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Old 05-10-2019, 10:36 AM   #1
Scott2
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Evap System Setup??

I'm trying to sort out the Evap system setup on my LS swap and have a few questions. Hopefully, someone here has a much better understanding of this than me?

I have 5.3/4L60e out of a 2004 Tahoe, I am in Colorado and plan to use all the Tahoe emissions to stay legal. Most of the emissions I am OK with, just trying to get the Evap system straight in my head and there are a few things I'm confused about. I did not get a canister with the motor and trans so I pulled one from an '03 Silverado.

First question is the fuel pressure sensor. I can either buy one as a replacement or grab one at the U-Pull. What I'm not sure about is how to set it up with an older, non-Chevy/no evap gas tank. I will buy an in tank pump to handle the EFI, but where do I mount the sensor? I think I saw a comment on t-ing it into the vent hose but what do you use for the mount or bung hole or whatever they insert into? I suppose If I got the right sized T I could just insert the sensor into a short length of hose the right size stuck onto the T? Attachment is a hose diagram from another thread but looks right for me.

Second is the fuel level sensor. I believe I saw a suggestion to use the Tahoe or similar fuel sending unit? How would that physically adapt?

My biggest area of confusion is the wiring. I pulled my harness off and sent it out for modification to standalone, but to keep ALL emissions connections. I know I unplugged a connector from the intake mounted purge solenoid, but do not remember another connector or connectors that would hook up to the canister, the pressure sensor and the fuel level sensor? My wiring diagram shows a C152 that looks like it should do this but there seem to be three connectors needed but C152 sounds like one? Any help with this?

Thanks!

PS- this is not going in my '51, I dropped a 6.0 in there but blocked off the purge solenoid because emissions don't apply.
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Old 05-11-2019, 12:11 PM   #2
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Re: Evap System Setup??

Hasn't anyone connected up the evap system? I don't think this is hard, I just haven't done it or seen the wiring connections.
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Old 05-15-2019, 09:31 AM   #3
77c10bowtie
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Re: Evap System Setup??

you would be emissions exempt in 51... they do not have the authority to say weather your engine is a 51 or an 04

as for the gas tank, you would need the correct gas tank as its a vented but pressurized system, with the evap system hooked up to a regular tank you would have evap codes like crazy, the most basic evap code would be on all the time showing a leak in the system, a small leak is considered the size of a .040 pinhole and a gross leak would be like a missing gas cap or disconnected line. without a pressurized system the codes will always be present

in my opinion it is not worth the hassle
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Old 05-15-2019, 10:22 AM   #4
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Re: Evap System Setup??

Quote:
Originally Posted by 77c10bowtie View Post
you would be emissions exempt in 51... they do not have the authority to say weather your engine is a 51 or an 04

as for the gas tank, you would need the correct gas tank as its a vented but pressurized system, with the evap system hooked up to a regular tank you would have evap codes like crazy, the most basic evap code would be on all the time showing a leak in the system, a small leak is considered the size of a .040 pinhole and a gross leak would be like a missing gas cap or disconnected line. without a pressurized system the codes will always be present

in my opinion it is not worth the hassle
This swap is in a Ď79. I already did my Ď51 and just deleted the evap. I am going junkyard hunting for a ~2004 tank.
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Old 05-15-2019, 10:26 AM   #5
77c10bowtie
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Re: Evap System Setup??

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This swap is in a Ď79. I already did my Ď51 and just deleted the evap. I am going junkyard hunting for a ~2004 tank.
Either way, I would just say the motor is a 79 and they can't tell you it isn't, they aren't certified or qualified to make that call.

Here in AZ we have the same emissions tests and I know several people who go that route.
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Old 05-15-2019, 05:01 PM   #6
Scott2
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Re: Evap System Setup??

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Originally Posted by 77c10bowtie View Post
Either way, I would just say the motor is a 79 and they can't tell you it isn't, they aren't certified or qualified to make that call.

Here in AZ we have the same emissions tests and I know several people who go that route.
I could, but itís really not a big deal to hook up emissions. I took the truck thru emissions here before I yanked the motor and they did a pretty thorough inspection. They looked under it with a mirror to see the cat and be sure itís all connected right, and then looked over the fuel cap, air injection and Evap systems to confirm it was all there and connected, then an idle and low speed test. I had to go get a new cat and go back and then it passed.

Stock is Kinda counter to the hot rod approach but this will be my sonís truck and when heís out of high school in two years he could end up anywhere for college and then someplace different for work. No point in setting him up for trouble later. If we just keep the Tahoe motor stock, install cats and O2 sensors, and hook up Evap itíll still be a sweet truck and he can get it registered anywhere.

For my Ď51 itís a different story! No emissions.
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Old 05-15-2019, 10:17 PM   #7
77c10bowtie
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Re: Evap System Setup??

Do what you want, Its just alot of work, $$$ and headaches that could easily be avioded.
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