How to Troubleshoot a Ford Expedition That Won't Startby Don Bowman
When troubleshooting a Ford Expedition for a no-start condition, the first objective is to determine in which system the failure lies. Looking at the problem from a technician's point of view is the most expeditious method. A technician will immediately go for the most common problems first. The possibilities are unlimited when taken into context--the electrical system, the ignition system, fuel system, computer or components within its sphere of influence (of which there are many), the security system and a mechanical failure in the engine.
Check the starting circuit. The starter must engage the flexplate gears and rotate the engine in order for it to start. This happens when the key is in the full, forward start position. If no noise is emitted when the key is in the start position, the problem area has been located. If this is not the case and the starter operates, the testing procedures for the starter circuit can be ignored.
Lift the hood and inspect the battery for any irregularities such as corrosion, loose or broken terminals and repair as necessary. If any of the problems to be covered are found defective, repair and retry the starter. Continue only if the problem has not been corrected.
Check the battery voltage with the voltmeter. Connect the red voltmeter lead to the positive terminal and the black lead to the negative terminal. The voltage should read 12.5 to 12.75. If the voltage is one or more volts lower, the battery is discharged or has a bad cell. Charge the battery and retest. If the voltage rises to the appropriate numbers, try the starter once more by having a helper turn the key to start while you watch the voltmeter. If the engine starts or if it doesn't, the important thing is the reading on the voltmeter when the key is in start. If the voltage drops to below 10.5 volts, the battery is bad and needs to be replaced. If the voltage does not drop and the engine starts, check the voltmeter again. The voltage should now be 13.8 to 14.5 volts if the alternator is good. If the voltage is wrong, replace the alternator. If the battery voltage is correct and the engine still does not try to start, the starter circuit is at fault.
Check the fuse and the relay in the fuse relay box on the driver's fenderwell. If the fuse and relay are OK, check the power to the starter solenoid by connecting the voltmeter's black lead to a good ground and using the red lead to probe the terminal where the large diameter red wire is attached on the starter solenoid. If there is no voltage, the wire between the solenoid and battery is bad. If there is voltage, pull the small wire off the solenoid. Probe this wire connector as the helper turns the key to start. If there is voltage, the starter is bad. If there is no voltage, the ignition switch is bad.
Check to see if there is a computer system failure by turning the key to the run position with the engine off. Plug the code scanner into the OBD port on the left underside of the steering column. Press the key marked "Read" and the scanner will display any failure codes for the faults it has recognized. The code is a letter followed by four numbers. The letter designates the location and the numbers the fault. Cross-reference the code with the accompanying code sheet and a description of the fault will be presented. Correct the fault and try again.
Check the fuel system. Open the fuel cap and have the helper cycle the key all the way on for three seconds and off for four seconds. If the fuel pump cannot be heard, try one more test for accuracy. Remove the air intake duct to the throttle body. Hold the throttle linkage open. Squirt a good shot of carburetor cleaner into the intake manifold and retry. If the engine starts and runs for a few seconds, the fuel pump has failed. If it still does not start, check the ignition.
Pull a spark plug wire off a spark plug. Insert the test spark plug and lay it on the intake or block where it will be grounded. Have the helper try to start the engine and watch the spark plug. A good spark indicates a problem internally in the engine. No spark means the ignition system is at fault.