gas tank fume pressure EFI

[Big Slim]

with warmer temps now i have been getting pressure built up in the gas tank. I don't remember it happening last year. i have a vented gas cap. in tank fuel pump for the explorer EFI swap. i seen some post where looks like they are using the newer charcoal canister Dorman 911-198 plumbed from the tank vent to the air cleaner. would i be able to do the same to the intake pipe before the throttle body? do i need to hook up a purge valve? the explorer had this but i think also had a tank pressure sensor.

 

[73azbronco]

do not need a purge valve.

the charcoal canister can work with just a larger fume line to intake well before throttle body, thats that shiney 1 inch or so flexible aluminum paper tube. thats what vents it. A purge solenoid used the a9l computer to open and it vented or sucked into air behind throttle body and really sucked the fumes out of the cannister.

so you will have one fuel hose looking line from tank vent to charcoal, and in that line might be a good idea to put a rollover valve or check valve. Then bigger vent line off charcoal cannister to intake.

 

[Big Slim]

guessing ill need to put one like dorman 911-060. looks like just about all mount on top of the tank.

 

[stretch]

I believe Duffy installed on directly in front of his MAF from the charcoal canister without a purge valve. I asked him about it once, and he said it worked great. Might want to look him up. Duffy Mahone

 

[76Broncofromhell]

How it's done from the factory as one similar way. Factory calibrations on fuel injected applications usually put the purge function when the engine is warmed up, has higher than idle vacuum and low load (e.g. cruising) with a few flags for RPM and speed. Before computers this was done with vacuum switches and the abomination of spaghetti vacuum lines below.

Do decipher this:

78/79 Emission & Vacuum Diagram Picture Reference

www.fullsizebronco.com

FAQ - Vacuum Diagram Acronyms - Ford Truck Enthusiasts Forums

'80-'86 FAQs (Frequently Asked Questions) - FAQ - Vacuum Diagram Acronyms - I have had such a hard time figuring out my vacuum hose routing and what each thing does I thought I would post what I have so far. I have a 1981 F-100 with a 302 2 BBL. I found about 30 different ways this engine has...

www.ford-trucks.com

A/CL: Located in the air cleaner
A/CL DV: Air Cleaner Diverter Valve
A/CL BI MET: Air Cleaner Bi-Metallic Valve
A/CL CWM: Air Cleaner Cold Weather Modulator
ACV: Air Control Valve
AIR: Ford calls this the Thermactor, short for Thermal Reactor. CA vehicles are installed with it as standard. Air Injection Reaction is what it stands for.
AIR BPV: Air Bypass Valve (aka Thermactor Air Bypass TAB)
BV: Bowl Vent (on top of the float tanks)
CARB: Carburetor
CPRV: Canister Purge Valve
DIST: Distributor
EGR: Exhaust Gas Recirculator
EFCA: Electronic Fuel Control Assymbly
FLTR: Filter
FPR: Fuel Pressure Regulator
IVV: Thermactor Idle Vacuum Valve
MAN VAC: Indicating Manifold vacuum-Vacuum source
MAP: Manifold Absolute Pressure
PVS: Ported Vacuum Switch
SOLV: Solenoid Valve
SV-CBV: Carburetor Fuel Bowl Solenoid Vent Valve
VAC: Vacuum
VCKV: Vacuum Check Valve
VRESER: Vacuum Reservoir
VREST: Vacuum Restrictor
VRV: Vacuum Regulator Valve
V CK V: Vacuum Check Valve
VRDV: Vacuum Retard Delay Valve
TVS: Thermal Vacuum Switch
TVV: Thermal Vent Valve
PURGE CV: Vapor Canister Purge Valve



Color Codes to do Vacuum Diagram
Red = Main vacuum
Green = EGR function
Orange = Heat control Valve (exhaust & intake) (AKA heat riser but more complex)
Yellow = Distributor advance
White = EGR vacuum (source)
Black = Mainly used for the Evaporative emissions control
Black = Thermactor ACV or Diverter valve
Blue = Throttle Kicker control
Pink = Thermactor Air Bypass Valve (BPV)

 

[Big Slim]

so i looked at a few of these canisters in the junkyard and looks like they were all hooked up differently. it has 2 small ports and 2 large ones. which ones need to be hooked up?

 

[DirtDonk]

Lots of vehicles have slight variations. But all Broncos were hooked up, basically the same way.
Plus or minus one hose.

You’re looking at a plastic canister, correct?
The small ports, was one small and one slightly larger? Or are they both the same size?
What year is your Bronco again? Does it have a carburetor with a vent fitting on the float bowl?

For starters, the smallest, or one of the two small ones gets hooked to the vent from the gas tank. This is usually oriented to the rear on the plastic canisters and metal as well I believe.

If you do have a bowl vent, it goes directly to the medium, or other small port on the front.
This usually has a one-way valve in it I believe. So if needed for temporary connection, and you don’t have the specific one way valve, just cap the vent and cap the other small port on the canister.

One of the large openings is left open to atmosphere. But it’s protected by mushroom cap.
The other one goes directly to the air cleaner housing. Not to vacuum, not to the manifold, just the air cleaner, outside of the filter.

Are you running a stock filter housing?

 

[Big Slim]

yes the plastic canister. mine is 69 but i have explorer 5.0 EFI swap. so i would have to plum into the intake tube. i have aftermarket tank that has vent connections but i think does not have any rollover or one-way valve. i saw in the jy and early explorer that had vent caps on both large ports and a F150 with both large ports being used.

 

[DirtDonk]

Yes, intake tube. Behind the MAF, but ahead of the TB. Or is it ahead of the MAF, so that it's counted by the computer?
Yeah, I think that's it. The PCV return is behind the MAF, and the EVAP venting is ahead of the MAF. Basically still in the air-filter housing, or filter itself if using an open element filter.

Paul

 

[Big Slim]

ok. but still the large port on the canister?

 

[Broncobowsher]

I would use a purge solenoid and let the computer control it. There is factory engineering for that, use it. Why fight to make ways around it.

I would NOT put it in front of the MAF. Thinking back to my alternative fuel conversion classes, you always put the flammable stuff behind the MAF, and as far downstream from it as possible. The MAF is a hot wire that is cooled by passing air. Hot wires, flammable gasses, why are you even considering this?

Quick recap of how the modern charcoal canisters work. They are double ended. As vapors exit the gas tank they travel through the charcoal and are caught as the air passes to the vent. When the engine calls for purge air enters the vent and travels toward the purge nipple. The fuel tank and purge nipple are on the same side of the canister of charcoal. The fresh air passes through the charcoal and it gives of the hydrocarbon vapors and the engine burns them.

OBDII added some pressure sensors and a vent control valve. When the computer does a self test the vent control valve closes. Engine makes vacuum to purge the charcoal canister and puts the cansiter, lines, fuel tank and gas cap under a light vacuum. Then it watches if it holds the vacuum. But it is more complex than that. Depending on how much fuel is in the tank and the temperature of the fuel it will change the vacuum decay time. That is why a stock OBDII system will through check engine lights for a bad gas gauge or fuel temp sensor. It can't calculate evaporation rates of fuel in the tank for the leak check test. Pre OBDII system didn't care to test, they just assume that everything is there and working. Pop the purge at cruise, suck the canister clean with fresh air so it can be charged again the next time you are parked.

I did a V8 Ranger 20 years ago and went ahead and hooked up the purge. It worked correctly. But if I left it in the garage for several months it would start smelling of fuel. The canister would get saturated with vapors. Go for a drive and the engine would suck the canister clean. Then I could park it again and not have the garage smell.

I know you said you have an Explorer conversion. Who did the programming? Ask them if they kept the purge control active in your program? If so, hook it up. If not, ask them if they could turn it on without all the self tests. Then hook it up.

 

[Big Slim]

so in that case i would need to add a pressure sensor as well? or just a purge? then if using the purge valve i would use the 2 small ports on the canister?

 

[Broncobowsher]

Just purge solenoid. No pressure sensor. No vent control valve. All the extra stuff is just so the computer can self test. The computer will say that it passes emissions test. So the yearly emissions test (for those that need it) is just plug the scan tool in, get the pass from the computer, go on your way. Not the old days where they put the vehicle on a rolling dyno, put test caps on the gas cap and filler neck, sniffer up the tail pipe. The OBDII will throw a check engine light if things are off and let you know to get stuff fixed that are not part of the drivability, durability, fuel economy, but make the car dirty to drive. The stuff is mildly complex as built, way more complex to retrofit, and not needed in a retrofit anyway.

Purge solenoid is basic stuff that was simple and worked back in the 80's. No feedback system needed.

 

[DirtDonk]

Where does it get the circuit to control the solenoid? I guess that would depend on what harness he’s using. Is it the original explorer harness with the purge valve control? A trimmed down setup? Is it aftermarket?
Either way, where does the control wire connect?

 

[Broncobowsher]

Any factory ECM (EEC IV or EECV) will have a control wire. Like any actuator, switched power is supplied to the solenoid and the ECM controls the ground.
Yes, it is often deleted when the harness is thinned out of un-needed wires. But it can be useful, such as for this.
Whoever did the reprogramming of the ECM needs to be contacted to see if they completely disabled the circuit or just turned off the self test. Turning off the self test is good, it will still work, just not throw error messages. Completely disabled to get rid of the error messages would mean using the solenoid will be a lost cause.

 

[EFI Guy]

PCM pin# 56 (green/black) will be your ground "control" side of the solenoid. Get your ignition hot power from pin # 36 (blue/orange) of the C115 connector.
I have never shut off the ability for the simple single purge valve to work. But I can't speak for anyone else.

Broncobowsher is 99% correct in all of his posts above. The Explorer does not monitor fuel temp though, only level and tank pressure, and not all of them even monitor level. The reason that some of them monitor level is just for testing purposes. When level monitoring is present it only allows the pressure test to take place when the fuel level is between 15% and 85%.
Neither of those should prevent purge cycles from happening under normal conditions.

It's funny that this topic comes up now because I'm mostly done shooting an in-depth video for the evap system. I just need to find time to edit it all together.

 

[Big Slim]

I have a trimmed down harness. i did keep some length of wire so to keep seal in tact and if i messed up and have to rewire something. i did leave the wire for pin 67 (purple/white) which the pinout i was using said it was for the evap canister purge valve. pin 56 (green/bk) says vapor management valve. im guessing i kept the wrong one but you can see why by the labeling.

with using the purge valve i would route the tube into the manifold?

My emission test is just checking the gas cap and a idle test. so no OBD check. but i have a light for check engine that i would like to not have on all the time.

i dont think i have the explorer valve anymore. is this the best one to use? maybe another ford has good form factor with same controls.

 

[Broncobowsher]

PCM pin# 56 (green/black) will be your ground "control" side of the solenoid. Get your ignition hot power from pin # 36 (blue/orange) of the C115 connector.
I have never shut off the ability for the simple single purge valve to work. But I can't speak for anyone else.

Broncobowsher is 99% correct in all of his posts above. The Explorer does not monitor fuel temp though, only level and tank pressure, and not all of them even monitor level. The reason that some of them monitor level is just for testing purposes. When level monitoring is present it only allows the pressure test to take place when the fuel level is between 15% and 85%.
Neither of those should prevent purge cycles from happening under normal conditions.

It's funny that this topic comes up now because I'm mostly done shooting an in-depth video for the evap system. I just need to find time to edit it all together.

I sometimes mix in what other manufacturers do as well. Work on other stuff as well.
The basics are the same, implementation and naming of parts sometimes changes.

 

[Jdgephar]

Rockauto has the purge valves if you can't find one. I bought one for my 90 Mustang setup and it works well.

https://www.rockauto.com/en/catalog...on,vapor+canister+purge+valve+/+solenoid,4936

 

[Big Slim]

So this is how I would want to hook it up?

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