WS4 & WS5

Fuel Pressure and Flow

This test was done on a nissan primera SR18 engine.

Measure the fuel pressure with the engine idling.

= 125kpa

Maximum : With engine idling, clamp the fuel return line.

= 500 kpa

WOT:  With the engine idling, disconnect the vacuum line going to the fuel pressure regulator.

= 425kpa

Residual :  Turn off the engine and watch, and watch fuel pressure for five minutes.

= 190kpa

Flow :

= 2.0 liters per minute or 0.5 liter per 15 seconds

Its important to know a vehicles fuel pressure/flow because if your vehicles fuel pressure is to low there could be a leak somewhere or fuel pump could be faultyor need to replace fuel filter. Or if your fuel pressure is to high there could be faulty fuel pressure regulator or blocked return line this will make the vehicle use a lot of petrol.

Describe the symptoms a vehicle would give with each case.

Low fuel pressure - vehicles may surge, stall, engine hesitation wile accelerating, lack power.

Low fuel flow - engine wont start, abnormal engine combustion, surging.

High fuel pressure - high CO emissions, hard starting , poor fuel economy

Faulty fuel pressure regulator - excessive fuel pressure, engine running rich, bad fuel economy



WS5 Scan Tool Diagnostics

Vehicle Make - Nissan
Model - Avernir
Year -1997

Test done at idle.

Trouble Codes or Fault Codes.

No Faults.

Lecturer put in a fault -

Code number 12, system affected -  mass air flow

Visual inspection to find fault.

Found the mass air flow connector plug was disconnected.

Found the TPS connected pug was disconnected.

So I reconnected plugs and rechecked fault codes, now the PIDs were back to normal then we cleared the codes by erasing them. Then rechecked fault codes - normal system

Discuss the importance of live data when fault finding.

Live data is very useful for fault finding because you can see the values of the sensors (voltages) also temperature, RPM etc. So pinpointing a fault is much easier.

Explain the need for parameters when checking live data.

Its important to know the parameters of live data so you can see if the sensors and actuators are operating within there specifications.

Discuss how a scan tool can aid you when fault finding.

Using a scan tool is a good aid because it can show you fault codes also fault code history and live data which shows you whats happerning at that moment.