If one tests a low pressure fuel pump[randimg src=//cdn.4wheelparts.com/somefuelpump.jpg ] with wrong tools, the diagnosis can be imprecise very easily. The main tool utilized is a fuel pressure gauge, which reads measured in psi (pounds per square inch). Depending on the vehicle and its fuel system, manufacturers recommend a PSI level for the fuel pressure generally anywhere from 30 to 80 psi. If a reading is below these values, it indicates low pressure.
First, the technicians connect the gauge to the Schrader valve on the fuel rail. This valve is a point of connection for measuring fuel pressure directly in the system. As the thought of flooding each engine with fuel would seem not quite right, automotive professionals suggest giving a turn to the ignition – ON but do not start it or they recommend no more than 5 seconds worth! If the gauge reading drops during this step, it usually means there is a leak or an issue with the pump.
Fuel pressure tests should be done under load as well. Mechanics simulate driving situations by revving the engine in neutral while watching the gauge. The gauge will hopefully tell them that pressure is not what it should be during heavy acceleration; if the gauge reads 25 psi and the manufacturer calls for 50, it’s proof-positive that the pump cannot deliver on demand.
Because of how a fuel filter, clogged line, or other blockage could trick the technician into thinking the pump has failed, flow rate tests are common. If the pump takes more than 30 seconds to supply around 0.5 liters of fuel, it is not working properly and should be replaced. ASE-certified mechanics have advised that you should compare these results to OEM (Original Equipment Manufacturer) specs to do the proper diagnostics.
In addition to this, voltage tests of the pump electrical circuit help gain a clearer understanding. When connected to a 12 volt output (the same output as the vehicle’s battery), a working pump will function. If it reads under this we would expect a voltage of around 9 volts which is much more indicative of wiring or relay problems and not pump failure. About 1/5th of the time, fuel pump failures are related to electrical problems, says data from the National Institute for Automotive Service Excellence.
A quality Fuel Pump makes sure your fuel is delivered, and this keeps the engine in its best condition. Fast-tracking low-pressure problems prevents more serious issues from damaging parts, such as injectors and regulators, that can be very expensive to repair.