Truck has no codes, fuel pressure is 60 psi when you turn key to on position, then kicks down to 56psi when pump kicks out,I pulled out the crank sensor then there is no firing at all. this truck did this before then ran for about three more days. I think the fuel pressure is ok but not sure. this truck has 90000 miles. this is a 1999 gmc suburban 5.7
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I would be suspicious of low fuel pressure. One psi in this system can mean the difference between starting and not starting.
Minimum fuel pressure should be 56psi. 54 or 55 will cause it not to start. It needs the pressure to open the mechanical poppets at the end of each injector. To low of pressure and the poppets will not open.
When end it does not start give it a couple shots or carb spray while s helper cranks it over. If it starts and stays running than stick with the low fuel pressure theory. Under vacuum, or once the vehicle is running, the poppets require less fuel pressure to open.
You may need someone to help with this, or not.Turn off the radio and any accessory that will interfere with hearing the fuel pump. Turn the key to the on position,the fuel pump should turn on for a couple of seconds to build fuel pressure, and then the pump will shut off. Turn key off. Turn the key on, the pump will do the turn on and off again. Do this about 5 times. Do not turn to the start position until after the 5 times of building the fuel pressure up in the lines. After the 5th time, turn the key to start the vehicle. If the vehicle starts, then you're loosing fuel pressure when it's not running. Most cars have about 60 psi of fuel pressure. You'll need a fuel pressure meter to check it.
you say fuel pressure is good, but what is it? what is the fuel pressure when it stalls out? Spec is 60-66 psi and it wont run if its 55 psi. the fuel pump relay should be good if the pump runs. Make sure the ground for the pump is good , G402 should be on left frame rail. you may have had it off to replace the pump? maybe? it may be time to stop guessing and have a repair shop diagnose it for you. You sure have replaced a lot of good parts.
Sounds like low fuel pressure. Check your fuel pressure. If you have the 3.1 liter engine and just turn the key to the "on" position you should have around 41 - 47 PSI. When running it should have about 31 - 44 PSI. If you have the 2.5 liter engine you should have 26 - 32 PSI of pressure when running. I hope this helps and good luck.
Check for correct fuel pressure. Connect pressure guage to schrader valve on fuel rail. Turn key to ON position without starting engine. Fuel pressure should be between 55 and 61 PSI. If it is too low, replace fuel pump in tank and fuel filter.
Fuel pump is bad. At idle pressure should read 50 PSI. Replace with original manufacture fuel pump after market pumps will burn out fast and are unreliable from my experience. Also could have a bad fuel regulator but that only works while driving down the road full throttle. You can unhook the fuel rail pressure regulator and that will give it full fuel and the pressure reading should read 60 PSI while it is running. If you turn the engine off and turn the key to run position it should read 50 PSI and hold for 60 seconds, if it drops below 30 PSI after 30 seconds Pump is defective. Many pumps are going bad here of late as people have been running them less than ¼ tank and this kills the pump. The fuel cools and lubricates the pump so the lower the fuel level the worse it is on the pump below ¼ tank. Not to hard of a job to do if you want instructions let me know.
Couple of things, the fuel pressure held before with the old regulator but now it doesn't. Are you sure you got the tiny o-ring out when you changed it and installed it on the new one? Is there any fuel in the vacuum line to the regulator? Does the white exhaust smell like fuel or coolant burning?
It sounds like a fuel pump problem. When you first turn the key on you should hear the fuel pump run for about 5 seconds then shut off. There is a fitting on the fuel rail on the engine that looks like a tire valve, try pushing on that to see how much pressure there is after the pump runs. There should be a good amount of pressure on it. If fuel just dribbles out or there doesn't seem to be much pressure it is definaly a fuel pump. The best thing is to use a fuel pressure guage that will attach at that fitting. There should be between 45 - 60 PSI of fuel pressure when the pump is running. Good luck with your problem.