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Checking Fuel Pressure of a Vehicle

To support automobile engine with steady fuel supply, proper fuel pressure is to be maintained in the fuel lines. Not delivering fuel at correct pressure and volume can consequently lead to engine performance issues such as hard start, reduced power and poor fuel economy. A check on fuel pressure readings will ensure delivery of fuel to the engine at the right pressure. Sometimes, the specifications may not match with the manufacturer’s standards due to faulty fuel lines or fuel pump problems. The pressure reading can go higher or lower than the manufacturer’s specifications, which may need further diagnosis to resolve the issue.

Using Different Pressure Testing Kits

Fuel pressure can be checked in many ways using different pressure testers. Before you choose the type of a tester, you need to understand its fuel system and engine type.

  • Understand the engine type – carburetor or fuel injectors
    Before you come to an understanding on which fuel pressure tester is right for your vehicle, it is essential to know which type of engine you are using, carbureted or fuel injected. Carburetors typically use mechanical fuel pumps which provide pressure lower than its electric counterparts. In carburetor fuel systems, pressure is tested using vacuum gauge or fuel pressure tester on both sides of the mechanical pump that is on the suction / input side and on the pressure / output side. For fuel injector vehicles, you can use pressure test kits or pressure gauges to measure fuel pressure reading. The kit is to be connected to the test port which is usually near the fuel injectors. If the test port is not available, adapter is required in order to connect the tester. By turning on the key without running the engine, readings are to be taken from the fuel pressure measuring kit.
  • Know the fuel system type
    To measure fuel pressure specifications, it is also important to know the type of fuel system. Typically fuel systems with fuel line returning back to the tank will have fuel pressure regulators located at the end of the fuel rail. But, in case of vehicles with no return fuel lines, there will not be any pressure regulators for regulating the pressure of the fuel flowing through the system. They require external pressure testing kits or pressure gauge to keep a check on the fuel pressure.

How to analyze fuel pressure readings?

Turn the ignition on and off for few times and note the pressure specifications. The pressure should go up and remain at the proper reading for some time before it shows any significant drop in the pressure. If you notice low or no pressure, check for fuel pump working, clogged fuel filter or faulty fuel lines. Sometimes, a faulty fuel pump may not build proper pressure at the output. This may give you wrong fuel pressure readings. Check for the fuel pump activity and see if it is working when you turn the key on. If the pump fails to activate and remains silent, then check on the relay fuses and fuel filter. If you notice they are fine, then it could be the issue with fuel pump. Take necessary action to resolve the fuel pump problem and repeat the process to check correct fuel pressure.

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