Electric fans / returnless fuel system questions

[turbo_bu]

Can you turn on the electric fans in the LS1-B PCM simply by using fan tables {G1203}? (and of course making sure that the wiring harness has the wires running to the necessary relay(s)). I am putting a 5.3 from a truck into a '56 Chevy and wanted to use electric fans. The only other option that I thought of was using a Corvette or Camaro file that had electric fans from the factory, but then that would require going to a returnless fuel system.

If using electric fans in truck software is not an option, and I have to convert to a returnless fuel system, other than changing the fuel rails (getting rid of the regulator), is changing the values in the Injector Flow Rate {B4001} table all that is required? Not sure if the actual driver for the fuel pump is different between the two systems. I thought that the returnless system ran the fuel pump at a lower speed (pressure) and didn't know how this was controlled or commanded.

[Taz]

A truck PCM can generally be programmed to control 2 electric fans (high & low). The problem is often getting the fans to both turn on when the AC is activated - truck PCMs often won't do this.

Easiest fix to swap the "System" segment from a Camaro with the same OS - should then control the fans in all modes. If running PCM controlled AC you will need the low pressure cycling switch (on the accumulator) and the automatic recirculating switch (in the AC line - lower near radiator) wired into the swap harness.

Regards,
Taz

[Taz]

You can run return or returnless fuel systems with truck / Camaro / Corvette tunes - just set the values in B4001 to those compatible with the particular fuel system.


Regards,
Taz

[Taz]

Hello Darren,

In the above answers I had assumed you wanted to use a ’99-’02 wiring harness (Blue & Red connectors), requiring the use of a 512Kb LS1-B PCM.

If you have, or want to use, a ’03-’07 wiring harness (Blue & Green connectors), this will require the use of a 1Mb LS1-B PCM. In the Holdencrazy repository, in the “Modified Tunes” section, there is a 2006 Express van tune – Drive by Cable, and will operate the fans with A/C.

Just another option …

Regards,
Taz

[turbo_bu]

Taz,

Yes, the engine that I have found is an 99-02 (512Kb) one. I guess I did not realize that you could copy over just the "system" segment. I had read about doing the segment swaps for the transmission or engine. But guessed those were the only two you could do.

Slightly off topic, but does a returnless fuel pump just have the relief built in vs. a return style fuel pump where the there is no relief since it has a return line?

[joecar]

The returnless systems have the FPR in the tank...

there's a line branching off immediately after the external filter, this line feeds the FPR, the FPR reliefs directly into the tank...

(i.e. it is actually a return type system, but the return is located completely at the rear);

the FPR on these systems has no manifold reference.

[Taz]

You described the engine is a "99-02". You can use a '99-'02 wiring harness and PCM, or a '03-'07 wiring harness and PCM. Most, if not all, of the connectors (to the engine) should be the same. If using a '03-'07 harness in a DBC application either add the TPS and IAC connectors to the harness, or begin with a DBC harness from an Express / Savana.

Keeps your options open ... and lets you find the most cost effective parts.

Regards,
Taz