TEST 2: Checking Fuel Pressure With A Fuel Pressure Gauge

How To Test The Fuel Pump (3.2L Isuzu)

Checking the fuel pump's pressure is made easy by the fact that you can connect a fuel pressure test gauge to a Schrader valve on the fuel injector rail (see photo below).

The Schrader valve looks like an over-sized tire valve stem and it's located on the fuel injector rail (the fuel injector rail is what holds all 6 injectors in place on the intake manifold).

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 Schrader valve. The shop towel's job is to absorb any fuel that may leak when doing step 2.

  2. 2

    Connect the fuel pressure gauge to the Schrader valve on your 3.2L Isuzu Rodeo's fuel injector rail.

  3. 3

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

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

  4. 4

    Your fuel pressure gauge should register: 42 to 55 PSI with the Key On Engine Off (KOEO) if the fuel pump is OK.

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

CASE 1: The fuel pressure gauge registered 0 PSI. This confirms that the cause of your 3.2L Isuzu's no-start problem is caused by a lack of fuel.

Now, I usually take one more precaution, before condemning the fuel pump as bad and this is to check that the fuel pump is getting 12 Volts as the engine is cranking. This is just to make sure that the fuel pump relay and fuse are OK and doing their job.

What you'll have to do to accomplish this is to attach a multimeter in Volts DC mode to the wire that supplies this voltage to the fuel pump and while a helper cranks the engine, verify that the fuel pump is getting this power. If the 12 Volts are being supplied to the fuel pump, you have now 100% verified that the fuel pump is fried and needs to be replaced.

CASE 2: The fuel pressure gauge registered 42 to 55 PSI. This fuel pressure gauge result lets you know that the fuel pump is working and delivering enough fuel to the fuel injectors. The reason your 3.2L Isuzu Rodeo (Amigo or Honda Passport) is not starting is due to another reason. The fuel pump is OK.

Location Of The Schrader Valve

Location Of The Fuel Pump Tester Schrader Valve On 1998-2004 3.2L Isuzu Rodeo And 1998-2000 3.2L Amigo (1998-2002 3.2L Honda Passport)

NOTE: The Schrader valve is located on the driver side of the engine on the fuel injector rail.

Where To Buy A Fuel Pressure Test Gauge

You can buy a fuel pressure test gauge just about anywhere and is one of the most important tools any serious DIY'er should have in his/her tool box.

The following fuel pressure test gauge kits are pretty good deals:

All of the fuel pump pressure test kits above have the fitting that will connect to your Isuzu's Schrader valve.

Isuzu Vehicles:

  • Amigo 3.2L
    • 1998, 1999, 2000
  • Rodeo 3.2L
    • 1998, 1999, 2000, 2001, 2002, 2003, 2004

Honda Vehicles:

  • Passport 3.2L
    • 1998, 1999, 2000, 2001, 2002