A Detroit Diesel has unit injectors, which pump the fuel to injection pressure as well as spraying it into the cylinder.

Adrian shows me all the parts of a unit injector and how they work, then pressure tests them (after setting up the cam rollers and oil pump).

Adrian then teaches me how to build and test a set of injectors: lapping the tip, spring cage and check valve, pressure testing the tip and timing the rack. In the video above we replace Renko's N60 injectors with N50s, then tune up her engine and the 4-53 in Mammoot: setting the valve clearances and injector heights and running the rack.