What is the correct fuel pressure, 5.3 engine?

AWD V8

Original poster
Member
Jan 12, 2015
463
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

Member
Oct 23, 2014
80
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).
 

AWD V8

Original poster
Member
Jan 12, 2015
463
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.
 

AWD V8

Original poster
Member
Jan 12, 2015
463
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

Member
Oct 23, 2014
80
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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