Gas Tank Venting Issue

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spikhead

Well-known member
Joined
Dec 28, 2012
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Location
Colorado
My Car
1973 Mach 1 351C
Hey again everyone. For some reason I can’t get rid of a venting issue on the 73. It only allows 9 gallons on the money to go in each time, yet is 23 gallons. We have tried some random things to help but doesn’t seem to work. Any tips or suggestions if this is a common problem?

 
Check the bottom of the tank to make sure it isn't caved in. Make sure the pick up tube is in the correct position, just above the bottom of the tank and not bent up.

 
Do you mean from an empty tank you can only put in 9 gallons

Or the self locking / filling pump handle clicks off at 9 gallons and then you can re latch it and put in more ?

 
Not sure if this will help, but there's a small tube in the tank filler neck, vent tube, is it clear? 

You may need to drop the tank and check the vapour return tube on top of the tank as well as the fuel sender unit as mentioned by Don @OMS

Also, these tanks are 20 US gallons. Maybe time for a fuel system update.



This tube cannot easily be seen through the filler.

 
Not sure if this will help, but there's a small tube in the tank filler neck, vent tube, is it clear? 

You may need to drop the tank and check the vapour return tube on top of the tank as well as the fuel sender unit as mentioned by Don @OMS

Also, these tanks are 20 US gallons. Maybe time for a fuel system update.



This tube cannot easily be seen through the filler.
Thank you for the pic I’ll have to drop the tank to see. The filler neck goes over that correct?

 
Not sure if this will help, but there's a small tube in the tank filler neck, vent tube, is it clear? 

You may need to drop the tank and check the vapour return tube on top of the tank as well as the fuel sender unit as mentioned by Don @OMS

Also, these tanks are 20 US gallons. Maybe time for a fuel system update.



This tube cannot easily be seen through the filler.
Thank you for the pic I’ll have to drop the tank to see. The filler neck goes over that correct?
Yes.

Filler neck goes through the rubber seal. I'm going to throw it out there, if you're going to drop the tank, it would be a great time to replace it. Depending of course on availability right now and of course your budget,  buy a Spectra-Premium 20 gal tank from RockAuto. best price by far and made in Canada, not China! With that buy the Dorman 692232 fuel sending unit. I did mine a couple of years ago, so I can offer tips if needed. At that time, I installed 3/8" SS fuel lines with fuel injector rubber hose where needed. Old steel lines rust inside.

EDIT: checked Dorman number, now correct.

 
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what u can try is use your air compressor. disconnect the hose at the passenger side fire wall canister. REMOVE GAS CAP... the blow air into hose and u should hear it coming out of tank. if u do then also check the canister might be plugged.

 
what u can try is use your air compressor. disconnect the hose at the passenger side fire wall canister. REMOVE GAS CAP... the blow air into hose and u should hear it coming out of tank. if u do then also check the canister might be plugged.
+1, Good points

 
what u can try is use your air compressor. disconnect the hose at the passenger side fire wall canister. REMOVE GAS CAP... the blow air into hose and u should hear it coming out of tank. if u do then also check the canister might be plugged.
I think I found it but does it remove? It looks like it’s maybe welded on there.

 
what u can try is use your air compressor. disconnect the hose at the passenger side fire wall canister. REMOVE GAS CAP... the blow air into hose and u should hear it coming out of tank. if u do then also check the canister might be plugged.
I think I found it but does it remove? It looks like it’s maybe welded on there.
 Sorry, I have no idea what you're refering to, what's welded on?

This is what delawarebill is refering to, see red arrow. This rubber tube connects to a steel line that goes back the the gas tank vent. At the tank, it is connected with another rubber tube. Pull the rubber tube off the canister and apply compressed air to it.... gently.

NOTE; this pic is for the 71, but the 73 I believe is similar.

 



Rubber vent tube on tank. TIP: Always use Fuel Injector grade hose, ethanol resistant, for ALL rubber pieces of the fuel system.

 
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what u can try is use your air compressor. disconnect the hose at the passenger side fire wall canister. REMOVE GAS CAP... the blow air into hose and u should hear it coming out of tank. if u do then also check the canister might be plugged.
I think I found it but does it remove? It looks like it’s maybe welded on there.
 Sorry, I have no idea what you're refering to, what's welded on?

This is what delawarebill is refering to, see red arrow. This rubber tube connects to a steel line that goes back the the gas tank vent. At the tank, it is connected with another rubber tube. Pull the rubber tube off the canister and apply compressed air to it.... gently.

NOTE; this pic is for the 71, but the 73 I believe is similar.

 



Rubber vent tube on tank. TIP: Always use Fuel Injector grade hose, ethanol resistant, for ALL rubber pieces of the fuel system.
I’ll have to see what I can find. Plan on dropping the tank today. Thanks so much

 
Anything special to know when dropping the tank? I am going to work on converting to EFI with an in-tank pump, so have to drop the tank to work on it.
EMPTY works best. Or as little gas in it as possible, Use a jack with a good size piece of wood to support it while removing the bolts and lowering it. Remove the filler tube first of course. When you put it back, use 3 1/2" x3/8| galvanizes carriage bolts, nuts and washers, no rust in future.

No sparks or smoking goes without saying.... Oh, I just did!

Good luck.

 
Ya, the last part goes without saying. Which is why Im torn on if I modify the original tank, or get a new one and start fresh. Mostly because Id have to clean it out super good before we can really modify it.

 
Ya, the last part goes without saying. Which is why Im torn on if I modify the original tank, or get a new one and start fresh. Mostly because Id have to clean it out super good before we can really modify it.
The Spectra Premium from Rock Auto is the best you'll get anywhere. It's made in Canada so no Chinese junk. An exact repop. I suggest R/A because of price. The sending unit I guess would be obsolete, but you'll still need to plug the hole with something. 

 
There is another site in Canada that I use when shipping from Rockauto is high. Its called thewrenchmonkey.ca and as long as you are ok with Canada Post its free shipping. And it looks like they have the Spectra one for less than Rock Auto too.

 
Hi,  One thing to double check is fuel pickup sending unit when putting it back together.  I had my tank changed by someone else and  'I ' should have doubled check the new sender resistance and fit angle before installing back in.  Sender works but  fuel gauge is not as linear while the fuel is consumed.   I really need to pull it but dread dealing  with getting the gas out again. 

 
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There is another site in Canada that I use when shipping from Rockauto is high. Its called thewrenchmonkey.ca and as long as you are ok with Canada Post its free shipping. And it looks like they have the Spectra one for less than Rock Auto too.
Wow, I'll have to check them out. When I got mine from R/A, I paid only 175 buck Cad to my door. The same one from my local store was 240 +tax.

 
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