Replacing The Fuel Pump In A 91 Suburban: Step-By-Step Guide

If you're looking to replace the fuel pump in a 1991 Suburban, you'll need to be prepared for a challenging task. This is because the fuel pump in this particular vehicle is located inside the fuel tank, which means dropping the tank or cutting an access hole will be necessary. It's also important to note that simply replacing the pump may not always solve the problem, as other issues such as a faulty fuel pressure regulator or a blown fuse could be the culprit. When attempting this repair, it is recommended to replace the entire fuel sending assembly, including the harness, to avoid future problems. Additionally, ensuring a good ground connection and checking the wiring diagram can help identify any potential electrical faults.

Diagnose the problem

There are several ways to diagnose a bad fuel pump in your 1991 Suburban. Firstly, listen out for any unusual noises. A damaged fuel pump might make a loud, whining sound coming from your gas tank. This could indicate an issue with the pump, or it could be due to low fuel or contaminated fuel. If you hear this noise, it's best to check your fuel levels and the condition of your fuel.

Another sign of a faulty fuel pump is trouble starting your car. If your vehicle struggles to start and run, it could be because the pump cannot push enough gas through to the engine. An old or worn pump may also cause the engine to overheat and stall.

If you notice that your vehicle loses power when driving up steep inclines or carrying a heavy load, the fuel pump could be the issue. The engine requires more fuel to operate under stress, and a faulty pump may not be able to provide enough fuel to maintain power.

You can also check for physical signs of damage. In some cases, the fuel pump relay may need to be replaced. This is typically located on the firewall in the engine compartment, on the passenger side towards the center.

To further diagnose the issue, you can use a pressure gauge to check the fuel pressure. Find the open air valve on top of your engine or fuel line, insert the pressure gauge, and tighten the attachment nut. Then, crank the engine. If the pressure gauge doesn't move, it's likely that your fuel pump is bad. A functioning fuel pump should show a pressure reading of 4-60 psi.

Additionally, you can use an OBD-II scanner to check for error codes. If your check engine light is on, insert the OBD-II scanner into the OBD port under the steering wheel and read the codes to identify any issues with the fuel pump or other systems.

Prepare the vehicle

Park your 1991 Suburban on a flat, solid surface, engage the parking brake, and allow the engine to cool if it has been running recently. Ensure you have a suitable workspace with enough room to work safely and effectively.

Remove the key from the ignition and disconnect the negative battery cable from the battery. This will prevent any electrical power from reaching the fuel pump and reduce the risk of fire or injury.

Next, you will need to relieve the pressure in the fuel system. To do this, locate the Schrader valve on the fuel injector rail, which is usually found on the fuel rail near the fuel injectors. Attach a hose to the valve and place the other end of the hose into an approved container. Depress the valve core with a small screwdriver and allow the fuel pressure to release. Be very cautious as the fuel will be under pressure and handle any fuel carefully to avoid spills or injury.

Now, you will need to remove the fuel tank. This process will vary depending on your specific model of 1991 Suburban, but it typically involves removing the rear seat and any necessary trim or panels to access the fuel tank. You may also need to disconnect any electrical connectors and fuel lines attached to the tank. Be sure to have a container ready to catch any remaining fuel in the tank. Once the tank is removed, place it on a suitable work surface and locate the fuel pump.

Remove the fuel tank

To remove the fuel tank from a 1994 Chevy Suburban, follow these steps:

First, remove the negative battery cable. Next, remove the two pipes that fill the tank. If the tank has a heat shield, you may need to remove the drive shaft to lower it. Put a support under the tank and loosen the straps holding it in place. Slowly lower the tank and remove the two connectors on top. Then, remove the fuel lines and the evap lines off the pump. Finally, carefully lower the tank, ensuring that all lines and hoses are disconnected.

This process may vary slightly depending on the model year and configuration of your Chevy Suburban. It is important to exercise caution when working with fuel and to refer to a qualified mechanic or repair manual for detailed instructions specific to your vehicle.

Replace the fuel pump

To replace the fuel pump in a 1991 Suburban, you will need to drain the fuel tank or drop the tank for a more straightforward access to the pump.

Firstly, locate the fuel pump relay, which should be on the firewall in the engine compartment, typically on the passenger side towards the center of the firewall. You can then try to jump-start the fuel pump by putting 12V directly to the single red wire hanging off the fuel pump relay. If the pump runs, your problem is likely on the fuel tank end, such as a bad ground, bad connection, or bad wire.

If the pump does not prime, you can try knocking on the gas tank with a rubber mallet to see if the engine starts. If it does, then the pump is likely faulty.

If you decide to drop the tank, you will need to disconnect the fuel lines and electrical connectors, and remove the straps holding the tank in place. Lower the tank carefully, ensuring that you have adequate clearance underneath the vehicle. Once the tank is lowered, you can remove the old fuel pump and sending unit, and install the new one.

Finally, raise the tank back into position, reconnect the fuel lines and electrical connectors, and secure the tank with the straps. Ensure that all connections are tight and secure before starting the engine.

Reinstall the fuel tank

To reinstall the fuel tank of a 1991 Suburban, follow these steps:

Firstly, ensure that all lines and hoses are connected to the tank. This includes the fuel lines, the evap lines, and the connectors on top of the tank.

Next, slowly raise the tank into position, ensuring that it is securely fastened with the straps. If your vehicle is equipped with a heat shield, you may need to reattach the drive shaft and remove the support from under the tank before raising it into place.

Once the tank is in position, reattach the two pipes used to fill the tank. Finally, reconnect the negative battery cable.

It is important to exercise caution when working with fuel systems to avoid any safety hazards. Always refer to your vehicle's service manual for detailed instructions specific to your model, and consult a certified mechanic if you are unsure about any part of the process.

Frequently asked questions