A fuel pump doesn't last forever and when it fails in your 3.2L Isuzu Rodeo (Amigo or Honda Passport), the engine will crank but not start.
If you suspect that the fuel pump is bad and need to know how to test it, I'll show you how in this tutorial.
With your fuel pump test results, you can pinpoint the cause of your no-start problem to a lack of fuel or rule it out and continue with your diagnostic process.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar La Bomba De Combustible (1998-2004 3.2L Isuzu Amigo, Rodeo, Honda Passport) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 3.2L Isuzu Amigo: 1998, 1999, 2000.
- 3.2L Isuzu Rodeo: 1998, 1999, 2000, 2001, 2002, 2003, 2004.
- 3.2L Honda Passport: 1998, 1999, 2000, 2001, 2002.
Symptoms Of A Bad Fuel Pump
Your Isuzu's engine needs three things to start:
And as you've guessed it, the fuel pump is the component that supplies the fuel the engine needs to start.
When the fuel pump fails, you'll see one or more of the following symptoms:
- Engine takes longer than usual to start (extended cranking).
- Engine idle is very rough.
- Engine backfires thru' the intake manifold under load.
- Engine starts, then dies.
- Lack of power when accelerating the vehicle under load.
What makes testing the fuel pump so easy is that your Isuzu has a Schrader valve that we can connect a fuel pressure gauge to and see if the fuel pump is actually delivering fuel to the injectors.
Where To Buy A Fuel Pressure Test Gauge
A fuel pressure gauge is one of the most important tools that any serious DIY enthusiast should have in their toolbox.
You can buy a fuel pressure gauge almost anywhere, and if you need to buy one, here are my recommendations:
All of the fuel pump pressure test kits above have the fitting that will connect to your Isuzu's Schrader valve.
TEST 1: Checking Fuel Pressure With A Fuel Pressure Gauge
Checking the fuel pump pressure is made easy by the fact that you can connect a fuel pressure tester to a Schrader valve on the fuel injector rail (see the photos in the image viewer above).
The Schrader valve looks like an oversized tire valve stem and is located on the fuel injector rail (the fuel injector rail 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:
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.
Connect the fuel pressure gauge to the Schrader valve on your 3.2L Isuzu Rodeo's fuel injector rail.
When ready, ask your helper to cycle the key ON and OFF but don't crank the engine.
Check the connection at the Schrader valve for fuel leaks.
Resolve the fuel leak before proceeding to the next step.
Have your helper crank the engine while you observe the fuel pressure tester.
Your fuel pressure gauge should register 42 to 55 PSI
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 concluding the fuel pump is bad, and that's to see if the fuel pump is getting 12 Volts while the engine is cranking. This is just to make sure the fuel pump relay and fuse are good and doing their job.
To do this you need to hook up a multimeter in Volts DC mode to the wire that supplies that voltage to the fuel pump and while a helper is cranking the engine, verify that the fuel pump is getting that power. If the 12 Volts are being delivered to the fuel pump you have now 100% confirmed that the fuel pump has failed and needs to be replaced.
CASE 2: The fuel pressure gauge registered 42 to 55 PSI. This is the correct test result and lets you know that the fuel pump is working and delivering enough fuel to the fuel injectors.
If your 3.2L Isuzu Rodeo (Amigo or Honda Passport) won't start, it is due to another reason. The fuel pump is OK.