Fuel pressure regulator w/ GM TBI

[dragbug]

Since I decided to get everything setup first before installing the GM TBI (electric fuel pump, trigger and spark, fuel return line, etc...), I had to use a fuel pressure regulator for the carb. Now I am at the point I am ready to put the TBI on but it has a built in pressure regulator and a return line. I was originally going to feed the TBI from the regulator and have the TBI return line routed back to the regulator and let the regulator return the fuel to the tank. If I do that, can I set the regulator pressure above what the TBI needs or will that cause issues? I could let the TBI return the fuel directly to the tank but can I cap off the return port on the fuel pressure regulator? Or should I remove the regulator all together and just let the TBI do everything?

[elutionsdesign]

Somewhat confusing as you're talking about two different regulators? Take the carb one off completely. One less thing.

[billr]

Agreed, why bother with the second regulator now? However, what you describe could work. Yes, set the first regulator higher than what the TBI is regulating to (9-13 psi?), I would say at least 20 psi. The TBI return line could "T" into the first regulator's return, but both of those returns must have free-flow back to the tank. I'm thinking that if that combined return isn't sized large enough, the two regulators could start influencing each other and maybe oscillate. Again, why risk it? Get rid of the "carb" regulator.

[dragbug]

Ya it is a bit confusing. Since the GM TBI has a built in regulator, the external isn't really needed. I am using it now because I am still running the carburetor. I will need the external regulator when I finally get the funds for a new intake manifold so I can go full sequential injection. I was hoping to be able to still use the external regulator though. The thing wasn't cheap and its capable of regulating for carb or injection.

[dragbug]

Agreed, why bother with the second regulator now? However, what you describe could work. Yes, set the first regulator higher than what the TBI is regulating to (9-13 psi?), I would say at least 20 psi. The TBI return line could "T" into the first regulator's return, but both of those returns must have free-flow back to the tank. I'm thinking that if that combined return isn't sized large enough, the two regulators could start influencing each other and maybe oscillate. Again, why risk it? Get rid of the "carb" regulator.

So the return line from the TBI can't go back to the external regulator "in" port but must go into the return line to the tank directly? I guess that makes sense and why I originally started the thread. Wanted to verify. Can the return port of the external regulator be capped off and then the return line from the TBI connected to the return line for the tank or maybe cap off the TBI return line instead?

I do understand it would be less confusing and easier to just remove the external regulator completely but I just don't like spending money for something I can't use. Sure, eventually I will be using it but still...

[billr]

Yes, you could cap the return from the first regulator and connect just the TBI return to the return line to the tank. The first regulator wouldn't regulate at all, just pass pump pressure on to the TBI. The first regulator would just be a glorified "union" for now, wouldn't cause any problems (other than a couple of extra fittings to possibly leak).

[dragbug]

Yes, you could cap the return from the first regulator and connect just the TBI return to the return line to the tank. The first regulator wouldn't regulate at all, just pass pump pressure on to the TBI. The first regulator would just be a glorified "union" for now, wouldn't cause any problems (other than a couple of extra fittings to possibly leak).

Awesome, that's what I will do then. Shouldn't be any additional fittings. I just have to cap off the return port. Thanks!