Testing fuel pressure, pressure regulator and holding pressure — AUDI

AEB
Test requirements:

Fuel pump relay OK, testing =>Page
24-31
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Fuel pump OK; testing:

=> 4-cylinder Engine, Mechanics; Repair group 20; Removing and installing parts of fuel supply system; Testing fuel pump
4-cylinder Engine, Mechanics
Removing and installing parts of fuel supply system
Testing fuel pump

Note:

Fuel pressure regulator regulates fuel pressure as a function of intake pressure.

Briefly open the fuel filler cap (to release pressure).

Cover the screw union of the supply pipe (arrow) which contains pressurised fuel with a cleaning rag to prevent fuel from splashing. Open screw union and collect fuel that flows out (place drip tray beneath cleaning rag).

Install pressure gauge V.A.G 1318 with adapters V.A.G 1318/11, 1318/12 and V.A.G 1318/13 in the supply pipe.

Note:

The shut-off cock of the pressure measuring device must be open (lever facing in the direction of flow).

Start the engine and run at idling speed.
Measure fuel pressure.
Specified value: approx. 3.5 bar

Disconnect vacuum hose (arrow) for fuel pressure regulator. The fuel pressure should rise to approx. 4.0 bar.
Re-connect vacuum hose.
Stop engine. Immediately after switching off the engine the fuel pressure drops to approx. 3 bar.
Test for leaks and holding pressure by watching pressure drop on gauge.
After 10 minutes the remaining pressure should be at least 2.5 bar.

If the holding pressure drops below 2.5 bar:

Start engine and, once the fuel pressure has built up, switch off again.
Close shut-off valve at the pressure gauge V.A.G 1318.

If the holding pressure does not drop, the following faults are possible:

Fuel pressure regulator defective
Injectors leaking
Unions on pressure gauge downstream of shut-off valve leaking

If the pressure drops again, the following faults are possible:

Union between pressure gauge and fuel supply pipe leaking
Supply pipe leaking at fuel tank
Non-return valve in fuel pump leaking; remove fuel pump and install.

=> 4-cylinder Engine, Mechanics; Repair group 20; Removing and installing parts of fuel supply system; Removing and installing fuel delivery unit
4-cylinder Engine, Mechanics
Removing and installing parts of fuel supply system
Removing and installing fuel delivery unit

Note:

To remove the pressure gauge, close the shut-off valve, unscrew the union on adapter V.A.G 1318/12, then open the shut-off valve to drain off excess fuel into a suitable container.