Fuel Pressure Gauge - Why You Need One

There are several tools that a mechanic must have in their toolbox. A Fuel Pressure Gauge is one of them.

The engine in any modern car will have several systems that all need to be in correct operating condition to enable the engine to run correctly:

• Electrical System
• Fuel System
• Ignition System

I'll talk about the Electrical and Ignition Systems in another post, but today, let's focus on the Fuel System, and why you must have a fuel pressure gauge in order to diagnose fuel system problems.

There are three main items in the fuel system of a fuel injected vehicle that can cause the engine to either stop, or at least, to run incorrectly.

• Fuel Pump
• Fuel Injectors
• Fuel Pressure Regulator

Here are a examples of symptoms, and the potential associated problems within the fuel system.

• Engine Runs Very Lean - May be due to - fuel injectors being dirty or even clogged, fuel pressure regulator failing, fuel pump failing (or even the over pressure return valve inside the pump may have failed, and this may cause low fuel pressure).
• Engine Uses More Fuel Than Normal - May be due to - fuel pressure regulator failing, due to one dirty or blocked injector (ECU in closed loop injects more fuel to bring overall mixture back to Lambda 1 and engine uses a little more fuel overall)
• Engine Will Not Start - May be due to - dirty or clogged injectors, failing fuel pump, failing fuel pressure regulator.

They are just a few examples.

If you just had an engine in front of you exhibiting one of the above symptoms, how could you determine what is causing the problem without a fuel pressure gauge?

Is the fuel pressure correct, is it a little higher than normal, or is it extremely low?

You might disconnect the fuel line and see a reasonable amount of fuel flow from the fuel line, but does that mean there is enough fuel pressure?

If you have the right tools, you can quickly determine what items on the engine are either working correctly, or may be working incorrectly, and may require more investigation.

If you are interested, you can get some more information on the EFI Fuel Pressure Gauge and some of the ways you can use it for engine diagnosis.