Rather than try to explain why it can't be this or it can't be that, let me start by describing what you WILL observe. The fuel pump gets turned on for only one second after turning on the ignition switch. That is to insure fuel pressure is up for starting in case it bled down overnight. That can be why you're measuring what appears to be good fuel pressure, and it does prove the pump is working. Logic would dictate the pump is turning on during cranking too based on the following, but that hasn't been proven yet.
Next, the fuel pump gets turned on again during engine rotation, (cranking or running). The Engine Computer turns the fuel pump relay and / or the automatic shutdown (ASD) relay on during cranking when it sees pulses from the crankshaft position sensor and the camshaft position sensor.
Besides the fuel pump or pump relay, the ASD relay sends power to the ignition coil pack, injectors, and other things. Since you have spark, we know the ASD relay is turning on, therefore the two sensors are sending signals to the Engine Computer.
You have spark, so you shouldn't be wasting time with the coil pack and spark plugs. You know all six spark plugs won't fail at the same time, so they won't cause stalling or a failure to start. The throttle position sensor and EGR valve also won't cause a no-start condition. By replacing random parts, you're inserting all kinds of new variables the Engine Computer may not be ready to learn yet. Besides wasting a lot of money and being the least effective way to diagnose a problem, you may be causing more problems that can result in a no-start even after you fix the original one.
Have you even checked yet for diagnostic fault codes? Those will indicate the circuit or system that needs further diagnosis. When you replaced the cam and crank sensors, were these new or used sensors? Are you aware of the need to use new spacers with them to set the very critical air gaps? If there was no spacer, that sensor can hit its tone wheel and be broken. Too large of an air gap can cause the signals to be generated at the wrong time or sporadically.
Replacing the automatic idle speed motor is going to cause a no-start condition due to idle speed being too low. You won't get the nice idle flare-up to 1500 rpm at start-up, the engine will tend to stall at stop signs, and you'll likely have to hold the accelerator pedal down 1/4" to get the engine to start. The same thing will happen if the battery was disconnected or run dead.
Once all these things are sorted out and the fault codes are read, it may be necessary to check some engine mechanical things. Check a spark plug to see if it's dripping with raw fuel. A scanner will display live data and will show if the cam and crank sensors are "in sync". If they are not, suspect a jumped timing chain. The MAP sensor has the biggest say in how much fuel goes into the engine, but if that was defective, the engine would have started on starting fluid. You might want to consider a compression test or a cylinder leakage test.
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Friday, March 13th, 2015 AT 10:58 PM
