Used to throw away every injector that failed a pop test, then a guy in Bakersfield showed me the shim trick

Emma Smith · 2026-09-24T00:20:05.39909+00:00

I spent about 6 years just swapping out any injector that did not pop right. Customer pays $400 for a rebuilt one, old core goes in the scrap bin, done. Last spring a guy at a shop off Rosedale Highway in Bakersfield watched me toss one and just shook his head. He took it, popped the top, pulled the shims, and measured the spring height with a caliper. Said the pop pressure was 80 psi low, which is one thin shim, not a dead injector. He shimmed it, tested it, and it sprayed a clean cone the first try. Since then I test and shim before I quote anything, and my core bin has basically stopped filling up. Most of the ones I was scrapping were just a little worn in the spring, not burned up. How many of you shim your own, and where do you get your shim kits from?

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Used to throw away every injector that failed a pop test, then a guy in Bakersfield showed me the shim trick | Diesel Mechanics - The Community Guide