See Figure 1
The fuel injectors are mounted on the left side of the cylinder head and are connected to the fuel pump by the high pressure fuel lines.
The injectors consist of the nozzle holder, O-ring, water seal, shims, spring, needle valve and nozzle. Fuel enters the injector through the top of the injector (fuel inlet) and is routed to the needle valve bore. The injector fires when fuel pressure rises to an amount sufficient to overcome the needle valve spring tension. For 1989-93 models, this pressure is 3,550 psi (24,65 kPa). For 1994-96 models, the pressure needed to overcome the needle valve spring tension is a little higher at 3,822 psi (26,252 kPa). This pressure is commonly known as the "pop'' pressure.
As the needle valve opens, fuel flows rapidly through the spray holes in the nozzle tip into the combustion chamber. After this injection, the fuel pressure drops and the needle valve is closed preventing further fuel flow, and conversely, exhaust flow into the injector.
REMOVAL & INSTALLATION
See Figures 2, 3, 4, 5 and 6
- Disconnect the negative battery cable. Remove the throttle linkage and bracket if necessary.
- Disconnect the high pressure fuel supply line to the injector.
- Disconnect the fuel drain manifold.
- Clean the area around the injector.
Certain types of injectors MAY have an O-ring located above the hold-down nut.
- Using the correct deepwell socket, remove the injector from the cylinder head.
- Clean the injector bore with a bore brush.
- Assemble the injector and 1 new copper sealing washer. Never use more than 1 copper washer.
- Apply a thin coat of anti-seize compound to the threads of the injector hold-down nut and between the top of the nut and the injector body.
- Align the protrusion in the injector with the notch in the bore and install the injector. Tighten the injector retainer nut to 6 ft. lbs. (60 Nm).
- Push the O-ring into the groove at the top of the injector, if applicable.
- Using new sealing washers, assemble the fuel drain manifold and high pressure lines. Tighten the banjo fitting bolt to 6 ft. lbs. (8 Nm). Leave the high pressure line loose temporarily.
- To bleed air from the system, run or crank the engine and tighten the fitting after the air has expelled. If more than 1 injector was replaced, tighten each fitting after the air has expelled before going on to the next injector fitting. Tighten the fittings for 1989-93 models to 18 ft. lbs. (24 Nm) and 1994-96 models to 22 ft. lbs. (30 Nm). The operation is complete when the engine runs smoothly. If the air cannot be removed, check the pump and supply line for suction leaks.
- Install the throttle linkage and bracket if they were removed.
See Figures 7 and 8
A leaking fuel injector can cause fuel knock, poor performance, black smoke, poor fuel economy and rough engine idle. If the needle valve does not operate properly, the engine may misfire and produce low power.
A leak in the injection pump-to-injector high-pressure fuel line can cause many of the same symptoms as a malfunctioning injector. First check the lines before the injectors.
- To check the injectors, start the engine and loosen the high-pressure line nut one-at-a-time at each injector. Listen for a decrease in engine speed.
- If the engine speed drops, the injector is operating normally. If the engine speed remains the same, the injector is malfunctioning. After testing each injector, tighten the line nuts for 1989-93 models to 18 ft. lbs. (24 Nm) and 1994-96 models to 22 ft. lbs. (30 Nm).
- If an injector is found to be malfunctioning, remove it and test it on a standard bench-mount injector tester. Follow the manufacturer's instructions for bench testing the injector.
- If the opening (pop) pressure is below specifications, replace the injector. For 1989-93 models, this pressure is 3,550 psi (24,65 kPa). For 1994-96 models, the pop pressure is 3,822 psi (26,252 kPa).