Gas tank replacement help

[vancelot69]

ok. The gas tank that was on my 1970 Jimmy when I bought it was all banged up and leaking from the inlet hose and the sending unit area, and the last time I drove it one of the straps that hold it on broke!

I got a replacement kit, and it only came with two j-bolts, but when I was taking the tank off, I noticed that the 7" squared u-bolt on the other side was in the wrong holes on the frame, so I was taking it off and it twisted the threads completely off and I can't find one of those ANYWHERE. I checked several auto parts stores, some hardware stores, and some spring shops that were supposed to be able to make custom equipment but nada. The only place I haven't checked yet is a junk yard, but I bet I'd find one just as ate up as mine was there.

I've been thinking of just using some regular bolts on it, and run a nut up it to hold it tight while tightening the nut on the strap. What I'm wondering about this is, typically when you cinch the straps up, doesn't it pull the edge of the tank flush up against the frame? Would having the extra nut in there holding the bolt be a problem since it wouldn't let the tank pull up flush?

On another note, I checked the thread about the curve in the stock metal inlet neck. I didn't realize it was brazed on and could be (or, was supposed to be) swapped to the new tank, so I went to a pipe & hose seller and got some reinforced fuel hose that I can bend around to how I want, although it won't retain shape (it's not flex hose), so I'm hoping that it will maintain and not get pinched on the body mount. Should I hold off and just go ahead and get the old curved neck put on the tank? Or, another thing I thought of is to cut the old neck off and use about a 6" piece of that hose to attach it to the neck stub on the new tank. In that thread though, someone said that would make it too long and it would hit the body mount. Any suggestions? Final thought on this is I was just going to try putting it on with the reinforced hose and hope it misses the body mount.

If anyone wants to see some pics, I can post them, just let me know.

Thanks for any help y'all can give me!

[71swb4x4]

I can't remember on the straps, but I do remember having the necks swapped. They wouldn't touch my old tank, so I had to take that one off but they did put it on the new tank since the new tank had never had gas in it. I had a radiator shop do mine.

[vancelot69]

So if I'm going to go that route, I need to do it before I put gas in it? Good advice. Reckon I need to go and mock it up and see if the reinforced hose will miss the body mount or not.

Another question I just thought of. On the tanks (both the old one and the new one) it had 3 vent tubes. I know the one goes to the filler neck, but when I took the old tank off, both of the other ones were plugged. I think I saw a diagram somewhere on this site (may have been another site, I can't remember) that showed one of them being plugged and showed putting a one-way check valve that lets air in for ventilation. I have just plugged them both because the truck ran fine with it like that on the old tank, but I was wondering what the proper way to connect them is.

[71jimmy]

If you haven't installed your new tank, take the extra time to remove the curved inlet pipe and install on your new tank. When I replaced my tank I did not do this at first, used marine grade gas hose that had wire wrapped inside to keep it from kinking, however I discovered after a while there was some rubbing going on around the body mount area. Nothing major but the next time I had to pull my tank I had the inlet pipe from my old tank put on, thankfully I kept that pipe.

You'll find that the old tank has the inlet pipe soldered, real easy to get off. The new tank with the short inlet pipe is brazed for some reason, I had to get a radiator shop to remove it. If the radiator shop is any good at what they do they will not have a problem removing or installing the pipe from a tank that had gas in it.

Welcome to the board.

[Yukon Jack]

Wouldn't it be nice if the new replacement tank had the correct inlet pipe - I can't think how many times I've seen posts about this problem. I too had to go the route of having my old tank inlet removed and put on my new tank.

Can you post a pic of the part you're needing to replace?

[vancelot69]

[vancelot69]

Edit:
I think I mentioned it in a previous post in this thread, but when I held the tank up to the frame, I noticed that the u-bolt was in the wrong two holes in the frame, so I was taking it off when the one side twisted completely off.

And, now that I think about it, those nuts were run up under the frame, so the old tank wasn't flush against the frame anyway, but I still wonder if that is correct or not.
/Edit

The new j-bolt is also in the first couple of pictures (I know, I'm Captain Obvious heh). I thought about just buying a couple more j-bolts for the other side, but when I put it next to the u-bolt, I noticed that the unthreaded area is LONG! I'm wondering if there's enough thread on it to cinch the straps up tight enough.

Also, which way to the j-bolts go on the '70 Jimmy? I was assuming the j goes to the top, in the frame, since getting to the nut between the tank and frame would be a bit difficult, but then again, if the j is to the top, where would it lean against to keep it from turning while tightening the nut on the bottom? If it hangs over the inside edge of the frame toward the tank, would it hang far enough to poke the tank?

[vancelot69]

A couple of people have told me to get a piece of allthread and bend it to the size of the old u-bolt. But again, I still wonder about how a nut between the lip of the gas tank and frame will affect it.

I found a radiator shop that said they could do it and took my tanks in yesterday. They said it may be a day or so before they could get to it, so hopefully I will get a call tomorrow saying it's ready.

[71swb4x4]

A spring shop should be able to make that U-bolt for you, no problem.

[69-72]

I would suggest using your old straps instead of the new ones. Thanks for the pictures of the U Bolt I will need to make one up for mine.

I am sorta in the process of swapping the fuel neck on mine. It is brazed on the new tank and is NOT fun at all to swap. You will need a oxy acetylene torch and some skills to get it done. After 2 hours of playing with a torch trying to get it all sealed I ended up with some stress cracks and some tiny holes. I decided that was a good time to stop and switch to JB weld to finish things up. Looks like it will hold though.

[vancelot69]

Using the old straps is going to be a little difficult. One of the original straps was missing and had been replaced with some kind of strap material with about 1/2" holes every 1/2" that 1. I'm not sure if I should try use it, and 2. I don't think I want to use. It also had one strap that I think was an original that had the hangar welded on one side, but that one broke a couple of weeks ago, so it can't be used.

[69-72]

Here is a set if you want to go this route

http://67-72chevytrucks.com/vboard/s...d.php?t=635728

[paul mora]

I do no remember exactly how I did it and it was on another truck. I just wend down to the store and got water heater strap kit and used that material to replace the old straps

[vancelot69]

The kit I bought came with straps, so I have those, it's just that it only came with two new j-bolts, and I broke the old u-bolt on the other side, so I need to figure out mounting bolt hardware. All of the options I can think of, they all have the same hiccup: having a nut between the tank lip and the frame making it impossible for the tank lip to pull up flush against the frame. Of course, when I took the old tank off, it had nuts between the frame and tank lip and it was working fine, but that doesn't mean it was original, the previous owner could have southern engineered it that way...

[mtully79]

I had the same issue when replacing my tank, I had to tighten down one side enough to be able to work with it. I was a pain in the a-- for a one-man job, maybe have a buddy give you a hand? After a while of fighting the tank it finally settled in just like the old one...keep with it.

Are you planning on running the charcoal line? If not be sure you vent a hole so when you fill it up at a gas station it won't spit up a few gallons of gas on your new sneakers like mine did!

[vancelot69]

I don't know if I'm planning on running a charcoal line... I got the new tank and saw there are 5 openings including the filler neck and the large sending unit hole. When I took the old tank off, it too had all of these holes. The filler neck and the line to the fuel pump were obviously connected, and the vent that goes back into the filler neck was connected, but the other two lines were just plugged. I don't know what to think of that because it ran fine. I saw a schematic, I think somewhere on this site, but I can't remember where, that showed to plug one of the vents and put a one-way check valve on the other to allow air in, but I wasn't thinking about doing that, only because it was running fine with them both plugged.

When I first got it, I tried putting some gas in, and the nozzle kept clicking off every couple seconds. I noticed that the filler inlet vent was leaking gas, so I replaced that. Then it seemed to take gas ok, but then I noticed it beginning to leak some gas on the filler neck rubber, and it was gushing gas out of the hole where the sending unit gets mounted. That's the main reason for getting a new tank, that and the old tank is all beat up and creased and could have small leaks in more places than what I've already seen.

Would it be possible for any of y'all to post a pic or two of your 1st gen Blazer/Jimmy gas tank mount bolts installed, stock or not, so I can get some more ideas on how to finish this project?

I saw a video where some fella was putting the sending unit into his gas tank, and he coated the fat O-ring with Vaseline or something similar. Is this something that you're supposed to do, or do you just put it in as-is with no coating?

Thanks!

[A1971Blazer]

It's raining here right now but I will get some pics for you as soon as I can.
Mine has the body off, but everything is still on the chassis.

[A1971Blazer]

here's a few

inside the frame rail..."u" bolt....driver's side

from underside........has nuts on top and bottom of straps to the "u" bolt

other side....has a crook on the end of each strap that fits thru the frame holes
and locks into place.

[vancelot69]

Thanks for the pics!

It looks like your tank is able to pull up flush against the frame. With the body off, it doesn't look like it's too hard to get a hand between the tank and the frame, so maybe getting "plain" bolts to replace the u-bolt I broke will work...

It looks like the u-bolt on your tank mount is in the outside frame holes, which is where mine was, but I thought that was wrong because the ends wouldn't be going through the holes in the lip of the tank. So now I wonder if I'm supposed to put the bolts through the tank lip holes or not...

[A1971Blazer]

I went for another look since it's dried up now.
The U bolt does not go thru the lip on the side of the tank on either side. The straps pull the lips up against the bottom of the frame rails to seat it in place.

You could use standard bolts by slipping them in from the top side and putting a nut to hold it in. Then use a nut and washer above and below the straps to tighten/adjust the tank into place. On mine it looks like there's room to do that since it's double nutted anyway.

Just need to be sure you get bolts that are fully threaded.

got a couple more pics.
you can kinda see where the u bolt comes thru the frame


there's some room between the top nut and the bottom of the frame rail.
(had to shade the sun with my hand)


hope this helps?

[vancelot69]

Yeah, that helps a lot, thanks!

The u-bolt on mine was in the outside holes on the frame just like yours is, and I'm pretty sure they were not going through the lip holes on the old tank just like yours. I don't remember how the side opposite the u-bolt was mounted, although I'm pretty sure the one remaining stock strap with the j part welded on was mounted just like yours, and I can only assume the one strap that was replaced was bolted in the outside frame hole and neither of them were going through the tank lip hole either. For some reason, I just got it in my head that the bolts needed to go through the lip holes, otherwise, what are those holes for anyway?

It also just dawned on me why my tank strap kit only came with two j-bolts: if you replace the original straps that came with the j part welded onto the strap, discarding the original strap you wouldn't have the j on that side, so you would need just two j-bolts for that side since you would likely reuse the u-bolt on the other side... unless you break it like I did haha. And, since the bolts are supposed to go through the outside holes on the frame, the j wouldn't be close enough to puncture the tank and would likely use the side of the frame, or the hole in front of it, as grip for tightening.

I love it when a plan (finally) comes together!

[vancelot69]

I've been searching threads regarding the vent lines on the gas tank. It seems like I should either get a charcoal canister, perhaps from a junk yard, or use a one-way check valve and just put it up high. Does anyone have any pictures of a one-way check valve? I went to a third-party motorcycle store this afternoon and asked about a one-way check valve for fuel, and he asked "for a dirt bike?" and I had no idea if that's what I needed, so he got one down and showed it to me, and at the time it looked kind of small (see pic - image is from Amazon, let me know if I'm not supposed to link stuff like that).

What are some of your thoughts?

[vancelot69]

Yesterday I was looking around again (internet and local hardware stores) and came SO close to finding the right size u-bolt... It is 3/8"-16 thread pitch x 7" wide x 3" long. Fastenal had a 6" wide 5" long one, and a local hardware store had a 7" wide one, but it had gigantic thread diameter, like 1/2" or something insane. I was thinking of seeing if Fastenal could order one, but after some more consideration, I think it would cost more to order a u-bolt than it would cost to get a couple of bolts and do it that way.

Then the other issue about the check valve or charcoal canister. I can't find that fuel system diagram I saw a few weeks ago, and I can't find any others that show what all the holes in my tank are supposed to go to. I'm tempted to just plug the two smaller vent lines since that's how the previous tank was set up and it seemed to run fine, and I'm not sure how well it took gas, I only ever tried to put gas in a couple of times, and both times I noticed inlet lines leaking gasoline so I attributed the constant clicking off to that and not improper ventilation, but I could be wrong. I want to get it back together so I can drive it! I guess I can go ahead and do it that way, and if I notice a problem, then reconsider the vent lines...

Thanks for the info, it really helped. I wound up taking my tank to a radiator shop to get the neck swapped, but they said they couldn't dispose of the old tank. So, anyone in Dallas / Ft. Worth know where I can dispose of an old gas tank?

[vancelot69]

So I'm impatient. I didn't want to wait for someone to order a u-bolt so I went ahead and got a couple of regular bolts and put the new gas tank in.

Then it wouldn't start.

At first, if I held the choke and had my son crank it over, it would act like it was going to catch, but then it would die out. I disconnected the fuel line at the carb and had him crank it over and barely any gas was spitting out.

So, something that crossed my mind is that the fuel hose on the sending unit is so old that I probably should have replaced it too, and putting it back on I may have split it somewhere and it's sucking more air than gas.

I was also wondering if the wires on the sending unit are only for the fuel gauge? And how do I get the gauge to be correct? I put in 15 gallons, which should put it at practically 3/4 of a tank, but the gauge is showing significantly less than 1/2 of a tank...

And does anyone know where I can dispose of the old gas tank? The radiator shop where I got the filler neck swapped said they couldn't do it.

Thanks again for the help!

[vancelot69]

Some pics of the new tank and bolts.