Fuel Pump: Testing and Inspection

Checking Quantity Delivered By Fuel Pump - Fuel System Without Return Line

WARNING: Observe the general safety instructions when working on the fuel system and when handling petrol and other fuels.

Attach or mount a warning notice on the vehicle in a clearly visible position -see Figure-.

Example of warning sign on engine compartment lid 996







Special tool for checking fuel quantity

Item A:

NOTE: The battery voltage may not fall below 12 volts during the fuel pressure check.

1. Check the battery charging condition e.g. using a voltmeter or the Porsche System Tester. The battery voltage may not fall below 12 volts during the check.
2. Reduce fuel pump supply pressure. To do this, remove the fuse carrier cover in left footwell and pull off the fuse for the fuel supply pump (level C, 4th fuse from the left). Then actuate the starter for a couple of seconds. This procedure does not cause an entry to be made in the fault memory. Insert fuse again and fit cover.
3. Connect the Porsche Tester PST 2 in the vehicle, switch on the ignition and switch off all loads, such as the radio and air conditioning.
4. Remove rear underside panel. To do this, the rear plastic nuts on the left side cover and the centre underside panel must be loosened, see items 4, 5 and 19.







5. Disconnect rapid-action coupling on the fuel supply line by pressing in the locking lug -arrow- and pulling off the coupling. Collect emerging residual fuel.







6. Connect special tool measuring adapter No. 9705 to the fuel pressure line with the rapid-action coupling -see Figure-. Be sure that the coupling is fitted correctly (must engage audibly) by pulling the line apart.
7. Place the drainage hose in a petrol-resistant canister. Be sure that the canister does not tip over.







8. Activate the fuel pump relay using the Porsche System Tester PST 2. To do this, select the line "drive links" in the DME control unit individual search and then select fuel pump relay. Activate by pressing "F8" -see Figure- until fuel emerges from the drainage hose. Deactivate the fuel pump relay by pressing "F8" and pour any leaked fuel from the canister into a petrol-resistant container. Keep a stopwatch at hand for the following measurement.
9. Activate fuel pump relay again and keep active for 60 seconds. Collect emerging fuel in an available container. Deactivate the fuel pump relay after 60 seconds.
10. Transfer collected fuel to a suitable measuring container and compare with the measure value specified in the following.

Target values for supplied fuel quantity:
- Boxster, Boxster S: at least 2.0 litres

11. Remove special tool and attach rapid-action coupling to fuel supply line. Be sure that the coupling is fitted correctly (must engage audibly) by pulling the line apart.
12. Install rear underside panel.
13. Switch off ignition, switch off Porsche System Tester and disconnect.