Vented Tank for Mach

[wwhite72]

So you are saying that the correct caps are air tight? And that all 1971-73 gas caps sold by FMC for mustangs are airtight and do not allow air to pass thru?

 

[OMS]

Not all caps by FMC

Starting with the 1970 with CA emmissions they were sealed.

All 71 -3's were sealed, all venting was thru the canister.

If you had a vented cap - there would be no reason to install a vapor line and canister system.

 

[wwhite72]

Ok, i will call scott drake and look to exchange the one i have. They said it is the right cap but must be for a 1970.


Sorry, scott drake D1ZZ-9030A is correct cap for 71-73. It is a vented cap......D1ZZ-9030B is same cap with the wire. It is for 71-73. It is a vented cap. Scott Drake DOES sell a non-vented cap....for 1970 california cars.


OMS, i believe the cap has a diaphram relief valve that allows air into the tank to compensate for low pressure created when vapors and fuel are sucked out of the tank, as i described above. The diaphram vent does not allow air/fumes to exit the tank thru the cap. Simple.

 

[marks73]

The vent fitting on 71-73's is on the top of the tank. About the same size as the sending unit fitting on the side.

 

[OMS]

Ok, i will call scott drake and look to exchange the one i have. They said it is the right cap but must be for a 1970.


Sorry, scott drake D1ZZ-9030A is correct cap for 71-73. It is a vented cap......D1ZZ-9030B is same cap with the wire. It is for 71-73. It is a vented cap. Scott Drake DOES sell a non-vented cap....for 1970 california cars.


OMS, i believe the cap has a diaphram relief valve that allows air into the tank to compensate for low pressure created when vapors and fuel are sucked out of the tank, as i described above. The diaphram vent does not allow air/fumes to exit the tank thru the cap. Simple.

I asked them this question a long time ago - they couldn't answer it

If 70 Mustangs had to have a special sealed system for CA emmisions to be sold in CA

And all 71-3's are vented like drake says, that would mean Ford could not sell a 71-3 Mustang in CA

 

[wwhite72]

Please be clear on this; the vented cap only allows air INTO the tank. Fuel vapor cannot escape from the tank thru the cap. The only exit for fumes is thru the vent hose from the fuel tank to the charcoal canister under the hood, which draws the fumes from the fuel tank by using that strange paper looking OEM hose hooked to the passenger side of the air cleaner housing base. The fuel cap has a one way vent.

 

[1FM05]

Ok, i will call scott drake and look to exchange the one i have. They said it is the right cap but must be for a 1970.


Sorry, scott drake D1ZZ-9030A is correct cap for 71-73. It is a vented cap......D1ZZ-9030B is same cap with the wire. It is for 71-73. It is a vented cap. Scott Drake DOES sell a non-vented cap....for 1970 california cars.


OMS, i believe the cap has a diaphram relief valve that allows air into the tank to compensate for low pressure created when vapors and fuel are sucked out of the tank, as i described above. The diaphram vent does not allow air/fumes to exit the tank thru the cap. Simple.

I asked them this question a long time ago - they couldn't answer it

If 70 Mustangs had to have a special sealed system for CA emmisions to be sold in CA

And all 71-3's are vented like drake says, that would mean Ford could not sell a 71-3 Mustang in CA

This was on the 429 mustang cougar site. "The D1Z pop open gas cap above was used on all 1971 Mach 1s. It incorporated a built in seal as shown by the red arrow at center. We believe the similar D2Z Pop Open cap, rear view shown below left (identical to D1Z, but no seal), was released to be used in conjunction with the screw on cap below right to help prevent fuel spillage during rear end collisions - this all in reaction to the Pinto gas tank issue."

 

[rutkak]

If you plug the charcoal canister you need to buy a repo gas cap that is vented. I noticed the issue when my fuel gauge was slowly (but much quicker than it should) going down. I thought I had a fuel leak but it was just the pressure building up. When I opened my gas cap I felt and heard the suction...gas gauge when back to normal.

This was the same on my 72 and my 70 with CA emissions. I replaced both caps without issue.

 

[tony-muscle]

I know this is a very old thread but wanted to share my findings while taking down the tank and examining the whole fuel delivery system. This will hopefully help future readers of this thread. I was confused for some time.

wwhite72 is correct that the D1Z... cap has a vent, and like he states in the post above, the vent only allows air in, not out (http://www.7173mustangs.com/thread-vented-tank-for-mach?pid=116854#pid116854). You can read about it here, http://429mustangcougarinfo.50megs.com/fuel_system.htm

I have a early 1971 Mach 1 and I have a D1ZA-9A112-BB gas cap. This gas cap has a diaphragm in the cap, which I assume, its function is to allow air in one direction. However, when I tested it, mine is allowing air in and out, which is perfect for what I want. I will use the vent on top of the tank as a return for my EFI so I was wondering how I was going to vent the tank. The gas cap is enclosed so I can't see the diaphragm. I assume my diaphragm being so old is broken up so that's probably why it allows air in both directions. I guess that in this case, aging of the product is working in my favor.

 

[LCB1]

I know this is a very old thread but wanted to share my findings while taking down the tank and examining the whole fuel delivery system. This will hopefully help future readers of this thread. I was confused for some time.

wwhite72 is correct that the D1Z... cap has a vent, and like he states in the post above, the vent only allows air in, not out (http://www.7173mustangs.com/thread-vented-tank-for-mach?pid=116854#pid116854). You can read about it here, http://429mustangcougarinfo.50megs.com/fuel_system.htm

I have a early 1971 Mach 1 and I have a D1ZA-9A112-BB gas cap. This gas cap has a diaphragm in the cap, which I assume, its function is to allow air in one direction. However, when I tested it, mine is allowing air in and out, which is perfect for what I want. I will use the vent on top of the tank as a return for my EFI so I was wondering how I was going to vent the tank. The gas cap is enclosed so I can't see the diaphragm. I assume my diaphragm being so old is broken up so that's probably why it allows air in both directions. I guess that in this case, aging of the product is working in my favor.

I'm going with EFI also and was told by Fitech not to use the vent line for a return. Was told it would be insufficient due to its size and I would need the vent. It was recommended that I use this from Summit for a return line.

https://www.summitracing.com/parts/mor-65385

 

[tony-muscle]

I know this is a very old thread but wanted to share my findings while taking down the tank and examining the whole fuel delivery system. This will hopefully help future readers of this thread. I was confused for some time.

wwhite72 is correct that the D1Z... cap has a vent, and like he states in the post above, the vent only allows air in, not out (http://www.7173mustangs.com/thread-vented-tank-for-mach?pid=116854#pid116854). You can read about it here, http://429mustangcougarinfo.50megs.com/fuel_system.htm

I have a early 1971 Mach 1 and I have a D1ZA-9A112-BB gas cap. This gas cap has a diaphragm in the cap, which I assume, its function is to allow air in one direction. However, when I tested it, mine is allowing air in and out, which is perfect for what I want. I will use the vent on top of the tank as a return for my EFI so I was wondering how I was going to vent the tank. The gas cap is enclosed so I can't see the diaphragm. I assume my diaphragm being so old is broken up so that's probably why it allows air in both directions. I guess that in this case, aging of the product is working in my favor.

I'm going with EFI also and was told by Fitech not to use the vent line for a return. Was told it would be insufficient due to its size and I would need the vent. It was recommended that I use this from Summit for a return line.

https://www.summitracing.com/parts/mor-65385

I guess depending on your system. I am going the FiTech route as well, but I am using the PowerSurge pump from Robbmc. Since that's a sump pump system it only needs a 1/4" return line. Our vent line is 5/16" so it should work. Also, i am drilling the little hole in the vent nipple so there is no restriction. Otherwise, i can see it being an issue becausr that hole is really small.

1971 M-code Mach 1

 

[LCB1]

I guess depending on your system. I am going the FiTech route as well, but I am using the PowerSurge pump from Robbmc. Since that's a sump pump system it only needs a 1/4" return line. Our vent line is 5/16" so it should work. Also, i am drilling the little hole in the vent nipple so there is no restriction. Otherwise, i can see it being an issue becausr that hole is really small.

1971 M-code Mach 1

I will have to look into thePowerSurge pump by Robbmc, I didn't want to use the Fitech system due to all the reported issues.

 

[tony-muscle]

I guess depending on your system. I am going the FiTech route as well, but I am using the PowerSurge pump from Robbmc. Since that's a sump pump system it only needs a 1/4" return line. Our vent line is 5/16" so it should work. Also, i am drilling the little hole in the vent nipple so there is no restriction. Otherwise, i can see it being an issue becausr that hole is really small.

1971 M-code Mach 1

I will have to look into thePowerSurge pump by Robbmc, I didn't want to use the Fitech system due to all the reported issues.

Yeah, you should look into this pump. I also was going to go FiTech command center route, but after reading about the issues I changed my mind. The good thing about the PowerSurge is that it has an actual return line, which avoids some of the issues the FCC has. By having a return line there is less risk of overflowing or spewing fuel up the vent line. The PowerSurge is still a sump pump that will work in a loop with the GoEFI. The difference is that when there is excess fuel it will be returned to the tank. Cost wise is comparable, and it is a bit smaller. It fits great in the area where the charcoal canister was, which is a great and safe location to get power and fuel to it. This location is also next to the vent hose from the tank that you could use as a return with no major replumbing. What you need to do is to at least drill out the small hole in the vent nipple.

 

[tony-muscle]

I am having another idea for a fuel return line. Instead of using the vent and having the fuel cascade from the top of the tank, what about if I use the sending unit that I bought from CJP that had a small leak at the connector? I can disassemble the float and just leave the pick up tube. The sending unit is the same diameter of the vent so it should fit on the top with no problem. The pick up tube can then be used as return. The tube will be immersed all the way into the gasoline. Since the electrical connector of the sending unit has a small leak I can easily seal it with POR-15 fuel tank sealer.