Johnson 150 Plugs Fouling Oil Consumption High

Riley C

Petty Officer 1st Class
Joined
Dec 23, 2018
Messages
239
Hey Guys,

I have always had an issue of slight over oil consumption. Just put it down to the OMC guzzler. No issues with it running to WOT and starts fine. I just cant sit and idle for extended periods, she likes to run mid-flat out or not on at all.

After running for a couple of hours she smokes on after sitting off for 10min, even with engine being warm. It bugs me because the plugs get glazed/oiled up from it. They aren't dripping but would be if I idled for a while.

I got back home to flush and the Port #6 was the oiliest. I had erratic revs from 900-1100, so fouled plug I guess.

I use QL78, but I got to clean them after each run almost.

To find this issue I have over the last year totally pulled the fuel system down.

Replaced Carbs & Bowls
Replaced fuel side parts of OMS (It smoked before I did this).
All new fuel lines and primer.
New fuel bracket screen filter and orings.
New fuel separator.
Inspected the vapour pump.
New oil tank vent cap.

I have not pulled the vapour separator float down.

After completing all the above there are no leaks. The primer bulb stays hard over 24hrs, so cant be anything prior to the VRO....

I would say I'm consuming alot more than the oil specs. Tank is 6.8Lts - For 40litres of fuel it would use close 1.8ltrs (Going by that oil tank photo, it was full on on that run). Assume the oil is consuming double what it should be.

I would appreciate what I should be doing next. It's not a show stopper issue, just annoying.

I'm getting pissed off with this OMS if it's that.

My neighbors hate me starting it in the street.
 

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Riley C

Petty Officer 1st Class
Joined
Dec 23, 2018
Messages
239
I have thought to know end how to fix this double consumption.

I'm on my last leg without further advice. I have decided to swap OMS pumps, from a rebuilt spare I had from an 99 that went in the drink.


I'll fire her up tomorrow and see if it does anything.

I would appreciate any other suggestions this Forum's awesome supporters have.


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Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,036
The OMS pump will over oil, if there is an air leak on the gasoline line. It will look like you are fogging the insects, even at cruising speed.
 

Riley C

Petty Officer 1st Class
Joined
Dec 23, 2018
Messages
239
The OMS pump will over oil, if there is an air leak on the gasoline line. It will look like you are fogging the insects, even at cruising speed.

Hi Chris

it doesn’t smoke at low speed or even some times at idle. It is consumes double what it should going by tank consumption.

For instance for just 40ltrs I used 2litres of oil. Epic

if there’s an air leak wouldn’t I struggle going WOT or bog and the vac switch alarm?

The primer stays hard overnight.

can the OMS fail on the oil side and use double oil?
 

Riley C

Petty Officer 1st Class
Joined
Dec 23, 2018
Messages
239
OMS - No more!

Running on premix perfectly now.

See video during quick start below.

https://www.dropbox.com/s/3dhxk9no0d..._4243.MOV?dl=0


I may be an idiot for trialing this, until I cap the lines and disconnect electronics properly. I have temporarily removed the oil from the oil tank and put mixed fuel in there as well as the fuel tank. No alarms or issues with running in tank.

I will disconnect electronics and cap the oil line, once I have gone for a good run early next week.

Double checked thermostats in hot water also, working fine.

This has solved the epic oil during idle issue going to premix.

I can now have it idle in the carport without major smoke. It has halved at the minimum.

I don't know what it was with the OMS, maybe the piston/plunger not sealing in the sleeve and letting to much oil through? I wish I could have fixed it. But with no alarms and no air leaks detected with everything replaced. I'm stumped by OMS ghost.

I honestly feel safer on a 22 yr old engine to go premix now.
 

Riley C

Petty Officer 1st Class
Joined
Dec 23, 2018
Messages
239
You put 50:1 mixed gas and oil in the oil tank ?----Why ?

Yeah not my smartest moment but I had a thought at the time.

I did it initially without having to disconnect the OMS hoses etc. To see if changing over would make any difference to the smoke. Which it did, reduced it enormously.

Easy enough to purge oil back through I find the fault.

my thoughts were I could easily change back to oil, if can find what’s going on with this fuel system. I wanted to retain the OMS as opposed to premix. I just haven’t been able to source the issue after replacing/inspecting so many parts.

it runs perfect just uses double the oil it should. So hence reason in finding the issue. Two stroke oil is costly in Aus.

Tomorrow was going to pressure test the pump housing per the manual tomorrow as a last ditched effort to get going correctly.

Appreciate any advice you might have in fault finding this race.
 
Last edited:

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,039
I believe a factory manual would have a procedure and a test for oil consumption on these mixing units.---
 
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