Technical Gas tank/gauge ?

On my 61 Apache, the fuel tank is under the frame in the rear. I was told this tank was purchased from LMC. LMC only sells under the frame tanks for 1963-1966 C10's and not 1961. I believe that is why it does not have conventional straps holding it up. The sending unit that LMC sells along with this tank is also for a 1963-66 C10 not a 1961. Is there an ohms difference between a 1961 sending unit and a 1963-66? If so, that may be why my 1961 gauge does not work.
Does anyone sell universal straps for a fuel tank? The ones on this tank are the strapping that is used on a wooden pallet and need to be cut off and cant be reused.
Thanks

 

i believe the ohms range may be the same, GM changed around 1965?

what is the ohms on your current sender? is your sender grounded?

 

I am not getting any ohms reading on the current sender wire up at the gauge. There is a wire that is grounded that appears to be coming from the sender but I have to drop the tank to really find out whats what.

 

What do you mean by that, is it "infinite" ohms? like an open circuit?

or is it "zero" ohms? like a short circuit?

yeah, I know this electricity stuff is confusing...but we kind of need to know what you are seeing, since we can't look over your shoulder.

 

Squirrel/Jim, when I turn on my multi function meter and switch it to ohms, the display says 1, when I touch the two leads from the meter together it displays 00.3, when I ground the black lead and touch the red lead to the wire coming from the sending unit the displays says 1. So is that a short circuit?
Thanks

 

that is an open circuit. A short circuit is when you connect the two leads together.

so it sounds like the sender is not working, or the sender is not grounded, or the wire is broken somewhere. Pretty much means you have to pull the tank to fix it.

 

Yea that's what I was afraid of. I contacted LMC customer service and they said the sender that comes with that tank is 2-96 ohms, and I think my original gauge is rated 0-30 ohms. So they wouldn't work together, is that correct?

 

I believe your 0 to 30 is correct , at least it is for my 60 chevy. Gary

 

I put a newer tank in one of my old trucks, with the 90 ohm sender, and the original 30 ohm gauge. The gauge said Full until the tank got down to 1/3 full, then it went down normally, and E was really Empty. Since it was a 40 gallon tank, it worked out just fine.

also on a couple different old trucks I've used the variable resistor off an old 30 ohm sender, put on a newer sender in place of the 90 ohm resistor, and the gauge worked normally.

 

Squirrel/Jim, was it difficult to install the old 30 ohm resistor on the newer sending unit? I am thinking of taking the old resistor off the original sending unit and installing it on the newer sending unit once I test the old sending unit.

 

Cl***ic Chevy catalog says sender would be 30 ohms.

 

It's a bit tricky, you have to take stuff apart that wasn't really intended to be taken apart. There are little tabs holding the resistor to the tube ***embly, and the contact strap is riveted on at the resistor, and bolted at the connector at the top. I think I just cut the straps a bit long, and soldered them together. To get the wiper part out of the resistor requires removing the float, and carefully taking the float lever arm out thru the hole in the resistor.

but this is all from memory, it's been a few years. I've been cobbling together pieces from various broken sending units for old Chevys for decades.

If you buy a new sending unit to use the resistor, it may be stainless, and the strap may be stainless. That could make it more difficult to work on.

 

I finally found some strapping to replace my gas tank straps, so I lowered the tank and removed the sending unit and it is marked 30 ohms. When I connect the two leads to the sending unit(black to ground and red to the screw terminal on the unit) and the float is in the empty position the meter reads 00.6 as soon as I move the float up the meter reads infinity. Is this correct or should it be slowly moving up to 30 ohms to indicate a full tank?

 

It should be moving slowly up to 30 ohms to indicate a full tank.

The resistor unit is probably shot, but you can poke around with the ohm meter and see if you can find where the open circuit is.

 

Should move to 30 ohms as the float is moved towards full. Bad sending unit....

 

I got the sending unit to work, at least temporarily. With the sending unit hooked up to the trucks wiring and the float is in the empty position, when I turn on the key, the gauge needle pegs to full and does not move at all when moving the float. When I hook up my meter to the wire coming from the sender going into the fuse panel, the readings are normal 0.5-32 ohms. I will pull out the gauge, but do you think the problem is in the wiring from the fuse panel to the gauge or the gauge itself?

 

I would check the wiring first, but it could be the gauge itself. You can connect the "sender" terminal of the gauge to ground, and see if the gauge goes to E.

 

Jim, if the gauge goes to empty when grounded, does that indicate that is is functioning properly?

 

yes, it should go to E when the sender wire is grounded. If it does, then the gauge is probably ok, and the wire has a break in it somewhere.

 

Well I really screwed something up this time. I used a test light at the terminals going to the fuel gauge and shorted something out because I have no juice to the fuse box at all and the truck wont start. Is there a fusible link or something like that where I should be looking?

 

There might be, but it's hard to see it from here.

Maybe you could use the test light a bit more carefully, and follow power from the battery, and see how far it gets. Also check the ground connection on the battery.

 

I found an inline 30 amp fuse that blew, and a bad connection at the gauge. At the moment all seems to be working

 

is the gas gauge working now?

if so, congrats!

 

One of the terminal's screws on the back of the gauge was all butchered and glued because no threads were left. I switched out the gauge with one I had laying around and the gauge and sending unit are all working now. As always thanks for the help.

 

The fuel gauge was very erratic so I purchased a new sending unit from LMC. Attached is a picture of the top of the unit. My question is what kind of an electrical connector do you use on the pictured terminal? It is not threaded, although I tried running a die over it but it kept turning. Any ideas on the connector?

 

That's a factory-style 'bullet' connector, and they 'snap' into place. If you've turned this while trying to thread it, it may have broken the connection on the other end; make sure you check this.

 

there are two sizes of bullet connectors , measure it to be sure

they are: .156 and .177

 

Where can you purchase these bullet connectors? If I went to the junk yard where would I find this style connector?

 

These were usually used on engine sensors; GM and I think Mopar used 'em most, Ford not so much...

 

I looked up Bullet connectors on the internet and it looks like radio shack sells them. Thank for the help.