Engine Controls - System & Component Testing: Diagnosis Audi A4 B5 facelift

FUEL PRESSURE TEST

Note. Volkswagen Audi Group (VAG 1551) scan tool is necessary to activate fuel system for fuel pressure test.

Fuel Injector Leak Test

1. Ensure fuel system pressure is within specification before performing this test. Remove fuel rail, complete with fuel injectors, from engine. DO NOT disconnect fuel supply or return lines. Using VAG 1551 scan tool, energize fuel pump.
2. With fuel pump running, visually inspect fuel injector for leaks. Maximum allowable leakage is 1-2 drops of fuel per injector per minute. If fuel injector leaks more than 2 drops of fuel per minute, replace leaking fuel injector. ALWAYS replace fuel injector "O" rings.

Fuel Injector Resistance Test

Turn ignition off. Disconnect fuel injector electrical connector. Using a DVOM, measure resistance across fuel injector terminals. See INJECTOR RESISTANCE table. If resistance is not within specification, replace fuel injector.

INJECTOR RESISTANCE

Fuel Injector Quantity Test (2.8L)

1. Remove fuel rail, complete with fuel injectors, from engine. DO NOT disconnect fuel supply or return lines. Place fuel injector being tested into a graduated container. Connect one terminal of fuel injector to battery positive terminal.
2. Connect other terminal of fuel injector to ground for exactly 30 seconds. Fuel quantity should be 2.9-3.7 oz. (85-110 ml). If fuel quantity is more than or less than specification, replace faulty fuel injector.

SPARK TEST

Note. When ignition coil is triggered, spark is supplied to 2 spark plugs at one time. One spark plug fires during compression stroke and the other plug fires during exhaust stroke (waste spark).

Check for a strong Blue spark at coil wire and at each spark plug wire by holding wire terminal no more than 1/4" from chassis ground while cranking engine. Disconnect and inspect all related ignition system connectors and harness. Clean or repair as necessary.

See also:
• WIRING DIAGRAMS