Installing an Auxilliary Fuel Tank - (on single tank equipped RV)

Froggy1936 · July 27, 2011, 08:00 PM

Hi TJ I cant tell from the pics but the top of the tank has to be up against something (the frame or the floor ) and it needs insulators also (you can use wood spacers if the distance is large) a tank full of fuel will have a mind of its own on bumps fast stops turns, and acceleration. Look at how original is mounted . Frank

DaveVA78Chieftain · July 27, 2011, 08:20 PM

I agree with Frank on making sure the tank is secure. Also, like Winnebago did, you will need to install a sheet metal heat shield at the location of the fuel select valve to help prevent vapor lock.

Dave

Froggy1936 · July 27, 2011, 08:29 PM

Aluminum flashing makes a very good heat sheild and is easy to work with I used piggybacked hose clamps to hold it in place (wrapped all the way around frame ) Make shure you protect the live 12v terminal from the heat sheild Frank

Froggy1936 · July 27, 2011, 08:39 PM

You can see the flashing and the hose clamp The brake lines are under the flashing and i have never had a fade problem - Frank

LJ-TJ · July 27, 2011, 08:56 PM

Hey guys, good ones.

That's why I keep posting on this project. I figure out a lot but I miss lots to. Didn't think about protecting the fuel filters etc. Good one. Thanks. Here's a question. I don't want the fuel gauge to come on until I switch to the Aux tank. If I found one of those y conectors and put it on the aux pin of the switch and connected the sending unite wire to the aux side of the switch would the gauge then come on when I put the switch to the on aux side of the switch? Hm?

LJ-TJ · July 27, 2011, 10:22 PM

One last quick question before I button things up. I found some old 3" fire hose and was thinking I'd wrap the gas tank in it where the brackets rest on the tank and were the tank tighten's up to the under side of the frame of the motorhome. What do ya think? Good idea,bad idea. Thanks gang see ya at Jim's......I hope

Froggy1936 · July 28, 2011, 10:54 AM

EXCELLENT !!

DaveVA78Chieftain · July 28, 2011, 01:35 PM

Are you talking about the switch you posted in you pic (reply 2 on page 1)? Or are you talking about the style of switch that was in the pdf file I posted for reference?

Your picture looks like a Single Pole, Single Throw (SPST) switch. Would only control the selector (valve) switch.
A Double Pole, Single Throw (DPST) would control 2 circuits (selector valve switch / fuel gauge) with just on/off [I think this is what you asking for]
The Double Pole, Double Throw (DPDT) switch in the PDF treats one circuit as a ON/OFF switch (valve) and the other side as a Fuel gauge Tank Selector switch (either main or aux as input to the gauge)

On the pdf:
The 3 top connections are for gauge selection. The center post is either tied to the left post (main) or right post (aux) depending on switch position.
The 3 bottom connections are for the selector valve. The center post (B+) is connected to the right post when switch in AUX position. This applies B+ to the valve causing it to switch to AUX tank. THe left post has no connection so B+ would not be routed to anything when MAIN is selected.

Dave

LJ-TJ · July 28, 2011, 02:54 PM

Aaaaaa ok thanks Dave

LJ-TJ · July 28, 2011, 06:48 PM

Well I'm just finishing up and hope to post the final pic's later tonight. NO I haven't had a chance to drive her yet to see if all my efforts have been for not. Took many of your suggestions but here is probably the dumbest questions ever asked D:oH! . I've never had vapor lock. What is it? What does it feel like? How will I know if I have it and how do I fix it if it happens. You guys have been fantastic through this hole project. Thanks a million.

DaveVA78Chieftain · July 28, 2011, 07:36 PM

Gas in the fuel line gets heated by the exhaust and or engine heat until it vaporizes in the fuel line. The result is only a pressurized vapor is delivered to the caburator rather than a pressurized liquid. Thats the problem I have been fighting. I have a fuel an aftermarket fuel pressure guage mounted at the carb inlet with a clear view fuel filter just before that (all on top of the engine). After about 12 miles of driving the Fuel pressure gauge says 6lbs, which is normal, but the fuel filter bowl is empty. No gas getting to carb. I have an electric fuel pump mounted on the "outboard" side of the gas tanks. I have replaced all the fuel lines, routed outboard of the frame rails, except for the section from radiator up to carb. I will replace/reroute that also. I also have clear view filters on the input side of the tank selector valve. When the pump is running (fuel line at engine disconnected and feed into a gas can, it was looking like it may be sucking air. I dropped the tank and have cleaned most the junk out. I was hoping to pull the pickup tube out but the way it is installed I was not able to. I have been combing the web trying to find a universal gauge/pickup tube setup that will mount in the gauge hole but no joy yet. I may migrate to a Ford F100 TBI fuel pump which increases pressure to 12-14lbs and use a regulator. This whole situation has me looking seriously at performing a GM 454 TBI conversion. Now that I have looked at that option, I can see It is not really that hard to do. A big part of the vapor lock problem is the ethenol being added to the gas. The higher pressure fuel systems with TBI or TPI overcome most of the vaporlock issues. As you can see, vapor lock is a real pain in the toush.

Part of my problem is most likely do the fact I am running both dual exhaust pipes down the passenger side. Both mufflers are in the region of the original selector valve location (I have moved outboard with the fuel pump).

Dave

LJ-TJ · July 28, 2011, 08:29 PM

Wow! Thanks again Dave, So once you get vapor lock you pretty much have to just sit and wait for things to cool down. I can see were that can be a pain in the bum. I forgot to put a heat shield around the two fuel filters and the solonied so that will be the first project in the morning. Finish installing the fuel gauge and head down to the gas station and fill her up and see if there are any leeks. The drive around the block and see if the fuel pump will pick up the fuel in the new rear tank.

Froggy1936 · July 29, 2011, 11:11 AM

Vapor lock feels like running out of gas engine stumbles then quits and wont restart till cooled off (a real pain in the a-- if your in heavy traffic) wich is where it usually happens. slow speed (no air flow) I had that problem in Texas summer 08 very hot but just turning on my electric pump cured it immeadiatly (i do not run electric pump unless necc) The main mechanical pump does well since i installed elec pump by pass for mech pump (so it does not have to pull thru elec pump) but that required a one way valve so elec pump did not pump in circles. With fuel line dissconnected at carb and engine running mechanical pump at 6 lb press will fill gallon can in 10 seconds The elec pump with engine off will do even better at 8 lb press and 9 seconds i also ran all fuel lines on the outside of the frame - Frank

LJ-TJ · July 29, 2011, 12:47 PM

Wow now that's a sweet job. Thanks Frank. Well I finished up today. The pic's I'm posting are the final completed installation. What your looking at is the installation of the fuel tank and fuel line. The next pic should be of the fire hose wrapped around the tank. The next is the pic of the heat shield and location of it in relation to the muffler and exhaust pipe. Thanks for staying with me on this project guys. Now we fill up the tank and see if she leaks, and will draw from the aux tank. Wish me luck. W%

LJ-TJ · July 29, 2011, 12:53 PM

Heat shield made of Aluminum - the end.

DaveVA78Chieftain · July 29, 2011, 02:04 PM

The end? N:(

or the beginning of a new adventure? Y!

Looks good,
Dave

Froggy1936 · July 29, 2011, 03:22 PM

Oh O ! The end picture shows that the heat shield will not stop flowing heat from exaust and muffler. It needs a front plate to stop heat from entering tunnel where filters and valve live It can be pop riveted on Frank

LJ-TJ · July 29, 2011, 03:38 PM

OK Mate, will do.

RedneckExpress · September 16, 2011, 11:51 AM

Nice Job on the conversion I've been planning to graft a 30 gallon tank from a Ram Charger onto my truck to add an extra 30 gallons of fuel capacity and always like to learn more about the selector valves before I start unhooking things. The only catch is I have to find a dual line selector valve as the TBI Dodge engines have a return line that comes back to the tank. Upside is the old TBI's have a maximum fuel pressure of 18 PSI in the line, which makes working with rubber fuel line possible.

DaveVA78Chieftain · September 16, 2011, 04:19 PM

Here you go Redneck:
http://www.autozone.com/autozone/parts/Duralast-Fuel-Tank-Selector-Valve/_/N-8ve9x?counter=1&filterByKeyWord=fuel+selector+valve&fromString=search&itemIdentifier=18894_0_0_&newYmme=true

and the Installation instruction that goes with it
http://econtent.autozone.com:24999/znetcs/psb/en_US/2/00/1765/selector_valve_installation.pdf

The from engine path is the TBI rerturn line.

Connector that attaches to it:
http://www.autozone.com/autozone/parts/Duralast-Fuel-Tank-Selector-Valve-Connector/_/N-9na46?counter=0&filterByKeyWord=fuel+selector+valve&fromString=search&itemIdentifier=908_0_0_&newYmme=true

These are on EBAY, Amazon, and most likely O'Rileys has them to (or can order them).

Dave

RedneckExpress · September 16, 2011, 05:27 PM

Thanks

, it looks like that one uses the switch in the cab to change which pump motor has power, but workable.

LJ-TJ · September 16, 2011, 09:41 PM

Final note: But first thanks a million guys for all the help. The installation works like a dream. We can now run for 150 miles a tank. Sweet!