Replacing Fuel Pump In '91 Corvette: Step-By-Step Guide

If you're experiencing problems with your 1991 Corvette's fuel pump, there are a few things you can try. Firstly, check if there is any fuel pressure present by using a test light to verify that all the fuses are working. If the fuses check out, you'll need to access the fuel pump, which is located under the gas door lid. If the pump doesn't activate, tap on it while someone cranks the engine – if the car starts, the pump has an internal failure and needs replacing. You can also check for battery voltage and ground at the fuel pump using a Digital Volt Ohm Meter. If there is no voltage or ground, the fuel pump relay may be at fault. This can be tested by removing the top of the relay and looking inside to see if the relay's coil energises and shuts the contact. If the fuel pump is definitely faulty, you can replace it with an electric fuel pump that mounts onto the fuel meter or sending unit inside the gas tank.

Locating the fuel pump relay

Once these steps are completed, you should be able to access the area under the glovebox, where you will find a row of fuses and relays. The fuel pump relay is one of the middle relays, and they are interchangeable.

It is worth noting that some sources suggest there may be two fuel pump relays in the 1991 Corvette. One is located on the right-hand side of the instrument panel, while the other is on the left-hand side. Additionally, the fuel pump prime connection is located under the hood, and you can jump that to power.

Gaining access to the fuel pump

To check if the pump is faulty, ask an assistant to turn the key to the 'Run' position and observe if the pump activates. If the pump does not activate, try tapping on it while the engine is cranked. If the car starts, the pump has an internal fault and will need to be replaced.

If the vehicle still does not start, check for battery voltage and ground at the fuel pump using a Digital Volt Ohm Meter (DVOM) while the engine is cranked. If voltage and ground are present, the fuel pump is faulty and will need to be replaced.

If voltage and ground are not present, the issue may lie with the fuel pump relay. This can be tested by removing the top of the relay and looking inside to see if the relay's coil energises and shuts the contact when the circuit is energised. Alternatively, you can manually close the contact on the test relay by pressing the points closed with your finger. If the fuel pump turns on and functions correctly, the problem is not with the pump or the wiring from the relay to the pump.

Testing the fuel pump

Firstly, you need to install a fuel pressure gauge on the Schrader valve on the passenger-side fuel rail, near the rear of the engine. When the key is turned to the "Run" position, the fuel pump should activate for two seconds, pressurising the fuel rails and giving a reading of between 40 and 42 psi of pressure. This reading should jump to 38-40 psi once the engine is started. If there is no fuel pressure present, use a test light to check that all the fuses are working.

If the fuses are functioning, you can then access the fuel pump, which is located under the fuel door in the back of the car. Have someone turn the key to the "Run" position and check if the pump activates. If not, tap on the pump while someone cranks the engine. If the vehicle starts, the pump has an internal failure and needs to be replaced.

If the vehicle does not start, check for battery voltage and ground at the fuel pump using a Digital Volt Ohm Meter (DVOM) while someone cranks the vehicle. If voltage and ground are present, the fuel pump has an internal failure and will need to be replaced.

Additionally, you can test the fuel pump by applying 12 volts to the fuel pump test terminal. This can be done by running a wire from the battery to the test terminal, which is located at the G terminal on the ALDL connector near the driver's right knee. If the pump runs, you should hear it. However, just because it runs does not necessarily mean it is functioning correctly, and further testing is required.

If the pump does not run, the service manual recommends checking for an open wire in Circuit 120 and an open pump ground in Circuit 150. These circuits can be found in the Fuel Injection section of the manual, chapter 6E2. Circuit 120 can be power tested at the fuel pump connector at the fuel tank.

Finally, when replacing the fuel pump, it is recommended to also replace the fuel meter strainer or sock to ensure that no debris or trash clogs the new pump.

Checking for battery voltage and ground

I'm sorry, but my search didn't find any relevant information about checking for battery voltage and ground when changing the fuel pump of a 1991 Corvette. Can I assist you with something else?

Replacing the fuel pump

The fuel pump in a 1991 Corvette is located under the fuel door at the back of the car. To replace it, you will need to remove the cover under the gas door lid to reveal the pump.

Before you begin, it is recommended that you replace the fuel meter strainer or sock when installing a new fuel pump to ensure no trash from the fuel system damages the new pump.

Step 1: Accessing the Fuel Pump

• Open the gas door lid and locate the cover under it.
• Remove this cover to access the fuel pump.

Step 2: Testing the Fuel Pump

• Have an assistant turn the key to the "Run" position to see if the pump activates.
• If the pump does not activate, try tapping on it while someone cranks the engine.
• If the car starts, the pump has an internal failure and will need to be replaced.

Step 3: Checking Voltage and Ground

• If the vehicle does not start, check for battery voltage and ground at the fuel pump using a Digital Volt Ohm Meter (DVOM) while someone cranks the engine.
• If voltage and ground are present, the fuel pump is faulty and needs replacement.

Step 4: Checking the Fuel Pump Relay

• If voltage and ground are not present, check if the fuel pump relay is being energised.
• You can test this by removing the top of the relay and looking inside to see if the relay's coil energises and shuts the contact when the circuit is energised.
• Alternatively, manually close the contact on the test relay by pressing the points closed with your finger. If the pump functions properly, the fault lies elsewhere.

Step 5: Further Diagnostics

• If the fuel pump relay is not energised, possible faults include the battery voltage supplied to the relay coil, the ground supplied to the coil, or the relay itself.
• For the fuel pump relay to become energised, oil pressure must reach 4 psi.
• An abnormally long crank time or a no-start condition could indicate a faulty oil pressure switch.

Step 6: Replacing the Fuel Pump

• Once you have determined that the fuel pump requires replacement, purchase a suitable replacement part. Ensure it is compatible with your 1991 Corvette.
• Install the new fuel pump by following the removal steps in reverse. Ensure all connections are secure and refer to a repair manual for your Corvette if necessary.

Step 7: Post-Replacement Checks

• After replacing the fuel pump, start the engine and check for any leaks or unusual noises.
• Ensure the fuel pump is functioning correctly and that the vehicle's performance has improved.
• If you are unsure about any aspects of the replacement process, consult a qualified mechanic.

Frequently asked questions