Fuel Gauge Issues

As you can see in the picture mine is a little bent on top (and bottom). It's not flat on top like this picture you posted of an original 16 gallon tank:



I wonder if my bent tank could be affecting the accuracy of the sender?

morbank wrote:Doni, you asked about the tank size. I'm pretty sure I have a 16 gallon tank, 10 x 28 x 17 (see picture below)

Man, that tank looks like it had an explosion in it, why is it so puffed out top and bottom? Could be part of your problem.

Are you sure you got a 68,,,,,I would of thought that the 67 was the only 2nd Gen to have  the useless 16 gallon 1st gen gas tank,,,,,,however,,,,,,you got a GMC,,,,,,,,,,,I set this sending unit up 1/8" to mimic the bent top of your tank,,,so it was not flat like it should be,,,,and what do I see,,,,it forces the float down to read about 1/2,,,,,so it is CRITICAL that the sending unit is level to read correct,,,,,,

Thanks for that example Doni. That seems to explain my issue! Any thoughts on how I might bend the tank back into shape? I might just leave it if I don't have any other issues with it.

btw, I do have a '68. This 16 gallon original tank isn't original to my van. The previous owner had put on what I think was a Blazer tank (which I still have if anyone is interested).

So the straps fit that little 1st gen tank?  a radiator shop could bend  that top back in shape,,,,,BUT,,,,this sure seems familiar,,,,,,,,,,,GMC Jacke has a 1st Gen,,,,they put hot rod gauges in it,,,,,,stock sender dont work with it,,,,so they cut the arm off and cut another hole in it and put a universal fuel sender in it that did not work,,,,,,I ended up putting a $35 universal one in it to make things work,,,,,,,You could probably sell your rebuilt sender and buy a universal to make things better,,,,,,your gauge sure will read EMPTY real fast now and you wont really know how much gas you got left,,,,,,,



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Just straighten the 90 degree bend enough to get the rheostat to the top when it's full..... Two pairs of vicegrips on either side of the bend, straighten a bit and done!

I dont think so,,,,,,the tank, float, and rheostat are are a matched 8 1/2" set,,,,,you can't  change one and expect it to be accurate,,,,,here is like Clays bent pick up tube, causing the float to hit the top of the tank while the rheostat is about 1/2 its travel sending the 1/2 Full signal to the gauge,,,,I bent the float down so that the rheostat now sends a FULL signal to the gauge,,,,,,thats fine for FULL, but that throws off EMPTY,,,,,now, when tank is empty,,,,rheostat never gets below 1/4 so you run out of gas  when gauge reads 1/4.....all this Geometry is making my head hurt,,,,














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As said, any good radiator/tank shop could cut your tank open and hammer it back to shape and then weld/braze it back together. The shop I used to re-core my radiator showed me a similar vintage tank he was getting major dents out of by cutting the top open to be re-welded back later, a good experienced craftsman could do it.

Fuel senders have a  rule, which is that the pivot point of the float arm is 1/2 way down the tank so it reads accurately Empty to Full,,,,,and there are charts that take the dept of the tank and tell you where to put the pivot point and how long to make the arm so the float measures the gas level and converts it to an electrical signal to the dash gauge,,,,,and I would say the bent top twisted the pick up tube raising  the pivot point,,,,so its not EXACTLY in the middle of the tank now,,,,,but how about step on the tank to bend it flat,,,,or put a couple of flat bars on a threaded rod to try and bend it,,,,but I think putting another universal sender on it would be the cheapest way to go,,,,,  

If I have a chance this weekend I'll drop the tank again and see if I can flatten it out any and take a look at the sender as well and report back. Thanks for all the feedback!

Here is some kind of an idea,,,,,you might use a pipe wrench to HELP you if you step on the tank,,,but dont damage that hole,,,or you can make a sandwich with metal or wood and a big bolt or threaded rod to protect the hole while you try and make the tank flat again,,,,,,

Doni, I don't suppose you have any pictures or info about how the 16 gallon tank was held in place on a 2nd gen? Not the straps but how it fits inside the wells. I read that you recommended using 2 x 4's but that was with a non-original tank.

not me,,,,,,,I never seen a 1st Gen tank installed on a 2nd gen,,,,,,,we surely would like that larger 2nd gen tank on our 1st gens,,,,but it requires cutting off our crossmember and moving it forward so  the strap J bolts can connect to it,,,,,,how is yours held in place,,,,,that crossmember also serves as  the upper  saddle for the tank,,,,,,I take it that your crossmember is just sitting there lonely above the rear end,,,,,,a 67 which uses that little 16 gallon 1st Gen tank just has the crossmember moved closer to the rear bumper to squeeze against the tank,,,,thats the REAL way to mount the tank,,,,,now you can invent something to hold that little tank,,, IF,,,,,you are going to keep using it,,,,,I dont know about ripping out your crossmember,,,,,the correct bigger tank sure would be a better deal for you and fit right in there,,,,,,do you have the longer straps holding that tank,,,what do you got?

Yeah, when I got this tank I didn't know there were two different sizes. It does seem like the larger tank would be the better way to go but I'll probably just keep the 16 gallon until I can find a larger one. In the meantime I have the 16 gallon tank held in with straps (which I shortened) and 2 x 6 that I cut down as an extension between the tank and the saddles.

,,,one step at a time,,,,,,,you can adjust the float to work for EMPTY,,,,you really dont care if it ever reads FULL,,,,,just as long as EMPTY is correct,,,,,I guess the tank aint fallen off yet so your straps are holding,,,,,,,that will get you on the road until you come up with a better plan,,,,,,,do you have pictures of your set up?

Just an update on my tank situation...

I tried to bend my tank back into shape but ultimately I couldn't get it to work correctly with the sender so I've moved onto a 2nd gen 22 gallon tank (the one Vanny posted a link to last week). Looking forward to finally having a tank that just fits! However, I was wondering if anyone here knew what the length is for the 2nd gen tank straps? Or where to get some? There used to be a guy on eBay that was making them but I can't find him anymore.

When I lift this 22 gallon (2nd gen) tank into place the back end fits nicely into the rear cradle (closest to the rear bumper), but the front side of the tank tapers downward and therefore the tank sits below the front cradles. I can push the front end of the tank upwards so that it sits in the cradle but then the whole tank will be resting at an angle, which can’t be right. Am I missing something? How do I get the tank to sit snuggly in-between both the front and rear cradles?  

Doh, nevermind... It does fit. For some reason it was going in crooked before.

But with the tank sitting in the cradles, how do you access the J bolts that the straps connect to? The J bolts I have are too long to even fit with the tank in place. But even if they were shorter I'm not sure how to get to them as the crossmember is in the way.

,,,here is what a REAL one looks like,,,,,,,,,,,

Ok, that confirms it. I just discovered that there were holes for the J bolts on the back side of that crossmember. The smaller tank I was using was J bolted via the hole in the front cradles. That's why I was confused about how to get at the J bolts. All makes sense again. Thanks for the clarity Doni!

,,,,dont throw away that bent up 1st Gen gas tank,,,,,,,,,,

Don't worry, I still have the 1st gen. If anyone wants it let they can have it for free.

One more question about instilling the 2nd gen tank...

I'm having a hard time starting my van with the new tank installed. I'm pretty sure its because the senders fuel tube faces the opposite direction than the fuel line on the van (see image below):



I didn't want to bend the sender fuel tube but it seems like I'll have to to keep the hose from kinking. Any suggestions?

What if you just drill a new "thru hole" about where the sender fuel tube is pointing? Just seems obvious to me. I dunno.

Well,,,,,,,a REAL one points forward to the hole,,,,,,,,yours dont,,,,,must not be the right one or the pipe is loose pointing it the wrong way,,,,,,,,,,,you can try a longer hose and sneak up to the pipe from behind,,,,,,,cut the end off the pipe so it dont kink or try and drill another hole,,,,,,,