The Stovebolt Site Forums The Shop Area Engine Shop fuel pressure

I'm still in the planning stages of swapping in a 350 TBI out of a '95 1 ton. The Hayes manual states that this fuel system only uses 9 to 13 psi. This seems really low for a fuel injection system. Can anyone confirm this? If so, could i just use an external electric fuel pump that would run around that pressure, like this one from holley? Also, what rate does this system flow at? If anybody's got any info, it would be greatly appreciated--i just haven't had time to really take a look at this motor as i'd like.

That sounds about right for stock TBI fuel pressure. TBI is basically a really fancy electronic carburetor.

Ok, one more thing--is the pump actually in the tank like I think it is? If not, where is it?

Yes, the pump is in the tank, with a pressure regulator and a bypass line back to the tank for unused fuel to return to the tank. The computer does a 2-second priming run to pressurize the fuel line all the way to the injectors if the ignition is turned on and the starter is not engaged immediately. Another circuit runs the pump conrinuously during cranking, and yet another circuit powers the pump directly once oil pressure builds up. That switch is located directly above the oil filter on most engines. In case of a rollover, the pump shuts down as soon as oil pressure is lost. It's much better to use the in-tank pump and the full factory wiring harness if you're considering such a swap. There's a lot of circuits involved that will put the system into "limp-in" mode with fixed injector pulse width and ignition timing if all the signals aren't present. Lousy performance and gas mileage in limp-in!
Jerry

Any sources for good wiring diagrams? I bought the Haynes manual, and it's pretty good, but are there others? I've seen the full set of shop manuals for this truck on ebay, but don't really want to spend like $50.

The factory shop manual for whatever vehicle you're using for a donor is the best investment you'll ever make on a swap job like you're planning. Each vehicle has minor differences in wiring, and unless you get it all correct, the gremlins will drive you nuts! Be sure and get the entire wiring harness from the donor vehicle, and follow the wiring diagram exactly. You'll need all the relays, etc, and probably the fuse block, too. Be sure to include the harness in whatever deal you make with the wrecking yard, or wherever you're acquiring the engine. Fuel tank, too, if you're planning to use the in-tank pump. I've done a few of these swaps, and it's a long, frustrating job without the factory harness and wiring diagram!
Jerry

http://www.diy-efi.org/gmecm is a great place to find information about the wiring and other issues involved with fuel-injection swaps.

Hotrod--

The computer does a 2-second priming run to pressurize the fuel line all the way to the injectors if the ignition is turned on and the starter is not engaged immediately. Another circuit runs the pump conrinuously during cranking, and yet another circuit powers the pump directly once oil pressure builds up.

Isn't this all handled by the ECM? The wiring diagram I have only shows one wire going to the fuel pump/sending unit. :confused: :confused: Do i need to find a better diagram? I have then entire truck, so I can pretty much scavenge any parts I need, which will help greatly. I would use the tank, but it's just too big, and won't physically fit under the truck. Thanks for the help!