I'm putting a 2000 Silverado LM7 5.3L & PCM into a Jeep. I'm swapping a TBSS intake on it with the returnless fuel rail and plan to use a corvette filter/regulator near the tank. Is the fuel pump modulated by the PCM? If so, will it need to be tuned to use the new returnless system?

 

The fuel pressure is regulated by the Corvette filter/regulator, to a set 58psi, the PCM only turns the pump on so it will run that way, but there are differences in return and return less tunes so ideally you would want to get it tuned for returnless.

 

So, basically a key on power source simply energizes the pump through the PCM. Once on it stays on for both applications, correct?

In general terms, how do the tunes differ between return & returnless fuel systems?

 

You could probably get away without a tune. The difference in fuel pressure between the 2 will be at low throttle, which is where the O2 sensors do most of the work.
You'll be getting a little extra fuel at low throttle and idle because of the extra fuel pressure.

You can use the gen 3 truck rails with the TBSS intake. You'll have to clip and drill the mounting tabs on the old rails to mount them to the TBSS intake. Then you'll use the TBSS crossover on the old rails.

 

Thanks.

I'll tune it when I put a cam in, but I want to use the TBSS intake right away. I plan to keep it returnless so as to not add additional plumbing on the Jeep (returnless from the factory). I guess I'll have to run it and see how it works.

 

It will work without a tune - IF the injectors match what is in the tune. If everything but the fuel system stays the same the difference will be refinements - but it will run and drive fine.
If you're swapping intakes and injectors at the same time, you need a tune to adjust for the intake itself (flows differently) the injectors that are likely different plus whatever other air modifications you have done from the stock vehicle (MAF location, exhaust, etc.). These seemingly little things add up quickly and sometimes make the difference between a project that runs and a project that runs very well - i.e. like stock.

Will it run? Yes.
Will it be right? Maybe.

 

True.
I plan to keep the stock injectors until the cam swap happens.