92 c1500 with 99 5.7 swap fuel pressure problems

[A-Z Auto]

I just did a 5.7 vortec with complete harness & interior swap on my 92 gmc. Everything came out of a 99 Tahoe except the trans. I kept my 5speed. During the swap.. I installed new spider, fuel pump, distributor & gaskets. I'm now getting a crank but no start. (Starts momentarily ) with the key on i get 50psi when it tries to start the pressure drops to about 40psi. I already swapped pump & filter... But I'm only getting 50psi to the fuel rail. I checked the pump before the filter & get 85+. I got everything connected back up & same thing.. So I pinched off the return line at the tank & still only get 50psi for just a second then drops to 45. Any input would be greatly appreciated.

 

[kennythewelder]

What year fuel pump are you using? A Vortec needs at least 60 psi to start. If you are using the fuel pump for the 92, it will not put out enough pressure. You need to put a fuel pump for a 96 or newer 5.7 L. You can get the truck to start by using starting fluid (ect) in the throttle body, (maybe) but the truck will loose power at higher RPMs once it starts.

 

[A-Z Auto]

The fuel pump is for a 97 5.7. It was the latest year that would fit the 92 sending unit. It's supposed to have the same pressure & flow specs as the 99

 

[A-Z Auto]

Could this be caused by a brand new regulator & spider? If so I can pull the plenum off. Just been avoiding it so I don't have to get more gaskets.

 

[skylark]

A 99 has VATS, Vehicle Anti Theft System. It will need to be tuned out of the pcm before it will run for longer than 2 seconds.

 

[kennythewelder]

skylark brings up a good point. As for pulling the plenum, as long as you didn't use gasket sealer, you should be able to remove it, and reuse the gaskets. They should be silicone and are reusable.

 

[A-Z Auto]

As far as vats... I have the complete 99 harness, column, lock cylinder & pcm & I'm not getting any security lights. Even still I did the 3x security reset just in case.