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 Always make sure you 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 and will and cause a fire. Eye protection and gloves are highly recommended. And remember, you are working with fuel so always be careful to keep open flame and sparks as far away as possible. We would not want you burning down your shop or yourself for that matter.


 Just a little inside information on the fuel pump: The fuel pump draws fuel from the tank and sends it through the fuel line. Fuel works its way through a fuel rail and into the fuel injectors. The fuel pressure regulator senses engine vacuum and maintains the ideal fuel pressure. Fuel injectors spray fuel according to varying engine loads and speeds. In a perfect world fuel is perfectly metered into each cylinder through the fuel injectors at exactly the right moment to produce the best combination of power and efficiency.

Under Pressure 

When things go wrong in the fuel supply chain, the first thing on the list of suggested things to fix or replace is often the fuel pump. Before rushing into replacing what is sometimes the most expensive and difficult to access component in the fuel system, it's a good idea to run a fuel pressure test. Peering into what's going on with the fuel pressure can provide a better idea of overall fuel system condition. Replacing a fuel pump can be an involved job. The problem could turn out to be an easy-to-replace 14-buck fuel filter or a dead fuel pump relay. 

Besides a fuel pressure gauge and fire extinguisher, the next most important tool in this test is a repair manual for your car or engine. Every automotive fuel system is slightly different and has fuel pressure specifications and requirements unique to the system. While modern fuel injection systems work more or less the same in theory, the service manual will outline test procedures and pressure ranges for your particular engine. If the engine is getting air and spark but still acting the goat, a fuel pressure test can help diagnose what's going on. Some possibilities are:

Too Much Pressure 

Excessive pressure will force too much fuel through the injectors and cause the engine to run rich. Poor mileage, fouled spark plugs, sluggish or surging idle, and black smoke out of the tailpipe can all be caused by an over rich condition. Test the fuel pressure regulator.

Not Enough Pressure 

Choppy idle, poor engine performance and misfire can all be caused by low fuel pressure. Low fuel pressure could mean a clogged fuel filter. Check and replace fuel filter before going after the pump. Fuel tank crud can also clog in-tank sock or in-line filters. Test the fuel pressure regulator.

Hopefully,  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.

 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.

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.

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

 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. Like i said before we do not want to start a fire and safety is always our first priority.

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