Fuel Pressure Regulator And Residual Pressure, Checking

Function

The fuel pressure regulator regulates the fuel pressure to constant 4.0 bar.

Fig 1: Identifying Special Tools -- Fuel Pressure Regulator And Residual Pressure, Checking

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Special tools and workshop equipment required

Pressure gauge VAG 1318
Adapter VAG 1318/9
Assembly tool for spring-type clamps VAS 5024A
Diesel extractor VAS 5226

Not illustrated:

Adapter VAG 1318/20
Adapter VAG 1318/20-1

Test requirements

Parking brake must be engaged or else daylight driving lights will be switched on.
For vehicles with automatic transmission, selector lever must be in P.
Delivery quantity of Fuel Pumps (FP) OK, check, Fuel Pumps (FP), checking.

Test sequence

Observe safety precautions.

Observe rules for cleanliness.

-- Remove fuses -13- and -14- for activation of Fuel Pump (FP) Relay -J17- and Fuel Pump (FP) 2 Relay -J49- from fuse holder.

Fig 2: Identifying Fuses

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Fuses nos. -13- and -14- are located in fuse holder of E-box, in plenum chamber, left.

-- Thread adapter (VAG 1318/20-1) on adapter (VAG 1318/20).

Fig 3: Identifying V.A.G 1318/20-1 & V.A.G 1318/20

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-- Turn valve at T-piece (arrow) counterclockwise until it is completely open.

-- Remove protective cap for bleeder valve on fuel rail.

-- Connect pressure gauge (VAG 1318) with adapters (VAG 1318/20, VAG 1318/20-1, VAG 1318/9) and diesel extractor (VAS 5226) as shown to bleeder valve -1-.

Fig 4: Connecting Pressure Tester V.A.G 1318 To Breather Valve Using Adapter V.A.G 1318/20, V.A.G 1318/20-1, V.A.G 1318/9 And Diesel Extractor VAS 5226

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-- Close pressure gauge shut-off valve (lever perpendicular to direction of flow).

Fig 5: Closing Pressure Gauge Cut-Off Valve

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-- Insert fuses -13- and -14- in the fuse holder.

Fig 6: Identifying Fuses

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-- Start engine and let run at idle.

-- Turn valve at T-piece of adapter VAG 1318/20 clockwise into bleeder valve to stop.

-- Open shut-off valve of pressure gauge briefly and close again to bleed the line to the pressure gauge.

-- Measure fuel pressure.

Specified value: approx. 4.0 bar positive pressure

-- Switch ignition off.

If specified value is not obtained:

-- Check flow quantity of Fuel Pumps (FP), Fuel Pumps (FP).

-- Replace fuel pressure regulator if necessary.

-- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.

-- Generate readiness code.

If specified value is obtained:

-- Check for proper seal and residual pressure. Observe pressure drop on pressure gauge for this. After 10 minutes at least 3.0 bar positive pressure should still be present.

If residual pressure falls below 3 bar positive pressure:

-- Check pressure gauge for proper seal.

-- Test check-valves of Fuel Pumps (FP), Fuel Pumps (FP), checking.

When removing pressure gauge after completed test:

-- Remove fuses -13- and -14- for activation of Fuel Pump (FP) Relay -J17- and Fuel Pump (FP) 2 Relay -J49- from fuse holder.

Fig 7: Identifying Fuses

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-- Open shut-off valve of pressure gauge to release fuel pressure.

-- Place a rag around separating point to catch escaping fuel.

-- Remove pressure gauge with adapters.

-- Insert fuses -13- and -14- in the fuse holder.

Fig 8: Identifying Fuses

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Final Procedures

After the repair work, the following work steps must be performed in the following sequence:

Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .