TEST 2: Checking Fuel Pressure With A Fuel Pressure Gauge

How To Test The Fuel Pump With a Fuel Pressure Test Gauge (1994-1999 2.0L Mazda 626)

A fuel pressure gauge can be connected to your 2.0L Mazda 626 by removing the banjo bolt that connects the fuel pressure line to the fuel injector rail. You then substitute this banjo bolt with a fuel pressure test fitting (usually known by its measurement as: M12 X 1.25 fitting). It's to this fitting that you can then connect your fuel pressure gauge to. You can see the fuel line's banjo bolt in the photo here: Where To Connect the Fuel Pressure Gauge Adapter

The cool thing about using a fuel pressure test gauge, to test the fuel pump's fuel pressure, is that we can find out if the fuel pump is behind the no start condition or behind a lean condition (if your Mazda starts, runs, but runs with a lack of power).

The fuel pressure specifications with the key on engine off (KOEO) is: 30-45 PSI.

NOTE: If you don't have a fuel pressure gauge, take a look at the section: Where To Buy A Fuel Pressure Test Gauge.

OK, let's get started with this test:

  1. 1

    Place a shop towel around the fuel line's banjo bolt. The shop towel's job is to absorb any fuel that may leak when doing step 2.

    To see the location of the fuel line's banjo bolt, go here: Where To Connect the Fuel Pressure Gauge Adapter.

  2. 2

    Remove the fuel filter's union bolt. Careful the union bolt's 2 copper washers don't fall and get lost in the engine compartment. You'll need to re-install them when you get done with the fuel pressure test. .

  3. 3

    Install the fuel test fitting in the banjo bolts place and tighten it. Make sure that you use the copper washers since these are like gaskets that keep the fuel from leaking out.

    Now, connect the fuel pressure test gauge to the fitting you just installed and tightened.

  4. 4

    When ready, ask your helper to cycle the key on and off several times but don't crank the engine while you observe the fuel pressure tester's gauge.

    Check the connection at the fuel pressure test fitting for fuel leaks and if any tighten the fuel pressure a bit more (by hand only) to eliminate them.

  5. 5

    Your fuel pressure gauge should register the specified KOEO fuel pressure of 30-45 PSI if the fuel pump is OK.

Let's take a look at what your results mean:

CASE 1: If the fuel pressure gauge registered 0 PSI: This confirms that the cause of your 2.0L Mazda 626 no start problem is caused by a lack of fuel.

CASE 2: If the fuel pressure gauge registered the specified fuel pressure for your vehicle's model year: This test result let's you know that the fuel pump is working and delivering enough fuel to the fuel injectors. The reason your 2.0L Mazda 626 is not starting is due to another reason. The fuel pump is OK.

Where To Buy A Fuel Pressure Test Gauge

One of the most important tools any serious DIY'er should have in his/her tool box is a fuel pressure test gauge. The cool thing is that you can buy them in just about any auto parts store (although at a higher price).

The following fuel pressure test gauge kits are pretty good deals and include the adapter (the M12 X 1.25 test fitting) to tests all 2.0L Mazdas covered by this tutorial:

All of the fuel pump pressure test kits above have the fitting that will connect to your Mazda's fuel injector rail.

Where To Connect the Fuel Pressure Gauge Adapter

Fuel Pressure Gauge Schrader Valve Location. How to Test the Fuel Pump (1994-1999 2.0L Mazda 626)

NOTE: The photo above is of a 1997 2.0L Mazda 626.

The orange arrow points to the banjo bolt that must be removed and replaced with the fuel pressure gauge fitting. This banjo bolt has two copper washers that seal against fuel leaks. As you're removing the banjo bolt, you need to be careful they don't fall down in the lower engine area. These copper washers are re-used when installing the banjo bolt back in its place (after doing the fuel pressure test).

Where To Buy The Fuel Pump And Save

The fuel pump in your 2.0L Mazda 626 is located inside the fuel tank. The fuel pump can be bought in any auto parts store, but I think you'll find the better price online. The following fuel pumps are pretty good deals:

Not sure if the above fuel pumps fit your particular 2.0L Mazda 626? Don't worry, once you get to the site, they'll make sure it fits by asking you the specifics of your vehicle. If it doesn't fit, they'll find you the right one.