What did you do to your NBS GMT800 Tahoe/Yukon Today?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

iddqd

Full Access Member
Joined
Dec 18, 2017
Posts
224
Reaction score
651
Location
San Francisco, Comifornia, USSA
Strange, my FPR is integrated into my fuel pump and is nothing like what's shown in the video. In older GMT800's, the FPR was located on the fuel rail close to the firewall and was easy to access and replace. I had to replace my fuel pump around 120k miles because the FPR was failing, and since it was built into the fuel pump assembly I didn't have a choice but to replace the whole thing.
In 2004 or 2005 GM went from return to return-less system. It depends on the production year of your rig. With the reurnless system they also eliminated a fuel filter under the belly of the truck, and change fuel injector flow map.

In return system, the flow numbers are constant regardless the intake manifold vacuum, and the fuel regulator makes necessary adjustments (that's why it has a vacuum hose from the intake manifold).

In returnless system, the regulator is too far away in the fuel tank to route a vacuum line there. So, the calibaration in the PCM now has different flow rates for different vacuum ##:

q.jpg
 

Fless

Staff member
Super Moderator
Joined
Apr 2, 2017
Posts
11,871
Reaction score
24,144
Location
Elev 5,280
In 2004 or 2005 GM went from return to return-less system. It depends on the production year of your rig. With the reurnless system they also eliminated a fuel filter under the belly of the truck, and change fuel injector flow map.

In return system, the flow numbers are constant regardless the intake manifold vacuum, and the fuel regulator makes necessary adjustments (that's why it has a vacuum hose from the intake manifold).

In returnless system, the regulator is too far away in the fuel tank to route a vacuum line there. So, the calibaration in the PCM now has different flow rates for different vacuum ##:

View attachment 360342

This is mostly correct, with the exception of the 2004 Flex Fuel trucks. It's dependent on your model year AND if Flex Fuel or not.

From a post at ls1tech.com (https://ls1tech.com/forums/conversi...ck-fuel-pressure-regulators.html#post16979237).

"1999-2003 4.8, 5.3, 6.0 all had a fuel rail with 3/8" supply line and a 5/16" return line. The fuel pressure regulator is on the fuel rail, and has a vacuum line to the intake manifold. In 2004, All engines went to a single 3/8" supply line, with no return (returnless) except 5.3L L59 Flex Fuel vehicles. For 2004, Flex fuel engines KEPT the return line, BUT used a fuel pressure regulator with a lower pressure ratting. 2005 5.3L L59 Flex Fuel engines switched to a single 3/8" supply with NO RETURN line in 2005. Non flex fuel engines, fuel pressure spec is 55 to 62 psi with vacuum line disconnected, fuel pump running. 5.3L Flex Fuel engine 2004 and back, 48-54 psi with vacuum line disconnected, fuel pump running. 2005+ with returnless fuel rail all shared same fuel pressure spec, 55-62 psi. There is no vacuum reference on these, so fuel pressure should remain constant under all operating conditions. The computer is programmed differently for fuel flow rate depending on type of fuel rail. This is important to know when having a PCM programmed."
 
Last edited:

ivin74

05 NBS Nali
Joined
Aug 3, 2014
Posts
2,372
Reaction score
2,479
Location
Htown, Texas
During the holidays and on vacation one of neighbors is a mechanic. I had him change out the front sway bar bushings, all 4 control arms and most steering components. I used all oem GM parts. I painted all parts black prior to getting the work done. SUV rides like new now.
 

Attachments

  • 20220101_144257.jpg
    20220101_144257.jpg
    728.9 KB · Views: 10
  • 20211226_195340.jpg
    20211226_195340.jpg
    368.9 KB · Views: 10
  • 20211226_195425.jpg
    20211226_195425.jpg
    338.8 KB · Views: 10
  • 20211226_195346.jpg
    20211226_195346.jpg
    296.9 KB · Views: 10
  • 20211226_195421.jpg
    20211226_195421.jpg
    335.1 KB · Views: 10
Last edited:

Rocket Man

Mark
Supporting Member
Joined
Dec 25, 2014
Posts
26,004
Reaction score
50,862
Location
Oregon
During the holidays and on vacation one of neighbors is a mechanic. I had him change out the front sway bar bushings, all 4 control arms and most steering components. I used all oem GM parts. I painted all parts back prior to getting the work done.
Nice. Perfect timing.:happy107:
 

Forum statistics

Threads
132,323
Posts
1,865,990
Members
96,919
Latest member
steezy5oh
Top