Car Repair Advice by Professional Automotive Experts
How Do I Repair My Car?
/
How Do I Check My Engine Fuel Pressure?
How to Check Fuel System Pressure
READ COMPLETELY BEFORE BEGINNING:
Your car's engine depends on constant fuel under pressure to supply the
fuel injection system properly. Your car's
fuel pump performs this action and is located in or near the gas tank. The
injection system meters fuel through the injectors and into the engine. Many
engine run ability problems can be related to a weak or failing fuel pump.
Problems can range from hard starting in the morning, low power and stalling
while driving. Most vehicles have a fuel pressure test port somewhere on the
fuel rail, use a flash light to locate it on your engine or consult a
repair manual. With the engine off remove the protective cap and attach the
fuel pressure gauge. Support the gauge for observation; now turn the key to the
on position. The fuel pressure gauge should jump up to your system pressure, in
most cases 45 p.s.i. to 55 p.s.i. is standard in port injection system and 14 p.s.i.
to 18 p.s.i. in TBI (throttle body injection) systems. When testing fuel pressure
may vary slightly but should be pretty close to spec. To find exact pressure for
your vehicle consult a
repair manual. (Note: Some cars do not have a test port; in this case you must
use a fuel filter bypass hose to "tee" the fuel pressure gauge in for testing)
Fuel Pump Pressure and Pressure Regulator Test
Tools needed to perform these tests:
Fuel Pressure Gauge
- Step 1 - Check pump performance, while observing the gauge
rap the throttle, the gauge should move up about 5 p.s.i. if the gauge moves
down you have a bad fuel pump or a plugged fuel filter, remove the filter for
inspection, if it's ok, replace the fuel pump with new and re-test system.
- Step 2 - Check the fuel pump and pressure regulator while
the engine is running. Start the engine and allow it to idle, while observing
the gauge remove the vacuum line, the gauge needle should move up about 5 to
10 p.s.i., if the gauge stays the same when the vacuum line has been removed
the regulator is bad and needs replacement.
Testing and Checking System Fuel Pressure Video
Common Problems:
- If too much amperage is being drawn through the fuel relay circuit it can
cause the relay contacts to "stick" not allowing the power to be shut off to
the pump and draining the battery down.
- A fuel pump can fail while driving for this you need to monitor the
gauge while driving. You can do this by attaching a small extension hose and
temporally attaching the gauge so it can be seen from the driver's compartment.
If the gauge drops at anytime the fuel pump system is failing. Anytime you replace
the fuel pump you should replace the fuel pump relay. The relay supplies power
to the pump and can be easily overworked by a failing pump.
How Do I Repair My Car?
/
How Do I Check My Engine Fuel Pressure?
Additional Resources
Additional "How to" Car Repair or Services
Find What You Are Looking For? Check Our:
ASK A CAR REPAIR QUESTION
| 
