New Monark Injectors were sent to local diesel shop for mating to the injector bodies using precise calibration (no shims) and set the spray pattern. I installed the new Monarks using new heat shields.

Recently, there has been some nailing on start up. Once the engine is warmed up, the nailing stops, the engine quiets down and sounds normal. I'm thinking of purchasing injector line heaters/fuel filter heaters in hopes of quieting things down. Any ideas as to why the cold start up noise/nailing?