Fuel Injectors

Remove injectors but leave hoses connected. Place injectors in individual measuring containers. Operate fuel pump to build up pressure, then turn pump off.
Lift air flow sensor plate half-way to operate injectors until one container has filled to 3.4 oz. (100 cc). Volume of fuel in other containers should not vary more than 10-20%.
If one injector is outside specifications, swap hoses from it and one good injector at fuel distributor and retest. If same container is low, injector is faulty or fuel line is restricted. If other container is low, fuel distributor must be replaced.

Relieve system pressure and remove pressure testing gauge. Turn on pump to build up pressure. Injectors may leak slightly, but should stop leaking within 15 seconds. If drops form, check air flow sensor plate height, sticking fuel distributor plunger, or injector opening pressure.

FUEL INJECTION PRESSURE TESTING

Application

Line Pressure psi (kg/cm² )

Warm Control Pressure psi (kg/cm² )

Rest Pressure psi (kg/cm² )

Nozzle Opening Pressure psi (kg/cm² )

Audi 500 Turbo

75-85 (5.3-6.0)

⁽¹⁾ 49-55 (3.4-3.9)

23-35 (1.6-2.5)

38-53 (2.7-3.7)

Audi 4000, 5000

68-78 (4.8-5.5)

⁽¹⁾ 49-55 (3.4-3.9)

23-35 (1.6-2.5)

42-59 (2.9-4.1)

BMW 320i

65-75 (4.6-5.3)

49-55 (3.4-3.9)

21 (1.5)

44 (3.1)

Mercedes-Benz

72-81 (5.1-5.7)

⁽¹⁾ 49-55 (3.4-3.9)

36-41 (2.5-2.9)

43 (3.0)

Peugeot 505

64-75 (4.5-5.3)

49-55 (3.4-3.9)

38-39 (2.6-2.7)

43-59 (3.0-4.1)

Porsche 911SC

65-75 (4.6-5.3)

49-55 (3.4-3.9)

16-19 (1.1-1.3)

36-52 (2.5-3.7)

Porsche 924

65-75 (4.6-5.3)

49-55 (3.4-3.9)

21-24 (1.5-1.7)

36-52 (2.5-3.7)

Porsche 924 Turbo

84-94 (5.9-6.6)

⁽²⁾ 50-56 (3.5-3.9)

⁽³⁾ 15 (1.0) Min.

39-55 (2.7-3.9)

Saab

64-75 (4.5-5.3)

49-55 (3.4-3.9)

22 (1.5) Min.

43-55 (3.0-3.9)

Volkswagen

68-78 (4.8-5.5)

49-55 (3.4-3.9)

35-38 (2.5-2.7)

51-59 (3.6-4.1)

Volvo 4-Cyl.

64-75 (4.5-5.3)

50-56 (3.5-3.9)

38 (2.7) Min.

46-55 (3.2-3.9)

Volvo 6-Cyl.

64-75 (4.5-5.3)

45-49 (3.2-3.4)

38 (2.7) Min.

46-55 (3.2-3.9)

⁽¹⁾	Vacuum lines connected.

⁽²⁾	No vacuum applied.

⁽³⁾	Minimum after 60 minutes.

Remove injectors from vehicle and use injector tester to determine opening pressure. See Fig 1. Check readings against specifications. See Fuel Injection Pressure Testing table. Replace injectors if faulty.

Fig 1: Fuel Injector Tester
Courtesy of AUDI OF AMERICA, LLC

If opening pressure of injectors is not within limits, replace injectors.