Tuesday, September 8, 2015

Replacing the oil pump -- Universal 5424 M30

Low Oil Pressure

The story begins when I finally got around to replacing the oil pressure switch. When I purchased Elizabeth the oil pressure idiot light did not work and it took me almost four years to get around to replacing it. Stupid, I know. When I replaced the switch and started the engine the light came on and would not go off. Stupid, I know. Still, the engine has always ran fine, sounds good, does not overheat. Oil obviously circulates as it gets dirty and the oil filter fills. I was not sure if the new oil pressure switch was bad or if indeed the pressure was low. I purchased an oil pressure testing gauge as well as a mechanical gauge to replace the idiot light so I would always know exactly what the oil pressure was. Testing the pressure at the switch port I discovered the pressure at idle was about 5psi and at half throttle around 15psi. The specs on the oil pressure switch suggest that it will circuit will be broken (the light will go off) between 30psi and 60psi. So theoretically, this should be the normal range of the oil pressure. Mine is way too low. I installed the mechanical gauge and the readings were the same. At this point I was feeling really stupid for waiting so long.

So now what? There are many potential causes for low oil pressure. I first went through the obvious and easy possibilities; wrong oil, low oil level, clogged or faulty oil filter. All were good. The next easy cause is one of the two oil pressure relief valves being stuck in the open position, tricking the engine into thinking the pressure was too high and returning the oil to the sump without sending it to the rest of the engine. I removed and cleaned them and still the problem persisted. The problem still could be as simple as the primary oil filter, just a screen really, being clogged with crud. This filter is located on the pickup tube in the crankcase. To get at it, however, is not so easy as the engine would have to be lifted out of the boat to remove the crankcase. Along the same lines the pickup tube that is immersed in the oil and carries the oil to the oil pump may have become disconnected. This, as well is under the engine in the crankcase. Uh oh, major expense.

So that brings me to where we are today. Before pulling the engine I can replace the oil pump itself and check the forward plug on the camshaft. These are two possible culprits as well and can be accessed from the front of the engine. A big(ish) job to be sure and one I have never undertaken before on this engine. Sigh. So here goes.

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