Yay I'm finally far enough along to contribute something
Anyway I tried the whole radio shack resistor but it wouldn't read past a certain ohm and when you bend it, the wound wire on it starts popping off.

So in the time I wasted doing that all I had to do was this.
Sometime's you just shouldn't over think things.
Dropped the old tank today, put the plastic one in with this on it.
Gauge seems to work on the dash just like normal.
I'll see better once it's running.

 

what is that, thats not the ls1 float...????

 

no it's the factory one out of my 3rdgen tank.
Why reinvent the wheel.

 

how is it atached doesn't look very sturdy in that pic. and must have been a tight fit going in.

 

Can you explain this a little better for me? This is something I really want to do, but not ever having taken the gas tank out of my third gen, I'm not entirely sure what's going on there.

 

top slides perfectly in to the hole in the stock ls1 unit.
Bottom happens to rest on the lower lip but that really doesn't matter, the hose clamp holds it from sliding down or out.
Yes it's a tight fit. But I'm big and it's small.


I just used the 3rdgen fuel level sender and float so the gauge reads right as opposed to the ls1 sender which throws our gauges way off.

 

Ahh the hose clamp makes all the differance.

 

All right I got ya. Keep it nice and simple, right

 

Does it have full travel? Looks like it might hit the hose clamp toward empty.

 

That's just a matter of moving the hose clamp down slightly or rotating the float out more.

 

Just to let ya know if you didnt already, you can adjust the gauges including the fuel gauge using a tech 2 or maybe some ls1 software, Makes it alot easier since everything goes through the computer first

 

Yeah but how do you get the serial output from the computer to work with a gauge??? The thirdgen gauge reads the resistance from the sender directly, as do aftermarket gauges. There would be no way to decode the info from the PCM so it would work in the gauge. Atleast to my knowledge. Pretty confident in that tho...

The way he is doing it...if it works...is probably the easiest way Ive seen to make the 4th gen tank work with the 3rd gen gauges.

J.

 

I'm with ghettocruiser

 

I'm still figuring all this stuff out, so I'll probably say something stupid (well, ignorant at least).

The PCM uses the fuel level info for purge control only, if I understand it correctly. If that is programmed out, it doesn't affect engine operation, and as long as you aren't trying to do an emissions-compliant installation, just use the existing 3rd gen circuit for the fuel gage - no need to feed it to the PCM.

I don't have an EFI car, so no in-tank fuel pump. I picked up a 2001 SS fuel tank w/pump & evap for less than an external aftermarket EFI fuel pump would cost. The purge was programmed out of the PCM for me by the seller. If I can run evap open (which cam- has suggested will work), and piggyback the 3rd gen sender on the 4th gen pump assembly, and splice the 3rd gen chassis harness to the 4th gen pump connector, that seems a much simpler solution than anything else I've seen to date.

 

The PCM uses the fuel level input for both EVAP functions and for fuel level gauge on the LS1 gauge cluster. By removing the input to the PCM, and disabling the eVAP system, you wont be effecting the functionality of the motor at all. It'll be fine.

What you are suggesting is essentially what the O.P. has done. Using the 3rd gen sender on the 4th gen pump bucket/assembly. Correct?? If so, then it SHOULD work... Ive never seen anyone strap it on the bucket like has been done in this thread, but the theory is sound. As long as it moves freely, and doesnt flop around, it should work. Cant say how accurate it will be...but should be pretty close.

I think there were some write ups on using the sender insides...but it always seemed alittle confusing to me. But then again I never looked into it, beacuse I was going to aftermarket gauges.

Im curious to see how that set up works once installed and hooked up.

J.

 

Thanks for the clarification.

It's nice when we can say to "normal" 3rd gen swappers, "The gage signals don't go through the ECM." Have to take on a different mindset when 4th gen systems get in the mix.