How to Test the Fuel Pump Pressure of a 1994 Jimmy

The 1994 GMC Jimmy, the near-identical twin of the Chevy S-10 Blazer, had two engines available. The standard engine was a 165-horsepower, throttle-body-injected, 4.3-liter V-6, and the optional engine was a 200-horsepower, central-multiport-injected, 4.3-liter V-6. Checking the fuel pressure varies greatly between the two engines, so knowing which one your Jimmy has is important. A quick way to tell is to read the eighth character in the vehicle identification number. If the eighth digit is a W, your Jimmy has the central-multiport-injected, 4.3-liter engine. If the eighth digit is a Z, your Jimmy has the TBI, 4.3-liter engine.

Instructions

Find the fuel pressure service port behind the upper intake manifold on the drivers side. Unscrew the cap from the fuel pressure, if applicable.

Unscrew the gas cap and set it aside. Connect a fuel pressure gauge to the fuel service port, using the pressure testers quick-connect fitting. Place the fuel pressure gauges bleed hose in a small container and open the gauges bleed valve to release fuel pressure.

Tighten the gas cap. Turn the ignition to the Run position for two seconds, then to the Off position for 10 seconds. Turn it to the Run position again and check for fuel leaks.

Start the Jimmys engine and allow it to idle. Read the fuel pressure gauges reading. A correctly operating fuel pump produces between 55 to 61 psi of pressure. Any lower than 55 psi indicates fuel pump pressure failure, which may be caused by a kinked line, clogged filter or a failed fuel pump..

Remove the gas cap. Turn the engine off and place the bleed hose back into the small container. Open the bleed valve to release the fuel pressure. Wrap the quick connect fitting with a thick shop cloth and disconnect the fitting from the service port.

Tighten the cap onto the fuel pressure service port. Tighten the gas cap until it clicks.

Repeat Step 3 to check for fuel leaks.

Remove the gas cap from the Jimmy to release the fuel pressure.

Trace the fuel feed line, the line on the drivers side of the throttle body, toward the rear of the truck until you find where it connects to a steel line. Loosen the union connecting the two lines using two line wrenches one to loosen the union nut and one to hold the other hose still.

Find adapters for your fuel pressure gauge that tighten smoothly onto the flexible hose and steel hose. Snug these adapters onto each hose with two line wrenches.

Tighten the gas cap. Turn the SUVs ignition to the Run position for two seconds, then to the Off position for 10 seconds. Turn it to Run again and check for leaks.

Start the SUV and read the psi displayed on the fuel pressure gauge. The correct pressure for this engine is between 9 to 13 psi. If the pressure is low, there is either a pinched fuel line, clogged filter or the fuel pump is failing.

Remove the gas cap to relieve fuel pressure. Loosen the fuel pressure gauge adapters from the fuel hoses, but do not remove them. Wrap the each connection with a thick shop cloth, then remove the fuel pressure gauge from the lines.

Reconnect the flexible line to the rigid line and tighten the union until it is snug, using two line wrenches.

Repeat Step 4 to check for leaks.