169/hkeiner/Mercury Oil Injection/MercuryPartsList.jpg

Parts Diagram:

http://i27.photobucket.com/albums/c169/hkeiner/Mercury Oil Injection/Mercurypartsdiagram.jpg

 

[gss036]

Re: Faulty check valves on oil injection system causing smoke?

You have it. If you are running your boat now, you can just loosen the cap on the 3 gal boat tank when you shut down. If that is the problem, then you should eliminate a lot of the smoke.

 

[hkeiner]

Re: Faulty check valves on oil injection system causing smoke?

Gary,

The logistics is not optimal right now to try out the fixes right away. I just put the boat into winterized storage this last weekend (after using it during the week of Thanksgiving) and I probably will not be taking it out of storage and using the boat again until spring break time. I live in northern California but keep the boat year round at my folk's place in Lake Havasu City, AZ. Because I keep the boat far from home, I don't have a whole lot of time to tinker with the motor when I go to AZ to use the boat. My kids prefer to spend their vacation time on the water with the boat rather than watch me work on the boat in my folk's driveway.

However, when I do go down to AZ in the spring, I'll bring a replacement check valve (#21-878105 ) with me. Swapping it out with the old one should go fast. I'll also follow your tip about loosening the cap on the 3 gal remote tank after shutdown, to see what happens to the smoke.

If neither of the above steps has any impact on the excessive oil smoke, then I'll have to bite the bullet and get the carbs cleaned and floats adjusted. For me, removing the 3 carbs and tinkering with all of the small carb parts is a fearsome task for me. I worry that the motor would run worse or not at all if I mess with the carbs myself. I'll probably have to take it in to a shop for carb cleaning, if needed.

Thanks again for your advice.

Hal

 

[gss036]

Re: Faulty check valves on oil injection system causing smoke?

Hal, at last resort give it a very strong does of SeaFoam. Most auto parts stores carry, especially NAPA. I mean like one can SeaFoam in 1 gal of gas. Check the FAQ for decarbing and follow those instructions, you probably need to do it since you have so much smoke.

 

[hkeiner]

Re: Faulty check valves on oil injection system causing smoke?

Hal, at last resort give it a very strong does of SeaFoam. Most auto parts stores carry, especially NAPA. I mean like one can SeaFoam in 1 gal of gas. Check the FAQ for decarbing and follow those instructions, you probably need to do it since you have so much smoke.

Gary,

I'll give that a try too. I'll get back to you in the spring and let you know how it all went.

Regards,

Hal

 

[hkeiner]

Re: Faulty check valves on oil injection system causing smoke?

Gary,

I now fully understand the function of of the "Crankcase pressure one-way check valve" and plan to install a new one the next time I have a chance to work on the engine in the spring. This may eliminate the possible oil injection pressurization condition that I suspect I have.

In the mean time, I have a few very granular questions regardng another check valve in the oil injection system. It is part number 22-818994 (Refr #6 per Mercury Parts Express diagram) and the Mercury Service Manual describes it as "2-PSI CHECK VALVE--This valve prevents gasoline from being forced into the oil lines." The Manual does not, however, say much more about the check valve nor does it describe exactly how it works.

While I understand the general purpose of this check valve, I don't clearly understand how it precisely works and how the oil/fuel mix may be impacted by this check valve, especially if it were to be defective. I am thinking that perhaps it is an additional potential culprit that is causing my earlier described problems of getting too much oil into the oil/fuel mix after shutting down the motor temporarily after running WOT. Also, I am the type of guy that wants to know exactly how stuff works in order to properly troubleshoot problems and I also just like to know what the heck I am doing. Perhaps sometimes to the point of obsession....

I assembled the following questions that help identify what it is I am interested in finding out about this check valve. These questions may also demonstrate my current limited understanding of what this check valve does in relation to how the oil injection system works. If you (or anyone else) can provide more specific information on what this check valve does, I would very much appreciate it.

1) What does the "2 PSI" attribute of this check valve mean? More specifically:

a) What does the valve do differently when the pressure on the OIL pump side of the check valve is above or below a POSITIVE 2 PSI?

b) What does the valve do differently if the pressure on the FUEL pump side of the check valve is above or below a POSITIVE 2 PSI?

c) What does the valve do differently if the pressure on the FUEL pump side of the check valve is above or below a NEGATIVE (vacuum) 2 PSI?


2) Does the check valve limit the oil pressure (like a pressure regulator) on the FUEL pump side of the valve to 2 PSI to ensure that the oil pump does not force oil into the fuel pump or fuel line (at the T-connector) when the engine is either on or off?

4) Does the check valve ALWAYS restrict the oil/fuel mix from flowing from the FUEL pump side of the valve towards the OIL pump side of the valve, regardless of the positive or negative PSI pressure conditions on either side of the check valve?

5) What keeps the oil from the reservoir (which is under pressure at time of engine shutoff) from pushing itself into the fuel line at the T-connection when the engine is shut off? Is it dependent soley on the timely release of system pressure by the Crankcase pressure one-way check valve or do the oil pump (which is no longer pumping and may thus be restricting oil flow) or the subject 2 PSI check valve also have a role in this?

6) If the oil/gas mixing is occuring at the T-connector, are the 50:1 thru 100:1 ratios controlled by the amount of pressure in the oil and fuel lines going to the T-connector?

7 ) The description of the 2-PSI check valve is "This valve prevents gasoline from being forced into the oil lines". Does the check valve prevent this flow only when the bulb on the fuel line is being squeezed (say before cold startup) or does it also need to prevent this from occuring while the engine is running or immediately after engine shut down?

8 ) If this check valve is supposed to limit the oil pressure on the FUEL pump side of the valve to 2 psI, but due to a defective valve the oil pressure exceeds 2 PSI, could this cause oil to be forced into the fuel line at the T-connector after the engine is shut down? If so, could this result in an oil/fuel mix that has too much oil in it going into the fuel pump (and carbs) when the engine is later started? Am I on to something here or have I got this all wrong and barking up the wrong tree?



Any thoughts would be appreciated.

Hal






Mercury Parts Express Fuel LInes Diagram:

http://i27.photobucket.com/albums/c169/hkeiner/Mercury Oil Injection/MercuryFuelLinesDiagram.jpg

Mercury Parts Express Fuel Lines Parts List:

http://i27.photobucket.com/albums/c169/hkeiner/Mercury Oil Injection/MercuryFuelLinesPartsList.jpg

Mercury Service Manual Oil Injection Description:

http://i27.photobucket.com/albums/c...ection/MercuryOilInjectionDescriptionText.jpg

Mercury Service Manual Oil Injection Diagram:

http://i27.photobucket.com/albums/c...ction/MercuryOilInjectionDescriptionDiagr.jpg

 

[gss036]

Re: Faulty check valves on oil injection system causing smoke?

Just read your thread over. I guess the short answer is that #6 acts as a check valve (one way) so the oil and fuel do not mix until the fuel pump pushes fuel into the system, blending with the oil.
Maybe you are looking for something more complicated, but it is just a simple system to mix oil and fuel together before entering the carbs.
It is probably the best and simplest of all of the fuel systems and easiest to work on by the average person. At low RPM, it is not all that efficent but as the RPMs go up, none of the outboards are all that great. They all use lots of gas to create horsepower, especially when you get in the 5000 rpm range. The DFI is probably the best and most efficient, but it is very complicated.

 

[hkeiner]

Re: Faulty check valves on oil injection system causing smoke?

Gary,

Thanks for responding so quickly. I did understand that the 2PSI check valve allows the oil to flow one way (from oil pump to the fuel pump) and not the other way. If the 2 PSI check valve were only a simple check valve without a "2 PSI" function I wouldn't be asking about this check valve at all. The thing that I don't understand about this 2PSI check valve, more concisely is:

1) What the 2 PSI check valve does differently when the pressure is above or below 2 PSI? Does it start, stop, or slow down oil flow at the 2 PSI threshhold? And if so, is it a positive or negative 2PSI pressure that causes the change in flow and in which direction is the flow affected? I don't expect that the check valve would function exactly the same way regardless of the PSI pressure level on either side of the valve, or else it would not have "2 PSI" in its name.

2) What keeps oil from being pushed through the 2 PSI check valve and into the fuel line at the T-connection (hose #2) when the engine is shut off and there is still positive pressure remaining in the system's oil tanks? Is it prevented by the upstream stationary oil pump, the subject 2 PSI check valve, the check valve on the fuel line's primer squeeze bulb, or something else?

I want to know this because if some oil is being pushed into the fuel line (hose #2) after engine shut down due to a defective component, this could result in too much oil to be initially in the oil/fuel mix when the engine is next started causing excessive smoke until it is burned off. This is the symptom I am trying to resolve on my motor.

Thanks,

Hal

 

[gss036]

Re: Faulty check valves on oil injection system causing smoke?


"I want to know this because if some oil is being pushed into the fuel line (hose #2) after engine shut down due to a defective component, this could result in too much oil to be initially in the oil/fuel mix when the engine is next started causing excessive smoke until it is burned off. This is the symptom I am trying to resolve"
I don't really know the answer to that one. I would assume that if you had pressure remaining in the oil tank, then it would allow oil to be pushed into the fuel mixing part of the line and then into the carbs. The float in the carbs should not allow fuel/oil flow past the needle valve in the carbs. It the needle valves are leaking, then yes, there will be a build up of oil inside the throat of the carbs. I think they all have to be working in conjunction w/each other. I have heard of the valve on the engine failing and I have had the one designed to prevent a vaccum (on the small engine tank) fail and that allowed oil to pushed out into the cowling.
Maybe you could ask a master Merc mechanic those questions as I am not a mechanic although I have worked on engines/ rebuilding carbs all my life.

 

[hkeiner]

Re: Faulty check valves on oil injection system causing smoke?

Gary,

Much thanks for you help by responding to my many questions on this subject. Your feedback, along with my just writing on this subject, has helped me a lot in better understanding the oil injection system and also what the consequences would be if this 2 PSI check valve were to malfunction.

While I am still unclear how or why the function of this 2 PSI check valve would differ depending on the PSI pressure level in the oil line, I concluded that this valve is probably not the cause of my smoking problem if it were in fact malfunctioning (i.e., valve stays open when it should stay closed or valve stays closed when it should stay open). My troubleshooting efforts will now be directed towards other components on the engine.

Thanks again and best regards,

Hal

 

[wilde1j]

Re: Faulty check valves on oil injection system causing smoke?

This is not all that complicated. If the boat mtd oil tank still has any pressure several minutes after shutdown, the check valve on the lower port side of the block needs to be replaced. When the tank remains pressurized, oil continues to seep beyond the oil pump, causing the motor to smoke like crazy atr the next startup. A bad check valve will cause the tanks to remain pressurized for days, even weeks, so a lot of oil can bleed through. The purpose of this valve is to bleed off system pressure, which is used to keep the engine mtd tank full, after the engine is shut down.

This is a very common Merc oiling issue and very simple to fix.

 

[hkeiner]

Re: Faulty check valves on oil injection system causing smoke?

Jim,

Thanks for the information you provided. The more I learn about the finer points of how the oil injection system works, exactly what each component does, and probable symptoms of a component's failure, the better chance I have of troubleshooting my current problem and also any continuing problems that may exist.

I plan to replace the check valve that you described above (Crankcase pressure one- way check valve - part number #21-878105) as soon as I get a chance to work on the motor again in the spring.The boat is currently in storage until spring. If replacing this component solves my problem, then I will be done and very thankful to you and Gary for all the advice..

In case replacing this valve does not solve my problem, I have a few contingent questions that would help me better understand what prevents oil from seeping past the oil pump during the few minutes that there is still pressure in the oil tanks after engine shutdown under normal conditions.

A) During the first few minutes after shutdown, are the stationary oil pump and the stationary fuel pump supposed to prevent the seeping of oil through the oil pump on their own, or are downstream valves supposed to prevent this flow?

B) Alternatively, are the primer bulb check valves and carb float valves supposed to prevent the seeping of oil through the oil pump (i.e., by not providing any room for the oil to be pushed towards the carbs or backwards through the fuel supply line)?

C) Would a leaking primer bulb check valve or leaking carb float valve cause oil to seep past the oil pump during the first few minutes after shutdown? It seems to me that they would.

D) Finally, are there any other components that, if defective, could allow oil to seep through the oil pump during the first few minutes after engine shutdown? I have already identified the two 2 PSI check valves, as discussed extensively earlier in this thread, as possible culprits.

I am trying to identify any additional component failures that might cause too much oil to seep into the fuel/oil mix immediately after engine shutdown. This way I can consider inspecting/fixing/replacing the component the next time I work on the motor.

Thanks for any thoughts that you or anyone else may have on this subject,

Hal

 

[jhebert]

Re: Faulty check valves on oil injection system causing smoke?

Perhaps the valve being discussed ought to be called a 2-PSI relief valve. If I understand what's been said, it apparently vents the oil line to the atmosphere if the pressure in the oil supply line exceeds 2-PSI above atmospheric.

Is that right?

This is the "2 P.S.I. CHECK VALVE" identified with the callout number 5 in

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

 

[jhebert]

Re: Faulty check valves on oil injection system causing smoke?

oops--edited above--

 

[hkeiner]

Re: Faulty check valves on oil injection system causing smoke?

jhebert,

It is my understanging that the 2 psi check valve (#5) your are referring to does not "vent the oil line to the atmosphere if the pressure in the oil supply line exceeds 2 psi". This check valve actually does the opposite. It allows air from the atmosphere to go into the oil line if the VACUUM in the oil line exceeds 2 psi.

A vacuum in the oil line would occur if the oil supply line coming from the remote tank is restricted and as a result the oil pump is sucking oil from the reservoir tank during normal operation. This would cause a vacuum in the reservoir tank and the oil line, preventing the oil pump from pumping sufficient oil towards the fuel pump. A bad thing that is prevented by this check valve.

I have learned that if this check valve were to be defective, it could either cause oil to leak from the oil line into the engine area or cause a vacuum to occur in the oil line resulting in lack of lubrication. It would not, however, be a possible cause of too much oil being pushed into the fuel line/carbs resulting in excess smoke.

Hal