Filler neck mod question for you guys in the know. - Diesel Forum

johndeerebones · 06-09-2007, 08:43 PM

Im gonna do the mod sometime in the near future. Only question i have is with it being a one way valve you effectively close off the tank to any vent, can you get a two way vented cap for our tanks? I know duramaxes have a cap that has check valves for both directions from when I worked at a chevy dealer, but don't know where to get one from our trucks. Also, what do you do with the vent hose that you take off the stock rollover valve, where does it go?

johndeerebones · 06-11-2007, 02:10 AM

Come guys I know some of you have done this one, or all of you older members from when this made was popular not posting anymore?

realbadlarry · 06-11-2007, 03:13 AM

the New rollover valves are open unless you roll over. They vent back into the filler neck,( you have to add the fitting) just make sure you have the lines so that you don't get a low spot that fills with fuel, that will block off your vent. I can fill mine to the brim now without shutting off. Love it. Took me a while to get the vent lines correct, but works good now.

johndeerebones · 06-11-2007, 04:19 AM

I'm getting excited about doing mine [img]/ubbthreads/images/graemlins/smile.gif[/img] thanks for the reply. Do you have any trouble with the tanks pulling too much vacuum? I wonder if we can get a cap to fit our trucks that vented both directions? Since we don't have evap there would be no problems with CEL or nothing.

W Miles · 06-11-2007, 12:24 PM

I have not had any problems in five years. However I used the kit from Transfer Flow. Easy to install and works great.

GJCAT · 06-12-2007, 08:03 AM

I did the mod using all ford parts and didn`t change the caps. haven`t had any problems with it in 3yrs. Sure does make fillups faster.

Blue_Mtn_Boy · 06-12-2007, 11:44 AM

Did mine 2 or 3 years ago and never had a venting problem. Even on 100+ degree days while pulling the 5er there has only been a slight sucking sound when I twist off the fuel cap(s). Makes me think the caps are vented in both directions.

Some have put spacers between the bottom of the frame rail and the top of the rear tank to move it down about 1/2" for more room to prevent the bigger vent hose from pinching. I need to do this because my vent mod doesn't work quite as well when filling the rear tank.

Go for it.

johndeerebones · 06-13-2007, 01:14 AM

[ QUOTE ]
Did mine 2 or 3 years ago and never had a venting problem. Even on 100+ degree days while pulling the 5er there has only been a slight sucking sound when I twist off the fuel cap(s). Makes me think the caps are vented in both directions.

Some have put spacers between the bottom of the frame rail and the top of the rear tank to move it down about 1/2" for more room to prevent the bigger vent hose from pinching. I need to do this because my vent mod doesn't work quite as well when filling the rear tank.

Go for it.

[/ QUOTE ]

I parked the ol girl and pulled the front tank filler neck and rov tonight. Yanked the hose from the neck and got the fitting down enough to need a sawzall, gonna take it to work tommorow and take out the fitting, hog out the rov and drill the neck, so my JB weld can sit up all day at work, then I'll put it in tommorow evening. Only problem though, that tank is full, so can't test it for a while. Gonna run the rear tank dry before I drop it.

One more question, on the front neck I think I'll put the hose barb in the front side, as in toward cab, maybe even like at the 10 or 11 o clock position if you are looking at the filler end, will that work fine, I think that would be optimum for getting the hose to slope from the neck to the tank, thought it would be no prob, but after looking at it tonight, the bed crossmember is RIGHT in the way for a straight sloping shot to the rollover valve. I gotta tee that is 5/8,3/8,5/8, so I'm gonna tee into the vent hose and put the factory vent into the system to eleimnate the vacuum worry, just gotta goto Lowes and get a 1/4 to 3/8 adapter, couldn't find a tee to go straight to the 1/4 from the 5/8

realbadlarry · 06-13-2007, 01:37 AM

The best would be to have the hose zip tied to the bottom of the bed so it goes from the filler neck at an upward angle, then down to the tank. You want to avoid low spots that will fill with diesel.

johndeerebones · 06-13-2007, 07:38 PM

[ QUOTE ]
The best would be to have the hose zip tied to the bottom of the bed so it goes from the filler neck at an upward angle, then down to the tank. You want to avoid low spots that will fill with diesel.

[/ QUOTE ]

Ya, that would work, I was thinking all has to run to the tank, but wether fuel in the vent hose runs to the tank or the filler neck won't matter, still won't fill up with fuel and stop airflow, duh me....

I'm gonna drill the neck and install everything tonight, modified the rov today and jb welded it. I went to lowes and got a 1/4 brass hose splice barb and brazed it in my "t", so now I have and "t" for 5/8 line and the "t" is a 1/4 hose barb, so I'll run the factory vent line up high from the "t" to eliminate the chance of vacuum.

johndeerebones · 06-14-2007, 01:06 AM

Well, finished up the front tank this evening, if it works as advertised I would recommend it to anyone thinking of it. Easy mod, worst part of it was driving around rounding up parts and getting the fitting for the internal hose cut up and bent out of the filler neck, but that wasn't hard, just a knuckle head pain in the butt job.... I beat the end of the bed crosmember to take the sharp edge away and ran zipties around my vent line right around the end of it, so I have a slope all the way, should work great.