Motobilt Stretch Underbody Fuel Cell Help

[OffKamberTJ]

So, my stock 2003 19 gallon gas tank has finally reached the point of no return; both the filler neck nipple and the rollover valve have completely deteriorated, and my temporary plastic epoxy fix didn't hold. So, I got the Motobilt Stretch Underbody Fuel Cell, confirming with their sales team that all I needed to make this tank work with my 2003 was the pigtail adapter, later years filler hose, later years vent hose, and the 2005-2006 fuel pump. I've gotten that far, and yet, I've run into 3 issues. 1. There are 2 rollover valves on the stock tank, but only one on the Motobilt tank. What do I do about the rollover valve connector that connects to the rollover valve and the evap/fuel lines? 2. The 2003 tank is compatible only with the filler neck, the vent hose is smaller in diameter and connects to the top of the filler neck and the evap/fuel lines; the vent hose doesn't connect to the tank as it does on the Motobilt tank. So, I'm not sure how I go about connecting the vent to anything, really. Would I need a whole new filler neck? But at that point, what would I do with the current evap line that's connected to the fuel lines? 3. How is the pigtail wired to the electrical connector on the fuel pump? There is no wiring guidance, but I know I can't mix and match colors and go at it blindly. I'm unsure if I'm explaining everything coherently, so I'll attach pictures. I removed the stock tank on Tuesday, under the impression that this was a straightforward install. Their lack of clear directions makse me believe that Motobilt never tried this on a 2003; unless it is clear and I'm missing it. Any and all help is much appreciated, I've been wracking my brain on this since I pulled the tank, no answer from the company after I've emailed them, and I'm coming up short and running out of waiting time (it's my only vehicle and my daily driver).

 

[macleanflood]

Never done that swap before...but here's what I would do:

Download the FSM - factory service manual in the resources section and look at section 8w and get familiar with the fuel pump wiring for your 2003 and 2005/06. You should be able to approximate things with wire colors and verify voltage and grounds.

Evap is seperate from rollover via a check ball so gas doesn't pour out. I'd buy a 2006 filler neck... here's a picture from Rock Auto and it appears to solve your smaller hose issue.

And I'd find whatever fittings and hoses were needed to plumb in the single evap. It's just engine vacuum sucking vapor into a charcoal cannister through a PCM controlled solenoid...nothing mysterious. Do make sure your solenoid isn't full of loose charcoal... that's what did mine in on my 97 and I ended up replacing both the charcoal cannister and solenoid.

Hopefully someone who's done this will chime in. All fixable problems!

-Mac

 

[Wildman]

So, my stock 2003 19 gallon gas tank has finally reached the point of no return; both the filler neck nipple and the rollover valve have completely deteriorated, and my temporary plastic epoxy fix didn't hold. So, I got the Motobilt Stretch Underbody Fuel Cell, confirming with their sales team that all I needed to make this tank work with my 2003 was the pigtail adapter, later years filler hose, later years vent hose, and the 2005-2006 fuel pump. I've gotten that far, and yet, I've run into 3 issues. 1. There are 2 rollover valves on the stock tank, but only one on the Motobilt tank. What do I do about the rollover valve connector that connects to the rollover valve and the evap/fuel lines? 2. The 2003 tank is compatible only with the filler neck, the vent hose is smaller in diameter and connects to the top of the filler neck and the evap/fuel lines; the vent hose doesn't connect to the tank as it does on the Motobilt tank. So, I'm not sure how I go about connecting the vent to anything, really. Would I need a whole new filler neck? But at that point, what would I do with the current evap line that's connected to the fuel lines? 3. How is the pigtail wired to the electrical connector on the fuel pump? There is no wiring guidance, but I know I can't mix and match colors and go at it blindly. I'm unsure if I'm explaining everything coherently, so I'll attach pictures. I removed the stock tank on Tuesday, under the impression that this was a straightforward install. Their lack of clear directions makse me believe that Motobilt never tried this on a 2003; unless it is clear and I'm missing it. Any and all help is much appreciated, I've been wracking my brain on this since I pulled the tank, no answer from the company after I've emailed them, and I'm coming up short and running out of waiting time (it's my only vehicle and my daily driver).

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I don't know if anyone here has used the Motobilt tank yet.

For the Rollover valve line can't you just reduce it to one line?

As far as wiring goes you can download your FSM & a 2005-06 FEM & compare wires to figure out what you'll need to so.

For the vent line I'm not sure what you're asking. I've got a 97 so mine comes off the filler neck and connects to the tank. If it's a size difference you can get adapters to go from one hose size to another.

I've got a GenRight Comp 23 gallon tank in mine. This is my 2nd GenRight tank. None of them are plug & Play... For the filler neck I had to just find a hose that would work but I did a 5" stretch on mine so I had very little room to play with.

 

[OffKamberTJ]

I don't know if anyone here has used the Motobilt tank yet.

For the Rollover valve line can't you just reduce it to one line?

As far as wiring goes you can download your FSM & a 2005-06 FEM & compare wires to figure out what you'll need to so.

For the vent line I'm not sure what you're asking. I've got a 97 so mine comes off the filler neck and connects to the tank. If it's a size difference you can get adapters to go from one hose size to another.

I've got a GenRight Comp 23 gallon tank in mine. This is my 2nd GenRight tank. None of them are plug & Play... For the filler neck I had to just find a hose that would work but I did a 5" stretch on mine so I had very little room to play with.

Okay, that makes sense. I can reduce a rollover valve to one line with connectors, I'll do some research on how to do that. I can probably do 3/8"s brass T connector to connect the lines and then have more hose connected to the T for the tank; correct me if I'm wrong. I think the size of the valve is -6AN 3/8"s. Wiring, makes sense to compare, thanks.

As far as the vent hose, let me see if I can explain it better. On the 2003, the vent hose is small and connects from the filler neck (not the filler hose) to the evap lines, as seen in the pictures. On the new tank, the vent hose connects directly to the tank and the filler neck, leaving that system out entirely from the evap lines. Hopefully you can see what I mean. What would I do about connecting the vent hose? How would I have to modify my stock system in order to make it work? If I get a new filler neck, that would leave the stock evap line disconnected from the evap lines and I don't think that would work. I don't think cutting the filler neck to adapt to it and finding a proper connector and sealant for it would work.

I'm trying to explain it, but it's hard! Sorry if that made it more confusing. I can add a little picture again.

 

[Wildman]

Okay, that makes sense. I can reduce a rollover valve to one line with connectors, I'll do some research on how to do that. I can probably do 3/8"s brass T connector to connect the lines and then have more hose connected to the T for the tank; correct me if I'm wrong. I think the size of the valve is -6AN 3/8"s. Wiring, makes sense to compare, thanks.

As far as the vent hose, let me see if I can explain it better. On the 2003, the vent hose is small and connects from the filler neck (not the filler hose) to the evap lines, as seen in the pictures. On the new tank, the vent hose connects directly to the tank and the filler neck, leaving that system out entirely from the evap lines. Hopefully you can see what I mean. What would I do about connecting the vent hose? How would I have to modify my stock system in order to make it work? If I get a new filler neck, that would leave the stock evap line disconnected from the evap lines and I don't think that would work. I don't think cutting the filler neck to adapt to it and finding a proper connector and sealant for it would work.

I'm trying to explain it, but it's hard! Sorry if that made it more confusing. I can add a little picture again.

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How about putting a T in the vent hose so it vents & goes to your EVAP system? Can only try it to see if it throws any codes. Or maybe hook the EVAP lines up to the rollover lines? Not sure which would work or be better/easier.

I just did a Hemi swap on mine and had to figure out how to get a EVAP system working well enough to make it not throw codes. Took me a few tries before I got it. On the 97 there is just a purge valve & charcoal canister.

 

[OffKamberTJ]

Never done that swap before...but here's what I would do:

Download the FSM - factory service manual in the resources section and look at section 8w and get familiar with the fuel pump wiring for your 2003 and 2005/06. You should be able to approximate things with wire colors and verify voltage and grounds.

Evap is seperate from rollover via a check ball so gas doesn't pour out. I'd buy a 2006 filler neck... here's a picture from Rock Auto and it appears to solve your smaller hose issue.

View attachment 611687

And I'd find whatever fittings and hoses were needed to plumb in the single evap. It's just engine vacuum sucking vapor into a charcoal cannister through a PCM controlled solenoid...nothing mysterious. Do make sure your solenoid isn't full of loose charcoal... that's what did mine in on my 97 and I ended up replacing both the charcoal cannister and solenoid.

Hopefully someone who's done this will chime in. All fixable problems!

-Mac

Hey Mac, thanks for your input. My TJ already has that style and size filler neck, the issue is finding a way to connect the larger vent hose from the new tank itself (a new feature, whereas the vent hose previously was connected to the evap lines itself, not the tank, liek the filler neck in the picture you sent has it), to the filler neck where it should be.

 

[OffKamberTJ]

How about putting a T in the vent hose so it vents & goes to your EVAP system? Can only try it to see if it throws any codes. Or maybe hook the EVAP lines up to the rollover lines? Not sure which would work or be better/easier.

I just did a Hemi swap on mine and had to figure out how to get a EVAP system working well enough to make it not throw codes. Took me a few tries before I got it. On the 97 there is just a purge valve & charcoal canister.

Hmm, I'm not sure I completely understand, but I can do some research and toy with the idea. Would connecting it to the rollover valve line cause any issues? Are they the same thing in the sense of evap, or would they be incompatible with what's flowing in the lines?

Hemi sawp is pretty nice, how are you liking it?

 

[macleanflood]

I wouldn't worry about integrating the vent hose into the evap system. It should not affect performance or codes.

I'd find fuel safe plastic fittings/reducers/bushings before I used brass. Brass is heavy. No other reason than race car...add lightness.

-Mac

 

[Wildman]

Hmm, I'm not sure I completely understand, but I can do some research and toy with the idea. Would connecting it to the rollover valve line cause any issues? Are they the same thing in the sense of evap, or would they be incompatible with what's flowing in the lines?

Hemi sawp is pretty nice, how are you liking it?

Don't know about the rollover valve if it'd work or not. But hooking into the vent line would work I'd think.

FSM are here: https://wranglertjforum.com/threads...ice-manuals-fsm-technical-documentation.4618/

The Hemi so far is a great swap. I had a 5.2 Magnum V-8 before that.

 

[OffKamberTJ]

I wouldn't worry about integrating the vent hose into the evap system. It should not affect performance or codes.

I'd find fuel safe plastic fittings/reducers/bushings before I used brass. Brass is heavy. No other reason than race car...add lightness.

-Mac

I personally would worry about the vent being connected to something, or else it’s emitting gasoline vapors, which aren’t good. An evap leak would throw a code and by assumption, this would be considered a leak by the ECM. I’m trying to get rid of the code from my old tank during this whole process, too. As far as a tee connector, I personally would go brass. It doesn’t add a lot of weight and it’s more reliable than a plastic, which is seen to erode time and time again (the plastic on my tank, which is supposed to be fuel safe, for example).

I’ve drawn up a draft of having one rollover valve, what that would require I do, but I’m thinking it might be possible to remove the aluminum cover/block that’s in the secondary rollover valve, and if that’s possible, I’m going to see if I can buy the brass -6AN rollover valve from the company. Not sure yet, but maybe.

 

[Wildman]

I personally would worry about the vent being connected to something, or else it’s emitting gasoline vapors, which aren’t good. An evap leak would throw a code and by assumption, this would be considered a leak by the ECM. I’m trying to get rid of the code from my old tank during this whole process, too. As far as a tee connector, I personally would go brass. It doesn’t add a lot of weight and it’s more reliable than a plastic, which is seen to erode time and time again (the plastic on my tank, which is supposed to be fuel safe, for example).

I’ve drawn up a draft of having one rollover valve, what that would require I do, but I’m thinking it might be possible to remove the aluminum cover/block that’s in the secondary rollover valve, and if that’s possible, I’m going to see if I can buy the brass -6AN rollover valve from the company. Not sure yet, but maybe.

I agree that you want everything hooked up. As far as I know if you didn't have the vent hooked up it won't see the vacuum needed and you'll get a code.
Now as far as the gas vapors being "bad" I'm not sure I totally agree but it's your rig so you do as you see fit.
And YES I agree I'd use brass too over plastic. I always seem to end up breaking some plastic tab or fitting.

Make sure to share what you come up with so others can see it. Might help someone else out at some point

 

[OffKamberTJ]

I'm back with a couple more questions, sorry folks. I was mistaken and the secondary valve I've been referring to in question is actually the Check Valve or the C/V. The Motobilt tank also has the ability for the aluminum cap to come off, but I'm not quite sure yet whether it will be able to connect to the C/V connector, and I read that the C/V must be connected in order for things to run properly (is that correct?). If this issue is solved, then I wouldn't need to connect the lines and configure my own system. However, this still leaves the filler neck and vent issue. I'm going to call Motobilt tomorrow to see if I can get some answers, but I wanted to do another updated post on here because I previously provided some wrong information, and I want to see if this offers some more understanding and I'm able to be guided in the right direction a bit. Thanks.

 

[sierradmax]

Revisiting this thread. I'm considering this tank for an 05 and I'm curious how you made out. Can you share a diagram for what you did with the EVAP, vents, and 2nd port on the motobilt tank?