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Discussion Starter #1
I just installed an aux tank with aux fuel filter. Everything appears to be plumbed correctly but when I switch to the aux tank it dies at idle. If I mash on it I can keep it running but if I have to slow down or stop it dies. Here is how I set it up:

Aux tank behind rear bed w/ Pollak 6 port valve, Facett 7psi lift pump, and Racor filter. The lift valve is between the tank and the Racor filter. I tied the Pollak to the IP input and the return rail by the front passenger side of the IP. The other side of the Pollak go to the stock filter and stock tank return.

I put a sight glass (glass fuel filter) right before the IP input and a pressure gauge between the Racor filter and the Pollak valve. I also added a bleeder valve just before the pollak valve. I can see that I have a full 7 psi and the bleeder shows plenty of flow. Just to eliminate fuel volume I plumbed a spare in parallel and I have plenty gushing out.

Does anyone have any suggestion besides never stopping? 7 psi may be a bit low based on some of the threads I have read but it doesn't make sense to me that it runs under full throttle but not at idle. Also, it dies when the sight glass is still full so I know it isn't being starved.

Is there anything related to the return that I should consider?

I appreciate any suggestions. I'm stumped.:help:

Stauby
94 2500 6.5 TD Silverado
Stock longbed ext cab
 

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perhaps there is a fuel pump in your aux tank that died. lift pump should be on the frame rail and you'd probably need a second pump to move fuel out of the aux tank. assuming it's internal. just a guess ???
 

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sucking air thru line in worn spot in a bend that is hard to see maybe, aux tank pick up tube not fully submerged and drawing in fuel/aix, or valve not fully shifting and you are getting air or flow reduction with valve trying to pull from both tanks at same time via partially opened up valve, any way to bypass valve with slaved in temporary fuel hose and try direction from aux tank only, thus getting change over valve out of the possibility of what might be going wrong
 

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If there is a restriction somewhere in the return fuel to the aux tank, that could cause this problem. Can you check the return flow to the aux tank to make sure that you're getting fuel there? Also, you could tee in your gauge to the return line off the pump, and see if there is a pressure spike when you switch tanks.
 

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" behind rear bed " where is this loaction? In bed of truck ?

Also if you are switching tanks, you need a 6 port selecter
valve, 1 side for fuel in and 1 side for fuel return,

" returned fuel must go to same tank as source,
Also fuel cap must be same as OEM tank.

I added my tank , under bed where spare tire was,
use a fuel transfer method, with over flow(vent)
going back to aux tank, System appears as 1 LArge
tank . Would not work if aux tank higher than main tank.
 

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Discussion Starter #6
Problem solved!

The prize goes to Texas Diesel Guy. I had a 1/4" fitting in the return line and it was restricting the return flow. Once it was upsized the issue disappeared. Thanks to everyone for the suggestions!!!

Qwestqaz- sorry to not be more descriptive- I do have a 6 port valve and the tank is behind the rear axle under the bed. I am keeping mine separate because I plan on experimenting with alternate fuels and I always want the stock tank as a backup.

That's an interesting thought on the fuel cap - why would it affect the fuel flow? Assuming both are vented I would think it could draw just as well from either.

Thanks again to everyone. I was doubting the IP and am very happy to find it is something simple.

Stauby
 

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Some people have posted that a replacement fuel cap
from a gas engine has caused problems.

I chose to tie mine together to keep the PCM thinking it
has one tank, Plus I can run my aux tank dry without
causing air in lines....70 gallons total and almost ran out
of fuel, WIFE WAS GETTING REALLY P'O'd,

Let us know how the alternate fuel works...
 

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Stauby & qwestqaz,

If you don't mind, I'd like to ask you guys some questions about your auxliary fuel tank set up behind the read axle. I've been trying to come up with something similar, since I have a short bed truck and don't want to give up much room in the bed if I can help it.
  • Do you guys have pictures of your installation? List of parts used and sources?
  • What size tank did you use? Where did you buy it? I found this tank on line (http://www.1aauto.com/1A/GasTanks/ChevyTruck/Suburban/GM43B/8825) Would this work on a 2500HD short bed behind the axle? How about this one (http://www.1aauto.com/1A/GasTanks/ChevyTruck/Suburban/GM25A/8599)
  • Are you using any type of skid plate to protect the tank?
  • How did you attach the tank to the truck? Did you use OEM tank straps?
  • How did you plumb your fuel lines? Did you use an electric lift pump? What did you use for switching valve?
  • Did you use the OEM sending unit on the aux. tank?
  • How/where did you route the fuel filler neck? Did you use the OEM filler neck?
  • How/where did you mount your spare tire?
  • Any problems one should be on the lookout for?
  • Any additional comments and suggestions will be greatly apprciated.
I think this type of aux. tank installation could be a very popular mod, particularly on a short bed truck with only a 26 gallon OEM fuel tank.

Thanks in advance for your assistance.:)
-Ray
 

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ray, dually, don't carry a spare.

had tank made to my spec's, came with gage.
filler behind rear wheel , dually space,
no skid plate, tank is flush with trailer hitch 35 gal

electric pump, similar to oem.
i transfer fuel into the main vent line, ' below filler neck'
both tank vents plumbed together at filler necks
- if you overfill main it runs back to aux.

truck see's 1 big tank

no straps, angle iron and threaded rod, bolted too existing
frame holes

no selecting sw, just turn on aux fuel pump...
 

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Thanks qwestqaz.

Your system sounds like a good way to go.

May I ask where you had the tank built for you?

Do you by any chance have some pictures of your setup?

I'm definitely going to need to add more fuel capacity and an auxiliary tank behind the rear axle seems like the best way for me to go.
 

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No pictures, still waiting for a good sale on a camera.

E mail me private, and I can send the drawings that the vendor made, Will look up his name, also,
he is in perry Fl, makes the tool boxes, good ones.

I would check into a factory long bed tank to see if it fits,
I believe the Dmax lb tank is a direct swap for a short bed
tank, maybe same for older chevy's
 
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