Fuel tank venting
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Trailering
Joined: May 2022
Posts: 17
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Fuel tank venting
I’ve got a 1997 7.3 obs powerstroke, and it will no longer fill up, I know that it’s a venting issue, but what I’m unsure of is if all the venting is done through the rollover valves, or if there’s a second vent tube that is supposed to be around the filler neck, any info?
Lead Driver
Joined: Mar 2006
Posts: 5,112
Likes: 1,553
From: western SD
When these trucks equipped with a pickup box left the factory, they were equipped with a smaller hose inside the larger filler hose. The small hose carried the fuel into the tank, and the air displaced by the fuel was supposed to escape out the large filler hose. This work with varying degree of success. The cab and chassis trucks had a different set up that used a 3/4 vent hose that hooked to the roll over vent valve and up to the filler neck. This setup worked the best.
Hotshot
Joined: Oct 2003
Posts: 17,799
Likes: 104
From: Ashland City, TN
https://web.archive.org/web/20201201....com/hutch.php
I cannot find the Harpoon mod that goes along with this.
But the old school thing to do, which has always been on my "to do" list, was to do the harpoon mod I think it was, where you gut the filler pipe and install an auxiliary vent like the cab and chassis trucks had up the filler neck.
Which then allowed you to also fill with the 2 inch at full chooch.
There is a lot of things that can go wrong with the filler tubes on the standard trucks.
And the only real way to fix it is is to really just drop everything and make it right.
And by drop everything, do it the smart way.
Pull the truck bed, dont drop the tanks.
I cannot find the Harpoon mod that goes along with this.
But the old school thing to do, which has always been on my "to do" list, was to do the harpoon mod I think it was, where you gut the filler pipe and install an auxiliary vent like the cab and chassis trucks had up the filler neck.
Which then allowed you to also fill with the 2 inch at full chooch.
There is a lot of things that can go wrong with the filler tubes on the standard trucks.
And the only real way to fix it is is to really just drop everything and make it right.
And by drop everything, do it the smart way.
Pull the truck bed, dont drop the tanks.
Tuned
Joined: Nov 2020
Posts: 404
Likes: 171
From: Greenville, SC
I found that the “hutch” and “harpoon” mods were more related to the Superduty trucks and not our OBS vehicles.
But you will definitely want to gut your filler necks and install a dedicated vent hose. You can see some photos from Khan’s build thread here:
https://www.ford-trucks.com/forums/1...l#post19456966
After you do this, no more fighting fuel pumps clicking off prematurely. An additional bonus is that larger nozzles at truck stops will now also fit.
But you will definitely want to gut your filler necks and install a dedicated vent hose. You can see some photos from Khan’s build thread here:
https://www.ford-trucks.com/forums/1...l#post19456966
After you do this, no more fighting fuel pumps clicking off prematurely. An additional bonus is that larger nozzles at truck stops will now also fit.
Hotshot
Joined: Oct 2003
Posts: 17,799
Likes: 104
From: Ashland City, TN
I found that the “hutch” and “harpoon” mods were more related to the Superduty trucks and not our OBS vehicles.
But you will definitely want to gut your filler necks and install a dedicated vent hose. You can see some photos from Khan’s build thread here:
https://www.ford-trucks.com/forums/1...l#post19456966
After you do this, no more fighting fuel pumps clicking off prematurely. An additional bonus is that larger nozzles at truck stops will now also fit.
But you will definitely want to gut your filler necks and install a dedicated vent hose. You can see some photos from Khan’s build thread here:
https://www.ford-trucks.com/forums/1...l#post19456966
After you do this, no more fighting fuel pumps clicking off prematurely. An additional bonus is that larger nozzles at truck stops will now also fit.
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I remembered out amazing sponsor here had this on his site also. =)
cheers.
Laughing Gas
Joined: May 2007
Posts: 793
Likes: 29
Got as far as buying a brass rollover valve for a racing system as a proof of concept. Have not tried it yet as clearances are very tight and I'd rather do this with the bed off to visually scope fitment before putting it all back together, rather than drop the tank and learn the hard way from a leak if things mash together.
Kahn seems to have the best solution but it calls for doing this with an empty tank in order to remove all metal debris.
Tuned
Joined: Nov 2020
Posts: 404
Likes: 171
From: Greenville, SC
You can reach in through the sending unit hole and hold a paper cup against the inside wall to catch the metal filings.
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Laughing Gas
Joined: May 2007
Posts: 793
Likes: 29
Good point 
Or perhaps a moist hollowed-out sponge held in a manner where the sponge gets held up against the drill site so that the bit goes into the hollow core. If the tank is not virgin, maybe wet the sponge with fuel instead of water.
Or perhaps a moist hollowed-out sponge held in a manner where the sponge gets held up against the drill site so that the bit goes into the hollow core. If the tank is not virgin, maybe wet the sponge with fuel instead of water.
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