Oil injection test

[drewmitch44]

Im trying to test the oil injection on a 115 hp yamaha 1986 115ELTJ. The manual that i have says run the engine at 1500 rpm with 50:1 gas mixed and disconect the tube where the oil goes into the cylinder. whyle the motor is running @ 1500 rpm im supposed to get 2.6 - 4.0 cc's of oil through the tube. First of all i dont know how to measure cc's and i dont know how to go about doing that. Also with the motor running and that tube disconnected there is suction where the tube connects i can hear it. When i put my finger over it it stops. So is the cylender supposed to suck the oil out of the tube? I collected the oil and im not sure how to measure it. It dripped about every 10 seconds or so. I bled the oil system like the manual said too before doing this test. Ive tested it on 2 cylinders and both get about the same result. Im just afraid to run strait gas into this motor before i know that the oil injection is working properly. Thanks for any help you can give me!!

 

[drewmitch44]

Re: Oil injection test

Sorry forgot to mention the 2.6 - 4.0 cc's is supposed to be for 3 min. of running at 1500 rpm.

 

[Ray Neudecker]

Re: Oil injection test

If oil dripped out of each line, you are very likely ok. Yes it uses crankcase suction to move into the cylinders.
Be sure you check all four cylinders. Mark a line on the boat mounted oil tank at the oil level. Run with a 50/1 mix in the fuel tank and check to be sure the level is going down in the oil tank before discontinuing the mixed fuel and go to straight gas.

 

[rodbolt]

Re: Oil injection test

instead of doing the output test, do a consumption test as well. I use a syringe from the vet. installed at the oil pump intake,multiply the output by the number of cylinders. consumption should equal output.
do all tests with a 50/1 premix.
precision blend rarely gives problems if properly maintained.