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Fuel Pump Pressure Test
By Mike Bumbeck/autoMedia.com
Printable version
Degree of DifficultyModerate
Moderate
Estimated Time120 minutes
120 minutes
Hooking Up
Selecting the right fuel pressure gauge kit depends on the make and model of vehicle and type of test fitting. If your Alfa Romeo Montreal's SPICA fuel injection or Mitsubishi Starion's Mikuni throttle body system is acting up then cobbling together a custom adapter may be the only way to test the system. Use only fuel injection line and hose clamps designed for fuel injection if making an adapter. Regular low-pressure fuel vapor line and hose clamps won't hold up to high-pressure fuel. Before beginning any work with fuel, start by finding a working fire extinguisher approved for extinguishing fuel and place it nearby. Don't leave fuel soaked rags in a heap as they can combust and cause a fire. Eye protection and gloves are highly recommended.
If you're lucky the fuel system will have a Schrader-type or similar access valve to easily and quickly tap into fuel pressure with the gauge and supplied kit adapters. Our luck had run out in the case of this throttle body injected Mitsubishi Starion. A few brass fittings, some fuel injection line, and fuel injection hose clamps were required to fabricate an adapter.
Tap into the Fuel Pressure with the Gauge and Supplied Kit Adapters
The service manual will reveal the test fitting location or where to tap into the fuel system. In this case, removal of a threaded plug was required to thread in the adaptor. If tapping directly into the fuel system, either relieve pressure first or be prepared for high-pressure fuel.
Find the Test Fitting Location
Some vehicles will energize the fuel pump with the key turned to ignition. Others have a jumper port. If neither of these options is available then connect the gauge and start the vehicle. Be ready to turn the engine right back off in case of fuel leaks. Monitor pressure at idle.
Monitor Pressure at Idle
Another test is to watch fuel pressure while increasing the rpm of the engine by manually opening the throttle. The service manual will tell you what's supposed to happen. In this case the pressure is supposed to remain steady.
Watch Fuel Pressure While Increasing Engine RPM
Disconnect the tester. Be prepared for pressurized fuel with a rag or catch container. If the engine is hot wait until things cool down first.
Disconnect the Tester
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