Troubleshooting a Bad Fuel Pump in a Dodgeby Don Bowman
Start by verifying that the Dodge has a fuel problem. Also, a fuel problem does not always mean that the fuel pump in a Dodge is bad. Locate the Schraeder valve on the fuel rail. Take the cap off and install a fuel-pressure tester. Turn the key on and check the pressure. It should be 49 psi. If there is pressure, the problem is elsewhere. If there is no pressure, disconnect the fuel-pressure gauge and test the fuel-pump relay. The fuel-pump relay is located in the relay center under the hood and is clearly marked. With the key off, there should be power at one of the terminals. With the key on, there should be two terminals that have power. Mark the terminals if necessary so that you remember which terminal has power. Check the remaining two terminals for ground. Put the red lead of the ohmmeter into one of the terminals and touch the black lead to a good ground. Ground will be shown if there is continuity (ohmmeter does not read 0). There should be ground on one of the terminals. If no ground is found or there was not power to two terminals a wiring problem exits.
Once the ground terminal is identified, jump the terminal that had power with the key off to the terminal that was not grounded and had no power (using a jumper wire). This is the terminal to the fuel pump. With these terminals jumped try to start the vehicle. If it starts, the relay is bad and needs to be replaced. If the vehicle still will not start, insert the relay back into its location and raise the vehicle enough to get under the fuel tank. Disconnect the fuel-pump harness, which is located on the back side of the fuel tank toward the rear of the vehicle. Use a voltmeter and test the harness side for power when a helper cycles the key. Remember that there will be power for only two seconds at a time. Since the computer does not see the engine turning, it shuts the fuel pump down. Just have the helper cycle the key on for five seconds and off for five seconds while the harness is tested.
If there is power to the pump, it is obviously a bad fuel pump. If not, the wiring between the relay and the fuel pump is faulty. It is worth mentioning that most technicians, for expediency, simply take a can of carburetor cleaner out to check if the problem is fuel-related. Just spray some carburetor cleaner into the intake manifold and try to start the vehicle. If it starts for a second or two, the problem is a bad fuel pump, and if it does not, some other problem is present.
Don Bowman has been writing for various websites and several online magazines since 2008. He has owned an auto service facility since 1982 and has over 45 years of technical experience as a master ASE tech. Bowman has a business degree from Pennsylvania State University and was an officer in the U.S. Army (aircraft maintenance officer, pilot, six Air Medal awards, two tours Vietnam).