I am currently working on my LSX swap and after all the reading and research I have tried to do, I can't seem to figure out what the purpose of the Fuel Tank Pressure sensor is on the EVAP system.

I would like to set up an EVAP system on the car when I am done the swap and I'm trying to figure out what my options are.

I was wondering if it was possible to retrofit the older style EVAP system from my TBI setup to the new engine using the old ECM. But I'm not 100% how the ECM is programmed so I don't know what input signals it would need to operate and whether the signals from the new sensors would even be the same as the old ones.

The other thing I was thinking about was setting up a newer style LS setup without the fuel tank pressure sensor because I don't have an LS1 tank. Would it work if I trick the ECM into thinking the pressure is constant within the working range of the sensor?

Or should I just take the EVAP system out or are there other ways to do it?

Thanks,

Steve

 

Im a little confused as to what you are trying to accomplish.. But here are a few links from a quick google search "purpose of fuel tank pressuer sensor".....

http://www.obd-codes.com/faq/fuel-ta...ftp-sensor.php

http://ls1tech.com/forums/fueling-in...re-sensor.html

Basically, it verifies that there isnt a leak in the EVAP system..which is a sealed system. It uses its information, plus the tank level (I believe) to determine if the pressure in the tank is correct. If not..it sets a code.

The only way to use the 4th gen LS1 evap system the way its intended, is to swap in the 4th gen tank, run BOTH an evap line and a fuel line, and use the evap solenoid up on the intake. You will also need to run the BCM and use the 4th gen cluster for the fuel sender. The reason being, is that the PCM reads the fuel level for both gauge operation (serial data through bcm) and for the EVAP. If you hook your sender wire to the PCM, then try to tap into it for a gauge, it will not work.

If you dont give the PCM fuel level...the EVAP system will not work.

To get the thirdgen system to work with the LS1...well Im not sure on that. But I know its been done. I dont know if I see the point though. If you are trying to do things by the book emissions wise, then the LS1 would need to have all of ITS emissions equipment intact. If you have a place that is willing to overlook the EVAP system, then just remove it. Thats what most of us do.

Again, I firmly believe the only way to get the LS1 EVAP system to work like its supposed to, is to install EVERYTHING associated with it from the 4th gen. Tricking it with resistors wont work, because the PCM is comparing the pressure to the tank level.

Does that help you any?

J.

 

Yah I have to apologize because when I wrote it I was thinking about a 100 things and trying to put them on to paper.

That being said you pretty much answered my question. The only reason why I wanted to have the evap system on was so that gas doesn't vent to atmosphere and nothing more because I won't have any other emissions stuff.

I was unsure how the PCM was programmed to manage the evap system so I thought I can trick one o the sensor but after reading into it you can't do that with the tank pressure because when it tests the sealing capabilities it is looking for the steadily increasing pressure and all the other issues you were talking about.

Anyways, long story short is i think I am going to do what most people do and get rid of the thing.

Now I just need to figure out how to delete the evap stuff.. Thanks for the reply.

Steve

Also I apologize for massive spelling or grammar mistakes as I'm typing this on my phone in a rush... Lol

 

Lol no worries...

To delete, when using the 3rd gen tank...I think you just remove everything and get a vented cap. I dont know if you can leave the line disconnector..or put a filter on it like we do with the 4th gen tanks. You can check around for how guys deleted it. You'll also want to tune it out of the LS1 PCM to avoid any check engine lights and all.

J.

 

I tried to delete the evap in my 88 bird and installed a vented gas cap. But when they tank is full and I turn right hard enough it leaks fuel through the gas cap and down the quarter panel. I tried installing a sealed cap and it seams to work ok, but when I unscrew the cap to fill up the tank, it is under a tremendous amount of pressure, which can't be good on it. I think I'm going to reinstall the original evap just to be on the safe side. But regardless of what engine you are running in the car, you should be able to retain the original evap.

 

I know this post is like 5 years old but I'll try lol

Why do you need the BCM? The serial data from the gauge cluster runs to the PCM not BCM I believe