What is the correct fuel pressure, 5.3 engine?

AWD V8

Well-Known Member
So I'm dealing with a hesitation and misfire, in another thread I will start, long story.

I just need to know right now what the correct fuel pressure is.

I checked the fuel pressure and had a reading of 40 psi. Jumps to 50 when I blip the throttle.

I replaced the pump, Bosch. Replaced the fuel filter, was clean.

Now fuel pressure is 45 psi. Jumps to 55 when I blip the throttle.

In my experience with S10s, I would expect to see 50-55 psi, and 60-62 when I blip the throttle.

I checked the fuel pressure in my 1999 4.3 Jimmy, 55 psi, jumps to 60 when I blip the throttle.

I've also replaced the fuel pressure regulator, no change.

I have not done a dead head to test the pumps maximum. My S10 experience would be to expect 70+ psi.

What say the masses?
 

Dan_G

Well-Known Member
According to AllDatadiy - for my 2006 Denali with the 5.3:

Fuel Pressure (Key ON, Engine OFF) 385-425 kPa (55-62 psi)

Not sure what this means in real life. My 99 5.7L was always a little below the low end of the fuel pressure specs - even with a new GM pump (still ran fine).
 
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AWD V8

AWD V8

Well-Known Member
Thanks for your reply.

Key on, engine off for my truck is 55 psi. Driving is 45 psi. I just can't believe 45 is enough for this engine.

Tomorrow I'm going to dead head the pump to see what it can make.
 
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AWD V8

AWD V8

Well-Known Member
Here is a video clip of my Fuel Trims and O2 readings on my Torque app.
https://www.youtube.com/watch?v=D5xM_rk084c&feature=youtu.be
 

Dan_G

Well-Known Member
Yeah, not sure. It might be enough. I never looked at the fuel pressure in my 5.3 since it's running fine. I did deal with some issues with my 5.7

The old Vortec 5.7L with the spider injector unit (single central injector with 8 poppet valves) needed good solid fuel pressure (let's say 60+) to work properly without misfiring. But the GM pumps can't deliver that. Once I switched out the old style central injector unit for the newer multi-port style (with injectors more like most modern engines have - including the 5.3) it seems like fuel pressure is not quite as critical. Now with 175K miles that old 5.7 runs great - misfires are gone. 50psi of fuel pressure is getting the job done on the 5.7 with the new style injectors.
 

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