Part 1 of 3

PFI Chart A-5 (Part 1 of 3):

Fuel Control Wiring:

DESCRIPTION:

This procedure tests for fuel pump's ability to deliver fuel to the injector fuel rail, the fuel injectors to deliver a metered quantity of fuel, and the vacuum signal to the regulator to control fuel pressure.

NOTES ON FAULT TREE:

1. Fuel pressure is OK at this point. An injector flow test will be run next. Used with the power balance test (Chart A-4), this will determine if a weak cylinder that does not give an rpm drop in the power balance test is caused by fuel flow or spark. A remote start switch can be used to actuate the fuel pump through the fuel pump prime connector.

2. To determine whether the excessively high pressure is caused by the pressure regulator or a restricted fuel line, connect the female end of J37287-2 to the pressure regulator side of the return line, and place the other end of the tool in a suitable container for FLAMMABLE liquids. The tool is near the fuel filter (which is connected to the feed line). DO NOT connect tool to fuel filter or feed line. Open the shut-off valve and pressurize the system by turning the ignition to RUN without starting the engine. With the return line by-passed, pressure above 50 psi indicates the pressure regulator is not working properly, and pressure below 45 psi indicates the fuel return line is restricted.

3. To determine whether the fuel pump or pressure regulator is the cause of the low pressure, install tool J37287-2 in the return line and shut-off the valve to dead head the system. The tool is connected to the return line at the coupling located near the fuel filter which is connected to the feed line. DO NOT connect tool to fuel filter or feed line. Pressurized the system by turning the ignition to RUN without starting the engine. If the fuel pump can produce 50 psi pressure, and the pressure holds, this verifies the fuel pump and internal check valve are working. If the fuel pump cannot produce at least 40 psi under dead headed conditions, the cause can be a faulty fuel pump or pulsator damper, a restricted fuel line or filter, or a leaking injector.

4. A leaking injector is indicated by a rich exhaust (smoke or a rotten egg smell) with low fuel pressure indicated in the above test. A leaking injector is indicated by a cylinder which does not produce an rpm drop during the Chart A-4 power balance test. Replace the injector on any cylinder which does not produce an rpm drop. If injectors test OK, check fuel pump and pulsator damper.