Howdy, this little vent device intended for a gasser sure jumps out at me as a likely spot to feed my stock F550 tank from a diesel bed tank by gravity.

Anybody BTDT?

 

That looks like a vent to me, probably not a good idea. They do make kits where you tap in to the filler neck, that's what I have.

 

What Gyppo said. I grabbed this fitting from ATTA tank along with all of the hoses and clamps I needed for my tool box/aux tank combo for around $50. All you have to do is cut the filler neck tube under the bed and slide it in.





I know some people have had issues with fuel leaking out of the top of the tank with a gravity feed once the main tank is full, so I would recommend this motorized valve. Simply run in to a switch, or one of your upfitter switches.






I wanted to be able to keep an eye on my fuel level, and I also wanted to be able to filter my fuel before sending it to the main tank. My tank was designed to be ran off of a pump, so I picked one up from Amazon for $50 and installed a small, inline pre-filter for large particles. I then installed a marine water/fuel separator for a final polish before sending it to the main tank. It may be overkill, but it helps me sleep better at night! I haven't found a spec of trash or a drop of water in my frame mounted fuel filter since I installed this setup. My tank came with a fuel sending unit, so I installed a gauge in my center console to keep me in the know of my fuel level.

 

Sukey, you got a long bed or short? That's a pretty slick setup you got there.

 

Thank you! I have a short bed. It's just a 45 gallon tank, but it extends my range out to between 1100-1200 miles between fill-ups if need be. I really like being able to be more choosy about where and how much I pay for fuel. I live in Fort Worth, but mostly work in east TX and Louisiana. I've seen fuel as much as .90 per gallon higher in LA after filling up at home on the same day.

 

Look again, those vents are closed. They're designed for the evaporative emissions control systems on a gasser. On my diesel SDs they are all closed off. Not sure how they come from Furd on a diesel, but we found them linked to each other (and leaking) on my 2000 F250. I know that if both are closed off the system works fine.

So why not use it to let fuel enter? I run a timer when I turn on the bed tank valve anyway, or yes it will start to seep out the standard tank cap.

 

How did you determine that these rollover vent valves are for a "gasser"?

If they were for a gasser, why would they be found on a diesel fuel tank?

How did you determine that the caps on these valves are not vented?

By what other means can make up air at atmospheric pressure enter the tank to keep it from collapsing under vacuum?

By what other means can pressure be relieved to prevent the tank from ballooning under pressure?

In addition to the rollover valve at the driver's side front of the tank, is there not also an identical valve at the passenger side rear of the tank?

What need might there by for two identical breathing valves in the free air zone of a non "harpooned" stock fuel tank, but positioned on opposing ends, and opposing sides, of the tank?

What happens to the fuel when driving up an steep incline?

What happens to the fuel when driving down a steep decline?

What happens to the fuel when banking laterally, severely inclined, leaning toward the driver's, or passenger's, side?

If fuel, as a liquid, behaves like water, and is self leveling, is it not possible that at one of these steep angles, one of the vent valves becomes submerged, as if the vehicle rolled over?

And would not the other valve, on the opposite end and opposite side of the tank, in the opposing direction of incline, be thus free to admit make up air or relieve pressure from the pocket of air in the tank it is thus exposed to?

Why would you want to hamper half of the breathing functionality of the OEM diesel fuel tank?

Have you considered using the auxiliary fuel port instead?

 

Rollover vent valves, as you call them, have been closed off on my 2000 for three years, one year on my 550. Look again at my OP pic. If they had been previously venting, I'd have tank troubles now, no?

Does Ford have distinct part numbers for gas vs diesel tanks? That would resolve that question. We see so few gassers in our shops in Texas.

That auxiliary fuel port looks like the bee's knees. Thank you.

 

Did you do something on purpose to "close them off"? Or is "closed off" your estimation of the as found condition?

Do the respective time periods quoted reflect the time period of your observation / discovery / ownership of vehicle, or the time period that has transpired since you made a specific change to the ends of those valves?

The OEM rollover valves for diesel applications come with special vented caps that are specific and unique to the diesel applications, not found on gasoline applications that otherwise have similar shaped and named valves, and those vented caps have the appearance at first glance of rendering the valve "closed off", but the air permeability of the caps is not readily apparent to the eye.

The aft axle tank on my 2000 F-550 is a bit different (3 gallons larger, and fabricated differently) than the tank on your 1999 F-550. Of interest on this topic is that I only have one rollover vent valve, that is centrally positioned, rather than two valves, positioned on opposing ends and edges.

I have a pickup type bed on mine that covers up my tank, so I found a similar photo of another chassis cab that has a tank similar to mine, and I've posted it below so that you can compare the difference between the two aft axle tank styles, both made in calendar year 1999.

Ford issued a TSB concerning the single centrally positioned rollover vent valve, due to the central position being at the bottom of a potential pool of water that can pond in the central depression on top of the tank that is recessed to give clearance to the fuel outlet elbows and fittings from the sending unit. The fix was to attach a hose... a simple fuel rated hose... to pipe the venting out of the potential pool area and above the frame. That little 18" hose retailed for $80.00... not because the hose was special, but because the cap on the end was vented, and yet appeared fully closed to my eyes when I installed it. I never had a problem with water or snow melt pooling on top of the tank, but knowing that others did was enough for me to do the TSB as a prophylactic measure for the promised earthquake and tsunami that I'll try to Ford through in bug out fashion.

If there is any doubt that the OEM rollover valve "breathes" with the OEM cap cover in place, the witness stains of dirt embedded diesel fuel on top of the tank in the photo below should provide some evidence.

No, you wouldn't have tank troubles if the vents have been venting. Did you alter something to stop them from venting?

Yes.

You're welcome.

 

Drinkin from a fire hose here. Love the pics, thanks. Yes, mine are plugged because in we plugged them, both trucks.

On the 2000 they are now interconnected so there is no passage of fluid to/from the outside. This was done three years by a mechanic to fix one that was leaking. Perhaps that was in error, but in three years no observable issues have arisen from his actions. I was there when he dropped the tank, as we did Harpoon then too. I don't recall what was on those nipples before the mod, just that it was leaking when full. They may even have already been interconnected, aamof. It seemed unimportant to me at the time, as my focus was on Big Fuel and Harpoon mods.

On the 99 they were perished of age. I suspected on seeing them that they were intended to vent at one point in the dim past, but in their state, neglected under a utility bed for 21 years, they were mostly decomposed rubber (pic below). I plugged the nipples with the silicone caps you see in the OP,. You're probably going to suggest that I purchase some new ones. I doubt that Furd still offers them, having increasingly deemed all vehicles older that 10 years as obsolete.They want us to buy a $90k Expodition instead that doesn't even have a shift lever. Don't get me started. In any case, I've run hard for a year, towing 22k, and the tank has not collapsed. I suspect that my fuel cap allows air in.

So again, in both trucks, those vents have been sealed off for 1-3 years and both trucks work fine. Your volley.

Apropos, I plan to purchase and install this Poly tank as soon as Riff Raff releases their new in-tank fuel pickup assembly, later this year.

OK, if Ford has distinct part numbers for gas vs diesel tanks as far back as 1999 then my mechanic's theory is incorrect. But as I mentioned we see few gassers in any of the 3 shops that I haunt.

 

I have a F550 too and always wonder about those little vent things, mine look terrible and old I wonder if they work at all.

 

@RenoHuskerDu

Interestingly enough, it looks like at some point Ford thrifted out the double rollover valve in their aft axle plastic tanks, now using only the forward driver's side position, while capping the rearward passenger side position.

The following two pics are of the 2021 that I'm toying with at the moment...


MODEL YEAR 2021: ONE ROLLOVER VALVE, ONE CAP IN LIEU OF SECOND VALVE, WHICH WAS THRIFTED OUT AND ELIMINATED


By comparison, below is the photo of the 2019 that I was messing with a couple of years ago:

MODEL YEAR 2019: TWO ROLLOVER VALVES, DIAMETRICALLY OPPOSING, AS ORIGINALLY ENGINEERED


.

 

I wonder if you can buy those valves and put them on a Super Duty, my dealer always says no longer avaialble when I look for parts for my trucks. I cry every time I go in there and the new trucks cost more than my house. My wife would kill me