Swapping an LS into a 50 GMC fuel questions

[suburban99]

I am swapping a 2004 4.8/4L60E into my 50 GMC on an s10 frame.
I bought the motor and tranny for $1000 and when I removed the vortec cover the intake had a large hole in it near the MAP sensor on the top. This manifold is returnless, and DBW.

I obtained another manifold off a friend that is DBC and swapped the DBW throttle body onto it and ran fuel and return as it has a return line. I repin my own harness and delete VATS etc with HPTUNERS. I have done a few of these swaps.

Truck cranks and starts for about 2 seconds but does not run. Fuel pressure is about 50PSI and falls off quick when pump shuts off (after the 2 second run form the ecm). Fuel relay has power during crank and run.

Question 1 Are the manifolds interchangeable or should I grab another DBW instead of the DBC.

Question 2 Why would fuel pressure fall off so fast after pump stops? Is their a check valve I am missing or is the fuel regulator leaking? Leaky injector?

Question 3 If I have the Tach module wired correctly should the throttle body flapper move with key on and pedal pushed?

Thanks.

[Joyridin]

Use HPTuners and there is an option for turning on the fuel pump. See what the pressure is while the pump is running. It should be 58 psi. My car drops off in seconds, but the regulator is mounted on the fuel rail. You can change the pre-start run time on the fuel pump also. I went to 5 seconds to give it a chance to build a little pressure.

1) I have used both. DBC and DBW makes no difference.
2) See above
3)Mine does not. The engine has to be running. It will jerk a bit with the key on, but it does not open and close like a cable.

[suburban99]

Thanks much appreciated..

[suburban99]

Originally Posted by Joyridin

Use HPTuners and there is an option for turning on the fuel pump. See what the pressure is while the pump is running. It should be 58 psi. My car drops off in seconds, but the regulator is mounted on the fuel rail. You can change the pre-start run time on the fuel pump also. I went to 5 seconds to give it a chance to build a little pressure.

1) I have used both. DBC and DBW makes no difference.
2) See above
3)Mine does not. The engine has to be running. It will jerk a bit with the key on, but it does not open and close like a cable.

Where on HPtuners do you extend the pump run time? Thanks

[Joyridin]

Go into the Fuel System tab at the top. Then go to Fuel Pump. There is an adjustment that says Fuel Pump Prime Time. I always change it to 5 seconds. I think the default is 3 seconds.

[suburban99]

Ok got it running thanks for the help.
Truck starts and runs decent with open headers. When I shut off the truck after about 5 seconds I heard the throttle control click and when I try to restart it has a U0107 code. Truck will restart, but no throttle control until I stop it and clear the code. I was told the TAC matches the motor/trans but I di not remove them personally. This is my first DBW swap. Any help appreciated.

[suburban99]

Ok just for reference the problem was the TAC module and ECM wee not wired to KEY ON. The TAC was wired to BAT. Apparenty they both have to power up together. And when I shut it off the ECM turned off but the TAC remained powered up. That's why I heard a click 5 seconds or so after turning it off. All good now.