Dual tank solenoid valve

[tophat36]

D

im surprised your engine has a canister. do you have a VECI underhood on your air cleaner or your core support?

Thats Vehicle Emissions Control Information

Will have your vacuum routing and stuff probably on it ,and state what emissions your vehicle is compliant to

And does that mean your truck had a LE9 or LT9?

im surprised your engine has a canister. do you have a VECI underhood on your air cleaner or your core support?

Thats Vehicle Emissions Control Information

Will have your vacuum routing and stuff probably on it ,and state what emissions your vehicle is compliant to

And does that mean your truck had a LE9 or LT9?

Do you mean this? Literally everything on this truck is original. Nothing has been fiddled with from what I can tell.

And yes it’s an LT9 5.7L 350cid V8
3/4 ton HD chassis Camper Special
Assembled in Fremont, CA
1980 110k miles

Any of that mean anything important?

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[tophat36]

the lines would have met under the cab for the valve , only one set of fuel and return would go up to the fuel pump
the vent was most likely tied to each tank then your canister, unless your truck didnt have a canister originally (then it would be vented at the tank and you would have gas caps with a hole in them)

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This would be the vented gas cap 1980

I’ll look at the gas caps tonight. Cool info!

 

[tophat36]

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SMallest line is vent, next biggest is return. largest is supply

The vent on mine goes a short distance to a vent that looks like an axle vent

What is the one in the middle? Hard for me to tell sizes.

 

[AuroraGirl]

D


Do you mean this? Literally everything on this truck is original. Nothing has been fiddled with from what I can tell.

And yes it’s an LT9 5.7L 350cid V8
3/4 ton HD chassis Camper Special
Assembled in Fremont, CA
1980 110k miles

Any of that mean anything important?

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AHhh california, thats why, even the HD emissions there had to be canister.
Holy cow that diagram is scary! LOL

What is the one in the middle? Hard for me to tell sizes.

to me it looks like the return

 

[Grit dog]

Truck started with no connector. I switched the in cab switch to RH and it dropped to empty but continued to run. Switched it back to LH and no change. Looked at the valve under car and 4 of the 6 hoses are capped. Only 2 hoses go anywhere. I’m assuming this means that tank isn’t connected at all?

If you want to continue driving it, don’t look at or touch the cobbled up fuel system. Also nothing in the fuel switching circuits will cause a no crank situation. Dead battery or not. And depending on the type of switch/solenoid (forget now but some years pull constant power to keep solenoid on one tank and cut power to default to other tank) if yours requires constant power on the side you reconnected, it would potentially drain the battery slowly, not immediately.
If you want to fix the whole issue and get 2 vented/return line tanks working properly you have another significant project ahead of you.
Parts cost, you could replace the entire system tanks and senders included for under $500. A shop around here will get you about $1k just to drop tanks and clean/replace hoses. Not including what may be needing a new tank and whatever else.
You can however get new hoses and get them installed and routed correctly for both tanks. But you don’t know why the previous hackery was installed.

 

[Broken85]

3/8 hose for the supply
5/16 for the return
1/4 for the vent

You can run the vent through a 6 port Pollak valve if you want, but originally they were just T-ed together right next to the Pollak Valve and sent to the canister.

 

[tophat36]

If you want to continue driving it, don’t look at or touch the cobbled up fuel system. Also nothing in the fuel switching circuits will cause a no crank situation. Dead battery or not. And depending on the type of switch/solenoid (forget now but some years pull constant power to keep solenoid on one tank and cut power to default to other tank) if yours requires constant power on the side you reconnected, it would potentially drain the battery slowly, not immediately.
If you want to fix the whole issue and get 2 vented/return line tanks working properly you have another significant project ahead of you.
Back to my post a few days ago about $ spent on an old truck.
Do you have the ability to drop tanks, route hoses, replace tank/sender, test/verify switch and solenoid/valve?
Gotta gauge your love for this truck vs your ability, motivation and thickness of your wallet.
Example, the 77 I bought last year (for $7k). Previous owner did a lot of work to it. More accurately he paid to have a lot of work done.
Guessing/hoping he got it for free as it was his dad’s truck since new, but he handed me a stack of receipts for over $15k he had spent on it at repair shops. $1k of which was getting the dual tanks cleaned out and working. And that didn’t include any new tanks and only 1 sender.
I understand this truck a hobby for you as are most old cars and trucks for most people. Just trying to help you recognize/minimize the costs.

Oh i absolutely appreciate the “are you sure you want to get into this” heads up. While I learn as I go and don’t have a mechanical background, I feel very capable to do most things on the truck. I am an aerospace test engineer so im very comfortable but know my limitations. I would never touch the carburetor or really much other than mechanical systems. I don’t like electrical so I avoid that. I do all of this completely on my own, no friends or relatives that work on their cars so I lean on YouTube and this forum as my resource. It’s why I ask so many questions lol. I really do love my truck and am not super concerned about the return on investment. I also refuse to cut corners and use ****** parts. I’m not in a rush to get the truck done, it will never be done lol!

I would mostly likely just lift the bed and slide it back to drop the tanks.

 

[Broken85]

Oh i absolutely appreciate the “are you sure you want to get into this” heads up. While I learn as I go and don’t have a mechanical background, I feel very capable to do most things on the truck. I am an aerospace test engineer so im very comfortable but know my limitations. I would never touch the carburetor or really much other than mechanical systems. I don’t like electrical so I avoid that. I do all of this completely on my own, no friends or relatives that work on their cars so I lean on YouTube and this forum as my resource. It’s why I ask so many questions lol. I really do love my truck and am not super concerned about the return on investment. I also refuse to cut corners and use ****** parts. I’m not in a rush to get the truck done, it will never be done lol!

I would mostly likely just lift the bed and slide it back to drop the tanks.

You dont need to remove the bed to drop the tanks. There are 4 bolts on each of the 2 saddle mount attaching it to the frame. Unbolt both of them, and unbolt the fill neck from the fill door and the ground wire and the tank drops straight down. There will be the three hoses on top and the wire for the sending unit. Snip the hoses when you can get your hand in there since you will want to replace them anyway and unbolt the wire from the sender with a 3/8 wrench. The tank should be on the ground.

When you put them back up, replace each hose with about an extra foot of new hose so you can attach them while it is still low and you have plenty of room and then raise the tank back up and let the extra just sit on top of the tank. Make sure the bolts on the saddle mounts are welded to the back of the saddles before you put them back up. Some are, and some are not from the factory. If they aren't, try to weld them or JB weld them on there yourself if you don't have a welder. Having those nuts captured is like 90% of doing that job.

 

[legopnuematic]

There is no need or benefit to remove/lift the bed to drop the tanks on these trucks.

These trucks are very simple, but one of your best friends should be a factory service manual (not a Haynes or chilton manual) for your year truck, along with, if applicable, a unit repair manual. If you have not found them already, there is a small library in the reference section of this forum with pdf copies of that literature. Especially in the late 70s-early 80s era as there were quite a few changes over that period and one or two year type things that are not the same as earlier or later trucks.

Revamping the fuel system in a square isn’t really that expensive of a thing to do, about $100/tank, reuse the old senders if in good shape and still function, figure about 8 feet each of 3/8, 5/16, and 1/4” fuel hose, if needed new straps about $20/pair, the switching valve has the potential to be a bit of a pain due to the various types these trucks used and the varying availability of some of them.

But having a fuel system that is fresh and clean is absolutely worth it in my opinion.

 

[AuroraGirl]

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If your sending units release from the tank, you can save your tanks (assuming no leaks) some vinegar to clean them out if they are rusty

My original tank here, did not cooperate when i was trying to remove the sender, so the whole ring that retains it came out

 

[Broken85]

If your sending units release from the tank, you can save your tanks (assuming no leaks) some vinegar to clean them out if they are rusty

My original tank here, did not cooperate when i was trying to remove the sender, so the whole ring that retains it came out

$90 for a new tank is well worth it especially if you are replacing your EFI with a $1,500 sniper and two $500 pumps. Pollack valves are usually less than $100. Those tanks collect dirt right on top where the sending unit is and then retain moisture and rust like crazy seizing the ring to the tank. IT is thin metal so you dont get many swings with the hammer and chissle before they are shot . 50/50 if you can get the ring to budge without destroying it or the tank in my experience.

 

[Grit dog]

$90 for a new tank is well worth it especially if you are replacing your EFI with a $1,500 sniper and two $500 pumps. Pollack valves are usually less than $100. Those tanks collect dirt right on top where the sending unit is and then retain moisture and rust like crazy seizing the ring to the tank. IT is thin metal so you dont get many swings with the hammer and chissle before they are shot . 50/50 if you can get the ring to budge without destroying it or the tank in my experience.

Good point. Not a well thought out original design making a duck pond and mud collector on the fuel sender. Same with the plastic tank guards.
I didn’t do it on either of my squares but if I was using the trucks for work, I’d fashion a simple cover over the fuel senders to keep them cleaner and drier.
I just gave them a little corrosion protection.
As it is I’ve had to clean off the top of tanks and inside the tank guards a couple times on the one truck after hauling loads of mulch, manure etc. loader operator spilled between the bed and cab every time….lol

 

[tophat36]

If you want to continue driving it, don’t look at or touch the cobbled up fuel system. Also nothing in the fuel switching circuits will cause a no crank situation. Dead battery or not. And depending on the type of switch/solenoid (forget now but some years pull constant power to keep solenoid on one tank and cut power to default to other tank) if yours requires constant power on the side you reconnected, it would potentially drain the battery slowly, not immediately.
If you want to fix the whole issue and get 2 vented/return line tanks working properly you have another significant project ahead of you.
Parts cost, you could replace the entire system tanks and senders included for under $500. A shop around here will get you about $1k just to drop tanks and clean/replace hoses. Not including what may be needing a new tank and whatever else.
You can however get new hoses and get them installed and routed correctly for both tanks. But you don’t know why the previous hackery was installed.

I will be doing all the work on this truck myself. $500 seems reasonable to me.

 

[tophat36]

@AuroraGirl is this part of the fuel system too? Fuel filter?

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[tophat36]

There is no need or benefit to remove/lift the bed to drop the tanks on these trucks.

These trucks are very simple, but one of your best friends should be a factory service manual (not a Haynes or chilton manual) for your year truck, along with, if applicable, a unit repair manual. If you have not found them already, there is a small library in the reference section of this forum with pdf copies of that literature. Especially in the late 70s-early 80s era as there were quite a few changes over that period and one or two year type things that are not the same as earlier or later trucks.

Revamping the fuel system in a square isn’t really that expensive of a thing to do, about $100/tank, reuse the old senders if in good shape and still function, figure about 8 feet each of 3/8, 5/16, and 1/4” fuel hose, if needed new straps about $20/pair, the switching valve has the potential to be a bit of a pain due to the various types these trucks used and the varying availability of some of them.

But having a fuel system that is fresh and clean is absolutely worth it in my opinion.

Thank you, I do have this book. Is there a better one?

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