Testing Fuel Pressure: 2023 Ford F250 Guide

Testing the fuel pressure on a 1993 Ford F250 is a relatively simple task that can be completed in 30 minutes or less. It is important to test the fuel pressure to ensure the vehicle is running efficiently and to diagnose any potential issues. The recommended fuel pressure for a standard Ford truck engine is 50-60 PSI, and a drop of more than 2 PSI below this recommendation indicates a fuel-sending problem or a possible leak. To test the fuel pressure, you will need to locate the fuel rail under the hood, which feeds fuel to the fuel injectors. You will then need to attach a fuel pressure tester to the port on the fuel rail and start the engine to read the pressure.

Testing the front or rear tank fuel pump

Symptoms of a Bad Fuel Pump

The fuel pump delivers the fuel the engine needs as soon as you crank and start the engine. When the fuel pump fails, it will do so in one of two ways:

• Complete failure: The fuel pump will not send any fuel to the engine, causing the engine not to start.
• Degraded performance: The fuel pump does not send enough fuel to the engine, causing the engine to start but run with performance issues.

When the fuel pump begins to fail but supplies just enough fuel to start the engine, you may observe one or more of the following symptoms:

• Engine backfires through the intake manifold when the engine is under load.
• The check engine light illuminates with lean air/fuel mixture codes or a MAP sensor trouble code.
• Lack of power when accelerating the engine under load.
• Engine stalls when the engine is accelerated under load.

Where to Buy a Fuel Pressure Test Gauge

You will need a fuel pressure test gauge to determine whether the front or rear tank fuel pump is faulty. The following fuel pressure test gauges have the Ford Schrader valve adapter required to test the fuel pump:

• Actron CP7838 Professional Fuel Pressure Tester
• OEMTOOLS 27167 Fuel Pressure Test Kit, Fuel Pressure Gauge, Fuel Pressure Tester, Fuel Pump Pressure Tester, Fuel Pressure Testers, Fuel Pressure Tool
• Performance Tool W89726 Master Fuel Injection Test Kit

Testing the Fuel Pump Inertia Switch (Test 1)

The fuel pump inertia switch is designed to cut power to the fuel pumps in the event of a collision (vehicle impact). Even jumping the curb will cause it to initialize and cut power to the fuel pumps. If it isn't reset, the engine will crank but not start due to a lack of fuel, regardless of the selected tank.

The fuel pump inertia switch is located behind the passenger-side plastic kick panel. This test only applies if the engine does not start when either the front or rear tank is selected on the fuel tank selector switch. If the engine starts with one tank selected but not the other, skip this test and proceed to the next one.

• Remove the passenger-side plastic kick panel to access the fuel pump inertia switch.
• Push down on the red button on top of the switch. You should hear a "click" when you push down on the button. Whether you hear a click or not, continue to the next step.
• Crank and start the engine.

You will get one of the following results:

• The engine started with either tank selected: This indicates that the fuel pump inertia switch was activated and was cutting power to the fuel pumps. Resetting the switch has allowed power to reach the fuel pumps.
• The engine did not start when the front tank was selected but started with the rear tank selected: Proceed to test the front tank fuel pump fuel pressure (Test 2).
• The engine did not start when the rear tank was selected but started with the front tank selected: Proceed to test the rear tank fuel pump fuel pressure (Test 2).
• The engine did not start with either tank selected: This usually indicates a problem with the fuel pump relay, the fuel tank selector switch, or the fuel pump inertia switch.

Fuel Pump Pressure Test (Test 2)

To perform this test, you will need to connect a fuel pressure test gauge to your Ford pickup's Schrader valve. Here are the steps:

• Disconnect the ignition coil from its 4-wire connector to prevent the engine from starting. This will allow you to observe the fuel pressure in the KOEO (Key On Engine Off) mode.
• Place a shop towel around the Schrader valve to absorb any fuel that may leak during the next step.
• Connect the fuel pressure gauge to the Schrader valve on the fuel injector rail.
• Ask your helper to cycle the key ON and OFF without cranking the engine while you check for fuel leaks around the Schrader valve. If fuel is leaking, tighten the fuel pressure gauge slightly by hand.
• Have your helper crank the engine for a few seconds and then release the key so that it stays in the ON position even though the engine did not start.
• Observe the reading on the fuel pressure gauge.

You will get one of the following results:

• The fuel pressure gauge registered 0 PSI: This confirms that the cause of the no-start problem is a lack of fuel. Before condemning the fuel pump as faulty, check that the fuel pump is receiving 12 Volts while the engine is cranking to ensure that the fuel pump relay and fuse are functioning correctly.
• The fuel pressure gauge registered 30 to 45 PSI: This indicates that the fuel pump is working correctly and delivering enough fuel to the fuel injectors. The reason your Ford F250 is not starting is due to another issue.

Using Starting Fluid to Confirm Lack of Fuel (Test 3)

Using starting fluid is a quick way to determine if a 'cranks but does not start' condition is due to a lack of fuel. If your Ford starts, even momentarily, after spraying starting fluid, it indicates that fuel is missing from the equation (engine start equation: fuel + spark + air = combustion).

Note: To ensure accurate test results, confirm that the ignition coil pack is creating and delivering spark to all cylinders by attaching a spark tester to the spark plug wires while a helper cranks the engine.

• Remove the intake air duct from the throttle body. You don't need to completely remove it, as you will reconnect it in one of the next steps.
• Open the throttle plate and spray starting fluid down the bore. As a safety precaution, reconnect the air duct after spraying a good squirt of starting fluid (you don't need to tighten the air duct's hose clamp).
• Crank the engine once the air duct is back on and you're clear of the engine compartment.

You will get one of the following results:

• The engine started and ran for a few seconds: This indicates that the no-start problem is due to a lack of fuel. Proceed to check the fuel pressure using a fuel pressure test gauge (Test 2).
• The engine did not start at all: This usually means that a lack of fuel is not the reason your car is not starting. However, for a more accurate diagnosis, check the fuel pressure using a fuel pressure test gauge (Test 2).

Using a fuel pressure test gauge

Testing the fuel pressure in your 1993 Ford F250 is a relatively simple task that should not take longer than 30 minutes. You can buy a fuel pressure test gauge from most auto parts stores, and some even rent them out.

Step 1: Locate the Fuel Rail

The fuel rail is located under the hood at the top of the engine. This is what feeds fuel to the fuel injectors.

Step 2: Remove the Screw Cap from the Fuel Pressure Testing Port

You will see a nipple protruding outward from the fuel rail, this is the fuel pressure testing port. It will have a green or black screw cap that you need to remove.

Step 3: Attach the Fuel Pressure Tester

Once the screw cap is removed, attach the fuel pressure tester to the port on the fuel rail. Ensure that it is securely connected.

Step 4: Start the Engine

With the fuel pressure tester attached, start the truck's engine.

Step 5: Read the Pressure on the Fuel Pressure Tester

This will show you the amount of pressure reaching the fuel injectors. The recommended fuel pressure for a standard Ford truck engine is between 50 to 60 PSI. If the pressure falls more than 2 pounds below this recommendation, then you likely have a fuel sending problem or a possible leak.

Step 6: Replace the Fuel Pressure Port Cap

After you have recorded the pressure data, remember to replace the green or black fuel pressure port cap.

It is important to take safety precautions when working around the fuel system. Avoid open flames, sparks, and static electricity.

Additionally, if you smell raw fuel in the engine compartment, it could indicate a line leak or a leak in the fuel rail.

Checking the fuel pump inertia switch

The fuel pump inertia switch is designed to cut off power to the fuel pump in the event of a collision or impact. Even a minor bump can activate it, so it's important to check and reset the switch if your Ford F250 is not starting due to a suspected lack of fuel.

Step 1: Locate the Fuel Pump Inertia Switch

The fuel pump inertia switch is located on the passenger side of the cabin, behind the plastic kick panel. On the 2000-2007 Ford F-250, it is in the passenger's footwell, by the kick panel. You may need to remove the lower scuff plate or the kick panel to access the switch. On the 2008-2010 Ford F-250, the switch is located on the passenger's side of the instrument panel. Open the front passenger door and remove the small access panel to locate it.

Step 2: Push the Reset Button

Once you have located the fuel pump inertia switch, look for a red button on top of it. Push this button firmly until you hear a "click" sound. This resets the switch.

Step 3: Crank the Engine

After resetting the switch, turn the ignition to the "ON" position, but do not turn it to "START." Wait a few seconds, and then return the key to the "OFF" position.

Step 4: Observe the Results

There are several possible outcomes at this point:

• Case 1: The engine starts with either the front or rear tank selected. This indicates that the fuel pump inertia switch was activated and was cutting power to the fuel pumps. Resetting the switch has resolved the issue.
• Case 2: The engine does not start when the front tank is selected but starts with the rear tank selected. This suggests an issue with the front tank's fuel pump or fuel pressure. Proceed to TEST 2: Fuel Pump Pressure Test.
• Case 3: The engine does not start when the rear tank is selected but starts with the front tank selected. This suggests an issue with the rear tank's fuel pump or fuel pressure. Proceed to TEST 2: Fuel Pump Pressure Test.
• Case 4: The engine does not start with either tank selected. This could be due to a problem with the fuel pump relay, the fuel tank selector switch, or the fuel pump inertia switch itself. Further testing of these components is required.

Important Safety Precautions:

• Do not reset the fuel system shut-off switch if you see or smell fuel from the fuel system.
• Always turn off the vehicle before checking and resetting the fuel pump inertia switch.
• Make sure to follow the steps in the correct order to ensure an accurate diagnosis and safe operation.

By following these steps, you can effectively check and reset the fuel pump inertia switch on your Ford F250, helping to identify and resolve any fuel-related issues.

Using starting fluid

Step 1: Remove the Intake Air Duct

First, remove the intake air duct from the throttle body. You don't need to detach it completely, as you will be reconnecting it in the next step.

Step 2: Spray Starting Fluid

Spray a good amount of starting fluid into the bore of the throttle body. This step is important, as it provides a temporary substitute for gasoline to determine if the fuel pump is functioning.

Step 3: Reconnect the Air Duct

Quickly reconnect the air duct to the throttle body after spraying the starting fluid. This is a crucial safety precaution to prevent any potential backfire and reduce the risk of flames from the throttle body.

Step 4: Crank the Engine

With the air duct securely back in place, have an assistant crank the engine.

Step 5: Observe the Results

You will observe one of two outcomes:

• Engine Starts Momentarily: If the engine starts and runs for a few seconds before dying, it indicates that the no-start issue is due to a lack of fuel. This typically implies that the fuel pump is faulty and requires replacement.
• Engine Fails to Start: If the engine doesn't start at all, even momentarily, it suggests that the no-start problem is not caused by a lack of fuel. However, it is recommended to perform an additional test using a fuel pressure gauge for a more accurate diagnosis.

Additional Precautions:

• Spark Check: Before performing the starting fluid test, ensure that all cylinders are receiving spark. This step is crucial for accurate results.
• Safety: Always exercise extreme caution when working with starting fluid and gasoline, as they are highly flammable. Work with a cold engine, avoid open flames or sparks, wear protective gear, and keep a fire extinguisher nearby.
• Fuel Pump Inertia Switch: Check and reset the fuel pump inertia switch before conducting the test. This switch is designed to cut power to the fuel pump in case of a collision or impact, and it can sometimes be activated by lighter bumps.

Symptoms of a bad fuel pump

A fuel pump is an essential part of your car, and when it begins to fail, it can cause major performance and drivability issues. Here are some symptoms of a bad fuel pump to watch out for:

• Engine not starting: If your vehicle is struggling to start or isn't starting at all, it could be due to a faulty fuel pump that is unable to send fuel to the engine.
• Slow or extended cranking: If your car takes longer than usual to start or requires more cranks than average to turn over, it may be a sign that the fuel pump is not delivering enough fuel.
• Engine sputtering or stalling: If your engine sputters, stalls, or dies while driving, it could be due to low pressure caused by a faulty fuel pump, resulting in an insufficient fuel-air mixture for combustion.
• Engine surging: A bad fuel pump can cause the engine to surge, leading to unexpected speed increases and decreases, even when you haven't touched the pedals.
• Whining or whirring noise: A failing fuel pump may produce a loud, whining or whirring noise, indicating that it is working harder than usual.
• Lower fuel efficiency: If your vehicle is consuming more fuel than usual, it could be due to a faulty fuel pump sending too much fuel to the engine, resulting in higher fuel usage.
• Loss of power: If your vehicle loses power when climbing steep inclines, carrying heavy loads, or accelerating, it could be a sign that the fuel pump is not supplying enough fuel to meet the engine's demand.
• Engine backfires: If your engine backfires through the intake manifold, especially under load, it could be due to a faulty fuel pump affecting the fuel-air mixture.
• Check engine light illuminates: A faulty fuel pump can cause the check engine light to turn on, indicating lean air/fuel mixture codes or a MAP sensor trouble code.

It's important to note that these symptoms can also be caused by other issues, such as bad fuel, damaged fuel lines, or a clogged fuel filter. Therefore, it's always recommended to consult a qualified technician for a comprehensive inspection and accurate diagnosis.

Frequently asked questions