Fuel Pump Pressure Test

Fig. 1 Bosch Motronic Electronic Engine Control System Terminal Identification:

Refer to Fig. 1 when performing the following test procedures.


ENGINE STATIC

1. Install fuel pressure gauge to fuel rail.
2. Locate fuel pump relay at right hand rear of engine compartment near strut tower. Disconnect relay electrical connector, then activate fuel pump by jumpering connector terminal 30 to 87. Fuel pressure reading should be 33.3-39.1 psi.
3. If fuel pressure is greater than specified, proceed to step 4. If pressure is less than specified, proceed as follows:
a. Pinch fuel return line slightly so as not to cause damage.
b. If fuel pressure increases to 72 psi, replace pressure regulator. Do not allow fuel pressure to exceed 87 psi.
c. If fuel pressure does not increase, check fuel line, filter and sock for blockage or damage.
d. If pressure still remains below specifications, replace fuel pump.
4. Disconnect fuel return line from pressure regulator, then connect a new fuel line to pressure regulator and position opposite end of line over a suitable container.
5. Activate fuel pump as specified in step 2.
6. If pressure is now within specifications, check return line for blockage.
7. If pressure is still not within specifications, replace pressure regulator.

ENGINE RUNNING

1. Install fuel pressure gauge to fuel rail, then start engine and allow to idle. Fuel pressure reading should be 26.1-31.9 psi.
2. If fuel pressure is within specifications, refer to ``Pressure Leak Down'' for further testing procedures. If pressure is not as specified, proceed as follows:
a. Check connection at pressure regulator.
b. Check blocked or damaged intake manifold-to-pressure regulator hose.
c. Check for blockage in intake manifold.
d. If pressure is still not within specifications, replace pressure regulator.

PRESSURE LEAK-DOWN

1. Install fuel pressure gauge to fuel rail, then start engine and allow to idle.
2. Stop engine. Fuel pressure should drop slowly to no less than 14.5 psi in 20 minutes.
3. If pressure does not remain as specified in step 2, check connections at the fuel tank, pump, filter, supply line, rail, injector, intake manifold, return line and pressure regulator.
4. Check pressure regulator spring diaphragm for leaks.
5. Inspect check valve allows fuel flow only in output direction.
6. Remove fuel rail injector assembly and inspect as follows:
a. Attach fuel line to fuel rail injector assembly.
b. Locate fuel pump relay at right hand rear of engine compartment near strut tower. Disconnect relay electrical connector and activate fuel pump by jumpering connector terminal 30 to 87.
c. Ensure no fuel drips from any injector within a 60 second interval. Replace individual injectors if leakage is other than specified.