GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 Wave 🢒 Engine 🢒 Engine Controls - 1.4L DOHC 🢒 Fuel Injector Balance Test with Special Tool

Caution: Refer to Relieving Fuel Pressure Caution in the Preface section.

Notice: Refer to Nylon Fuel Lines Notice in the Preface section.

Notice: Refer to Fuel Injector Balance Test Notice in the Preface section.

A fuel injector tester is used to energize the injector for a precise amount of time, thus spraying a measured amount of fuel into the intake manifold. This causes a drop in the fuel rail pressure that can be recorded and used to compare each of the fuel injectors. All of the fuel injectors should have the same pressure drop.

Fuel Injector Balance Test Example

Cylinder

1

2

3

4

First Reading

296 kPa (43 psi)

296 kPa (43 psi)

296 kPa (43 psi)

296 kPa (43 psi)

Second Reading

131 kPa (19 psi)

117 kPa (17 psi)

124 kPa (18 psi)

145 kPa (21 psi)

Amount Of Drop

165 kPa (24 psi)

179 kPa (26 psi)

172 kPa (25 psi)

151 kPa (22 psi)

Average Range: 156-176 kPa (22.5-25.5 psi)

Injector OK

Faulty Injector - Too Much Pressure Drop

Injector OK

Faulty Injector - Too Little Pressure Drop

Test
  1. Turn the ignition switch to ON in order to get the fuel pressure to its maximum level.
  2. Allow the fuel pressure to stabilize and then record this initial pressure reading. Wait until there is no movement of the needle on the fuel pressure gage.
  3. Follow the manufacturer's instructions for the use of the adapter harness. Energize the fuel injector tester once and note the fuel pressure drop at its lowest point. Record this second reading. Subtract it from the first reading to determine the amount of the fuel pressure drop.
  4. Disconnect the fuel injector tester from the fuel injector.
  5. After turning the ignition switch to ON, in order to obtain maximum pressure once again, make a connection at the next fuel injector. Energize the fuel injector tester and record the fuel pressure reading. Repeat this procedure for all the injectors.
  6. Retest any of the fuel injectors that the pressure drop exceeds the 10 kPa (1.5 psi) of the average pressure drop value.
  7. Replace any of the fuel injectors that fail the retest.
  8. If the pressure drop of all of the fuel injectors is within 10 kPa (1.5 psi) of the average pressure drop value, then the fuel injectors are flowing normally and no replacement should be necessary.
  9. Reconnect the fuel injector harness and review the symptom diagnostic tables.
  10. An engine cool down period of 10 minutes is necessary in order to avoid irregular readings due to hot soak fuel boiling.
  11. Connect the fuel pressure gage carefully to avoid any fuel spillage.
  12. The fuel pump should run about 2 seconds after the ignition is turned to the ON position.
  13. Insert a clear tube attached to the vent valve of the fuel pressure gage into a suitable container.
  14. Bleed the air from the fuel pressure gage and hose until all of the air is bled from the fuel pressure gage.
  15. The ignition switch must be in the OFF position at least 10 seconds in order to complete the engine control module (ECM) shutdown cycle.