Taking the advice of members on the board, i deceided to use the 4th gen plastic tank and remove the EVAP stuff for my swap.
The plastic lines coming out of the tank seemed to be damaged so I ran Goodyear fuel injection hose with the stock GM quick disconnect fittings. Instead of buying compression fitings like others I spliced the plastic hoses off and just added FI hose. Do you guys think it's safe?

 

Why no Evap? My Walbro in my stock tank took a crap on my while driving so now I have to swap out to a 4th gen tank, I've got the tank with the Evap and everything but I've been putting it off because I dont know how to wire up the evap.

 

Per ghettocruiser who is really experienced with ls1 swaps, his thoughts on the EVAP..

I get what he means and I'm pretty sure someone can figure it out but I just want to get my car running asap so i just deceided to bypass it.

 

Looks a lot like mine! I did the same thing. Ditch it all, less weight ftw.

 

Haha...thanks for the props man...

As long as you have a good clamp on those hoses you should be fine. Ide keep your eye on it for alittle to make sure you dont have any drips or anything.

The EVAP still has me stumped alittle. There is just no way to hook up the fuel gauge, and still relay fuel level to the PCM. Im trying to research and see what exactly the PCM uses the fuel level to do.

I still havent confirmed that the absense of the fuel level input completely disables the system, or if it just puts it into a "default" venting mode of some sort.

The only solution Ive come up with, is to add some sort of resistance to input for fuel level in the PCM. Kind of trick it to think the fuel level is being relayed. But like I said, that all depends on how the PCM uses that input in the first place.

Yeah is saves weight, yeah it subtracts a line from the car as well as wires. But, I wanted it to vent properly, and I also put some effort into installing the 4th gen hardlines...along with relocating the evap solenoid and all that other nonsense.

Ill be sure to post up if I come up with something. If I dont come up with something, I suspect Ill be ripping out a bunch of stuff and my tank will look similar to yours. haha.

Justin

 

just picked up my LS1 tank today. going with a dual in-tank pump setup and planning on ditching the evap hardware as well. although I may just leave it installed on the tank and clip the wires as I have nothing to hook them up to.

 

I want a good alternative to the EVAP system too.

I have the corvette manual and i thought it uses a pressure sensor? Then the sylanoid on the tank puts fresh air into the canister, while the one on the engine emits the vaports into the intake to get burned off. I don't have the manual here with me, but this weekend i might be able to look again.

I left the wires back there figureing if it does use a pressure sensor then i would have everything to hook it all up as long as the computer is programmed to work with it. But i'd still just rather vent it out the back if theres a way to not get a gas smell.

 

Leave the LS1 charcoal canister on the tank and vent it through there. No smell

 

From looking at a 2002 manual, the problems you will have with the EVAP will be when the fuel pressure sensor (or related parts) is non-functional, not when the fuel sender is non-functional. Playing with the the fuel sender probably sets a DTC due to the fact that the sender isn't sending the "correct" signal values (40-250 ohms stock vs. 0-90 ohms modified) to the PCM.

 

So should you run it through canister then into a filter, like the one in TPIERR's picture? Or just out put a rubber hose on the end of the canister?

If there is no smell then why does the factory route the vapors to the motor from the canister?

 

The PCM uses the fuel level for two main things. One is to tell the gauge where to sit, and the other is to determine how much fuel there is in the tank to compare that to tank pressures and what not. The EVAP does use the fuel level to perform its operations. Otherwise, there would be no reason to run the sender into the PCM...it would just go right to the cluster like it used to. The only senders that go through the PCM are the ones that are needed for things other than the gauges. Like the temp sender, and the fuel sender. Oil presure doesnt go through the PCM because the PCM only uses the low oil sensor when it comes to engine oil.


The DTC that sets isnt a "CE light" DTC. No light is triggered. So Im actually starting to think the EVAP might still function. I was told by a couple trustworthy people that it does infact disable the EVAP system. But Ive yet to confirm.

 

The smart side of the system ( the PCM controlled evap solenoid ) routes fuel vapors to the engine to be burned. It reads tank pressure and when it reaches enough it purges the evap into the engine so the idea is there is zero atmospheric evaporation of the fuel which makes for cleaner emissions etc.

As for the stock LS1 charcoal cannister it is there for any static pressure evaporation just like any car from 1975 or so on has a charcoal can it still does this same effect so when the car is sitting off and cannot burn the fuel it at least filters it through the charcoal to reduce its harm. All you need to do if you dont want to run evap is not hook up the wiring and leave the LS1 charcoal can in place and by default it will not pressurize the tank so it still works just as a stock third gen charcoal can by filtering the fuel vapors through it before releasing them to atmosphere.

Hence no smell.

If you search around there are pics of the stock LS1 piping and you can see a rather large one coming out of the tank and into the charcoal can. I also think this is where it vents during fuel filling.

 

Ok.. I'm bringing this back from the dead. Doing the fuel tank swap and need to figure out the evap system. I just dont want the fumes. Any luck guys?

 

The evap not functioning will not cause any fumes you can smell at all. The evap system is electronically controlled and only opens the solenoid if all systems are a go and the PCM calls for release. Otherwise it does not vent out anything at all and the tank relies on the atmospheric venting that still routes through the charcoal can mounted on the LS1 tank ( provided you leave it in place and hooked up ) So do not hook up the evap wiring and your still left with an atmospheric evap system that is light years better than your stock third gen set up.

 

Ok thanks! that was my biggest complaint on my old setup. The purge never worked and built up way to much pressure and smelled like gas all the time. It'll be nice having something a lil more self contained.

 

The Evap system is only triggered between a minimum and maximum fuel level(among other things like temp), so sender input is needed for the PCM to trigger Evap function.

Also, if you hard wire a resistor into the circuit to fool the PCM, it is pretty smart, noting fuel level change over mileage. If the change doesn't match after an extraordinary amount of time(I believe 150 miles with no change off the top of my head) it will disable to Evap and set a code.

So the Evap code means the system is indeed disabled.

Luckily the vent solenoid defaults open and the purge defaults closed, so no problem should arise from a non wired in Evap system, which as posted, is still better then the 80's set ups.



...Jim
W.E.D.

 

If you disable evap its going to trigger the check engine light ... Ok like my 3.8 camaro if you leave the gas cap off or its loose enough the check engine light will flash. So it would be the same as leaving that filter thing on the evap line the ecm would sense a leak. But maybe LS1 tanks and programming is different ..... But I was told prior to startup a 3.8 pressurizes the fuel tank not sure if this is true or not or how it could since I've never seen any type of pump on the car to pressurize the fuel tank. But the car has to be doing something to know the fuel cap is off or an evap leak.

 

I'm pretty sure all or most OBD2 cars have pumps for the evap. I couldn't tell you where its at. I think its the little box by the charcoal canister on top of the tank. Could be wrong. This setup is all new to me.

 

The Evap system uses engine vacuum to test the fuel systems integrity. At random times, the system is tested. The PCM seals off the Evap "Vent" solenoid which seals the system. It then opens the purge solenoid, which is duty cycled at a predetermined rate based on several factors as determined by it's programming. At a certain point the PCM will close the purge solenoid and keep the vent solenoid closed as well, testing the system under a vacuum(Not pressure as is sometimes thought), for a leakdown test, which is also variable, based on fuel level, baro, etc.

Usually when the engine is first started, the system leaves the vent open and opens the purge as well, to bring the fuel vapors into the engine during cold starts and to bring down the vapor content in the canistor.

The way the PCM knows the cap is loose, or there is a leak (P0442 small leak or P0445 large leak) is by a rapid rise in pressure out or range from expected.


Basically all this means is without a completed in tact system, that an aftermarket programmer is needed for custom application to avoid an SES light giving your knuckles sunburn, or the dreaded black tape over the light, LOL.


Hope this clears some of this up,
...Jim
W.E.D.

 

how much of a weight diff is there.....I might look into this if is is enough

 

Due to the plastic lines, plastic evap tank and solenoids, the wieght difference is negligable. I would not be concerned unless your building a really serious race car(no evap either way with that though). For a 350-400 hp car, I wouldn't sweat the 5-8 lbs everything weighs that you could remove. At the least you could leave the canister so it will handle the fumes and be a "little" enviornmentally friendly.

Consider this; Going from a 15 inch wheel to an 18 inch will add the weight of 12 evap systems, but everyone has big wheels! Same can be said for stereo equipment, etc....

jmo


...Jim
W.E.D.

 

that is a bad comparison, my 17's weight alot less they my old 16's did

 

I was cleanin up the tank the other day and carrying it around. I must say it still has a bit of weight behind it. Really dont think it'll make a huge diff between my old and this. I figure it'll save some room in the engine bay by removing old canister also I dont have to have a fuel pressure regulater mounted for every one to see. So it'll look that much more stock. Plus it a more modern setup. Picked it up with module for $150.00.

 

Once you carry the old metal tank around you will see a difference. Most of the differences are in the entire systems, not one component though.

Just like the wheel issue, which it seems is still being debated. Although every time i've weighed a wheel, the bigger they are, the more they weigh.
In fact in my experience a 15 inch steel wheel and tire was a good bit lighter then a 17 inch cast alloy and tire. Of course the CNC machined racing wheels are usually substantially lighter then either. Also substantially more expensive as well though, .

I actually went from 17's to 20's on my truck and lost fuel mileage and ET. My truck was faster with the smaller wheels!(same overall tire diameter)

If speed matters, that is something to consider.


...Jim
W.E.D.

 

Wow... More EVAP discussion going on in here than anywhere else I think!! Thats a good thing!

I found out the long way how the EVAP wont work without the fuel level input. And Im trying to decide what I want to do with the EVAP system now. Because I have to rebuild the whole car. Ide like to leave the EVAP hard line out of the picture...one less line to run up front.

If the new concensus is that the system will be ok without that line at all, or any of the evap wiring hooked up, then Ill just leave it. Have the codes programmed out of my PCM.

I guess Ill need to leave that line vented then... And without looking back, I think some people put a filter on the main line?? Ide like to have it do as much as possible I guess... And if I cant make it function like factory, then Ide still like it to do whatever it can.

J.

 

Question about evap (As i was talking to you on AIM about justin).

Is the EVAP a fail proof system? Is it engineered so that, if the wiring is not hooked up, the pressure in the tank mechanically opens a valve & Vents pressure?

If this is the case. I could just run the charcoal canister on the tank with one end open, and no evap hardline. So when the tank vents itself, the fumes run through the charcoal canister cleaning the smell out and then just releasing it. Then i have no evap to worryabout, a working fuel guage, and no gas fume smell.

All info appreciated!

 

On a modern OBDII system, the venting, or pressure relief is handled by the evap/canister system. That is it's purpose, to dispell fuel vapor emissions and reduce them to a safe level, during vehicle non use... Some caps may have an over pressure relief function, or a valve to allow air entry through, but I have not seen any on the latest 4th gen Camaro/Firebirds.

If the vent/purge portion of the system is disabled, the canister will eventually become saturated and fuel vapor odor will be a problem, at that time a new canister will solve the issue....temporarily. How long this will take depends on your gas cap design, where the car is parked (due to sun exposure), or if you tend to run the car with the tank lower or more full, etc.

At the very least I would run the factory purge lines from your car, to the new canister in back, where the purge line was connected on the 4th gen and eliminate the 3rd gen canister. This will give you a mechanical purge and a more environment friendly car.


...Jim
W.E.D.

 

Hmm. Im a little lost on this one. Ill try reading it again in the morning and see if i can get my head around it when im awake.

 

I seem to remember someone saying they found a vented gas cap that works with the LS1 filler neck. So... If I were to ignore the wiring for the EVAP completely, leave the hardline off the car, leave the everything else alone on the tank, and possibly run a vented cap, that should be sufficient for tank ventilation and probably not stink too bad...

Does that sound reasonable? I mean...my 67 bonneville didnt have EVAP and it didnt smell like gas all the time. And that was a 26.5 gallon tank haha...

Having only the rear brake line, and main fuel line going up front would be a nice change. Especially since Im planning on "hiding" those lines in the chassis to keep them away from the headers.

J.

 

This is not that complicated.

Dont hook up the evap wiring or the line that runs to the TB. Leave as is everything else that has to do with the stock charcoal can in place and thats it. Presto your done.

No vented cap nec it will vent through the charcoal can. Heck even the filler tube vent also vents through the charcoal can its a MUCH better system over stock third gen stuff.

 

Awesome! Just what i needed to hear! THanks cam!

 

I know it SHOULDNT be complicated... And what you are saying makes sense. But then I read the idea that the charcoal canister can become saturated and the fuel smell can be a problem. Im no expert when it comes to how that system works...so now I have to opinions on what should be done.

Im leaning towards just doing what you said to do cam... I just dont watn to make more work for myself later is all. If I can just leave it all unhooked and unplugged, then cool. Thats what Ill do. Im a big fan of things working the way they should...so not being able to have the evap function is burning at my insides. hahaha. So whatever the best solution is, will be what Im going with.

J.

 

I have no idea about charcoal can saturation problems and this is probably because this is the first I have heard about it. That being said I have serious doubts about the fact that you will begin to smell fumes after ( if it even ever becomes ) saturated. Its certainly not a worry to me I've never once heard of anyone on any car having to change out a charcoal canister for saturation problems.

I know I have never ever changed the stock one on my 89 Iroc and it doesn't smell and its a POS evap system in comparison.

 

Good point... Another thing I need to remember is... My car burns my eyes now as it is. haha. So even if it were to smell alittle more like fuel I probably wouldnt notice.

Ok... Sold. Ill leave it all disconnected and call it good. That just saved me work, and also cut down on my engine bay clutter. haha. I went through a good bit of work relocating the EVAP solenoid too... to clean things up a bit. haha. Oh well.

J.

 

Really? Do you have exhaust leaks? Mine doesn't burn my eyes at all and I was quite amazed at how odorless it is in general. I have the oil cap vent trick too and still no smell unless I open the hood and stuff my face down by it

 

The exhaust gets pretty nasty. If its running, and you go stand near the back of the car, it will get to ya. I was told it was fairly normal for my set up with no cats. But the tuner I was working with was going to try to make sure there was nothing in the tune dumping too much fuel. Unfortunetly I never got that far...

This time around it might be getting a new cam though. So Ill need to get a tune anyway and Ill make sure its where it needs to be. Its jsut alittle obnoxious right now. Sitting in traffic sometimes I can smell it too but only if the wind is blowing right.

I have no smells under the hood though. Everything up there is nice and dry and doesnt give off much odor at all. I have a homemade oil catch can, which i dont think is doing much, but other than that, its all normal.

J.

 

does anyone know which autometer gauge ohm level reading is meant for a ls1 sending unit ...i did the swap and doing my dash iwth all autometers need to know this b4 i try to order teh gauge....thanx guys

 

If I read everything right...

Put in a 4th gen tank, and the stock fuel gauge can't work anymore?

Is everybody with a 4th gen tank switching to aftermarket gauges? Or running no fuel gauge at all?

 

https://www.thirdgen.org/forums/ltx-...want-swap.html

You might wanna check out the second link under the section thats says;

"What about fuel"

Oh yeah. Read the what about fuel section too!

 

I've stood behind and around a lot of cars, even race cars, that did not make your eyes burn. That is of course unless they were too rich. That is for street and race cars both. Cats are not the cause, but rather calibration which was for a setup with cats that have been removed and other mods without proper tuning, including removing the cats.

I would definately head to a good tuner, or get a Diablo, etc. to get it right, asap. A charcoal canister will only help fuel vapors from the tank, nothing to do with the exhaust, although it will run even richer when cold if the system is connected properly and your ECM is already out of cal and doesn't recognize the added fuel and remove it at the injectors.

Hope that makes sense?


...Jim
W.E.D.

 

Update, car is running but I can't pump gas due to the fuel tank not venting!! Anyone have this problem? Took me five minutes to pump 2 gallons



I plugged the line underneath the fuel pump assembly at first and then "T-ed" it to the green vent valve but no luck. It's a pain in the but to take down the tank so I was hoping to get some input before taking it down again this weekend.

Maybe the green vent valve is plugged and not releasing pressure?

 

tpi did u ever figure out why it wasnt venting so u can pump gas?

 

Will the fuel tank from a 97 Camaro swap into our cars? Is it a direct fit replacement?

I am thinking it will fit nicely, but I am not 100% sure.

Here is what I want to do....

Swap the entire tank/fuel pump assembly from the 97 into my car, and just wire it the way it is wired now in the 97 Camaro, since I will have all the wiring and plugs from the 97.

As long as the fuel tank fits, it seems that would work perfectly--the only thing is the fuel gauge in my 86--not sure how to wire that up.