Fuel Injection Testing

Component List

To test pressure regulator release fuel pressure then install pressure gauge between main fuel line and fuel filter. Start engine and run at idle, pressure should be between 28-37 psi.

To perform leak down test install pressure gauge like above. Use a hose plier clamp to pinch off the fuel return line on the pressure regulator. Locate the 2-pin yellow test connector near the fuel filter and install a jumper wire accross the 2 pins. Make sure the opening relay is connected and turn the ignition switch to the on position for 10 seconds to run fuel pump. Turn the key to the off position and remove jumper wire from test connector, watch fuel pressure for 5 minutes. If pressure is below 21 psi replace the fuel pressure regulator.

Note: If faulty may cause a "rolling" or "hunting" idle may also cause hard start when engine is warm.

Start testing by verifying the solenoid is getting vacuum, this can be done by starting the truck and removing the orange vacuum line from the solenoid, place thumb over the port and feel for vacuum. If no vacuum is felt repair the vacuum leak this may fix a rough idle or hard start problem.

Locate the Blue with Black stripe terminal wire and ground it with a jumper wire (solenoid connector still on). Hold thumb over part and verify no vacuum is felt. If you are sure the jumper wire made contact then check the solenoid.

To test solenoid, disconnect the connector and blow through the orange vacuum line, air should flow from the opposite port. Disconnect the solenoid and connect to 12 volts and again blow through the port for the orange vacuum line. Check that air comes out of the valve filter which is the cylindrical piece on the opposite side of the connector. If solenoid fails either check replace it.

Note: A bad PRC will cause similar or same problems as a bad pressure regulator.

Note: A faulty pulsation dampener will NOT cause a major drivability problem.

Testing is done with engine running and again with ignition on:

Blue with Yellow stripe wire should measure 12v.
Green with Orange should measure 0v.
Green with Black should measure 1-2v key on, .9-5v engine running.
Green with Yellow and Black with Orange stripe wires should both read about 0v