Join Date: Jun 2002
Location: SF, CA
250 Yamaha oil pump problems....
Here is an article from Bass and Walleye Boats....
Troubleshooting Yamaha's Precision Blend oil
system is easy. We show you how
More than a mere convenience for boaters, automatic oil injection helps two-stroke outboards run at peak performance. When the system is functioning properly, the engine will produce less smoke, while resisting carbon buildup and spark-plug fouling. Because of its complexity, however, glitches sometimes cause rough-running engines, excessive smoking, oil leaks or even alarms to sound and lights to flash. While we cant address every possible situation for every outboard, well take this opportunity to examine Yamahas Precision Blend oil system. With proper troubleshooting techniques and a thorough understanding of how the system works, most problems are easily corrected.
Over the years, Yamaha has refined the electrical operation of the oil-transfer system to increase its reliability. Before you tear into any job, have the appropriate service manual, test equipment and tools needed. Naturally, you'll want to use common sense when working around gasoline, oil and electrical parts and be sure to observe all safety procedures outlined in the manual. A word to the wise: A few moments spent reading the instructions beforehand will save grief and time in the end.
Yamaha's system consists of two lubricant reservoirs, an electric pump, a crankshaft-driven metering pump, float-activated switches, filter screens, hoses and an electronic oil-control system. A 2.7-gallon reservoir (actually, a remote tank) mounted inside the boat contains the electric pump, filter and a fluid-level sensor switch. An oil hose from the remote tank attaches to the engine-mounted main tank, and a wiring harness connects it to the outboard's electronic circuitry. The main tank also contains a filter screen, float and three switches that send information to the oil-control unit. Two-stroke oil is fed via gravity through a hose on the bottom of the main tank to the crankshaft-driven oil pump, where it is metered to the engine.
All decisions about transferring oil (as well as sounding any alarms) are made by the electronic oil-control unit. On V-4 and older V-6 outboards, it consists of an external black box with a momentary toggle switch. In later V-6 models, Yamaha incorporated the switch and electronics into the CDI unit.
Located in the boat, the remote tank holds oil that is pumped to the powerhead as the engine demands. Mounted in a recess on the side of the tank, the electric oil pump receives the lubricant through a filter element and transfers it to the main tank, which is located on the powerhead. A float activates a switch (SW B) inside the reservoir when approximately 1-1/2 quarts remain. The switch signals the oil-controller to turn on the yellow warning LCD on the tachometer, and to stop the transfer of oil to the outboards main tank.
Inside the main tank, three float-activated switches inform the control unit when the tank is full, when to transfer more oil, and when to sound the alarm if the level drops too low.
As long as the remote tank contains enough oil, a green LCD lights up on the tachometer and the electric pump will transfer oil to the engine as needed. In the main tank, as oil is consumed and the level drops, a float triggers the middle switch (SW 2), which informs the control unit to turn on the electric transfer pump. The additional oil allows the float to rise up and initiate the upper switch (SW 1) to shut off the pump. In the event no lubricant is transferred and the oil level decreases enough for the float to pass the bottom switch (SW 3), the oil-control unit sounds a warning alarm, the red \"no oil\" LCD lights up, and the outboard slows to around 2000 rpm for its protection. This warning alerts the skipper that only one-third of a quart remains in the main tank.
As long as theres sufficient oil in the remote tank, it can be manually transferred to the main reservoir by pressing the momentary switch to bypass the oil-control unit. The toggle switch turns the pump on for as long as it is held in position; the upper float switch (SW 1) will not turn it off. This allows you to refill the main tank and continue with normal engine operation as long as the float remains above the lower switch (SW 3).
When additional oil is added to the boats remote tank, the float rises above SW B, which allows the controller to turn off the yellow warning LCD. If the outboard is running, the electric pump begins to transfer oil to the engine until the main tanks full switch (SW 1) shuts it off.
Depending on your outboards model year, various methods are used to prevent oil from transferring when the outboard is tilted up. On models with a separate oil-control module, an internal mercury switch will not allow the electric pump to energize if the outboard is tilted above 30 degrees. The trim sender senses the tilt angle to prevent the oil transfer on V-6s from 1990 through 1995. Starting in 1996, new electronics in the controller unit keep the pump from operating if the engine is not running. Do not forget to check these items when troubleshooting a \"no oil transfer\" situation.
SYMPTOMS TO WATCH FOR
Common symptoms of trouble include a lack of oil transfer, overfilling of the main tank, and oil leaks while the outboard is tilted. Most of the time, these problems are due to operator error and are not the components fault.
Non-transfer of oil to the engine-mounted main tank can be as simple a problem as a neglected filter. Moisture gets into the remote tank from spray, rain, condensation, or from being located in the bilge where it can be splashed or submerged. The water forms a sticky emulsion in the bottom of the tank and plugs up the fine screen in the filter element.
An overflowing main tank sometimes results from someone twisting or incorrectly installing the rubber cap on the float assembly and screen element. The tubular screen has an offset nipple that fits into the bottom oil-outlet going to the metering pump, and can bind the float if moved out of place. The arrow marks on the cap and tank should be aligned.
Leaving the key on by mistake can also cause overflow problems. As the battery run drops below 9.5 volts, the oil-controller electronics go off line, and a ground path is formed which starts the electric pump turning very slowly. Eventually, the main oil tank overfills and spews excess oil out a vent tube into the air silencer box.
While the outboard is tilted, a leaking rubber cap on the main tank can result from improper assembly or from twisting out of place. A plastic tie-wrap snugged around the rubber lip usually cures the leak. The clear sight tube on the bottom of the tank can become brittle with age, and oil may seep between it and the nipple. Replace the tube if it feels stiff, and secure it with a tie-wrap.
Since the electric oil pump and each switch have voltage going to them at all times, troubleshooting is fairly simple. The electric pump turns on when the ground circuit is complete, and each switch (when activated) completes a circuit. The oil-controller cannot be tested, though and can be considered faulty only through a process of elimination.
When no oil transfer occurs, lift the toggle bypass switch to see if the pump runs and starts to fill the main tank. If it does, either the tank's float assembly is inoperative or the oil-controller is faulty. To check the float assembly, disconnect its wiring plug and ground out the brown (on early engines) or the blue-green wire on the wiring harness side. If the pump and wiring are in good condition, the pump should stay on. Grounding the white (on early engines) or blue-white wire will turn the pump off.
In cases where the pump does not operate or runs without delivering oil, remove the boats remote tank and inspect for corrosion, bad wiring or a plugged filter. You can test the pump by using jumper wires to put 12 volts directly to it. The brown wire is positive and the blue is negative.
Overflowing can result from several factors. If the pump continues to run and the oil level rises above the upper line on the tank, disconnect the wiring and ground out the white (on early engines) or blue-white wire. The pump will stop unless the oil-controller module is bad or there is a grounded blue wire in the harness somewhere between the pump and controller.
TESTING THE FLOAT SWITCH
An ohmmeter can be used to check the switches inside the main tanks float assembly. Carefully remove the unit, making sure the black foam sealing washer stays with the tubular filter element. If it remains in the tank, the seal can be forced into the feed hose going to the engine-driven metering pump which could block the flow of oil.
Hook up the negative lead to the black ground wire, and the positive lead to each other wire in turn. When you move the float, the ohmmeter should show that each switch \"closes\" when the float passes by. If any switches are defective, the assembly must be replaced. Be sure to install a new foam sealing washer every time the assembly is reinstalled.
Follow the service manual procedure when testing the remote tank's float switch. It is normally closed, and opens when activated by the float. Early models have electronics inside the assembly and require different test methods than later models containing the circuitry in the oil-controller.
Yamaha's Precision Blend oil-transfer system is very reliable, but as an outboard ages, problems may develop. Fortunately, it is a relatively easy system to troubleshoot with ordinary tools and an ohmmeter. Armed with this article and a service manual, you can enjoy the smug satisfaction of avoiding expensive shop time should a malfunction ever occur.
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