I'm swapping a 99 LS1 into my 97 V6 firebird and am doing fueling right now.

I picked up a 99 LS1 tank and pump.

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First question, How do I go about removing the evap. I am NOT going to route wires to the PCM just to keep the evap functional. I remember reading someone on this forum has done this. Perhaps he can be of assistance.

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Second, will a walbro 255 low psi pump be ok for a light weight cam/converter/long tube LS1 never to see power adder?

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Third, The 99+ has 1 fuel feed line and 1 vac return line correct? Is there ANY fuel return line? What is the purpose of the return vac line?

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Fourth, I'm looking at the top of the sending unit. Hoses point away from me. Big hose on left, vac for evap in middle, medium hose on right. Can anyone please explain to me what each of these does.

Left, Big hose: Fuel feed?
Middle: Goes to evap and dump
Right, Medium: Vac from engine?

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Fifth, How does the FPR work? I see it under the top but I can't figure it out.

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Sixth, Still looking at the top of the sending unit, there is this black delco electronics device, what is this for?

I'm thinking this test the pressure in the tank to make sure the evap system is working.

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I am VERY greatful for the answers to these questions. It will make my swap go a lot smoother and less painful.

Thank you.

<small>[ March 26, 2003, 08:11 PM: Message edited by: Magnus ]</small>

 

<strong> First question, How do I go about removing the evap. I am NOT going to route wires to the PCM just to keep the evap functional. I remember reading someone on this forum has done this. Perhaps he can be of assistance.</strong>[/QUOTE]

LS1Edit to turn the EVAP and AIR system off in the computer. I used the EVAP lines on my 2001 Z28 for my fuel return line when I converted to the 97/98 style vette vuel rail (regulator on engine).


<strong>Second, will a walbro 255 low psi pump be ok for a light weight cam/converter/long tube LS1 never to see power adder?</strong>[/QUOTE]

It would be better to go with the high pressure version. The LS1 runs close to 60 psi stock.


[QB}Third, The 99+ has 1 fuel feed line and 1 vac return line correct? Is there ANY fuel return line? What is the purpose of the return vac line?.[/QB][/QUOTE]

no....all the LS1 F-bodies had a return line near the tank and the pressure regulator in the tank. The fuel did not go to the engine and then cycle back to the fuel tank. I converted to the 97/98 vette fuel rail that mounts the regulator on the engine and ran the return through the EVAP line (didn't have to run a new hard line).


<strong>Fourth, I'm looking at the top of the sending unit. Hoses point away from me. Big hose on left, vac for evap in middle, medium hose on right. Can anyone please explain to me what each of these does.

Left, Big hose: Fuel feed?
Middle: Goes to evap and dump
Right, Medium: Vac from engine?.</strong>[/QUOTE]

Left is the fuel feed
Middle is the evap
right is the fuel return line (feeds into the pressure regulator)


<strong>Fifth, How does the FPR work? I see it under the top but I can't figure it out..</strong>[/QUOTE]

It restricts fuel comming back into the tank. If it opens up all the way (low pressure) lots of fuel bypasses the engine. If it chockes way down (high pressure) then all the fuel goes to the engine.


<strong>Sixth, Still looking at the top of the sending unit, there is this black delco electronics device, what is this for?

I'm thinking this test the pressure in the tank to make sure the evap system is working..</strong>[/QUOTE]

hmmmm....don't know there....as I said, I just dissabled all the emissions equipment and only worried about the important things <img border="0" alt="[burn out]" title="" src="graemlins/gr_burnout.gif" />


<strong>I am VERY greatful for the answers to these questions. It will make my swap go a lot smoother and less painful.

Thank you. </strong>[/QUOTE]

hope I was of some help <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Chris

 

I forgot to mention, since the LT1s and all the V6 cars had the fuel pressure regulator mounted on the engine (have a return line running from the engine). Dig around and find one of the 97/98 vette fuel rails (fuel pressure regulator on fuel rail) and get an adjustable fuel pressure. It makes it much easier to adjust and since you already have the lines, it would just be a mater of connecting (plug and play). Then take the fuel pressure regulator out of the fuel tank and you will be all set.

Chris

 

Chris, thank you a TON for that reply! <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Let me clarify some questions

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I know I can use LS1 edit to remove it, but I'm more concerned about the physical modification of the tank. Looking at the tank now there appears to be 2 fittings on the tank for the evap system, one white one, and one black one with a big hose coming from it.

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will 255 be enough for a cam/long tube/converter car?

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Where does the return branch off of the feed?

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I know how the FPR works.. thanks for that very good explination though and sorry for not making my question more clear. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> But really I'm curious how the FPR gets its vacuum from? On the unit I'm looking at now it appears the vac stem for the FPR is just open inside of the tank.

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Thanks again! <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Magnus:
<strong>will 255 be enough for a cam/long tube/converter car?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">If you're doing it, do it once and use the Walbro GSS 340, and never worry.

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Magnus:
<strong>Where does the return branch off of the feed?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The fuel goes out of the tank to a y-block mounted above the axle next to the fuel filter. One line to the engine, and the other to the regulator.

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Magnus:
<strong>But really I'm curious how the FPR gets its vacuum from? On the unit I'm looking at now it appears the vac stem for the FPR is just open inside of the tank.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The FPR is mechanical. It's just a spring that releases anything above 62PSI back into the tank through what looks like a vacuum stem. The fuel pressure is kept constant and the PCM does all the enrichment calcs. This is only possible now due to the near real-time calcs that the faster generation of processor can perform.

SC-

<small>[ March 27, 2003, 09:47 AM: Message edited by: SS00Blue ]</small>

 

SC, thanks a TON, that helps a lot. Things are becoming more clear.

In my V6, as I gave it throttle and introduced less vacuum, my PSI would EASILY go up.. from 42 at idle to 50 at WOT. I assume this is why LS1's fuel pressure doesn't rise and sometimes even falls at WOT?

Also, to add another quesiton, without EVAP, there is NO reason for the return vac line back to the tank correct?

Thank you!!!

 

My setup is a bit "different," as I basically built a complete fuel system from scratch. When my car caught on fire back in January 2002, it pretty much took out all the fuel lines, evap, fuel pump wiring, etc...

I started by sumping the tank, and installing a #10AN fuel cell fitting in the sump to supply fuel to the external Aeromotive A1000 pump. The entire supply line to the rails is a 1/2" aluminum hard line. The rails are modified stock rails, and are fed from the front of each side. The stock supply location on the rails is now used as a return, and is plumbed through a #6AN line to the regulator, then through a 3/8" aluminum hard line back to the top of the tank.

The EVAP system is nowhere to be found. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> I welded up all of the tubes on top of the tank except two (which I can't remember specifically which ones, but it doesn't matter). One is a vent line, the other is used as the return.

Like I said, I doubt my configuration is typical, since I pretty much started completely from scratch (out of neccessity).

 

Thanks for the e-mail and the reply George! <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

I'll drill a 1/8" hole in the filler cap and keep the white vent thing still as is. I'll plug up the black transfer vent tube thing on the top of the tank as well as the little connection that goes to the top of the sending unit.

I hope that provides enough ventilation.