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Discussion Starter · #1 ·
Little project idea here guys. Ive got a 2.8 dmax canyon and it has been upgraded to no longer require def a while ago but now it sits with an empty 5.5gal tank in the back that could be used as an aux fuel tank imo. Thought process is i tap the power and ground to the pump and put in an inline switch somewhere in the cab. maybe in the glovebox or center console idk yet, then use the stock level sensor to read how full the tank is. For the fluid side i remove the stock hose for DEF and route a new one into a tee fitting that is cut inline for the filler neck.

when i am low on diesel i flip the switch, which turns on the pump, pumps down the aux tank into the main tank, and then when i read say 20% in the aux (the info pannel DEF level page) i shut it off gives me an additional 100 miles of range more or less.

Thoughts? anyone know if there is a way to mod the dashboard to read AUX level from the stock DEF level?

I havent really taken anything apart yet back there to see if i have always on power to the def tank pump but i assume i do somewhere i can tap into.
 

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Sounds a bit worm canny, but also could work. Wonder if the mil spec fuel tank is larger, id almostgo that route instead but maybe run some miles on your delete to make sure no issues first?
 

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Discussion Starter · #3 ·
I dont have any issues with the delete been good for a while. just interested in using the spare tank for something useful.
 

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I guess if its made of the right material, same as the fuel tank, it could work. Your question made me wonder about the military spec fuel tank and if its available to us civilians and if it would be installable on our civilian trucks. Keep us posted on the proj. I would assume its a far larger capacity than ours.
 

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Discussion Starter · #5 ·
Didn't know there was a difference. stock tank goes 500+ miles be surprised the military one for the IFV would be larger. kind of irrelevant as that vehicle has only started production a few months ago and its not like we can order parts from it anyway.
 

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Yeah im hypothesizing, its def a new thing and it may or may not be different. Having just been rodgering with my def tank on a recent issue i noticed a few things that could limit your idea.

The filler neck connection to the tank is pretty light duty and would likely need upgrading to keep seal to the tank, not sure if diesel fuel would kill the rinky dink connection and seal it uses. Also not sure the material of the filler neck itself, but the diameter might not be big enough to accept a fuel nozzle.

The pump module would be my next area of wonder, im sure it wouldnt handle or pump diesel well or for very long. I wonder if the diesel pump module is the same flange size so you could swap it with an oem diesel fuel pump.

The def tank has no drain. Youd have to install one somehow. I had to hand pump mine empty of def last week after getting some bad def.

It is however pretty easily accessible once you drop the spare. It doesnt look horrendous to remove the tank, as i was sizing it up for possible removal to fix my problem, thankfully didnt have to.
definitely interested to see what you come up with.

Another option would be finding a fuel cell that would fit the space there and installing it, could yield more than 5.4 gallons, but the $texas might kill that idea.

If you havent read road fever by tim cahill, check it out. It was a factory backed effort in early 90’s and they talk a bit about their truck and fuel tank setup for it. Not in any technical detail but interesting nonetheless. They carried 100 gals of diesel fuel.
 

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Discussion Starter · #7 ·
Yea i have alot of the same questions you do. diesel is fairly non corrosive as far as hydrocarbons go and i have to imagine if the tank is designed to handle ammonia it can handle some diesel. of course i could be way off base lol.

Some notes i have based on your comments;

The filler nozzle is too small for a pump nozzle to fit in, but i have a funnel i keep in the truck for additives anyway so that should be good enough for the 5 gal it holds.

i dont need to gravity drain the tank out i can hook the pump to a spare 12v battery and some speaker wire to jump the pump and pump it down to 0. gotta put a bucket under the end of the hose thats near the flex pipe at the front for the guys who still have the original hose installed. I did this to the fuel pump on my old rado gas tank and if i remember the pump has 4 wires. center two are for the pump and outter two are for the level gauge. i havent verified this the the def pump but as gm uses the same things for years across various vehicles i bet its close to this.

how weak the neck is at the tank connection.. we just gonna have to see if it fails 🤷‍♂️

I will probably post a videa and post here with what i come up with.
 

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Yeah, please do, curiosity has got my cat so to speak. Also seems like wouldnt be hard to get a second fuel filler neck and swap it in in place of the smaller def neck, or with some racing type fuel filler neck. Ive had to replace my def cap before and was dirt cheap, id imagine the cap needs some sort of venting, not sure if def cap has that or not. Your idea Could be crazy enough to work.

Grab that book if you can, short read, interesting as hell, maybe even avail as audio book. Was the record run at the time, but they ferried around darien gap. They didnt try to suffer and toil thru it as some do, it sounds borderline impossible and plenty hateful on four wheels.

Have a look at the tank connection, its pretty puny but looks easy to increase its soundness. The ammonia/urea is nasty stuff so it could be sound enough already in its materials. Its approx 22-25mm in ID.
 

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Discussion Starter · #11 ·
so my initial blind tests went poorly and i wasnt able to make it pump down on its own but that was because matching black ones to black ones and guessing around till i pop a fuse is way to lucky of a repair method haha.

I found the connector diagrams 19_ColoradoCanyon_Body_Builder_SM_U_2018AUG01.pdf (gmupfitter.com)

basically what i think i need to do is put pin 1 of X1 to a switch in the cab and then that switch to pin (1-3?) of X2 and short pin 4 of X1 to pin 5 of X2 and that should do it...

theoritically... I dont have a gauge this way :( maybe i figure a way to jump those back together... it shows "serial data" vs sensor data meaning i would need the reductant controller installed to encode the signal voltage to serial data for the BCM
 

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I’ve been thinking of turning my def tank into a camp shower unit. Figure it’s got a pump and maybe if even be able to use the heater somehow for some warm/hot water. Going to look into it hopefully this weekend. Good luck on the second fuel cell idea would be nice to flip a switch and go another 100mile.
 

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Discussion Starter · #13 ·
I’ve been thinking of turning my def tank into a camp shower unit. Figure it’s got a pump and maybe if even be able to use the heater somehow for some warm/hot water. Going to look into it hopefully this weekend. Good luck on the second fuel cell idea would be nice to flip a switch and go another 100mile.
not a terrible idea, however i would probably take the tank out to really scrub the tank and filler neck hard before i did that... let me know what you find trying to jump the pump started!
 

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not a terrible idea, however i would probably take the tank out to really scrub the tank and filler neck hard before i did that... let me know what you find trying to jump the pump started!
Oh I’ll for sure be cleaning it out once I see if it can actually work
 

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Discussion Starter · #15 ·
Looking for the "proper" connectors and think i may have found the male mating connector that goes to the input.

The input connector to the reductant controller is 2109441-4 : AMP MCP 2.8 Automotive Housings | TE Connectivity (MCP 2.8 from TE connectivity)
The input connector to the pump is Molex Connector Part Number - 33472-2006 (molex MX150 series)

I think the mating plug for MCP2.8 is 1-1564522-1 : AMP Automotive Housings | TE Connectivity (could be wrong here idk exact one)

Purchase the molex and the mating plug with some crimp pins for the connectors and 1mm wire and this could look like a factory job... theoretically.
 

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so my initial blind tests went poorly and i wasnt able to make it pump down on its own but that was because matching black ones to black ones and guessing around till i pop a fuse is way to lucky of a repair method haha.

I found the connector diagrams 19_ColoradoCanyon_Body_Builder_SM_U_2018AUG01.pdf (gmupfitter.com)

basically what i think i need to do is put pin 1 of X1 to a switch in the cab and then that switch to pin (1-3?) of X2 and short pin 4 of X1 to pin 5 of X2 and that should do it...

theoritically... I dont have a gauge this way :( maybe i figure a way to jump those back together... it shows "serial data" vs sensor data meaning i would need the reductant controller installed to encode the signal voltage to serial data for the BCM
Is this tank fuel resistant? "Coated" doesn't count. It was designed to hold essentially urea, which is obviously aqueous. I'm guessing that the tank is plastic (i.e. hydrocarbon) based, which might be problematic.
 

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Discussion Starter · #18 ·
Is this tank fuel resistant? "Coated" doesn't count. It was designed to hold essentially urea, which is obviously aqueous. I'm guessing that the tank is plastic (i.e. hydrocarbon) based, which might be problematic.
I agree bob its pushing the limits considering its design. However it appears to be the same plastic as what the diesel tank is made of other than the filler neck. if anything it might need the filler neck replaced and im not sure about any internal liner or what gasket is used for the pump. so far ive had diesel in the tank for a month and its not leaking... so thats good lol. it if fails it fails. ill just drain the tank down and remove it entirely. purchasing the connectors soon to start wireing up things.

I also think that the reason the wireing diagram shows smart pump 1/2/3 for the pins on the pump is because its a brushless DC pump instead of the older style simple 12v + and - that im used to. so i would need to wire a dc controller for brushless motors which apparently can be found on ebay for cheap. i can make up a little connector box simular to the one that it had stock with a dial to control flow speed or maybe just pin it on full and tuck the dial away. anyway ill post an update after i start putting parts together and see what happens.
 

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I agree bob its pushing the limits considering its design. However it appears to be the same plastic as what the diesel tank is made of other than the filler neck. if anything it might need the filler neck replaced and im not sure about any internal liner or what gasket is used for the pump. so far ive had diesel in the tank for a month and its not leaking... so thats good lol. it if fails it fails. ill just drain the tank down and remove it entirely. purchasing the connectors soon to start wireing up things.

I also think that the reason the wireing diagram shows smart pump 1/2/3 for the pins on the pump is because its a brushless DC pump instead of the older style simple 12v + and - that im used to. so i would need to wire a dc controller for brushless motors which apparently can be found on ebay for cheap. i can make up a little connector box simular to the one that it had stock with a dial to control flow speed or maybe just pin it on full and tuck the dial away. anyway ill post an update after i start putting parts together and see what happens.
Thx vogner. I stand better informed...
 
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