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I was running my truck earlier and it was running fine i parked it let it sit for a little while and the battery was dead i thought it was jus the battery so i tried jumping it off and it was barley turning over like it wasnt getting ni feul or something but i checked the fuse and feul pump relay they were good i could hear the feul pump come on so i disregarded that the alternator is good still got magneteted charge, ive changed the started about 8 months ago. I need to change the mass air flow sensor bc i pulled the fuse and it was still running i just dont know what it is it will crank but you have to hold the key on while being jumped off somebody help please anything would be great
 

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Is this a 5.7 vortec? They need over 60 PSI of fuel pressure to start. Less than that, and the truck gets hard to start. Next thing, if the battery is low, this can also cause a low fuel pressure issue. When you turn the key on, ( before you turn it to the start position) the fuel pump cycles for 2 seconds. This ( if the fuel pump is working rite) it builds up to about 62 PSI. As you crank the engine, the fuel pump runs keeping the pressure up. Once the engine starts, the fuel pressure will drop to around 50 PSI. When the fuel pump gets old, it get week, and will not build up enough fuel pressure to force the fuel through the poppet valves. First off, the battery needs to be fully charged, and the cells need to be tested to be sure the battery is good. If it fails this, it will need to be replaced. Once you know that the battery is good, the next step will be to do a fuel pressure test. You tube is full of videos that will help you. Keep in mind that you need to do your fuel pressure test before the truck is started. Here is a grate video to get you started. I know its kind of long, but it has grate info.
 

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2010 Silverado 1500 LTZ
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Fyi, if still not fixed, fuel pump harness grounds to the chassis above the fuel tank. That connection corrodes and fuel pressure can drop because of it. Fresh ground connection can make a huge difference in fuel pump performance. Good luck.
 

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A simple test is to when it's cool, ture on the headlights, then go and turn the ignition key as to start the engine, if the lights dim, go low or even low, the battery is weak. Or if the headlights go out all together you have a short in the line or the starter is shorting out internally. Good luck !
 
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