Venting fuel tank ?

[tuke]

Hi All,

I been wondering why is it everytime I go to put fuel in the rear tank I hear a sucking sound like its not venting. I switched caps with the front tank which doesn't make the sucking sound but its still the same. Anyone have a clue as to why it does it? Truck seems to run the same on either tank. Thanks Ed

 

[93turbo_animal]

sounds like your roll over valve which is the vent for the tank has gotten plugged somehow

 

[6 Nebraska IDIs]

Well, all of the IDI's had crappy fueling systems. The early ones worse than the rest. Best fix I've found out to speed up fueling time is to hack out the neck until its just the outer pipe. Then shove a spring inside and bore the vent tube out to an almost elongated oval opening.

 

[Exekiel69]

I lost the link I had but there are some upgrades for the fuel tanks if Yours is not done yet. The inner hose is much bigger.

 

[Mr_Roboto]

Right the tank vents through the evaporative emissions system which most vehicles have had since the 70's. The caps are made to NOT vent under normal circumstances.

I've found out the hard way that lack of venting can ruin a fuel pump. You can ensure venting by drilling an @ 1/8" hole through the fuel cap. Diesel isn't nearly as volatile as gasoline and you shouldn't have significant losses from evaporation.

 

[rubberfish]

You can ensure venting by drilling an @ 1/8" hole through the fuel cap. Diesel isn't nearly as volatile as gasoline and you shouldn't have significant losses from evaporation.

X2
Mine was doing the same thing.
Couple holes in the cap fixed it.

 

[Agnem]

Well, all of the IDI's had crappy fueling systems. The early ones worse than the rest. Best fix I've found out to speed up fueling time is to hack out the neck until its just the outer pipe. Then shove a spring inside and bore the vent tube out to an almost elongated oval opening.

That's a rather bold statement. Why haven't I had a problem in almost a quarter of a century then?

 

[Double-S-Diesel]

need to mod it the same as we do on the OBS PSD's

http://www.gts-motorsports.com/fillerneckmods.html

I know Dale at tymar has the parts all set up also.

pretty much what it involves is taking the small vent out of the top of the tank, replacing it with a new gasket and rolover valve , the running the vent hose up to the top of the filler neck.

 

[6 Nebraska IDIs]

Man you do sure come off as one cocky little sucker to me in almost every one of my posts. I am not even close to being sure as to why. You seem to know allot about these trucks, and even though Im young, my family has been in ford diesels and diesel pickups since before Ford actually made Diesel pickups. So if you'd give me the same amount of respect and curtisy as everyone else, you'd realize, I do have my own experiences and solved problems with these trucks. I've been working on Navistar International engines since I was 10. So cut me just a little slack, until I can proove I know what Im talking about to you. And in the mean time, dont hesitate to pipe in if I am having a problem, just try not to be so gruff.

That's a rather bold statement. Why haven't I had a problem in almost a quarter of a century then?

 

[Double-S-Diesel]

Dont be too ******* Mel, he only puts fuel in once a year.

 

[Agnem]

Well I'm sorry if you feel I'm being ******* you. I wasn't trying to disrespect you, just trying to find out if you knew something I didn't. Sorry if it comes off as cocky, but one thing you will learn as you get older is to avoid blanket statements. The more I learn, the more I realize what I don't know. I was hoping you would actually have a technical explaination. I've been aware of people having reports of slow fill-ups for some time, but have yet to find a rhyme or reason why it occurs. I have 3 IDI's now, and none of them have this issue, so I feel the design is sound, it's just a question of what has happened to the trucks that exhibit the problem. And yes Nick, it's true I don't run the trucks as much as many others, but my diesel fuel bill is around $500 a month, and the Moosetang drinks it like it's going out of style, so I have one foot in the garage queen boat, and the other in the "real world" if you will, so my days of accumulating only 2000 miles of IDI usage a year are over. I'm doing that 110 miles a day at a time now. I should be getting close to 30,000 miles of IDI time this year.

 

[Mr_Roboto]

I don't see what the fuel inlet restrictor has to do with the fuel tank not venting. And I don't see how removing the restrictor will help a lack of venting.

Yea I'm a cocky SOB too.

 

[Double-S-Diesel]

FWIW
had trouble with most of my IDI's
also had trouble with the PSD's also
that is why the mod.
granted cutting off the tube will help some.
but no where near as well as the mod.

Mel is also correct
it is possible that the PO of your trucks did something stupid and that is why the fuel wont go in, or it is possible that the vent is plugged. or what not.
when I got my 96, rear tank would not fill fast.
come to find out the stock filler was cut in 2 and a piece of rad hose was in the center.

 

[Agnem]

If I recall, there is a plastic hose that is suspended in the filler neck, between the fill and the top of the tank. I'd think it possible if anybody ever did anything like a body lift, or if they had the tank out for some reason, it would be fairly easy to not have one end of that tube or the other in the right place. I'd think also that any cracks in it would result in it being non functional. That's probably why the mod Nick points out is so popular. It basically takes the system Ford engineered, and moves it to the outside of the fill pipe instead of the inside. Outside you can see it and can tell what's going on.

 

[troutwest66]

I modded both tanks on my '94. They filled slow. So I gutted the filler necks amd removed the rubber hose inside the neck. The air vents back through the stock filler neck and the passage is way too small. So what I did was remove the rollover valve from each tank, replaced it with a 1" heater hose elbow and ran rubber hose from the elbow back up to a copper elbow brazed to the top of the neck. The air rushes out when filling and the foaming of the diesel while filling is practically eliminated. I think this is what all the confusion is all about.