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• You may wish to remove the air filter assembly and cold-side intercooler tube to improve access to the fuel pressure test port plug on the fuel filter housing. If you're installing a schrader valve test fitting that you plan on leaving connected to the fuel filter housing, you will not necessarily need to remove these items in future tests.
• The fuel filter test port plug is on the bottom of the fuel filter housing and points towards the driver side fender. Remove the plug with a 6 mm Allen wrench/drive bit and install your test fitting. If the test fitting has an o-ring, coat it in clean motor oil before installing.
• We've selected a schrader valve adapter that is compatible with most common fuel pressure gauges. This way, the test fitting can be installed and left permanently for future diagnostics. It can just as easily be removed and stored to used as a diagnostic tool for multiple trucks. The valve pictured is available here.
• Once you've installed a fitting that is compatible with your fuel pressure gauge, connect the gauge to the pressure fitting and ensure that all fittings/lines are secure.
• If you removed the air filter and intercooler tube, reinstall them.
• Fuel pressure KOEO and KOER at idle need to maintain greater than 45 psi or there is likely a restriction (plugged chassis mounted filter, for example) or lift pump problem.
• Under WOT (wide open throttle), fuel pressure must maintain or exceed 45 psi. Checking fuel pressure at WOT may help identify rough running, stalling, bucking, jerking, or other driveability concerns under load. You will need a relatively long hose for a fuel pressure gauge in order to perform this procedure.
• Consider performing the blue spring upgrade, an updated fuel pressure regulator spring recommended by Ford Motor Company that results in roughly 10% greater fuel pressure. It's cheap insurance against injector failure resulting from a low fuel pressure condition.