another 6NZ fuel preasure ??

The Valve in the transfer pump is a safety valve as the return Valve in the filter head is the one that "Should" control Fuel pressure.

The Transfer pump must have a safety Valve in it incase the fuel filter gets blocked or there is another restriction in the system between the pump itself and the tank.

 

Change the fuel valve... its the one under your fuel filter base next to where the filter screws on

 

The filter base has two valves and a air bleeder screw. The main fuel pressure regulator/check valve is located on the underside of the filter base on the right side towards the firewall. Why is it called a check valve/pressure regulator valve? Because it traps the fuel in the head when you shut the motor off. But it also regulates fuel pressure when the engine is running.

The second check valve is located on the right side of the base facing the firewall. This valve only functions when the primer pump is used.

The air bleed screw is the one on the left side of the filter base and face out towards you. This is only used when trying to prime the fuel system

 

What he said

Now the reason they are being shimmed is CAT has a weak spring in them allowing fuel to bypass internally in the fuel transfer pump. Shim it up and then the valve in the filer base is controlling fuel pressure. The problem I've seen is this also increases the flow of fuel through the cylinder head and causes the fuel to pick up more heat. Fuel temps can easily reach 150*F by the end of the day in the summer months

 

so what your saying is, the check is in the mail?

 

One day " my" unresolved problem will also be behind me.
CAT said zero blow by on injector seats and O rings when they ( under my platinum warranty) swapped out all 6 injectors trying to resolve my issue.
Bottom gears from a stand still , all the clean smooth power I want. After the truck sits a few days, the same, smoooth running.
After 10+ hours truckin, the same, all good.
But the 90% of the time over and above that, shake, sputter, pop.
If I'm off the throttle for 5+ seconds,
( coasting down a grade, rounding a curve to get on a big road, etc)
I can put foot to floor through all 18 gears and no issues.
Any time I'm off the throttle 5+ seconds all is Good thereafter for usually the next 5 to 15 seconds of regular throttling .
But otherwise, I'd swear I was running out of fuel or timing is being thrown out.
Coolant temps climb, fan comes on and no way can I get RPM's above 1500 as it feels like I'm gonna rip the crank out with the vibrations and low power.
Tank vents all good. Fuel supply lines new. Pump is a year old. TPS also a year old. Both wiring harness replaced.
All sensors replaced. Dropped tanks to check suction tubes all good. Zero air in Fuel, both pre and post head ( CAT hooked up sight glasses we drive for 90 minutes)
Zero blockage in exhaust. Fuel pressure great. Always use CAT filters.
Fuel pressure regulator valve changed 3x. Divider and divertor valves changed.
ECM swapped out 2x.
It's driving me insane.
Open to ideas if you've got one.
Thanks guys .
P.S...the throttle positioning sensor was never calibrated was told not needed . But I called around and the consensus is that if the sensor and pedal ( complete) is changed then no, no need to calibrate. But if the sensor "only" is changed then yes, it should be calibrated but the guy's at CAT say it won't make a huge difference ...hmmm. Gonna get it done anyway, gotta get to the bottom of this.
"HELP"......