What To Do if your Vehicle Fuel Pump Checks Out Okay, but the Engine Still Won’t Start
If the fuel pump is running and delivering normal pressure to the engine, and the engine has spark and compression, but will not start, the fuel injectors are probably not opening. The PCM uses the trigger signal from the crankshaft position sensor, and/or camshaft position sensor to pulse the injectors. The injectors should receive battery voltage when the key is turned on, and the PCM driver circuit provides the ground connection to energize the injectors.
The first check would be to check for voltage at the injectors when the key is turned on. No voltage? The problem could be a blown injector circuit fuse, a bad fuel injector power relay, or a fault in the wiring harness to the injectors. The injector fuse and relay are usually located in the relay box or power distribution center in the engine compartment.
If the fuse is okay, try swapping the relay with another to see if that gets voltage to the injectors so the engine will start. No change? Then the PCM may not be pulsing the injectors, or there may be a shorted injector that is robbing power from the circuit preventing the other injectors from opening.
TIP: Try unplugging the injectors one at a time and cranking the engine to see if it will start. If the engine starts when a particular injector has been unplugged, that’s the shorted injector that needs to be replaced.
TIP: You can also measure the resistance of each injector with an ohmmeter. Unplug the injector and measure the resistance between the two terminals. If resistance is outside specifications (high or low), replace the injector.
If the injectors appear to be working, but the engine is still not starting, the engine may be flooded with TOO MUCH fuel (remove a spark plug to see if it is wet). Let the engine sit awhile, then try again, or hold the gas pedal all the way down when cranking to put the PCM into the “Clear Flood” mode when starting the engine.
NOTE: Hard starting problems are sometimes the result of an improper starting technique on the part of the driver. On a fuel injected engine, DO NOT push or pump the gas pedal when trying to start the engine. This just puts the engine into the Clear Flood mode, which will cut off fuel to the engine temporarily making it even harder to start. Just crank the engine without touching the gas pedal. Don’t forget after reading also share with friends and family, it can do a lot more in helping someone.