Converting auxiliary fuel tank to diesel.

Forest24551

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Joined
Jul 18, 2023
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26
Location
Forest VA
We recently took delivery of a 2024 Momentum 351 toy hauler and a 2024 GMC Denali diesel to tow it. Because we carry an electric golf cart the auxiliary fuel tank is useless to us with regard to it’s intended purpose. However, I would like to be able to carry extra diesel for the truck.
Today I removed the fuel filler neck and modified it to accept diesel fuel nozzles.( I understand that the tank manufacturer, ECI, actually makes a diesel filler neck but I have had a difficult time getting a price so decided to modify my existing filler neck)
I ordered an in-line combination particulate/water diesel filter which I will mount at the pump outlet. I also ordered two 20 foot 3/4 inch fuel hoses and the appropriate cam lock fitting to easily connect them together and to the to the existing fuel hose. This will provide plenty of length to reach the fuel fill on the truck when it is hooked to the truck. I also ordered caps and plugs for the extra hoses to prevent dust and dirt from entering them when they are stored. Total cost was about $250.
This will give us a total of 66 gallons of available diesel fuel for longer trips. Not only were the parts much less expensive than the cost of installing a larger aftermarket tank but the additional weight of the extra fuel will be carried by the trailer axles rather than the truck.
I will update when I receive the parts and get them assembled.
 
Personally I'd rather be carrying the extra weight in the truck rather than the trailer. With about 15 gallons of fuel, no water, and toys loaded we are sitting at a touch over 17,000 lbs., 14,400 lbs. of that on the trailer axles. Since you don't have the generator, you gain some of the weight back. But be aware the 351's gain weight fast.
 
We have a generator which has it’s own fuel tank. It has the 8k axles and disc brakes. When we weighed it on Cat scales with the golf cart aboard and it was well within limits on all axles but had more leeway with the trailer axles.
 
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We recently took delivery of a 2024 Momentum 351 toy hauler and a 2024 GMC Denali diesel to tow it. Because we carry an electric golf cart the auxiliary fuel tank is useless to us with regard to it’s intended purpose. However, I would like to be able to carry extra diesel for the truck.
Today I removed the fuel filler neck and modified it to accept diesel fuel nozzles.( I understand that the tank manufacturer, ECI, actually makes a diesel filler neck but I have had a difficult time getting a price so decided to modify my existing filler neck)
I ordered an in-line combination particulate/water diesel filter which I will mount at the pump outlet. I also ordered two 20 foot 3/4 inch fuel hoses and the appropriate cam lock fitting to easily connect them together and to the to the existing fuel hose. This will provide plenty of length to reach the fuel fill on the truck when it is hooked to the truck. I also ordered caps and plugs for the extra hoses to prevent dust and dirt from entering them when they are stored. Total cost was about $250.
This will give us a total of 66 gallons of available diesel fuel for longer trips. Not only were the parts much less expensive than the cost of installing a larger aftermarket tank but the additional weight of the extra fuel will be carried by the trailer axles rather than the truck.
I will update when I receive the parts and get them assembled.

Where did you get 66 gallons? I assume you must not have the genset, so did you pipe in the fuel lines that go to the front of the trailer into the tank with the pump, so you can use both to pump diesel? I have 2 tanks, one for genset, one for trailer, each are 30 gallons, so curious how you did it. Sounds like you were thorough too, please post pics if/when you can, curious to see what you have done. Where do you plan to keep the 40 feet of fuel hose and are you able to buy cam locking covers for the hose so where ever you keep it, bugs cant get into it, and the smell does not get out of it?
 
Where did you get 66 gallons? I assume you must not have the genset, so did you pipe in the fuel lines that go to the front of the trailer into the tank with the pump, so you can use both to pump diesel? I have 2 tanks, one for genset, one for trailer, each are 30 gallons, so curious how you did it. Sounds like you were thorough too, please post pics if/when you can, curious to see what you have done. Where do you plan to keep the 40 feet of fuel hose and are you able to buy cam locking covers for the hose so where ever you keep it, bugs cant get into it, and the smell does not get out of it?

I could be wrong, but I think what he is saying is 66 gallons total......the truck diesel tank, and the 30 gallon rear tank of the Toy hauler. I don't believe he is talking about using the 30 gallon tank that is for the generator.
 
You are correct. I should have been more specific. The truck holds 36 gallons. With the additional 30 gallons from the auxiliary tank on the trailer it gives me a total of 66 gallons. The separate 30 gallon tank which supplies gasoline to the generator is unchanged.
As far as storage goes, Cam Lock makes plugs which seal the female fittings and caps which seal the male fittings that are liquid tight. I will use those both to prevent dirt and critters from getting in and any drippage from fuel clinging to the interior walls leaking out. I plan on storing the two additional sections of hose in the truck bed when traveling.
I will be happy to post pictures when the parts arrive and I get them installed, hopefully by next week.
 
You are correct. I should have been more specific. The truck holds 36 gallons. With the additional 30 gallons from the auxiliary tank on the trailer it gives me a total of 66 gallons. The separate 30 gallon tank which supplies gasoline to the generator is unchanged.
As far as storage goes, Cam Lock makes plugs which seal the female fittings and caps which seal the male fittings that are liquid tight. I will use those both to prevent dirt and critters from getting in and any drippage from fuel clinging to the interior walls leaking out. I plan on storing the two additional sections of hose in the truck bed when traveling.
I will be happy to post pictures when the parts arrive and I get them installed, hopefully by next week.

One thing to keep in mind when you are depending on having "30" gallons of diesel in the trailer rear tank. It has been reported many times that you simply cannot get the 30 gallons out of that tank. The issue seems to be that the pick up tube in the tank sits off of the bottom of the tank and I've seen some people report that about the best they can do is maybe 23/24 gallons out of it......just a word to the wise.
 
You are correct. I should have been more specific. The truck holds 36 gallons. With the additional 30 gallons from the auxiliary tank on the trailer it gives me a total of 66 gallons. The separate 30 gallon tank which supplies gasoline to the generator is unchanged.
As far as storage goes, Cam Lock makes plugs which seal the female fittings and caps which seal the male fittings that are liquid tight. I will use those both to prevent dirt and critters from getting in and any drippage from fuel clinging to the interior walls leaking out. I plan on storing the two additional sections of hose in the truck bed when traveling.
I will be happy to post pictures when the parts arrive and I get them installed, hopefully by next week.

gotcha, thanks!
 
You are correct. I should have been more specific. The truck holds 36 gallons. With the additional 30 gallons from the auxiliary tank on the trailer it gives me a total of 66 gallons. The separate 30 gallon tank which supplies gasoline to the generator is unchanged.
As far as storage goes, Cam Lock makes plugs which seal the female fittings and caps which seal the male fittings that are liquid tight. I will use those both to prevent dirt and critters from getting in and any drippage from fuel clinging to the interior walls leaking out. I plan on storing the two additional sections of hose in the truck bed when traveling.
I will be happy to post pictures when the parts arrive and I get them installed, hopefully by next week.

At one time, I had thought about doing something similar to what you are doing. The big difference is that I have a F350 Dually with 5270 lbs of payload capacity and I felt that there was enough payload available on the truck to add a 60 gallon aux. tank in the bed of the truck. So between the aux. tank, and the truck's 37 1/2 gallon onboard tank, I can leave the house with approx. 95 gallons of diesel fuel. On our trip out west a couple of years ago, between the loaded Momentum's pin weight, the truck's crossbed toolbox, the aux. tank being full, and of course a fairly heavy B&W Companion 25K hitch in the bed, my truck weight came in at ~ 13,800 lbs.....a couple hundred under the GVWR of 14,000 lbs. Of course the longer we drove, the lighter the truck became because of fuel consumption.

The other, and bigger factor was that we sometimes haul our motorcycles with us, so the possible need for gas from the rear tank on the trailer was greater than the need for diesel for the truck.
 
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We have a generator which has it’s own fuel tank. It has the 8k axles and disc brakes. When we weighed it on Cat scales with the golf cart aboard and it was well within limits on all axles but had more leeway with the trailer axles.

You are correct. I should have been more specific. The truck holds 36 gallons. With the additional 30 gallons from the auxiliary tank on the trailer it gives me a total of 66 gallons. The separate 30 gallon tank which supplies gasoline to the generator is unchanged.
As far as storage goes, Cam Lock makes plugs which seal the female fittings and caps which seal the male fittings that are liquid tight. I will use those both to prevent dirt and critters from getting in and any drippage from fuel clinging to the interior walls leaking out. I plan on storing the two additional sections of hose in the truck bed when traveling.
I will be happy to post pictures when the parts arrive and I get them installed, hopefully by next week.

I agree, 95 gallons is better than 66 gallons. ��

[MENTION=56638]Forest24551[/MENTION] -

Here are a few forum tips that can be helpful in longer threads:

1) If you use "Reply With Quote" (to the right of "Reply") as I have here, folks will know to whom you are responding and that person will get a notification.

2) You can also tag folks using the "@" symbol and their user name (as I have done yours) - they'll also get a notification that way.

3) You can create a signature block with your RV and tow vehicle information (see mine below). That way you won't have to repeat that information whenever you post or ask a question - and others won't have to ask. You can create a signature by going to:

Forum Actions (on menu bar) -> Edit Profile -> Edit Signature (under My Settings on the left)

Rob
 
[MENTION=56638]Forest24551[/MENTION] -

Here are a few forum tips that can be helpful in longer threads:

1) If you use "Reply With Quote" (to the right of "Reply") as I have here, folks will know to whom you are responding and that person will get a notification.

2) You can also tag folks using the "@" symbol and their user name (as I have done yours) - they'll also get a notification that way.

3) You can create a signature block with your RV and tow vehicle information (see mine below). That way you won't have to repeat that information whenever you post or ask a question - and others won't have to ask. You can create a signature by going to:

Forum Actions (on menu bar) -> Edit Profile -> Edit Signature (under My Settings on the left)

Rob

Thanks for the tip!
 
We recently took delivery of a 2024 Momentum 351 toy hauler and a 2024 GMC Denali diesel to tow it. Because we carry an electric golf cart the auxiliary fuel tank is useless to us with regard to it’s intended purpose. However, I would like to be able to carry extra diesel for the truck.
Today I removed the fuel filler neck and modified it to accept diesel fuel nozzles.( I understand that the tank manufacturer, ECI, actually makes a diesel filler neck but I have had a difficult time getting a price so decided to modify my existing filler neck)
I ordered an in-line combination particulate/water diesel filter which I will mount at the pump outlet. I also ordered two 20 foot 3/4 inch fuel hoses and the appropriate cam lock fitting to easily connect them together and to the to the existing fuel hose. This will provide plenty of length to reach the fuel fill on the truck when it is hooked to the truck. I also ordered caps and plugs for the extra hoses to prevent dust and dirt from entering them when they are stored. Total cost was about $250.
This will give us a total of 66 gallons of available diesel fuel for longer trips. Not only were the parts much less expensive than the cost of installing a larger aftermarket tank but the additional weight of the extra fuel will be carried by the trailer axles rather than the truck.
I will update when I receive the parts and get them assembled.

Another thing to look into; the vent for that rear tank is on top and will vent out gasoline when it is filled too much. If I remember when I used my camera to view it, it does not have a filter. For gasoline, I believe it recommends no more than 80% fill to allow for expansion. I have no idea how much room is recommended for use as a diesel tank. If it allows for more liquid, I would lengthen or raise the vent hose so it wont spill out so easily. And as already noted, it was difficult to get 24 gallons of gasoline out of that tank. Lastly, fill it slow so it wont come rushing back out its full. I only did it once. :eek:
 
Another thing to look into; the vent for that rear tank is on top and will vent out gasoline when it is filled too much. If I remember when I used my camera to view it, it does not have a filter. For gasoline, I believe it recommends no more than 80% fill to allow for expansion. I have no idea how much room is recommended for use as a diesel tank. If it allows for more liquid, I would lengthen or raise the vent hose so it wont spill out so easily. And as already noted, it was difficult to get 24 gallons of gasoline out of that tank. Lastly, fill it slow so it wont come rushing back out its full. I only did it once. :eek:

Thanks! Will do.
 
�� Totally agree!

I went through 635 gallons of diesel back in 2021 when we took our trip out west to Grand Canyon, Zion, Bryce, and Moab, leaving from the Knoxville, TN area. My total fuel cost was right at $1800 for the entire trip. I paid as low as $2.49/gallon in the OK/TX area, all the way up to $3.98/gallon in Moab. Living where we live, diesel is now $3.94 to $3.99 a gallon, and I'm sure that same trip would probably be at least twice as expensive today for that much diesel fuel....635 gallons. Whew!
 
Having had a 40' Weekend Warrior toyhauler for Seadoos, I think you made an excellent decision to convert the tank to diesel.
 

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