vapor lock problem

[rob10858]

i tried posting this on another forum and didnt have much luck. i have a 2001. 5 3500 that last week suddenly refused to take fuel thru the filler tube without suddenly gushing out. dealer rep and cummins told me to take check the top of the tank and remove a small nipple that covers the vent in shipping. i did this and now can fuel the truck but very, very slowly. never had any problems the first 10000 miles and prob started at 12600. just something interesting to add to the whole equation is that my aux fuel tank is now only pumping at about 1/4 volume that it was before. this means that i now have to stand and baby 35 gals into my tank, and cant use the aux because it started pumping so slow. i need some help on this one, because this is a work truck and cant go into the shop on something that is irritating but not life threatning to the truck. ive had truckers tell me that theve had the same problem, but no good advice. i know that theres a simple solution, so lets here it. by the way we had a psd with the sme prob, and it turned out to be a kink in the vent tube that wrapped around the filler. not so lucky so far.

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[illflem]

You have a clogged or kinked vent somewhere, that is only thing it could be. Check the vent line in-between the tank and fill spout.

 

[JohnE]

I was thinking the check (choke) ball in the filler neck was jammed until you mentioned the auxilliary tank think. I've had lumpy gasoline cause problems in tanks, carb bowls, jets, etc. Not sure if diesel will get lumpy, outside of the winter gelling.

BTW, my choke ball is going this summer. Tired of not getting to the first click on the delivery pumps at truck stops. That's the only place I can get diesel around here for a reasonable price.

Good luck

John E

 

[rob10858]

took a look again under the truck to see if i could find any type of vent hose connecting to the filler tube, no luck. its almost impossible to "see" anything, you just have to reach up and feel around. i can trace where the tube goes into the tank. no connecting vents or lines there that i can see. could it be the rubber gasket on the sending unit has gone bad? if anyone has a schematis of the new 35 gal tanks, it would sure be handy.

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[rob10858]

oh, by the way john and ifflem, where would the choke ball be? the filler is solid about half way down and the transitions to a rubber tube [about two inches od] into the tank. is it at the point that the tube goes into the tank or higher up? it makes sense that the aux tank pump would also be laboring if that ball were constricting the filler tube, because the hole that the aux tank intake enters the filler is about four inches down from the top. thats how i discovered the flow problem, i prefer to fill the main from the aux when stopped.

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[JohnE]

I've got a 97 and believe the choke is near the end of the filler tube closest to the rubber connection. I did a quick check with a tape measure to see where that annoying thing was located in order to estimate the removal time. I also used my fingers and felt a crease inwards in the pipe at that end. I'm hoping removal is as simple as re-rounding the pipe.

From your added description, I think the ball is your problem. Neuter that bugger, quick!

John

 

[illflem]

When someone figures how to remove the ball let us know. I'd like mine out just to make it easier to siphon. I still wouldn't place the blame on the ball for your problem though. If it's stuck part way up you can push it down with a long screwdriver. I've seen hoses such as the 3/8" vent hose that have several layers of material and have seen them installed with the connection pipe in-between layers, especially when doing the install blind.

 

[Blkdawdg]

Mine does this same thing and it started when I tied into the spillover line for my fuel return. I haven't a clue what it is but if you figure out what's the cause make sure to post it because I'm going to have to get this fixed. I can fill up the tank fine when the truck is off but if it's running, then you can forget about it.

 

[Alan Reagan]

Packman, I didn't look under the truck but the vent tube is about 2 inches down inside the filler tube on the forward side. so the tube should be on the forward side of the filler tube. I'll try to check it at lunch.

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2001 HO 6 spd 2500, 4. 10 LSD, Towing Package, Electric Brakes, SPA EGT/Boost Gauges, Fog Lights, Real Backup Lights, Molded Running Boards, Lucerix X Mount Heated/Power Mirrors

 

[rob10858]

okay folks, turns out the aux tank uses the vent hole to fill the main tank, thats why i was missing the obvious. so basically the vent has been turned into a feeder for the main tank. a vent prob in one would cause a vent prob in the other. oddly enough, my trucks twin has a similar prob, you cant fill the main from the aux without fuel gushing all over the place. hopefully, it will go to the shop in the next few days and ill let you know what the outcome is. if it is in the factory system im sure alot of guys will have this prob and will know how to correct it. if its in the aux system, the same holds true. i trust my service dept, they are the best. also my fuel sending unit is going to be replaced while the truck is at the dealers, it is totally unreliable and has obviously been a problem because my service rep said that he had one ordered after my first discussion with him about all of this. as ive said before this is a minor problem, especially after repairs on our psds with identical mileage for a blown turbo, blown flywheel, three trannies, and numerous computer problems. so there's an independent overview of the quality of ford vs dodge.

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[Alan Reagan]

Thanks for letting us know what is causing the problem. Good luck.