Testing the fuel pump on your 1997–2003 4.6L or 5.4L V8 Ford F150, F250, or F350 pickup simply involves checking the fuel pressure to see if it's within spec.
What makes this test so easy is that the fuel injector rail comes with a fuel pressure test port (commonly known as the Schrader valve). This is where we connect a fuel pressure gauge to check the pressure being produced by the fuel pump.
In this tutorial, I'm gonna show you step by step how to do this and find out if the fuel pump is behind an engine no-start problem or a performance issue.
I'm also gonna explain how to do a starting fluid test, to see if the engine isn't starting because of a fuel delivery problem.
NOTE: This tutorial applies to the non-FPDM (fuel pump driver module) equipped F-Series pickups.
Contents of this tutorial:
- Symptoms Of A Bad Fuel Pump.
- Where To Buy A Fuel Pressure Test Gauge.
- TEST 1: Checking Fuel Pressure With A Fuel Pressure Gauge.
- TEST 2: Using Starting Fluid To Confirm Lack Of Fuel.
- Fuel Pump Inertia Switch Check.
- More Fuel Pump Troubleshooting Help.
- More 4.6L, 5.4L V8 Ford F150, F250, And F350 Diagnostic Tutorials.
APPLIES TO: This tutorial applies to the following non-FPDM equipped vehicles:
- 4.6L V8 Ford F150: 1997, 1998, 1999, 2000, 2001, 2002, 2003.
- 5.4L V8 Ford F150: 1997, 1998, 1999, 2000, 2001, 2002, 2003.
- 4.6L V8 Ford F250: 1998, 1999.
- 5.4L V8 Ford F250: 1998, 1999, 2000, 2001, 2002, 2003, 2004.
- 5.4L V8 Ford F350: 1999, 2000, 2001, 2002, 2003, 2004.
MORE FUEL PUMP DIAGNOSTIC RESOURCES: You can find fuel pump circuit wiring diagrams, related fuel pump tests, and the inertia switch tests in this section:
Symptoms Of A Bad Fuel Pump
The fuel pump in your Ford F-Series pickup is going to fail in one of two ways:
- Complete failure: In this scenario, the fuel pump failure is total and the engine doesn't start.
- Slowly dying fuel pump: In this case, the fuel pump still works and sends fuel to the engine, but it's not enough to keep it running optimally. In other words, the engine starts and runs, but as soon as you stick it in Drive or place it under any kind of load, the engine stalls or runs pretty badly.
If your Ford pickup does start but the fuel pump is failing, you'll probably see one or more of the following symptoms:
- Rough idle: Since the fuel pump isn't delivering enough fuel, the engine's gonna run lean, and this can end up causing a rough idle condition.
- Hard start: You've got to crank the engine a while before it starts.
- Lack of power: You'll feel this lack of power when you stick it in Drive and step on the gas, or when accelerating at cruising speed.
- Backfires: Popping sounds coming from the intake manifold when the engine is under load.
Both of these conditions can be tested with a fuel pressure gauge. Alright, with this info under our belts, let's get testing.
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 and include the adapter to tests all Ford with a Ford-type Schrader valve:
All of the fuel pump pressure test kits above have the fitting that will connect to your Ford's Schrader valve.
TEST 1: Checking Fuel Pressure With A Fuel Pressure Gauge
All right, this is the test you signed up for —checking the fuel pressure output of the fuel pump with a fuel pressure test gauge.
The fuel pressure test port (Schrader valve) is located on the fuel injector rail, on the passenger side of the engine.
Before you start your test, I suggest checking the fuel pump inertia switch to make sure it hasn't tripped. If it has, power won't reach the fuel pump, and your fuel pressure reading will be zero. See this section for more info:
NOTE: If you don't have a fuel pressure gauge, take a look at the section: Where To Buy A Fuel Pressure Test Gauge.
FUEL PRESSURE SPECIFICATION: You can find the specific fuel pressure specification for your particular F-Series pickup here: Fuel Pressure Specifications (1997-2010 4.6L, 5.4L V8 Ford F150, F250, And F350).
OK, let's get started with this test:
- 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
Connect the fuel pressure gauge to the Schrader valve on your 4.2L V6 Ford's fuel injector rail.
- 3
When ready, ask your helper to cycle the key ON and OFF but don't crank the engine while you check for fuel leaks around the Schrader valve.
If fuel is leaking, tighten the fuel pressure a bit more (by hand only).
Key On Engine Off (KOEO) Test: Engine doesn't start
- 4
Have your helper crank the engine, then release the key. NOTE: After cranking, the key should stay in the RUN position. If your helper turns it all the way to OFF, the test won't work —you'll need to do it again.
- 5
The fuel pressure gauge should show the fuel pressure within spec.
Key On Engine Running (KOER) Test: Engine starts and stays running
- 4
Have your helper start the engine and let it idle.
- 5
The fuel pressure gauge should show the fuel pressure within spec.
Key On Engine Off (KOEO) Test: Engine starts, but you need KOEO results
- 4
Disconnect both ignition coil packs or all 8 COP ignition coils from their electrical connectors.
- 5
Have your helper crank the engine, then release the key. NOTE: After cranking, the key should stay in the RUN position. If your helper turns it all the way to OFF, the test won't work —you'll need to do it again.
- 6
The fuel pressure gauge should show the fuel pressure within spec.
Let's take a look at what your results mean:
CASE 1: The fuel pressure gauge registered 0 PSI. This confirms that the engine's no-start problem is caused by a lack of fuel.
But we can't call the fuel pump bad just yet. We've got to check one more thing —and that is, we've got to make sure the inertia switch is actually getting power from the fuel pump relay.
And if the inertia switch is getting power, we've got to make sure it's channeling that power on to the fuel pump. This is a very easy test, and I've written a tutorial on how to do it. You can find it here:
So, if after confirming that the fuel pump inertia switch is getting power —and that it's sending that power to the fuel pump— you can confidently conclude the pump is toast and needs to be replaced.
CASE 2: The fuel pressure gauge registers a pressure that's lower than spec. This usually means the fuel pump is weak and on its way out. Replace the fuel pump.
CASE 3: The fuel pressure gauge registers the correct fuel pressure spec. This result lets you know the fuel pump is working and delivering the correct amount of fuel pressure to the fuel injectors.
Whatever's causing the engine to not start on your F-Series pickup isn't the fuel pump. You'll need to keep troubleshooting to get to the bottom of the no-start.
TEST 2: Using Starting Fluid To Confirm Lack Of Fuel
I've been using starting fluid to diagnose engine no-start problems since the beginning of my automotive repair career. And back then, most of those vehicles ran with carburetors!
This test is so effective at pointing your troubleshooting efforts in the right direction, it even works with modern fuel-injected vehicles.
Now, I do want to point out that this test isn't as accurate for diagnosing a bad fuel pump as using a fuel pressure test gauge. But it will let you know if the engine no-start problem is due to a fuel delivery issue —with the fuel pump easily fitting into that category.
The most important thing to keep in mind is that this test will only confirm the problem is due to a lack of fuel if you've made sure that all eight cylinders are getting spark.
So, if you haven't checked for spark yet, you need to do that first.
The way this works is: if by spraying starting fluid your Ford pickup starts —even if only momentarily— then it tells you that fuel is missing from the equation (engine start equation: fuel + spark + air = combustion).
IMPORTANT: To get an accurate test result from the starting fluid test, you need to first confirm that all cylinders are getting spark.
IMPORTANT: This is a very fast and easy test but you do have to take one very important safety precaution and this is to reconnect the air intake duct after spraying starting fluid down the throttle bore (although you don't have to fasten it). This will prevent any backfire, that might occur, from scaring the heck out of you when cranking the engine.
This is what you have to do:
- 1
Remove the intake air duct from the throttle body. You don't have to completely remove it, since you'll have to reconnect it in one of the next steps.
- 2
Open the throttle plate and spray starting fluid down the bore.
- 3
Reconnect the air duct after you have sprayed a good squirt of starting fluid.
You don't have to tighten the air duct's hose clamp. - 4
Crank the engine once the air duct is back on and you're clear of the engine compartment.
- 5
You'll get one of two results with this test:
1.) The engine will start momentarily and after a few seconds will die or.
2.) The engine will only crank but not start at all.
OK, let's find out what your results mean:
CASE 1: The engine started and ran for a few seconds. This test result tells you that the no-start problem is due to a lack of fuel.
Most of the time, that points to a bad or non-functioning fuel pump. I still recommend confirming it with an actual fuel pressure test. Go to: TEST 1: Checking Fuel Pressure With A Fuel Pressure Gauge.
CASE 2: The engine did not start, not even momentarily. This usually means that a lack of fuel IS NOT the reason the engine isn't starting.
Now, remember what I said about this test not being very accurate? Well, I suggest you do one more test and this is to check the fuel pressure with a fuel pressure test gauge. Go to: TEST 1: Checking Fuel Pressure With A Fuel Pressure Gauge.
Fuel Pump Inertia Switch Check
Your Ford F-Series pickup is equipped with a very important safety device that shuts off power to the fuel pump in case of an impact —like crashing into another vehicle or having another vehicle crash into you.
The purpose of this device, called the fuel pump inertia switch, is to make sure the fuel pump doesn't stay running if the fuel lines break and fuel starts spraying everywhere after a crash.
Unfortunately, since the fuel pump inertia switch is a mechanical device, it can be tripped by something as simple as hitting a pothole too hard, bumping into a curb while parking, or even slamming the door too hard.
So before going through the trouble of checking fuel pressure with a fuel pressure test gauge, it's a good idea to check if the fuel pump inertia switch has tripped. And it's super simple to check.
The fuel pump inertia switch is located behind the plastic kick panel on the passenger side. This is the plastic cover right below the dash on the passenger side of the pickup cabin.
All you have to do after locating the inertia switch is press firmly on the red button at the top of the switch. If the switch has been tripped, you're gonna hear and feel a click as the button is pushed down and the switch resets.
More Fuel Pump Troubleshooting Help
FUEL PUMP PRESSURE SPECIFICATIONS:
FUEL PUMP CIRCUIT WIRING DIAGRAMS:
- Fuel Pump Circuit Wiring Diagram (1997-1998 4.6L, 5.4L V8 Ford F150, F250 Light Duty).
- Fuel Pump Circuit Wiring Diagram (1999 4.6L, 5.4L V8 Ford F150, F250 Light Duty).
- Fuel Pump Circuit Wiring Diagram (2000-2003 4.6L, 5.4L V8 Ford F150 Pickup).
- Fuel Pump Circuit Wiring Diagram (2000-2004 5.4L V8 Ford F250 And F350 Pickup).
More 4.6L, 5.4L V8 Ford F150, F250, And F350 Diagnostic Tutorials
You can find a complete list of tutorials and wiring diagrams in this index:
Here's a small sample of the tutorials you'll find in the index:
- How To Test The Throttle Position Sensor (1997-2004 4.6L, 5.4L Ford F150, F250).
- How To Test The Coil-On-Plug Ignition Coils (1997-2010 4.6L, 5.4L Ford F150, F250, F350).
- How To Test The Fuel Injectors (1997-2002 4.6L Ford F150, F250).
- How To Test The Alternator (1997-2003 4.6L, 5.4L Ford F150, F250 Light Duty).
If this info saved the day, buy me a beer!
