Faulty check valves on oil injection system causing smoke?

[jhebert]

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

Hal--Thanks for the clarification. Looking closely at the diagram there does seem to be a spring shown in the check valve #5 which makes in appear to be oriented as you described.

Best regards,

--Jim Hebert

 

[wilde1j]

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

The Merc shop manual has an excellent section on the operation of and trouble shooting the oil injection system. There is nothing that positively stops oil from flowing past the pump after shutdown. If the tank remains pressurized, which it shouldn't, oil will continue flowing into the fuel at the tee and you will have a lot of smoke at the next startup.

I owned two '95 150HP Black Maxes until a couple of years ago and had one oil system failure, so I got a little first hand experience with those beasts.

 

[hkeiner]

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

Jim.

Thanks for the reply. I definately plan to replace the Crankcase pressure one- way check valve (part number #21-878105) the next time I work on the motor in the spring.

As it happens, I have three shop manuals (Mercury, Clymer, and Seloc) for my engine. Each one is a little different, so I like to read all three when I want to check something out. While they are all good manuals, I found that they were all somewhat deficient in regards to troubleshooting my specific problem. They all focused on troubleshooting symptoms where too little or no oil is being injected by the oil injection system. None of them provided much troubleshooting help when TOO MUCH oil was being injected. For example, the manuals didn't explain:

1) What is the normal PSI pressure level in the tanks when the engine is running? By knowing this, one could accurately test that the oil injection system is not being over-pressurized. Watching for a bulge in the reserve oil tank seems imprecise.

2) What component relieves pressure in the oil tanks when the engine is shut off? I have learned from this forum that it is the "crankcase pressure one- way check valve" and that this valve actually serves a dual purpose...... as a CHECK VALVE converting the crankcase pressure/vacuum cylces into positive pressure for injection into the oil tank (which the part's name implies) and also as a PRESSURE RELIEVE VALVE (which the parts name does not clearly imply).

3) How quickly should the PSI pressure in the tanks be relieved to atmospheric pressure levels after engine shutoff? I learned on the forum that this happens within a few minutes after shutoff. Before I knew this, I didn't know that the delay of several hours on my motor was an abnormal condition.

4) What keeps the oil from being pushed from the reservoir tank into the carbs and/or fuel line right after engine shutoff and before the pressure is relieved? I still suspect that the system is designed to prevent such a flow DURING THE FIRST FEW MINUTES AFTER SHUTDOWN AND BEFORE THE PRESSURE IS RELIEVED, but I am unsure which of these downstream components are definately involved and which are definately not involved (i.e., oil pump, 2 PSI check valve, fuel pump, carb float, and check valves on fuel line primer bulb.) Knowing this "definitively" from the shop manuals would have helped a lot in identifying or eliminating potential culprits contributing to my excess smoke problem.

Well, this is my rant on the service manuals in regards to troubleshooting an oil injection system that may be causing too much smoke. If it were not for the great information that I have gotten on this forum, I would have been lost...

Regards and thanks again to all of you who responded to my posts.

Hal

 

[wilde1j]

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

Jim.

Thanks for the reply. I definately plan to replace the Crankcase pressure one- way check valve (part number #21-878105) the next time I work on the motor in the spring.

As it happens, I have three shop manuals (Mercury, Clymer, and Seloc) for my engine. Each one is a little different, so I like to read all three when I want to check something out. While they are all good manuals, I found that they were all somewhat deficient in regards to troubleshooting my specific problem. They all focused on troubleshooting symptoms where too little or no oil is being injected by the oil injection system. None of them provided much troubleshooting help when TOO MUCH oil was being injected. For example, the manuals didn't explain:

1) What is the normal PSI pressure level in the tanks when the engine is running? By knowing this, one could accurately test that the oil injection system is not being over-pressurized. Watching for a bulge in the reserve oil tank seems imprecise.

2) What component relieves pressure in the oil tanks when the engine is shut off? I have learned from this forum that it is the "crankcase pressure one- way check valve" and that this valve actually serves a dual purpose...... as a CHECK VALVE converting the crankcase pressure/vacuum cylces into positive pressure for injection into the oil tank (which the part's name implies) and also as a PRESSURE RELIEVE VALVE (which the parts name does not clearly imply).

3) How quickly should the PSI pressure in the tanks be relieved to atmospheric pressure levels after engine shutoff? I learned on the forum that this happens within a few minutes after shutoff. Before I knew this, I didn't know that the delay of several hours on my motor was an abnormal condition.

4) What keeps the oil from being pushed from the reservoir tank into the carbs and/or fuel line right after engine shutoff and before the pressure is relieved? I still suspect that the system is designed to prevent such a flow DURING THE FIRST FEW MINUTES AFTER SHUTDOWN AND BEFORE THE PRESSURE IS RELIEVED, but I am unsure which of these downstream components are definately involved and which are definately not involved (i.e., oil pump, 2 PSI check valve, fuel pump, carb float, and check valves on fuel line primer bulb.) Knowing this "definitively" from the shop manuals would have helped a lot in identifying or eliminating potential culprits contributing to my excess smoke problem.

Well, this is my rant on the service manuals in regards to troubleshooting an oil injection system that may be causing too much smoke. If it were not for the great information that I have gotten on this forum, I would have been lost...

Regards and thanks again to all of you who responded to my posts.

Hal

The only manual you can really count on is the OEM book. BTW, the Merc manual has an excellent diagram of the oiling system. Now for your questions:
1) Don't know what the pressure is but it can only be a few psig or less for the plastic not to explode or deform.
2) The crankcase check valve is the one that dumps the tank pressure at shutdown. Forget the name inconsistency!
3) The pressure in mine remained for weeks until I replaced the check valves on both motors. The oil tanks were vented to atmospheric pressure very quickly afterwards (i.e. less than a minute).
4) As I indicated, the pressure gets dumped right now after shutdown, and the static head in the engine mounted tank is not enough to force oil past the pump, which is a positive displacement type pump, and provides enough resistance to flow to keep oil from going past it.

In my case, the startup heavy smoking dissapeared after the second start (there was oil still in the gas when the check valves were replaced.

 

[robalofish]

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

**** IMPORTANT **** Do a search on my name for an old post re: smoking engine and the remote tank pressure valve on the engine --- I'll bet this is your problem.

Please advise status.

Found info here it is below.... This was many hours of checking in order to find this was the problem.

»UPDATE ** UPDATE I found what the problem was on my rig now you can check yours

The reserve tank has been holding pressure for weeks at a time. I didn’t think anything of this as it has done this sense I have had the boat. I found that this is NOT normal. The valve that comes from the engine and supplies the pressure to the remote tank is supposed to bleed off the pressure after 5-10 min. When I checked the valve there was no bleed off occurring. Purchased a new valve and it bleed off as described. So after changing the pressure check valve I have cured the problem.

Check Valve number 21-878105 1

Just a note letting you know the outcome.

Thanks
*** Sombody should make this a sticky !!!8)8)8)
---
RFish >()>

 

[jhebert]

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

Rfish--Thanks for the clarification on the specialized check valve which both pressurizes the remote oil tank from the crankcase and then bleeds the presssure off when the engine stops running. This specialized valve is mentioned in the main drawing of the oiling system as

CRANKCASE PRESSURE WITH ONE WAY CHECK VALVE

The manual does not mention the ability of the valve to bleed off pressure. This makes the valve seem to function as a two-way valve, that is, it allows flow of pressure both into and out of the remote oil tank, and thus the nomenclature used ("ONE-WAY") seems confusing.

Also, if the system permits the remote oil tank to remain at operating pressure after the engine has stopped running for 10-minutes, this raises a question:

Won't a significant amount of oil flow into the mixing system in 10-minutes? During that time there would be no flow of gasoline because the fuel pump would not be operating, so you would expect that the fuel would become rich in oil. Perhaps this was intentional so that the next start-up of the engine would be with fuel that had a lot of oil in it, giving rise to a smokey start characteristic.

 

[hkeiner]

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

jhebert

"Won't a significant amount of oil flow into the mixing system in 10-minutes? "

I asked a Mercury mechanic (at my local boat shop) this very question yesterday. He explained that the oil pump (when stopped) will sufficiently prevent any meaningful seepage of oil towards the fuel pump or fuel tank as long as the oil tank's air pressure is not higher than design and the pressure does not persist longer than design. If the crankcase valve is defective, however, then the pressure may be too high or persist too long and could cause too much oil to seep through the oil pump after motor shutdown.

Hal

 

[robalofish]

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

jhebert

"Won't a significant amount of oil flow into the mixing system in 10-minutes? "

I asked a Mercury mechanic (at my local boat shop) this very question yesterday. He explained that the oil pump (when stopped) will sufficiently prevent any meaningful seepage of oil towards the fuel pump or fuel tank as long as the oil tank's air pressure is not higher than design and the pressure does not persist longer than design. If the crankcase valve is defective, however, then the pressure may be too high or persist too long and could cause too much oil to seep through the oil pump after motor shutdown.

Hal

Absolutly correct - the few min is nothing like days of pressure --- I found the answer when I removed the primer line from the top carb and it was solid oil -- heavy thick oil not just gas with oil in it. Has worked like champ after changing valve.

RFish >.).).)

 

[hkeiner]

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

As the original poster of this thread, I thought I would report back on what I did to address my problem and how things turned out. This might be of interest to others who have a similar problem regarding excessive smoke at startup.​

Is summary, I replaced two check valves on the oil injection system (the one at the crankcase and the one near the fuel pump). I also used some SeaFoam to clean the carb float valves. I got an external 3 gallon tank and filled it with two gallons of fuel and one can of 16oz Seafoam. I ran the motor (on a hose) with the external tank for 10-15 minutes at idle and then let it sit overnight. I ran it again (on a hose) the next day for 10-15 minutes at idle and then let it sit again overnight. On the third day I took the boat out on the water and ran the motor at moderate speed until the fuel in the remote tank just about ran out. I then switched the fuel line to the internal tank and ran the boat at WOT. The motor now starts fine and runs as it should without excessive smoke at startup.​

I can't be sure whether replacing the PSI check valves (to keep excess oil from being pushed into the fuel line) or running the Seafoam through the carbs (to clean the float valves so they don't leak) was what fixed my problem since I did both at the same time. However, the cost and effort to do both of these steps was minimal and the overall result was sucess!​

 

[dave4881]

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

I want to THANK those of you who participated in this discussion, because I have just bought a boat (Larson 18') with a 96 Merc 150 Black Max that exhibits this horrible smoking on start-up.

After reading the threads, I took the boat out for a run on the lake this afternoon. At shut-down, I removed the cap on the remote oil tank and relieved the pressure. When I restarted the engine, no excess smoking.

I will be buying some check valves and a case of Sea Foam very soon.

Thanks again for this informative thread.

Dave
2000 Larson SEI186
96 Merc 150 XR4 Black Max

 

[ray67]

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

To dave 4881, I am having the same problems with excessive smoking on startup. I have a 1992 150 h.p. Merc. Black Max. I have read all the posts and have changed the check valves as well as cleaning the carbs with sea foam. This seems to have worked for others but to date I am not having any sucess.
If anyone out there has any other suggestions I would appreciate hearing them.

 

[j_martin]

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

Note:
Excessive smoke on startup -> check for pressure letoff on the boat oil tank. If it doesn't let off to 0 in a few minutes, replace the crankcase check valve.

Oil dripping from the drop tube on the second check valve (between the boat tank and the engine tank) -> replace the second check valve.

The second check valve, even if malfunctioning, will have nothing to do with the excessive oil in the fuel at startup. Save your money.

Decarboning (seafoam) just cleans up the mess made by the excess oil.

hope it helps
john

 

[ray67]

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

Thanks for the info John. However I have replaced the crank case check valve and the 2 psi check valve coming from the oil pump. The 4 psi valve coming from the engine mounted tank seems to be functioning correctly as no oil is coming from the vent. I am now considering a test by running the engine from a remote fuel tank with a 50 :1 oil mixture and bypassing the oil pump to see if the excessive smoking will stop. At this point i am truly confused as to why the cylinders might be loading with excessive oil. I have to wonder if the oil pump is pushing more oil than needed into the mix.

 

[bajacharlie]

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

This is a great thread... just had the exact same issue this last 4th of July. It was a nightmare trying to troubleshoot this out in the water... with friends and relatives on-board. Hopefully it's just the valve that will solve my problem. Thanks to everyone for contributing!

 

[hardcore23]

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

Gents,

Thanks for all of this great information. I have a '95 2.5l Black Max (200hp) exhibiting similar symptoms. I will have these valves replaced when the boat gets put away in the fall.

Cheers!
Darren

 

[Capt. Gregory]

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

Dear boatfriends,

Just a question on the check valve, my mercs 200HP are from 1998, one has a faulty oil check valve however from my repair guy I understood the new check valves would not fit on the older models? I am in the midst of ordering one. Could anyone advise?

1) would part number; #21-878105 (Refr #14) fit?
2) any suggestion for where to order online?

Thanks a mill,
Gregory

 

[bajacharlie]

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

Dear boatfriends,

Just a question on the check valve, my mercs 200HP are from 1998, one has a faulty oil check valve however from my repair guy I understood the new check valves would not fit on the older models? I am in the midst of ordering one. Could anyone advise?

1) would part number; #21-878105 (Refr #14) fit?
2) any suggestion for where to order online?

Thanks a mill,
Gregory

What I found what work best is to first use your engine serial number in the www.mercurypartsexpress.com website and go through diagrams to find the part you're looking for. (http://www.mercurypartsexpress.com/us/parts-search.html#epc::machine_find).

After you find out exactly what part you need, the cheapest place i've found is w w w . b o a t s . n e t (not always) buy they will most likely have your part. I was able to to find your check valve using just P/N 878105.

My motor is a 94 150 HP Black Max, and I've been able to find every part on w w w . b o a t s . n e t , hope this helps!!

Good Luck!

Carlos.

 

[Capt. Gregory]

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

What I found what work best is to first use your engine serial number in the www.mercurypartsexpress.com website and go through diagrams to find the part you're looking for. (http://www.mercurypartsexpress.com/us/parts-search.html#epc::machine_find).

After you find out exactly what part you need, the cheapest place i've found is w w w . b o a t s . n e t (not always) buy they will most likely have your part. I was able to to find your check valve using just P/N 878105.

My motor is a 94 150 HP Black Max, and I've been able to find every part on w w w . b o a t s . n e t , hope this helps!!

Good Luck!

Carlos.

Hi Carlos, thanks for you information. I tried to enter the both serial numbers as I have from the engines however they do not seem to be on the list. Would you know where to find the correct info on the engines?

My Serial numbers look like;

97880 and 131243.

Thanks, Gregory

 

[Capt. Gregory]

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

Dear friends, i am going nuts, finally gor the part (one way check valve) as described and conform the merc partslist. While trying to replace the one i recieved has a screwtap, the one currently in the engine has a tube end.. The import guy says that part is not available? Would anybody know what i am talking about? Same problem or knows where to get the correct part?

Thanks in advance,
Gregory

 

[hkeiner]

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

As the original poster I have received private messages in the past asking about this old thread and the Mercury oil injection system's check valves in particular. More recently I was asked to bump/reactivate this thread for the potential benefit of others that might not easily find it buried in the past. My initial inclination is to not do this as my thread is probably no more special/helpful than many other old threads out there. Anyway, I was convinced by the latest private message I received asking me to do this. My apologies if this is a 'bad'.