3 gas tank switch

[acl]

My son just bought a 68 with factory 327. it has 3 gas tanks with a switch that say left right and main. the switch will rotate between these but not sure if it works. Replaced fuel pump and will start and run with pouring fuel in carb but then dies. We did put gas in and the gas gauge will not move when adjusting switch between tanks. Lots of snow on the ground and have not had chace to climb under, any thoughts to save me time and steps.
Thanks
Gary

[tsetsaf]

Carburetor First
I would check the carburetor first. Have you cleaned it thoroughly and checked for leaks? My 71 had the same problem when I went to pick it up; all it needed was a good cleaning and it fired right up.

Pick a Tank
I would start a troubleshoot using the cab tank only.

Fuel Filters and Lines
Inspect the lines, switch, and filters. Plan on replacing them as they are most likely old and rotted or dirty and clogged. The switch can be cleaned.

Get her running
With one tank connected to your clean carburetor via new lines and filters the truck should fire. If it does not, start looking for problems somewhere else.

[Wootdog]

Sounds like you have a camper special from back in the day. I bet the switch is on the left side under or to the left of the seat. Seen a few.
Kerry

[So.Cal.Super]

I have a 72 with 3 tanks and have recently replaced the fuel pump due to a leak and replaced all the lines for good maint.

couple of thoughts.
1. did you get the push rod back in when you replaced the fuel pump. this would cause the pump not to work?

2. look under the truck as soon as you can and see if all the tanks are connected to the selector valve. the previous owner had cut the side tank lines on mine when he removed the tanks to have them lined.

3. you should have a selector switch (mine is near the headlight pull knob) that says left, main, right, make sure that is set the same as the selector valve on the floor. my switch has a short I have yet to trouble shoot. when i select any tank other than main my fuel gauge goes haywire.

4. the carb. if its the factory q-jet you may want to check the in-line fuel filter in the carb.

5. when you can get under it check for a fuel filter after market installed.

6. did you re-connect the fuel lines? mine confused me for a moment because I wasn't familier with the vapor return system.

Hope this helps.

[El Jay]

I'm not trying to hijack the thread, but I have a '72 GMC w/ 2 tanks. The switching valve is frozen. Where can I find 1?

Thanx

[So.Cal.Super]

I'm not sure where to get one but mine was very stiff when I first got my truck from lack of use. I soaked it with Pb blaster. it has sort of an order if you have never used it so I made sure not to get any on the carpet. I love that stuff for anything thats stuck.

[Fishwacker]

Originally Posted by El Jay

I'm not trying to hijack the thread, but I have a '72 GMC w/ 2 tanks. The switching valve is frozen. Where can I find 1?

Thanx

Try soaking it in an equal part solution of distilled white vinegar and distilled water for awhile. You can speed things up a bit by heating the solution in a stainless steel pot but don't over do it. I.E. do not bring to a boil. This could damage the valve or any seals it might contain. There's also a great product called "Kroil" that works really well at freeing up stuck/frozen mechanisms but it's kind of on the pricey side. Good luck.

[68350]

I can't really help other than I have had about 3-4 trucks with the switch on the floor and none of them worked(I think most people resorted to one tank in the gas crunch days), so I only ran it off the in cab tank(main tank). I know you might want to use all 3, but it may be just easier to use the one and forget about the other 2.

[So.Cal.Super]

One thing I have noticed about using all 3 tanks. Since the Vapor return line only goes to the main cab tank I have to drain this tank first. the side tanks will actually refill the cab tanks as you drive. this has resulted it pushing gas out of the cab gas cap. and even with the cab tank empty it will blow vapors out of the cab gas cap and leave's a nice trail down the side of the bed. I replaced the gas cap on the cab tank but have not yet run the saddle tanks with the new cap on so i'm not sure if this problem is fixed.
But its worth it when I tow the buggy out to the desert. Except the $175 bill to fill all 3 tanks.

[El Jay]

Thanks, So.Cal.Super & Fishwacker,
I didn't wanna force it & have it break "between tanks", so I've just been running off the main tank. BTW, it was like this when I bought the truck, almost 2 yrs. ago.
I'm familiar w/ Aero Kroil. It's great stuff, but I haven't seen it since I left a previous employer 10 yrs. ago.
I still have a few friends there, maybe I can score a can, or 2.

Thanks again, guys.

El Jay.

[El Jay]

Originally Posted by So.Cal.Super

One thing I have noticed about using all 3 tanks. Since the Vapor return line only goes to the main cab tank I have to drain this tank first. the side tanks will actually refill the cab tanks as you drive. this has resulted it pushing gas out of the cab gas cap. and even with the cab tank empty it will blow vapors out of the cab gas cap and leave's a nice trail down the side of the bed. I replaced the gas cap on the cab tank but have not yet run the saddle tanks with the new cap on so i'm not sure if this problem is fixed.
But its worth it when I tow the buggy out to the desert. Except the $175 bill to fill all 3 tanks.

My switching valve has both the fuel lines & return lines on it. So the return line goes back to the same tank that the fuel pump is sucking outta.

I put saddle tanks (for 3 tanks, total) on my old Jimmy & had to install 2 switching valves, 1 for the fuel, 1 for the return.
When I switched tanks, I had to turn both valves.

For whatever that is worth to you.

[So.Cal.Super]

Originally Posted by El Jay

My switching valve has both the fuel lines & return lines on it. So the return line goes back to the same tank that the fuel pump is sucking outta.

I put saddle tanks (for 3 tanks, total) on my old Jimmy & had to install 2 switching valves, 1 for the fuel, 1 for the return.
When I switched tanks, I had to turn both valves.

For whatever that is worth to you.

As far as I can see, granted i've not had the bed off or the saddle tanks down to look at the top. Mine don't have a return inlet, just an outlet. And, my return line is piped directly into the cab tank. maybe I need to investigate more because this would fix the problem. Thanks El Jay.

[El Jay]

Originally Posted by So.Cal.Super

As far as I can see, granted i've not had the bed off or the saddle tanks down to look at the top. Mine don't have a return inlet, just an outlet. And, my return line is piped directly into the cab tank. maybe I need to investigate more because this would fix the problem. Thanks El Jay.

An anecdote, as an aside; when I would run all 3 tanks, I'd run out the saddle tanks 1st, & then switch to the main tank.
Well, we went on a camping trip, & unbeknownst to me, I broke the shaft on the return line valve. Everything was returning to the main tank.
I pulled into a convenience market for something & I had gasoline running out of the carbon canister, & all over the place.
I was thinkin' then, just like now, it's a damn miracle I didn't set the car on fire & burn every thing to the ground.
Aftere that, until I could get a replacement valve, I ran the main tank down 1st & then switched over to the saddle tank(s).

Just an incident that happened & maybe in the long run it'll save somebody some grief.
Car fires can't suck enuff!

[dazza]

I think I found a replacement for my original valve. It looks identical, including being all brass! See it here:

http://velvac.thomasnet.com/item/fue...60004?&seo=110

[haysonj]

I had one on a C30 and I didn't use one tank for a long time then when I did fill and use it the old gas had turn to varnish and plugged the valve. The valves can be taken apart and cleaned.

[Camper Power]

Originally Posted by So.Cal.Super

3. you should have a selector switch (mine is near the headlight pull knob) that says left, main, right, make sure that is set the same as the selector valve on the floor. my switch has a short I have yet to trouble shoot. when i select any tank other than main my fuel gauge goes haywire.

i never knew that the extra tanks were stock, i thought the guy befor me just built custom ones.just to clarify, they mount up inside the fenders just behind the cab right? dont know bout the return inlet and out let stuff is about, thats if it came in a 70. and if they r stock were would i find the switch socalsuper was talking about for the fuel guage.

srry but i dont know too much bout these trucks

[dazza]

I don't believe they came from the factory that way, but it was a dealer option. I recently pulled mine, cleaned it up, repainted it and got it working... had a bit of trouble with the sending units but all is well now.

I only have this and the main tank, behind the seat, with one return line going to it. I can switch or use either tank regardless of how much fuel is in them, but I don't know if this is different with three tanks.

Camper Power, the switch is just a toggle switch mounted under the dash, and yes, inside the fenders, behind the cab.

[CG]

I have three tanks in one of my parts truck. I thought about running the two spare tanks and removing the behind the seat tank. Is that a doable thing? I havent looked to see how it all hooks up yet.

[WorkinLonghorn]

Sure it's pretty easy.The only problem you might come across is the condition of the saddle tanks internally. They saw seldom use on any truck I'm sure,and condensation-caused rust makes one of mine unusable (clogs up the big extra fuel filter I have before the carb).I keep one with about 5 gallons in it for reserve,but I see no reason you couldn't lose the in-cab main if you cleaned up a good condition saddle tank.Mine never had sending units though,so I'd have to use the odometer as a gauge.

[Wreckless_71]

I don't mean to hijack the thread or anything but while we are on the subject... I am in the process of running my fuel lines for the stock tank and I'm not sure where the vapor return lines run to, on the engine side of the line? any help would be greatly appreciated. Thanks a ton.

[badpeanut]

I'm in the process of adding one old aftermarket saddle tank to my '72, so I'll share a few things:

• If you don't have to deal with the fuel return line on your truck, new manual switching units are available at many auto parts stores or throughhttp://www.nwmp.com. I couldn't find a manual switching unit that would handle a supply and return line so I went with an aftermarket electric unit that does. My saddle tank did not have a return line, but I added one and after hearing El Jay's story I'm glad I did.
• My '72 truck has a charcoal canister and non-vented gas cap on the in cab tank, but I'm going to use a vented gas cap on the auxilliary tank since it won't be plumbed in to the charcoal cansister.
• I chose to install a metallic body inline fuel filter between the saddle tank and switching unit per the switching unit manufacture's instructions even though many on this board don't recommend having one until after the pump.
• You may want to consider cleaning and sealing your saddle tanks. Many of the old ones (like mine) were raw steel so I'm looking at POR-15 Fuel Tank Sealer or the Eastwood kit.

[69CST20]

acl ??

Are you still here?
Can you (anyone) post a picture of the selector label for the 3 tanks ??
Ijust got a 1969 CST20 and cant seem to figure it out.


Thanks,

Mike..

[tsetsaf]

I don't have a picture of mine but it was a 3 way switch: left = driver side saddle tank, center = in cab tank, right = passenger side saddle tank. It is very easy to figure out; simply look underneath the cab at the switch. Trace the fuel hoses back to their respective tank.

[MusicMan70]

From my 70

[69CST20]

Thanks guys ..
I'm gonna have to crawl under the truck and check things out as soon as it stops raining, maybe in June or so ..

(I'm in Oregon)

Thanks again,

Mike..