Fuel Delivery System

Check System Integrity

Visually inspect entire fuel delivery system. Check fuel lines, connections, relays, fuel tank, fuel pump, fuel pressure regulator, fuel pulse damper and fuel injectors. Inspect fuel system for possible collision damage. Visually inspect electrical wiring harnesses and connectors. Check for loose pins, corrosion, abrasions and other damage. Inspect electrical system for possible collision damage. Verify vehicle has been maintained. Verify fuel pump shutoff switch is set (on). Verify battery voltage is 12.5 volts or more. Check integrity of fuses. Verify fuel level is sufficient. If any problems are identified, repair as necessary. Rerun QUICK TEST under SELF-DIAGNOSTIC SYSTEM. If no problems are found, go to next step.

Check For Voltage At Fuel Pump Harness Connector

Using scan tool, verify fuel pump shutoff switch state. Perform fuel pump shutoff switch procedure. See INERTIA FUEL SHUTOFF SWITCH under SWITCHES in SYSTEM & COMPONENT TESTING - B2300, B3000, B4000 & TRIBUTE article. Disconnect fuel pump harness connector at fuel pump. With KOEO, connect a DVOM between fuel pump power circuit (Pink/Black wire) and fuel pump ground (Black/Yellow wire) at fuel pump harness connector. Enter Output Test Mode and turn on fuel pump circuit. Monitor voltage reading. If voltage is more than 12.5 volts, exit Output Test Mode. Reconnect fuel pump harness connector. Restore vehicle. Go to next step. If voltage is 12.5 volts or less, check for opens and shorts in fuel pump power and ground circuits. See WIRING DIAGRAMS article. Restore vehicle.

Check Fuel Filter For Proper Maintenance

Locate and inspect vehicle maintenance records. Check last service date. If fuel filter was replaced within the last 1000 miles, go to next step. If fuel filter was not replaced within the last 1000 miles, replace fuel filter. Go to next step.

Check Fuel Pressure

Release fuel pressure. See FUEL PRESSURE RELEASE . With KOEO, using scan tool, access Output Test Mode. Run fuel pump to obtain maximum fuel pressure. Fuel pump will run for approximately 8 seconds when Output Test Mode is selected and activated. If fuel pressure is 56-72 psi (389-499 kPa), go to step 5 . If fuel pressure is not 56-72 psi (389-499 kPa):
- For fuel pressure more than 72 psi (499 kPa), replace faulty fuel pump. Restore vehicle. Recheck fuel pressure.
- For fuel pressure less than 56 psi (389 kPa), go to step 7 .

Check Fuel Injector Flow & Leakage

Using a fuel injector tester, flow test fuel injectors following equipment manufacturers instructions. See FUEL INJECTOR FLOW RATE SPECIFICATIONS table. If flow rate values are within specification, verify no other leak is present. Replace faulty fuel pump. If flow rate values are not within specification, replace faulty fuel injector(s). Restore vehicle. Recheck fuel pressure. Go to next step.

FUEL INJECTOR FLOW RATE SPECIFICATIONS

Engine	Lbs. Hr. (kg/hr)
2.3L	21 (9.6)
3.0L	12 (5.5)
4.0L	19 (8.7)

Check Pulse Damper Diaphragm

Install fuel pressure gauge. Start engine and idle for 10 seconds. Turn ignition off. Wait 10 seconds. Start engine again and idle for 10 seconds. Turn ignition off. Disconnect pulse damper vacuum hose. Inspect for fuel in vacuum hose and pulse damper port. If vacuum hose and pulse damper port are free from fuel contamination, go to next step. If vacuum hose and pulse damper port are not free from fuel contamination, replace components as necessary.

Check Fuel Supply Line For Restriction

Disconnect fuel supply line at fuel rail. Disconnect fuel supply line at fuel pump. Inspect fuel supply line for restrictions. Apply 3-5 psi (21-34 kPa) regulated air pressure to fuel supply line. Observe air flow. If air flows freely, replace faulty fuel pump. If air does not flow freely, repair fuel supply line restriction. Restore vehicle. Recheck fuel pressure.