How to Diagnose Car Problems When It's Not Starting

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If a vehicle doesn't start, it may be a result of a wide variety of problems, so the first questions to answer are whether or not it has a spark or fuel. Determine whether or not a vehicle has fuel pump operation with help from an ASE-certified master automobile technician in this free video on diagnosing car problems.

Part of the Video Series: Auto Repair & Maintenance
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Video Transcript

Why a vehicle doesn't start can be a complicated question. But in many cases we have to start our diagnoses with some of the basics and so there's basically two things that we look for first and that is, "Does the vehicle have spark and does it have fuel?" Those are probably the two most common reasons why a vehicle doesn't start. So on this vehicle here we're going to do our preliminary checks to determine if that's one of the reason why it doesn't start. So the first thing we're going to do is we're going to hook up a fuel pressure gage to the shredder valve test port on the fuel rail and it, that way when we turn the ignition on we'll be able to tell if the vehicle actually has fuel pump operation; of course that's very important. As always when dealing with gasoline, be careful not to spill the gasoline on anything hot and keep a fire extinguisher close at hand. The next thing we're going to do is we're going to; we know that, you know, this will prove whether or not the fuel pump works; we need to know whether or not the computer is sending signals for the vehicle to inject. So I've disconnected one of the wires from one of the six fuel injectors on this car. I'm inserting a little test light that's called the noid light and this way when we crank it over we should get some indication as to whether or not that signal is being sent. Lastly, we need to know if the vehicle has spark. So what we're going to do is disconnect one of the spark plug wires from a spark plug and we're going to install a spark tester and see whether or not it has spark. So now what we're going to do is we're going to crank it over and see which one of these things that we have. So first off we'll just turn the key on and see what happens. Alright, so you're going to need to focus on that. Ready for that shot? I came up to 40 psi hopefully. You got that with the movement. When we turn the key on it came up to 40 psi and that indicates that the fuel pump works and that should be enough fuel pressure to actually have to start the vehicle. The next thing we're going to do is we're going to crank the vehicle over and we're going to check and see whether or not the noid light lengths and that'll give us some indication of whether we have a signal coming from the computer to turn the injectors on and off. The noid light blink and that indicates that we're getting a good signal from our computer and it gives the computer probably conscious and so that's a good sign.


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