Hi all, new to this forum and welcome some comments, advice etc. Here goes. I have a 2010 GMC Sierra 4WD 6.0 liter with the manual/standard transmission. Tow vehicle we wanted for some time. bought it used and does everything I need. Anyway, sorry, back to eh help thing. I added an auxillary tank / box so we have extra gas with us where ever we go and to lengthen our possibilities of off the beaten path trips. my problem is that the "CHECK ENGINE" light comes on periodically when the gas in the extra tank gets down to less than half about 8 to 10 gallons. My theory, the extra air space in the aux tank is too large to allow the truck equipment to sufficiently maintain vacuum, so question at hand. Is there a way to add a vacuum pump, or something to strengthen what is already in the truck? We have had a smoke test done and already replaced a line that had a itty bitty leak, and double sealed around the fill neck. Gas cap is new and all works great. Anyone else with this issue? advice, etc????? Thanks from here and as always Good Luck & Be Safe ! ! !

How is the tank connected to the main fuel supply, In my research I was told I could not connect an auxiliary tank to the main fuel supply lines....

My aux tank auto fills main tank and I do not see this action. I have had bad fuel and chk eng light would come on at times. More when tank got lower vs full.

thanks for the replies. The aux tank sits in the bed, top inside of tank has a typical assembly on it with barbed hose fittings with tubes to the tank. The tubes connect to hoses, one to the pump and one to the vacuum side. hoses are fed through the bed into the original fill neck by an adapter with hose connections. So when the switch is flipped the fuel is pumped out of the aux tank into the neck of the fill for the truck. you can fill while driving or whatever. Thanks again and Good Luck & Be Safe ! ! !

Not sure of all the right teams, but when you leave you fuel cap off it will set off the ck light too. I think it has to do with all the emmision stuff on the newer trucks

All the caps are on and the aux cap is non vented but all tied into the main tank and plumbing assembly. Should be and is tight. not sure of how many cycles it makes before resetting the light. Good Luck & Be Safe ! ! !

Auxillary Fuel Tank | Good Sam Community

15 Replies

jffkrn
Explorer
Feb 28, 2014
Thanks all for the comments. We believe the problem has been resolved. The capacity in the tank, more empty than full, has a lot of "AIR" space, so when the fuel gets a bit lower it is more difficult of the vacumm to be maintained. then again, a re-seal of the gas caps seems to work as well. The check engine light has gone off on its own and all seems to be working well. The dealer, and my service adviser will work with me on this next time in the shop. Again, Thanks for all the comments. Good Luck & Be Safe ! ! !
MrWizard
Moderator
Feb 22, 2014
Moved from technology corner
mlts22
Explorer II
Feb 21, 2014
Transfer-Flow is one place that sells DOT rated tanks that are legal to use on the road.

I know DOT standards got a lot tighter these past few years... in the past, just a simple fuel pump between the two tanks would do the job, but now, there are other issues, and oftentimes, the only pump available for a pickup truck model is one that sits in the bed, and has its own fuel nozzle. To use it, one has to stop, pull the nozzle out, put it in the fuel filler receptacle and hit the pump lever like one does at a gas station.
Admin
Moderator
Feb 21, 2014
Moved to Technology Corner from General RVing for more responses

Admin
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jffkrn
Explorer
Feb 18, 2014
Tank is from KSK marine in Lake Havesu, also RDS makes one for gasoline. As far as the cap, I believe it is vented but short not like the ones we have on our vehicles. The gas is run through a pump and I have to use a switch to fill, it does not gravity feed. And, as far as running down the road for 50o or 600 miles before stopping, that don't happen either. we use it as additional fuel, if running low while driving I can flip a switch and keep on keeping on, but still stop at least every 2 hours max and get out and do the stretchy thing and usually bathroom stop or whatever. So thanks for the info, I will check on the cap thing as well. Good Luck& Be Safe ! ! !
buzzard616
Explorer
Feb 18, 2014
double post:S
buzzard616
Explorer
Feb 18, 2014
What tank are you running, Jeff? I have been looking but have yet to see a tank made by a company whose lawyers would allow it to be filled with gasoline.

Stu
64thunderbolt
Explorer II
Feb 18, 2014
That feed into your fill neck is illegal. Why not just add a transfer pump to the aux tank and top off the fact tank when needed. Or do you drive till they both need filled without stopping?
rodknocker
Explorer
Feb 18, 2014
Your aux tank also needs a vented cap, just as the main tank does. Also,gravity or siphon thru your transfer pump may be keeping the truck tank full or possibly level in the man tank is falling slower than the computer thinks it should which can throw a code. Mine would do this, with diesel, until I put a solenoid in line with the pump that opens when I turn the pump on, closes pump off. That stopped the fuel from flowing to the main tank all the time. Now fuel level goes up and down like the computer thinks it should.
wa8yxm
Explorer III
Feb 17, 2014
Get a reader and check the code. Without double checking. I think P0440# (440-449) is the Evaporative Emissions Control system, I think 445 is the most likely for a vacuum leak (Don't bother asking how I know this, NO I did not have one) same code you get when you forget to put the gas cap back on (not how I know it, but there was an On-Star commercial that featured that boo-boo).

(Ok, I'll tell you. There is a solenoid valve on my "new" towed that was sticky)
(Plus I have a low end reader, it just gives me the codes, so I naturally have a PDF file on the hard drive... And I searched it).