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Location: Oregon
the easiest way to check for spark is to pull a spark plug wire off the coil. Pull a spark plug wire off the coil before you start the engine. Place the boot back on the coil but don't press it all the way down until it clicks on. This way when you start the engine you can lift the wire slowly off the coil watching for the spark to jump to the wire. You don't want to get your hand close to the coil electrode or you could get shocked. hold the wire a ways back and only lift so you can either hear or see the spark jump then put the wire back on the coil. If you have spark you have CKP (crank position sensor) signal.

If you have spark then you check for fuel pressure and injector pulse. You check injector pulse at the injector harness connector at the injector. Unplug one of the injectors and use a yest light that goes from one wire to the other wire in the harness connector. When cranking the engine the test light should flash when the computer tells the injector to fire. If it does flash you should measure your fuel pressure. You will need a gauge. You can't just push on the valve and say you have pressure. You have to measure how much pressure you have. Spec. is 41-47 psi.

if you have no spark, ignition module, CRK sensor, power to the module would have to be checked. If you have no injector pulse it could be the computer, power or the passlock. If you have no fuel pressure it could be power, computer, relay or fuel pump. Or other things... It gets complicated sometimes.


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My car randomly won't start. I'll turn the key, the lights will work, the radio
works, but does not start. The battery, alternator and starter are all new.
Sometimes if I let the car sit for a few hours it will start. Then it will start fine
for a few days then won't start again. I've even had the Neutral safety switch
replaced. What other reason could make the car not start like this?


   
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contributions: 2092
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Location: Oregon
need more information.

when you say it won't start - what do you mean? What actually happens when you turn your key to the start position?

you said you have a new battery, alternator and starter. Why did you replace all these items?

AS you probably know it doesn't take much from the battery to turn on the lights and stuff. Nothing like when you try to start your engine. So, a good battery is important. It's number one. Number two is the starter. It has to take power from the battery and turn the engine over. Is you starter turning the engine over when you say it doesn't start? If the starter isn't cranking the engine over then we need to look at what is happening with your starting system. If the engine is turning over but won't start then we have to see if you have spark, fuel pressure and injector pulse.

I will need to know make, model, year and engine size to go from there...


   
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