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VIDEO: Oil Pump Lost Its Prime

Can you answer this ASE G1 test prep question? This video is sponsored by FRAM.

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After an engine oil and filter service, a technician can’t get the oil pressure warning light to go out after 10 seconds of running and is not in the correct range.
What is the MOST likely cause?
A) The oil filter
B) Wrong viscosity oil installed
C) All the oil has run out of the pump
D) Air trapped in the pressure sensor

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The answer is C.

Although not a common occurrence, it is very possible that the oil pump may lose its prime during the oil change. When the used motor oil is drained from the engine the oil may also drain from the oil pump pickup tube and possibly from the oil pump itself. When new motor oil is installed the pump’s pickup tube inlet again becomes submerged, trapping air in the tube on the suction side of the oil pump. Sometimes this problem can be avoided by limiting the time the oil is drained. The trapped air will cause cavitation of the pump and prevent it from producing oil flow and pressure. Many techs tend to blame this on the oil filter and assume that the filter is blocking the flow of oil. The point being made is the oil filter was not the problem and in most cases there is a simple solution.

If after the oil and filter change, the red light or low oil pressure remains for ten seconds, shut the engine off, remove the oil filter and, using an oil squirt can with the correct motor oil, squirt oil several times into the oil filter base outlet on the engine. Next, fill the filter with new motor oil and reinstall. Start the engine and check for oil pressure. In most cases, the problem will be solved. DO NOT allow the engine to run for more than ten seconds without oil pressure. Use a watch to time the ten seconds and be sure of the elapsed time. In some instances, the full ten seconds is needed for the pump to recover oil flow. If this fails, again remove the filter and crank the engine until oil spills from the engine base. DO NOT crank over ten seconds at a time. When oil spills, reinstall the oil filter, correct the oil level and restart the engine. Oil pressure should now be back to normal.

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This video is sponsored by FRAM.

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