Fuel Tanks Pulling A Vacuum
- Thread starter icanfixall
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LCAM-01XA
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Good call, I got a few good parts guys, I'll run this by them next time I hit the A/Z.
MIDNIGHT RIDER
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Like RSDL already said, you guys need to check to see if your tank-vents are actually venting and not clogged by mud-daubers or a dead mouse.
I clamped a piece of screen over my vent to prevent such intrusions.
The factory roll-over valves are notorious for NOT ALLOWING THE TANK TO VENT.
Before I over-hauled my vent lines and erradicated the roll-over valves, it took next to forever to fill the tanks, with fuel puking out into my boots, no matter how slowly I squeezed the pump trigger.
After I opened things up, I can use the high-volume pumps at the truck-stops and it will take the fuel as quick as the pump delivers it.
I clamped a piece of screen over my vent to prevent such intrusions.
The factory roll-over valves are notorious for NOT ALLOWING THE TANK TO VENT.
Before I over-hauled my vent lines and erradicated the roll-over valves, it took next to forever to fill the tanks, with fuel puking out into my boots, no matter how slowly I squeezed the pump trigger.
After I opened things up, I can use the high-volume pumps at the truck-stops and it will take the fuel as quick as the pump delivers it.
Goofyexponent
Mentally Unstable..
This is what makes me scratch my head. I don't think I have my roll over valves, because I can take fuel as fast as the pumps deliver it....no problem.
But it still draws a serious vacuum.
Where are the factory cents? In the filler neck?
My tanks don't cause the pump to advance....or at least I don't think it does..
But it still draws a serious vacuum.
Where are the factory cents? In the filler neck?
My tanks don't cause the pump to advance....or at least I don't think it does..
LCAM-01XA
Full Access Member
Damon, both I and Gary have no rollover valves, we removed them (I used a huge barb fitting for the purpose) and ran 1/2" hose from there to the top of the filler necks right under the cap. So if the caps are not vented, we are not getting any venting in our tanks when the trucks are running. Obviously when we fill up the caps are off and the tanks purge the air properly, I can run the small pumps wide open and the big pumps about halfway down...
Goofy, what factory cents are you talking about?
Goofy, what factory cents are you talking about?
MIDNIGHT RIDER
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The actual tank vent hoses in no way connect to the filler-necks; they poke through big rubber grommets in the tops of the tanks.
Like I already said, 1/2" hose will fit right into those grommets and replace the 7/16 hose that is currently in there.
Lube those old hoses with some sort of rubber-friendly slick-um; tire-lube or vegetable-oil is good.
Pull out and discard the old hoses, complete with the silly roll-over valves.
Slick up the new 1/2" hoses and poke a healthy amount through the grommets.
Route the two new hoses high and dry.
I TEEed all THREE of mine ( I have three tanks ) into one main vent hose.
I routed this up high and dry, using a barb and pipe fittings to make a downward-pointing "U" shape that prevents water getting into the vent.
A piece of screen-wire hose-clamped over the opening keeps out critters.
On writing/typing this, it came to me that one could also drill many many little insect-proof holes into a pipe-cap and this would look neater than the clamped on screen.
You are correct in that the way you guys have routed your main tank vent hoses into the filler-necks has effectively eliminated the ability of your tanks to vent; who on earth came up with such a plan ??
Plumbed thus, if those tanks are venting at all, they must be sucking air past the grommets, or through a rusted pin-hole.
Honestly, it surprises me that the engines still run.
Like I already said, 1/2" hose will fit right into those grommets and replace the 7/16 hose that is currently in there.
Lube those old hoses with some sort of rubber-friendly slick-um; tire-lube or vegetable-oil is good.
Pull out and discard the old hoses, complete with the silly roll-over valves.
Slick up the new 1/2" hoses and poke a healthy amount through the grommets.
Route the two new hoses high and dry.
I TEEed all THREE of mine ( I have three tanks ) into one main vent hose.
I routed this up high and dry, using a barb and pipe fittings to make a downward-pointing "U" shape that prevents water getting into the vent.
A piece of screen-wire hose-clamped over the opening keeps out critters.
On writing/typing this, it came to me that one could also drill many many little insect-proof holes into a pipe-cap and this would look neater than the clamped on screen.
You are correct in that the way you guys have routed your main tank vent hoses into the filler-necks has effectively eliminated the ability of your tanks to vent; who on earth came up with such a plan ??
Plumbed thus, if those tanks are venting at all, they must be sucking air past the grommets, or through a rusted pin-hole.
Honestly, it surprises me that the engines still run.
LCAM-01XA
Full Access Member
You are correct in that the way you guys have routed your main tank vent hoses into the filler-necks has effectively eliminated the ability of your tanks to vent; who on earth came up with such a plan ??
Plumbed thus, if those tanks are venting at all, they must be sucking air past the grommets, or through a rusted pin-hole.
Honestly, it surprises me that the engines still run.
Hey, I always thought the darn caps are vented, if they were indeed vented then there would be no issue whatsoever - it's a great plan if it the caps were what I was told they are, lol. I do think my tanks are sucking air through the caps anyways tho cause of their old and cracked seals, I know it sure as heck ain't from the rubber grommets on top of the tanks cause I sometimes fill the tanks so much the fill hose becomes part of the tank all the way to the cap, and I spill no fuel in the process... No rust holes either, as both my tanks are no older than year.
MIDNIGHT RIDER
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I forgot to add that, with my three tank vent hoses all TEEed together, should I forget to switch the RETURN valve and over-fill a tank, instead of pouring on the ground, the excess fuel simply finds it's way into whichever tank has room for it; this feature is very important and saves a lot of fuel.
Also, although I have not yet done it, one should install a ball cut-off valve in the main vent hose, in an easily accessible position; then, should the truck actually lay onto it's side, or keel over bottom side upwards, and you are not killed in the process, you can close the valve and shut off the flow of fuel.
Also, although I have not yet done it, one should install a ball cut-off valve in the main vent hose, in an easily accessible position; then, should the truck actually lay onto it's side, or keel over bottom side upwards, and you are not killed in the process, you can close the valve and shut off the flow of fuel.
Black dawg
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the ford caps on both my 89s are vented.
LCAM-01XA
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How can you tell?
CDX825
filtration nut
I had the same problem with my truck when I got it and the rubber line was indeed plugged.
Cleaned it out with a wire and all has been good since then.
Cleaned it out with a wire and all has been good since then.
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