FUEL PRESSURE AND FLOW (PETROL ONLY)
Safety goes first, especially while working on the fuel system. Fire extinguishers were located. Any sources of sparks, flame or job related with high temperature expose were excluded. Eye protection must be used during this test.
Fuel pressure specification for Toyota Corolla with engine 4A-FE: 265 – 304 kPa (2.7 – 3.1 kgf/cm2, 38 – 44 psi).
To relieve pressure from the system fuel pump fuse was taken off, engine cranked to make sure it did not start. All line was checked for the fuel leaks. With no leaks the experiment started.
First record of 44 psi was done with the ignition key on and engine off.
While the engine was idling, the pressure gauge had shown 40 psi.
With the clamp on the fuel line for a short period of time pressure increased up to the 80-85 psi
Disconnected the vacuum line which goes to the fuel pressure regulator we recorded 49 psi pressure.
After the engine was turned off for five minutes residual pressure in the system changed from 38 psi to 44 psi
Flow rate for this engine is ½ litre in 15 seconds
After all measurements were done whole system were double checked for leaks. There were no leaks.
The fuel system provides fuel injectors with constant supply of fuel under stable pressure. This system is fully independent from EFI. Pressure regulator is mechanical device which is controlled by air from intake manifold. Thus, injectors opening for a certain amount of time spray fuel accordingly to the fuel pressure.
Less than needed pressure as well as low fuel flow (fuel filter is clogged) will bring problems with air fuel ratio. As a result, lean mixture, rough idling, and losses in performance and flat spots are likely during acceleration and cruising.
Excessive pressure due to pressure regulator fault or faulty fuel pump will lead to the enrichment of fuel mixture. Black smog from exhaust pipe, increasing fuel consumption, and misfire are possible symptoms of these faults. Consequences can be fouled spark plugs with time being and heavy start in the cold temperature conditions.
Any fluctuations of the fuel pressure will result in rough engine idling.
That’s why, it is important to control proper condition of fuel pump, pressure regulator and fuel flow in the system.
There are a couple of system differences between fuel low pressure and low fuel flow. Noticeably With low flow the engine usually idles fine but under load, up hills it loses power, while fuel pressure will affect idle.
ReplyDelete