TMS Outboard Motor Parts - testing VRO pumps

How to test a Johnson Evinrude VRO pump

Using diagragm for reference, install and carefully secure a 10" length of 1/4" clear vinyl hose to oil inlet on pump. A few inches from the loose end, measure carefully, and mark hose every 1/2" for 3 inches.

Fill the hose with outboard oil and run the engine to eliminate air from the base of the hose. Shut off engine, and add or eliminate oil until level is even with the highest mark.

Start the engine, and monitor the pump cycles by using a fuel pressure gauge or by putting light finger pressure on the outlet hose.

At 800 RPM, the oil level in the hose should drop 1" in approx. 5 pulses.
At full throttle, the oil level should drop 1" in approx. 3 pulses.

If results vary from above, the pump could very well be bad, but check the pulse limiter fitting before replacing the pump. Disconnect pulse fitting hose and crank motor. Is there a good strong pulse of air through fitting? If so, fitting is ok. If not, first check that compression on bottom cylinder (which operates pulse valve) is up to snuff. If compression is low, then the bottom cylinder needs attention to correct. If compression is ok, replace fitting and repeat previous test to assure oil throughput is ok. If results still vary, replace pump.