Hello there I'm new to this forum and Am having a heck of a time diagnosing my truck. First off no codes or check engine light. When then truck sits over night with fuel Preasure gauge on by morning zero fuel Preasure. Turn key on jumps to 50 but still very hard to start. Once started if I shut off zero issues. It's just when it sits for long periods. It don't matter temperature outside cause I tried in heated shop with still same results. I've already threw a $350 fuel pump at it with exact same issue reoccurring. 2010 slt Sierra 5.3litre engine Any help would be greatly appreciated. Thanks a lot.
Fuel Preasure
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Has to be a leak in the system or a leaky injector. Something is allowing the pressure to release on the fuel lines.
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Most fuel pump assemblies have the fuel pressure regulator along with assembly. However some are seperate. After vech sits over night turn key to run position listen for pump to engage after about 5-10 seconds, turn key to off then try to start vech. If it fires right up most likely loosing prime. Look to see if regulator is with the pump assembly or in the engine compartment. Also what brand of pump did you use?
I second the injectors if its hard to start with pressure. Cycle the switch a few times through just in case and see what it does. Do you floor the accelerator and try to clear the excess fuel? If that works try some injector cleaner. Do you have a high alcohol content?
I got an oem delco fuel pump. If I turn the key to the on position it immediately goes to 50ish psi. But when you start it's like it's out of fuel then starts fine. If I shit it off again and start its ok. Thanks a lot for the replies!! How do you suggest I clean injectors? Can of seafoam in the tank?
Seafoam... MMO. I'm sure there's some other injector cleaners also. The seafoam will probably work faster but not much lubricant. If it were me I'd try the seafoam or the Wal-Mart version of it with some MMO as well. Then keep adding the MMO for the next few tanks. It should treat 80 gal.
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