Fuel Injector: Testing and Inspection

Each individual injector can be easily quick-checked to evaluate its spray pattern and to check for leakage. A more involved test, using special equipment, compares the injection quantity from all four injectors to check that both the fuel distributor and the injectors are suppling the same amount of fuel to each cylinder. Finally, a special injector tester can be used to clean injectors, measure opening pressure, or check and flush new injectors prior to installation.

If the quick-check suggests that more testing is necessary and the special equipment is not available, we suggest having the injectors tested by a qualified and properly equipped repair shop.

INJECTOR QUICK-CHECK

1. Remove one injector, leaving the fuel hose connected. Aim the removed injector into a fuel-resistant container.
2. Remove the large rubber duct from the top of the air flow sensor.
3. Remove the fuel pump relay from the fuse/relay panel and install a fused jumper wire assembly to run the fuel pump.

NOTE: Unless the fuel pump relay receives an rpm signal from the ignition system indicating that the engine is running, the fuel pumps will operate for only a few seconds when the ignition switch is turned ON. To operate the pumps longer, (for example fuel system tests without the engine running) the fuel pump relay must be bypassed to power the pumps directly.

Fuel Pump Relay Location:

One method is to remove the relay and connect a jumper wire between two sockets on the fuse/relay panel. The sockets to be used are socket #48 and socket #52 of the fuse/relay panel, which correspond to terminals #30 (battery power input) and terminal #87 (output to fuel pumps) of the relay

The jumper wire should be at least 16 ga. (1.5 mm) wire and include an in-line fuse holder with a 15 amp fuse. To avoid fuse/relay panel damage from repeated connecting and disconnecting, also include a toggle switch in the jumper wire assembly.

With the ignition switch OFF and the fuel pump relay removed, use the jumper wire assembly (toggle switch OFF) to bridge the sockets (#48 and #52) in the fuse/relay panel. Turn the toggle switch ON to operate the fuel pumps as needed for testing.

Lifting Air Flow Sensor Plate:

4. Using a magnetic tool, lift the air flow sensor plate and observe the injectors spray pattern. The injector should discharge a fine mist of fuel in an even cone-shaped pattern.

WARNING: Fuel will be expelled from all four injectors during this check. Keep the test time short and discharge as little fuel as posible. Do not disconnect any wires that could cause sparks. Do not smoke or work near heaters or other fire hazards. Keep a fire extinguisher handy.

5. Release the sensor plate and hold the injector in a horizontal position. It should not drip fuel.
6. Turn the fuel pump jumper wire assembly OFF to stop the pump.
7. Any injector that has an irregular spray pattern, or drips when the sensor plate is at rest with the fuel pump running, should be cleaned or replaced.

INJECTOR FUEL DELIVERY

Fuel Delivery Comparison:

1. A similar but more complicated test is used to compare the rate of fuel delivery from all four injectors as a means of isolating a bad injector or fuel distributor. Remove all four injectors from the engine, with the fuel lines attached, and connect them to four identical measuring containers.
2. Use the jumper wire assembly in place of the fuel pump relay to run the fuel pump during the test, as described above.

Air Flow Sensor Plate Positioner:

3. Install VOLKSWAGEN special tool #1348/1 (or equivalent). Carefully push the center sleeve all the way down, then turn the adjusting knob clockwise until the tool's magnetic tip just contacts the sensor plate center bolt. Turn the adjusting screw counterclockwise to raise the sensor plate to a point just before any of the injectors start spraying.

WARNING: Do not smoke or work near heaters or other fire hazards. Keep a fire extinguisher handy.

4. Run the fuel pump (using jumper wire assembly) and raise the air flow sensor plate to conduct the test. The tools center sleeve has two detents- one raises the plate to a position simulating idle and the second raises it higher to simulate full throttle. At the idle setting, with 20 ml collected from each injector (approximately 2 minutes) there should be no more than 3 ml difference between any two. At the full throttle setting, with 80 ml collected from each injector (approximately 40 seconds) there should be no more than 8 ml difference.
5. If the difference in the fuel quantity is greater than allowed, select the two injectors with the lowest and highest values. Loosen the unions, remove them from their fuel lines, exchange them, and repeat the test. If the same injector delivers a low amount of fuel, it is faulty and should be replaced. If the same container collects a low amount of fuel from a different injector, then that fuel line is blocked or kinked, or the fuel distributor is faulty. Reinstall the fuel injectors to the fuel lines and tighten the unions to proper torque.

CAUTION: Absolute cleanliness is essential when working with fuel circuit components of CIS-E. Even a minute particle of dirt can cause major trouble if it reaches the fuel distributor or fuel injectors. Before disconnecting any of the fuel line connections, throughly clean the unions. Always use clean tools.

CLEANING INJECTORS

Fuel Injector Pressure Tester:

1. The special tool for cleaning injectors and testing injector opening pressure is VOLKSWAGEN special tool #US 8034. Remove the injector from its fuel line by loosening the union. Inspect the injector's inlet for signs of rust. If any rust is found, the injector should be replaced.
2. Install the injector on the tester and tighten the union bolt. Pump several times to purge the air from the line. When spraying normally, the injector will make a high-pitched squeal. Pump slowly and read the injector opening pressure on the gauge as the injector starts to spray. CIS-E injectors should open at:

44 to 59 psi (3.0 to 4.1 bar)

3. Any injector which leaks, opens at a lower pressure, or has an uneven spray pattern should be replaced.

WARNING: Use only Shell mineral spirit 135 or equivalent when testing or cleaning injectors using a pressure tester. Shell mineral spirit 135 is flammable. Do not smoke or work near heaters or other fire hazards. Keep a fire extinguisher handy.