Purging sealed fuel tank to Ls engine

[cerial]

I have a 87 square body V10 with the stock equipment that I am currently running around in.

I pulled the saddle tanks and installed a 72 in cab eec sealed tank that vents to the current 87 charcoal canister and the fumes are pulled into the throttle body when that purges.

I am using the 72 vent style lines which allows for some fun off camber angels without any need for a roll over valve or to think about fuel spilling. The cap is basically a alum plug that turns then you push a tab down to seal it.



The tank gravity feeds to a pre filter, walboro pump, post filter then goes up to the regulator before going back and returns to the tank through the old 72 feed line running without the sock.

Been running this for the last couple months without a issue

I picked up a 02 5.3 truck ls engine with everything. All the accessories and a uncut harness with the computer.
Going to remove the vats and flash that then run it all 2 wire style running the orlieys ps hoses and flywheel with ls7 bearing to a sm465 brownie then 205.

But I need to vent that tank somehow. Now I live in a non emissions state so I could just vent the thing to the atmosphere. But if possible I would like to run a purge. So would it be best to use the 87 canister and have that purge into the intake of the ls blocking the ls purge or use the ls purge and remove the purge valve from the 87 canister?

I would like to activate the purge valve using my break light switch. Just have it open every time I hit my breaks activating a timed relay for 2 or so seconds pulling that pressure out of the lines and into the intake.

But if I could use the factory ecm to open that on decel that wont make a vacuum leak so looking on advise on this.

[kipps]

Am interested in this also. Was asking similar questions in a thread a little lower, but getting no response.

Admittedly, I'm just trying to make state safety inspectors happy with minimal parts to fail in the future, so my goals are a little different than yours.

My current plans are to vent my two side-saddle tanks to the charcoal canister, and run a line from that to the air filter box. Thus skipping both the purge valve and the vent valve. It won't actually do anything, since there's no vacuum applied to the canister, but will look good enough to give me an A for effort.

[BR3W CITY]

I'm pretty confident that no one has rigged an extra electronic purge control here. Half of us live in non emissions counties/states etc, most of the rest either have historic/classic/collector registration (which doesn't require it).

It also seems like a lot of extra room for failure on a non critical component.

If I had to use one, I'd just leave the purge on the LS and let the default purge cycle run off the computer. Just tell your tuner so he doesn't remove it by default with the VATS flash .

[Wgesnerjr]

I used a factory purge solenoid and canister from a 2004 Chevy truck. Took the parts and hard plastic/metal lines as well. All used from pull-a-part.

Put the canister on the outside frame rail under passenger door. The purge solenoid on the frame in the center up high near the bed to avoid and water.

Georgia is emissions exempt after 25 years but I wanted to be as compliant as possible in case they change their minds in the future. Also needed to vent the tank and the LS PCM lives where the 85 charcoal canister was. Left everything hooked up on the engine and wired per 2004 schematics. I let the PCM control the purge as factory designed.

All has been fine for 2800 miles.

[cerial]

After looking this over i am just going to run a vent out the back of the cab on that passenger side and up under the top of my headache rack which puts it just above the back glass.
Put a rollover valve on top with a downward facing 180 tube and call it good. Thing will be leak free on its side and the roll over is there if it is on its roof.

Less parts to replace and thinking 1" copper line will let me fill this up quick also.

[87chevy.com]

I'm confused
. You want to rig up a purge system to operate via stock ecu? Why not simply wire in the stock components, pressure sensor and purge valve?

[Wgesnerjr]

Originally Posted by 87chevy.com

You want to rig up a purge system to operate via stock ecu? Why not simply wire in the stock components, pressure sensor and purge valve?

This was my thinking on my set up. adapt the factory set up to work on my truck.

[LH Lead-Foot]

I may have to read the post again but using a late model carbon canister, factory purge valve is the best option for during fuel fumes you paid for. Also, this will keep higher pressure build up in the tank that helps during refueling and keeps the hydrocarbons stored. The canister has three connections, purge goes to the engine the opens during highway speeds with warm engine. The PCM will take charge of this operation via pulse width modulation, while monitoring the o2 sensors to keep it from running rich or lean if canister is empty.
The vent connection is normally run to a solenoid that is normally open, until the PCM's clock says it's time to run an EVAP test. That's the only time the vent is closes. During refueling, the vent is open to allow hydrocarbon rich air to pass out thru the canister to allow it to capture the hydrocarbons. If equipped with a third connection, that says tank, this goes to the fitting that has an "Roll-Over" protection device or called a vent check valve. When liquid hits it, it simply closes and backs up fumes in the tank and liquid fuel backs up into the filler neck to shut off the gas pump via the aspirator tube inside the nozzle.

If you have an aftermarket fuel pump assembly and tank, depending on the piping, one should be there for vent. Aftermarket pumps usually don't come with a vent valve, so one can be added on the outside.

A tank fitting marked vent, can be used to solve two problems. If the pump has piping marked vent, a hose would normally go into the filler necks little pipe near the top, if that is what you have. The hose that goes from this little pipe back into the tank fitting can have a "Tee" fitting & run a hose up under the bed as high as you can get it fastened into place, make a "U" turn loop in the hose, then run that into the canister vent inlet. Aftermarket roll-over valves or vent valves work like the factory ones, except they are on the outside. If you purchase one, place it in the "Tee" hose as high up before the loop. This keeps liquid from going into the canister.

Factory fuel tanks have a bulge or high spot stamped into the tank. The factory fuel pump assembly has the overfill protection device inside, high up on the bottom side of the fuel pumps flange. It has a simple spring loaded float, that pushes against a silicone rubber seal and closes off any liquid fuel from passing.

Using a brake switch to purge gas rich fumes out of the tank, won't work correctly if you think about it. If you are hitting the brakes, you are decelerating. Normally, the PCM shuts of the injectors and no fuel or fumes go into the combustion chamber. This may cause backfire or just raw fuel fumes not burn't because they would run extremely lean...like a misfire.

Just have your programmer disable the EVAP operation, but leave canister purge on. Using the factory solenoid purge valve will work best as it is metered how much it can flow, the internal resistance of the solenoid is check during OBD-II check upon start up and the fumes dumped into the intake, has to be at the front to be equally distributed to all of the cylinders so there is no rich or lean condition in any cylinder.

Hope this helps.

[cerial]

Well looks like Ibb image hosting has either went down or is offline. All my links like the picture of the one showing how my fuel vent lines are ran are not showing up.

I am running the vent lines on my 72 eec tank just like they did in the 72 chevy truck. it has a loop going up to the passenger seat belt mount then down.

The passenger port runs to the drivers side port. Then I am using the 2nd drivers side port to run back to the passenger side and up to the seatbelt before going down through the floor below the tank and along the inside fuel rail. Makes it impossible for fuel to get out of the cab in a roll.

Here is a thread showing the vent loop I am using. My lines are ran a bit diffrent so that if I am on the passenger side fuel cant leave the cab. But it shows the loop I am using.
http://67-72chevytrucks.com/vboard/s...d.php?t=733068

So yea, 72 in cab tank in a 87 truck with a soon to be swapped 02 5.3 engine turning a sm465.


I would like to use the purge valve on the engine. But, do I need to use a 02 charcoal canister or can I use my 87 canister with a line running to the 02's purge valve? Is there any 02 tank components/sensors that will need to be added inline for the thing to purge right?

[LH Lead-Foot]

#1. The size of the canister is chosen for the size of the tank. The bigger the canister, the better. Late model version are rectangular so perhaps easier to mount with a simple bracket. It does not have to be in the engine compartment like the old round ones found on many 80's cars. you can grab the click-on type fittings at the bone yard for reuse or not.

#2 "PURGE" line is marked at canister and is just run in appropriate fashion to the engines purge valve and has no pressure in a non-purge condition, but vacuum when purging. Normally a 3/8" line is use and a hose clamp at the canister is fine and the factory fitting at the engines purge valve works great. The plastic line can be heated gently to bend and reshape to clean up routing. Just have welding gloves handy. You can get rid of the "GRN" cap for EVAP testing if appropriate.

#3 The canister's "TANK" fitting is 1/2" and low pressure depending on the gas cap. It is supplied with fuel rich fumes from tank, using precautions to keep raw fuel from entering. Your hose looped high in the cab, above the seat belt shoulder mount should be fine.

#4 The "VENT" fitting is 1/2" and if you have some left over seat foam, something breathable, can be cut & trimmed and glued to fit directly on the canister with a fabric spray glue like 3M high temp 90 or WeldWood contact cement.

To reshape the plastic purge hose, I found a 2" X 8" length of wood, can be used, with a couple of nails at the new curves and a little piece of sheet metal pre-bent for sharp curves will allow the hose to reshape without indentations as it cools. Some use boiling water if the make you feel safer. You may have to repeat the water heating in other hose locations as needed. If you choose to use a rubber hose over it, find a piece of copper or steel line that fits inside the plastic line to keep it from collapsing during tightening the hose clamp.
Otherwise, it you are careful, you can cut the plastic hose off completely from the purge valve and just use rubber hose mark for fuel / emissions.

Otherwise, I see no reason for it not to work. Just contact you PCM re-programmer in advance to make sure he or she has no issues with purge only. They will erase the EVAP codes to eliminate that function with no fuel tank vent solenoid, no timer, no fuel tank negative pressure sensor (Measures in inches of water vacuum), etc.

Note on Fuel Caps: There are three type of fuel tank caps, the early type have no pressure outlet if fuel generates pressure. Although they have an inlet for air to enter as fuel is used. These where marked with "Caution Fuel May Spray".
Prior to July 1999, fuel caps had air inlets, but the pressure they held was at 1 PSI.
After July 1999, all vehicles had to use unleaded fuel with cats. The caps pressure release was increase to 2 PSI, to keep the pesky hydrocarbons from escaping. With the use of a carbon canister, fuel tank pressure escapes thru the tank vent line and captured in the thousands of activated carbon inside the canister, allow only pure air to exit thru the vent.

Below, just for curiosity, I attached photos of the inside of a late model carbon canister where a spring loaded vented panel is used to push all of the activated carbon to one end of the canister for maximum exposure and sealing. Also, a magnified particle of activated carbon, exploded under pressure and heat to open thousands to tiny holes to capture any organic gases that include hydrocarbons.

[kipps]

Originally Posted by LH Lead-Foot

#3 The canister's "TANK" fitting is 1/2" and low pressure depending on the gas cap. It is supplied with fuel rich fumes from tank, using precautions to keep raw fuel from entering. Your hose looped high in the cab, above the seat belt shoulder mount should be fine.

Question. What provision did a stock '87 have to keep fuel out of the canister? It was roughly on the same level as the tank, and I did not find any gizmo that might have stopped the fuel. Do I worry about this, or no?

I was going to just run a combination of 3/8" nylon and 1/4" rubber hose between the stock tank vents and the canister. Sufficient?

I'm considering leaving the purge valve on the engine. It sounds like once everything else(pressure sensor and vent valve) is deleted, it will still operate until it fails, but will not cause any run-ability problems when it does fail. Correct?

[LH Lead-Foot]

Originally Posted by kipps

Question. What provision did a stock '87 have to keep fuel out of the canister? It was roughly on the same level as the tank, and I did not find any gizmo that might have stopped the fuel. Do I worry about this, or no?

Kipps, I don't have any paper books for the older trucks, but years of holding tech seminars for Delco, allow me to find info. See "Conventional EVAP type 1"
They simply used a small metered hole that keeps most any fuel from entering a canister.
Type 2, is more advanced and uses and "Over-Fill-Protection-Device" for this function. As stated, if this hose can be run up high in a loop, will work fine, but I suspect there is a tiny hole in the vent fitting at the fuel sender.

I was going to just run a combination of 3/8" nylon and 1/4" rubber hose between the stock tank vents and the canister. Sufficient?

These are vapor only lines, the size is not an issue. The PCM during purge will monitor the 02 sensors, full temp at Highway Speed only. So it will adjust fuel trim.

I'm considering leaving the purge valve on the engine. It sounds like once everything else(pressure sensor and vent valve) is deleted, it will still operate until it fails, but will not cause any run-ability problems when it does fail. Correct?

The pressure sensor you refer to is on the newer pump assembly's only. It is used to measure the vacuum in the tank when purge flood the tank with a vacuum and the vent solenoid is closed, creating a seal. If it looses vacuum, that's an EVAP leak. You won't have any worry since a re-programmed PCM won't be able to close a tank vent solenoid that's not there. So no problem. The air the fuel tank needs to replace fuel as it's used, come thru canister, taking out fuel fumes to be burn't in your engine. It's good, but ask again if needed. Take photos or draw a diagram of your current system and hose routing. But as long a liquid fuel does not go thru the carbon canister from the tank, is the only thing you need to worry about. These tiny particles will come loose and be drawn into the engine thru the purge valve. So loop that hose, up high as shown in the photos below.

[cerial]

The thing is my cap does not vent. No air in no air or fuel out. It is a sealed cap.

This is what I am running for a cap.

https://www.fillernecksupply.com/aer...e-race-cap2f-/

The thing fits inside a grove, then I rotate it, before moving the tab down which presses the rubber against the body sealing the thing. It is a simple design that is proven and I don't need to do anything with special keys or screwing the thing on.

I did not want a solid hose sticking out the side to catch on a tree etc so I placed it in the back with a hard 90. I also built a flatbed with a headache rack which further protects the tank.











So there is no venting AT ALL out of the cap.

My current round canisters VENT port allows air to come from under the hood all the way back into the tank. The same vent port also vents when the thing is sitting not running. The thing purges when the truck is running.


I am thinking of placing the rectangular canister on the back of the cab on the passenger side just below the door locks height wise. Run the vent line up above the seat belt then down through the floor before going into the canister. Have a 3/8" purge line going all the way up to the purge valve and the vent line having a axle breather valve to keep out derbies set slightly above the canister.

So if I have the programmer just retain the purge function and only that function the ecm will open that and pull vacuum moving the vapors into the engine while retaining fuel trim. Great. I was thinking those other sensors would block that but if I can get around them then that will work.



Now the big question. When the truck is off and the temperature goes from 30F to 75F with that sealed cap. Is the "Vent" port which was designed to work with a vented cap still going to allow that thing to vent that pressure and not cause my tank to rupture dumping 16 gallons of gas onto the cab floor.


If there is no question yes it will vent when it reaches 3psi etc. Then good.




If there is a uncertainty and there is ANY chance I might rupture this now custom fuel tank then screw it. I live in a non emissions state I will simply run the vent line through a hole below the back window and up to a inline roll over valve located at the top of my headache rack which vents to atmosphere after going through a filter. I would completely eliminate and block off the purge valve if going this route.

[ls1nova71]

You put a tank in the cab on a square body? Usually people with older trucks take them out, never seen it done the opposite way!

But for what its worth, I have my vent line run to the charcoal canister and a sealed cap a d have never had an issue with it. It is not hooked to the engine at all, just using it as a vent.

[LH Lead-Foot]

I have never cut open the old school round carbon canisters open, but the vent is just that... a Vent.

So during re-fueling, air trapped in the tank has to go somewhere, so I you system, it passed thru the vent hose into the canister and goes thru the tiny activated carbon pellets. They trap fumes...no smell, no gas fumes, no tank pressure.

During purge, then engine opens the valve to the intake creating a vacuum and pulls fume thru the vent, backward thru the connector mark carb, into the engine. This removes the hydrocarbons the canister trapped and held onto.

(Note: Many Toyota's & Honda's have activated carbon panels in the air cleaner to trap hydrocarbons from escaping a non-running engine, that fumes can work backward and escape into the atmosphere.)

The PCM handles the rest. No harm, no foul. If ever thing is working correctly, when you remove the gas cap on the tank from 1/2 to full, if you have no pressure spit-back or tank fart...It's working. You passed the test.

The old round canisters have a serviceable $2 - 3 filter on the bottom, where air is pulled in. Just make sure it's not mounted flat as to not allow air in, but not covered with too much grease, dirt and plugged.

After wise, good to go.
I have not seen the tank mounted in the cab either in a GMT400 as most want the extra room, but if you happy. just run with it.

Just don't let CBS tv crew place a bottle rocket with the tank and start filming. I would think that "Bogus" fake TV is on youtube somewhere.

[cerial]

I put the tank in the cab for a couple reasons;
Less rust-scratching, salt, and just plain dirt sitting around and on the tank.
No need for a skid plate
No need for baffling or pads to put fuel where it needs to be. The thing sloshes side to side a bit if driving the truck stupid. But forward to back there is no effect full throttle or emergency stopping. Generally the sloshing is not noticeable if driving normal. With the radio on you cant hear it.

But the big 3 were
I want to run fender well exhaust and those saddle tanks where where the pipes are going.

I have some side to side sloshing when driving stupid. But for the most part it is not that bad.
Front to rear is where the in cab tank shines. I can mash the gas or slam on the brakes and my fuel needle barley moves. No "bobbing" 1/4 a tank until it settles or risking running dry requiring pads, baffles, or special pickups.

I did not want any tank that would require skid plates or be at risk of being punctured. Also less rust having the thing in the cab which matters in Michigan.

Kind of fun to have nothing below the frame rails to worry about.








Back to the vent I rummaged around and found some bits in a tool box put them together and made this.








Nothing more then a pcv valve Going to use 2 of them. Both mounted vertical.

One will just be the pcv valve with a hose at the top going into the tank. When the thing is running this will allow air to be drawn into the tank. But it will not allow pressure out.

The 2nd one will use the brass valve and hose. I will run a T barb from the tank with the Top of the T going to the to the bottom of that brass fitting. When the tank has enough pressure to unseat that spring(guessing around 3psi) it will push up on the pcv's spring releasing vapor briefly into the "new" upper line do a loop above the tank and go down through the floor below the tank venting to the atmosphere.

Now that 2nd one is just to prevent a buildup of pressure in the tank in excess of say 3psi. But below 3psi the vapor remain in the tank till the purge valve opens. Then it will be pulled through the t up the current vent line above the tank do a 180 going below the tank and go to the purge valve.

[LH Lead-Foot]

Nebraska has rust just like your's. Mount your tank to please you and how you plan on using it, whether off road or just to work. Either way, it your's to brag...I did it.

The T valve and re-purposed PCV valve work for me. Just make sure it works while running and communicate that purge operation with the PCM programmer.

Most of Eastern NE. under water with 860 mile of roads covered at one time, 78 counties, 92 cities, towns, communities and un-incorporated locals flooded. It weather. We had over 50" of snow, deep frost because no warm temps in between snow events, then 2 -3" of rain then all hell broke loose.

Drive safe my friend as my new doctor had nothing good to say today. Almost done and 11 months from 62.

Enjoy your build.

[Scott2]

moved

[KevsClassics]

Back to the vent I rummaged around and found some bits in a tool box put them together and made this.








Nothing more then a pcv valve Going to use 2 of them. Both mounted vertical.

One will just be the pcv valve with a hose at the top going into the tank. When the thing is running this will allow air to be drawn into the tank. But it will not allow pressure out.

The 2nd one will use the brass valve and hose. I will run a T barb from the tank with the Top of the T going to the to the bottom of that brass fitting. When the tank has enough pressure to unseat that spring(guessing around 3psi) it will push up on the pcv's spring releasing vapor briefly into the "new" upper line do a loop above the tank and go down through the floor below the tank venting to the atmosphere.

Now that 2nd one is just to prevent a buildup of pressure in the tank in excess of say 3psi. But below 3psi the vapor remain in the tank till the purge valve opens. Then it will be pulled through the t up the current vent line above the tank do a 180 going below the tank and go to the purge valve.[/QUOTE]How did that pcv system work out?

[LH Lead-Foot]

Originally Posted by KevsClassics

Back to the vent I rummaged around and found some bits in a tool box put them together and made this.








Nothing more then a pcv valve Going to use 2 of them. Both mounted vertical.

One will just be the pcv valve with a hose at the top going into the tank. When the thing is running this will allow air to be drawn into the tank. But it will not allow pressure out.

The 2nd one will use the brass valve and hose. I will run a T barb from the tank with the Top of the T going to the to the bottom of that brass fitting. When the tank has enough pressure to unseat that spring(guessing around 3psi) it will push up on the pcv's spring releasing vapor briefly into the "new" upper line do a loop above the tank and go down through the floor below the tank venting to the atmosphere.

Now that 2nd one is just to prevent a buildup of pressure in the tank in excess of say 3psi. But below 3psi the vapor remain in the tank till the purge valve opens. Then it will be pulled through the t up the current vent line above the tank do a 180 going below the tank and go to the purge valve.

How did that pcv system work out?[/QUOTE]
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[LH Lead-Foot]

Bravo. The work we have to do to make the “Hydrocarbon Police” happy is crazy, but for your purpose I believe you have nailed it.
I am making a correction on my earlier post; it was July 1979 not 99 when unleaded fuel was mandatory with CAT. I forget which decade things happened. Part of being in a hurry and having an older brain.

As for the other post where they ran the vent into the carbon canister without PCM purge or thermal vacuum valve, once it has absorbed its capacity of hydrocarbons depending on size, gas fumes will escape thru purge connector and the smell of gas will occur.
I am using the PCM to control the purge solenoid for pre-programmed operation. Since the engine runs best with fuel in vapor form along with oxygen, I want to burn the liquid and fumes I paid for.
Keep us in the loop on the results. Have a good one.
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