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). Other container volume 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. If other container is low, fuel distributor must be replaced.

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 5000 Turbo

72-81 (5.0-5.6)

49-55 (3.4-3.8)⁽¹⁾

23-37 (1.6-2.6)

38-53 (2.7-3.7)

Audi 4000, 5000

64-74 (4.5-5.2)

49-55 (3.4-3.8)

23-37 (1.6-2.6)

41-59 (2.9-4.1)

BMW 320i

64-75 (4.5-5.2)

49-55 (3.4-3.8)

24 (1.7)

44 (3.1)

Mercedes-Benz

72-81 (5.0-5.6)

49-55 (3.4-3.8)⁽¹⁾

36-41 (2.5-2.8)

43 (3.0)

Peugeot 505

64-75 (4.5-5.2)

49-55 (3.4-3.8)

38-39 (2.6-2.7)

43-59 (3.0-4.1)

Porsche 911SC

64-75 (4.5-5.2)

49-55 (3.4-3.8)

⁽²⁾

36-52 (2.5-3.6)

Porsche 924

64-75 (4.5-5.2)

49-55 (3.4-3.8)

21-24 (1.5-1.7)

36-52 (2.5-3.6)

Porsche 924 Turbo

78-87 (5.4-6.0)

49-55 (3.4-3.8)⁽³⁾

14 (1.0)

38-55 (2.7-3.8)

Saab

64-75 (4.5-5.2)

49-55 (3.4-3.8)

24-34 (1.7-2.4)

43-55 (3.0-3.8)

Volkswagen

68-78 (4.8-5.5)

49-55 (3.4-3.8)

35-38 (2.4-2.6)

46-55 (3.2-3.8)

Volvo 4 Cyl.

64-75 (4.5-5.2)

50-56 (3.5-3.9)

24-34 (1.7-2.4)

37-51 (2.6-3.6)

Volvo 6 Cyl.

64-75 (4.5-5.2)

45-49 (3.1-3.4)

24 (1.7)

37-51 (2.6-3.6)

⁽¹⁾	Vacuum lines connected.

⁽²⁾	Information not available from manufacturer.

⁽³⁾	No Vacuum applied.

Relieve system pressure and remove pressure testing gauge. Turn on pump to build up pressure. Injectors may leak slightly, but no drops should form in less than 15 seconds. If drops form, check air flow sensor plate height, sticking fuel distributor plunger, or injector opening pressure.

Fig 1: Fuel Injector Tester
Courtesy of NOT AVAILABLE
Remove injectors from vehicle and use injector tester to determine opening pressure. Check specifications in "Pressure Testing" chart and replace injectors if faulty.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Fuel Injectors

Use the Manual With the Right Hardware

When to See a Mechanic