Failure to Prime the Engine
We’re all familiar with the process of priming. Small engines like those on most gas-powered weed trimmers need to be primed with fuel before you can crank them. The replacement engine going into your customer’s car needs to be primed as well, but with oil. Failing to prime the engine with oil will cause it to lock up and require yet another replacement engine. Prime the engine, seriously, and avoid this costly engine installation error.
The Priming Process
You might think that it’s best to put the entire engine together and install the drive belts before worrying about priming the engine. That’s wrong. Stop what you’re doing. Before you install the drive belts, the engine’s oil pump needs to be primed, and you need to purge all the air from the oil system, especially when it comes to a used engine for sale.
How do you prime the oil pump and engine, though? The exact method will vary depending on the type of vehicle you’re working on (distributor versus modern ignition, for instance), but here are some of the options available:
Use a pressurized system to push clean oil through the entire oiling system. This is the simplest, easiest method available and requires very little physical effort. It does require the purchase of a pressurized system to push the oil, though.
For engines with a distributor, use a priming tool (this should be part of an expert mechanic’s setup), and a drill motor. Rotate the oil pump shaft to bring oil to the top of the engine. Make sure the oil reaches the rocker arms.
Before you install the drive belt or the sparkplugs, disable the fuel and ignition systems. Now, manually crank the engine in short busts until pressure builds within the oiling system. Once you’ve built up pressure, continue cranking in short bursts for about two minutes to bleed the air out of the oiling system. If you’re unsure that the system is fully purged, crank for an additional two minutes.
If you’re following the manual crank method listed above, once you have purged the air from the system, check the oil level and adjust it as needed. Make sure the oil filter is in place before you start this step.
Don’t forget to REPLACE the oil cooler. Never reuse the old oil cooler. If you decide to reuse the cooler lines, make sure they’re completely clean and free of any debris.