Checking Fuel Pressure In A Mini Cooper: Diy Guide

To check the fuel pressure in a Mini Cooper, you can use a digital volt ohm-meter (DVOM) to confirm that the fuel pump has received the correct voltage when commanded on by the fuel pump relay. If the correct voltage is present but the pump does not activate, it is likely faulty.

You can also test the in-tank fuel pump pressure using a test adapter. For turbocharged models, you will need to use a T-adapter to test the in-tank fuel pump. You can also test the cylinder head-mounted high-pressure fuel pump using a Mini scan tool.

Check the fuel pump relay

To check the fuel pump relay, you will need to test the voltage at the fuel pump connector. This can be done by using a digital volt-ohm meter (DVOM). The DVOM should read battery volts (around 12 volts) when the key is turned on. If no voltage is found, check the relay and fuel pump fuse.

• Locate the fuel pump connector. It is usually located near the fuel tank.
• Connect the DVOM to the fuel pump connector.
• Turn the key to the "on" position, but do not start the engine.
• Read the voltage on the DVOM. It should be around 12 volts.
• If the voltage is present, the fuel pump relay is functioning correctly. If there is no voltage, check the relay and fuel pump fuse.

It is important to note that the fuel pump relay is integrated into the junction box and gets power from a fuse in the junction box. The relay position may vary depending on the year of your Mini Cooper.

If you are experiencing issues with your fuel pump, it is recommended to check the voltage at the fuel pump connector first to determine if the issue is with the relay or the pump itself.

Check the fuel pump fuse

To check the fuel pump fuse in your Mini Cooper, you will need to locate the fuse box. The fuse box is located underneath the rear seat cushion, on the left side of the fuel tank. The fuse box contains two fuel level senders, one on each side of the tank. The left side of the tank holds the fuel pump, while the right side holds the fuel level sender and fuel filter.

Once you have located the fuse box, you can check the fuel pump fuse. The fuel pump fuse is typically located in the fuse box, and it is important to identify and fix any issues with the fuse before replacing it. The most common causes of a blown fuel pump fuse include short circuits, damaged fuel pumps, clogged fuel filters, and incorrect fuse usage. If the fuse is blown, it is important to identify the cause of the overload before replacing it to prevent further issues.

In addition to checking the fuel pump fuse, it is also recommended to check for other potential issues with the fuel pump. This includes checking for power reaching the pump during startup, as well as inspecting the fuel pump relay, impact sensor, Engine Control Unit (ECU), fuel pressure regulator, and fuel lines for any signs of damage or malfunction.

Check the fuel pump voltage

To check the voltage of the fuel pump of your Mini Cooper, you will need a digital volt ohm-meter (DVOM).

Step 1: Check the voltage

First, confirm that the fuel pump has received the correct voltage when commanded ON by the fuel pump relay. If the correct voltage is present, but the pump does not activate, it is likely faulty.

Step 2: Use a wiring diagram

Use the DVOM in conjunction with a wiring diagram to determine the correct terminals for testing.

Step 3: Access the fuel pump terminals

Accessing the fuel pump terminals can be done without removing the fuel tank. There are access panels underneath the rear seat cushion that allow servicing. The fuel tank is two-lobed. There are two fuel level senders, one in each lobe on the left and right sides underneath the rear seat cushion. The left fuel tank lobe holds the fuel level sender and fuel filter, while the right tank lobe holds the fuel pump.

Step 4: Be careful with the paint and trim

To avoid marring the paint and trim, work with a plastic prying tool or wrap a screwdriver tip with masking tape before prying out body or interior items.

Step 5: Prepare for different size fasteners

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts may differ from what you have, so be prepared with different size sockets and wrenches.

Step 6: Protect yourself and the vehicle

When performing electrical tests, be sure to use a digital instrument such as a DVOM. Using an analog device may lead to damage to sensitive electronic components. Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.

Check the fuel pump terminals

To check the fuel pump terminals of your Mini Cooper, you will need a digital volt-ohmmeter (DVOM). The fuel pump terminals can be accessed without removing the fuel tank. There are access panels underneath the rear seat cushion that allow servicing.

• Remove the rear seat cushion.
• Remove the access panel lid from the body by lifting it up.
• Working at the fuel pump housing, remove the electrical connector by sliding the lock and pulling the connector up.
• Connect the DVOM across the fuel pump terminals. These are the two terminals on the vehicle.
• Turn the key on. The DVOM should read battery volts (around 12 volts). If no voltage is found, check the relay and fuel pump fuse.
• With the key on, the fuel pump will receive voltage for three to five seconds to prime the system (if the engine doesn't start).
• Load testing can be done using a test light and a DVOM. Connect the DVOM across the fuel pump electrical connector terminals and take a reading. It should read battery volts when the key is turned on.
• Connect an incandescent bulb-style test light to battery ground and touch the test light probe tip to the positive wire you are back probing with the DVOM. Your reading should hold steady; a maximum drop in voltage of 0.5 volts is acceptable.

Check the fuel pump pressure

To check the fuel pump pressure of a Mini Cooper, you will need a fuel pressure gauge. The type of gauge you need depends on the model of your Mini Cooper.

Mini Cooper R56 (2007-2011)

If you have a turbocharged model, you will need a T-adapter to test the in-tank fuel pump pressure. You can find the fuel supply line to the high-pressure fuel pump by following it down to the subframe junction. Press the button and pull the fuel lines apart, then install the T-adapter and fuel pressure gauge. Make sure all test hoses are installed and routed properly.

If your Mini Cooper R56 has a normally aspirated engine, you can locate the fuel rail test port on the right side of the fuel rail, just below the intake air housing outlet. Remove the fuel test port cap (Schrader valve located behind the cap), then install the adapter and fuel pressure gauge into the valve. Make sure all test hoses are installed and routed properly.

Mini Cooper R56 N14 Engine

The fuel pressure should be 5 bar (72.5 psi) at idle.

Mini Cooper R56 N18 Engine

The fuel pressure should be 700 psi at idle.

Mini Cooper R56 Base Model

The fuel pressure should be 50 psi.

General Instructions

Once you have installed the fuel pressure gauge, start or attempt to start the engine. Take note of the fuel pressure, then recharge the fuel system by cycling the key or running the fuel pump. Allow the fuel system to sit under pressure for 15 minutes. Pressure should drop no more than 0.5 bar in that time period. If it drops, you could have a faulty fuel pump check valve or a leak in the fuel system.

Other Ways to Check Fuel Pump Issues

You can also check the voltage across the fuel pump terminals. First, disconnect the battery before working with the electrical system. Then, connect a digital volt-ohm meter (DVOM) across the fuel pump terminals. Turn the key on and check the voltage. If there is no voltage, check the relay and fuel pump fuse. With the key on, the fuel pump will receive voltage for three to five seconds to prime the system (if the engine doesn't start).

You can also load test using a test light and a DVOM. Connect the DVOM across the fuel pump electrical connector terminals and take a reading. It should read battery volts when the key is turned on. Then, connect an incandescent bulb-style test light to the battery ground and touch the test light probe tip to the positive wire you are back-probing with the DVOM. Your reading should hold steady; a maximum drop in voltage of 0.5 volts is OK.

If you have a turbocharged model, you can also check the high-pressure system using a Mini scan tool. Use the scan tool to view DME, then fuel pump/pressure. Look for the rail pressure set point (desired) and rail pressure actual. These two values should be close. If they are off by 10 bar, you may have a faulty high-pressure fuel pump.

Frequently asked questions