Published on October 17, 2025 Author DW STAFF Share article Facebook 0 Twitter 0 Mail 0 Changing Injector O-Rings on “Jan,” the 7.3L Power Stroke Changing Injector O-Rings in “Jan”—the 7.3L Power Stroke Diesel Replacing Injector O-Rings on a 7.3L Power Stroke The 7.3L Power Stroke diesel is known for its reliability, but like any engine, it has a few maintenance issues that are critical to keeping it running strong. Today, we are dealing with “Jan,” our 7.3L-powered F-250, putting oil through the fuel system, and returning it back into the tank—about three gallons of it. These small seals play a big role in fuel delivery and oil pressure, and when they fail, you’ll notice hard starts, white smoke, fuel in the oil, or even oil in the fuel like we are dealing with now. Replacing them isn’t the most glamorous job, but it’s straightforward if you follow the right steps. Final Checks The folks over at DmaxStore.com have it covered when it comes to transmission coolers with the company’s Maxflow Arctic series coolers. This cooler design has been on the market for a bit now with great results, but the team at DmaxStore just did a refresh and added a few key features that might make this one the best coolers for your money.Subscribe Our Weekly Newsletter Why O-Rings Matter Each injector in a 7.3L uses multiple O-rings to keep high-pressure oil, fuel, and combustion gases where they belong. Over time, these rubber seals can harden, crack, or wear out. If left unchecked, bad O-rings can cause fuel contamination, leaks, and eventually injector failure. Preventative replacement is far cheaper than replacing an entire injector set. Getting Down to Business Before starting, make sure you’re working on a cool engine and have the necessary parts on hand. A full injector O-ring kit is recommended (pictured here) rather than piecemeal replacements, and to handle the job, you’ll need basic hand tools, a torque wrench, and clean shop rags. Many technicians also suggest replacing valve cover gaskets at the same time since you’ll already have them off. Step 1: Power down and get your valve covers off. Always disconnect both negative cables, especially with the injector solenoids being electronically powered. After that, get to tearing down your charge tubes so the valve covers are exposed. Step 2: Remove valve covers and injector harness. Unbolt and carefully remove the valve covers to access the injector wiring and injectors. Then disconnect the valve cover harness plug, along with the plugs from each injector. Step 3: Remove injectors. Using the proper socket and pry bar method, remove each injector carefully, avoiding damage to the injector body. Step 4: Replace O-rings. As you can see, the O-rings on six out of eight of these injectors have had oil pass through at least one of the O-rings on each body, which is definitely the cause of our issue of oil in the fuel tank from it passing the oil through the return system. On the workbench, clean the injector body thoroughly. Remove the old O-rings and carefully install the new ones using clean engine oil or assembly lube for proper seating. The new color-coded O-rings will make it easier to replace in the future if one fails. Step 5: Reinstall injectors. Place injectors back into the head, ensuring correct alignment, and torque them to factory spec (usually around 120 in-lbs for the hold-down bolt, but always verify with the service manual). Step 6: Reconnect wiring. Plug the harnesses back into each injector, making sure connections are snug. Step 7: Reinstall valve covers. Replace gaskets if needed, then reinstall and torque valve covers. Step 8: Reconnect batteries and prime system. Hook the batteries back up, cycle the key a few times to prime the fuel system, and then start the engine. Final Checks The folks over at DmaxStore.com have it covered when it comes to transmission coolers with the company’s Maxflow Arctic series coolers. This cooler design has been on the market for a bit now with great results, but the team at DmaxStore just did a refresh and added a few key features that might make this one the best coolers for your money. Photo by Mach1Media Total 0 Shares Share 0 Tweet 0 Pin it 0 Share 0
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