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I was driving down road, started missing, then like ran out of gas. tank 3/4 full. codes for misfires 1,3,5 & 6. A neighbor mechanic had computer. High press fuel 75#,
Press from fuel tank 65#. Battery is 2 months old, Good charge. Why is there only 75# from the high pressure pump and why is the computer only requesting 75 # ? Is this the ECM? Is there another sensor that could be throwing this off? I drained the gas tank and replaced the gas to rule out any water. I schrader tapped the fuel line from the tank, it's 65# on gauge. I drove it from NC to Michigan and back just prior to this happening.
 

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Do you mean 75 psi from the high-pressure pump? If so, that's way too low and your high-pressure fuel pump sounds like the culprit. It should range from ~500 psi at idle to over 1,700 psi at WOT.
 

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Do you mean 75 psi from the high-pressure pump? If so, that's way too low and your high-pressure fuel pump sounds like the culprit. It should range from ~500 psi at idle to over 1,700 psi at WOT.
The high pressure pump reading was 75 #. It is being commanded to 75 #. I thought that also and have changed it. What determines the HP pump pressure? Does that come from the ECM? Could it be 1 or more injectors are stuck open? A bad relay for the HP pump? This all started after I filled the tank on the way home from a Dr. apt, It ran OK before fueling, that's why I thought it might have been water in the gas.
 

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Fuel pressure at the HP pump is controlled by a variety of inputs, but yes, ultimately it's the ECM that determines rail pressure. Here's a very detailed page about the DI system on the GM 3.6s.
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I've had water in fuel before. While not a GDI engine, it didn't cause quite the extent of shut-down you experienced. I had some hesitation and a CEL (don't remember the code) but it subsided after about a day.
 
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