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How to Diagnose a Failed Car, Truck & SUV Fuel Pump

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Uh-oh, maybe we have a bad fuel pump. That's what we're gonna talk about in this video.

The fact the engine is cranking fast leads me to believe that it's not a battery problem. It's always good to check the battery and make sure the battery fully charged before starting any diagnosing though. So, first thing we wanna do is check the fuses, make sure they're all okay, find the fuse block, and use a test light. You can put one end on the negative side. Just double check the test light, make sure it works, and just go through and make sure all the fuses work. It's important to find the fuel pump fuse, and actually make sure that one's working as well. Let's just go around. As long as your fuses are good then we can continue on. And if you do find a bad fuse, and it happens to be a fuel pump fuse, and you put it back in, everything works fine, it's probably not the only problem. Fuses don't just pop on their own. Normally there's something wrong, whether either the pump is sucking too much amperage, or there happens to be a short where it's shorted to ground, and that's popping the fuse.

So, near your injectors there's gonna be fuel rail, and you're gonna look for the service cap. Looks like this. And there should be a little Schrader valve where you can actually hook on a fuel pressure gauge. Just like this. So, most fuel pressures are gonna be right around this 50 psi or a little bit more, sometimes even a little bit less. You're gonna have to do your research to figure out what your fuel pressure should be on your particular vehicle. Let's say you didn't have any pressure, what's your next step?

Some vehicles you can actually access the fuel pump from the back seat. So, we just pull the back seat up, and there's normally a cover under there. Some vehicles you actually have to lower the fuel tank and get it from up top. Before you disconnect the connector, just take look at it. Maybe wiggle it, make sure it's not loose, and you can disconnect it. Like most vehicles, there's two thicker wires and two thinner wires. The thicker wires are the power and the ground for the fuel pump, and the two thinner wires are the float for the level sensor that sends a signal to the gauge cluster. Now, what you wanna do is take a test light with the correct jumper wires, and you can put one in one side. The brown wire on this vehicle should be the ground, and the white and blue wire should be the power. Put the jumper on there. So, this is set up like this. Now, if I have a friend turn the key on and the test light lights up, then I know I have good power, and ground going to the fuel pump.

So, we know we have power and ground at the fuel pump, so in that case, the fuel pump's not doing it's job. It's not giving us pressure. We would need a fuel pump. Now, if you didn't have that light kicking on, you need to find out whether you lost power or whether you lost ground. So, you would take you test light, put it on a good known ground, and then do the same thing, and check to see if you have power when you turn the key on and off. And then if you had power, then you would go check the ground. To check the ground circuit, what you wanna do is put this end on battery positive. And then with your test light, go onto the ground circuit. You can cycle the key, and see if the light comes on. That will determine if the ground circuit's good.

So, there's some tips on how to diagnose a bad fuel pump. I hope this video helped you out. If you enjoyed it, make sure you subscribe to our channel. Ring that bell, turn on all notifications, so you don't miss any of our videos.


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