Delimas and Decisions 69 CJ Gas Tank

You have to match the sender to the gauge. Here is a list of some common values (from the VDO site I think):

Stewart Warner sender, 240 - 33 Ohms (most common aftermarket)
VDO sender 10 -180 Ohms
Beetle O.E. sender 73 -10 Ohms
GM sender (from 1965) 0 - 90 Ohms
GM sender (until 1965) 0 - 30 Ohms
Ford/AMC sender (up to 1986) 73 - 10 Ohms
late model Ford, (1987 and up) 16 - 158 Ohms

Trying to match a new sender to an old gauge can be tricky. Not only does the ohm range have to match, but the gauge's full/empty to sender's hi/low ohms relationship has to match as well. If the gauge is "looking" for 10 ohms empty, but your sender reads 10 ohms full, it won't work.

Original Jeep gauge wants to see 73 ohms empty, 10 full. The general standard for aftermarket "universal" gauges for auto and marine (boating) is 240 ohms empty, 33 ohms full. You can get a "universal" 240-33 sender kit from NAPA that can be adjusted to fit most tanks, but you'll have to use the gauge in the kit (or any other 240-33 gauge) to make it work. And regardless of what sender/gauge combo you want to use, you must give the gauge and sender good grounds!

Stan

 

Thanks for the good info.

I have found a universal sender from Summit that sends 70 empty and 10 full, but its 72 sheckels. I am going to shop around a bit to see if I can find one a bit more reasonable.

 

My 69 has both the under the seat and the 15 in the rear. Since the motor is out and I'm waiting for the machine shop to get it done I'm tackling the fuel system.
I removed a lot of the pumps and hoses today as they needed replacement. I think it was set up to run off the front tank and then pump from the rear into the front. Darned if I can figure how it worked and I'm not crazy about it anyway. The front tank vent was sealedwhich I found odd. There was a pump a filter and switch between the seats that input was from another pump under the the body. That pump had an input from each tank the output went up to the top pump and then to the motor.
Anyway, my thought is to just put two pumps one for each tank feeding into a tee and going to the motor. Run either one dry and just flip the switch to the other tank.
Am I thinking right at all?

 

Sounds like the front tank had to be sealed so when pumping from the rear to the front, it didn't pump it out the vent. If your going to use electric pumps, make sure they can run dry without hurting them. I believe the old autopulse units could do that. Not sure about what's available now

When you get it up and running, I would like to see how the rear tank was mounted.

 

But the front tank has to be vented or it is going to pull a vacume seems to me.
Anyway Barry, I am probably going to drop the rear tank cause I want to see what shape it is in. if you want come on down and watch and we can learn together.

 

How to do pumps and lines with two tanks

My 69 has both the under the seat and the 15 in the rear. Since the motor is out and I'm waiting for the machine shop to get it done I'm tackling the fuel system.
I removed a lot of the pumps and hoses today as they needed replacement. I think it was set up to run off the front tank and then pump from the rear into the front. Darned if I can figure how it worked and I'm not crazy about it anyway. The front tank vent was sealed which I found odd. There was a pump with one in and one out, a filter and switch between the seats with another pump under the the body. That pump had an input from each tank the output went up to the top pump and then to the motor.
Anyway, my thought is to just put two pumps one for each tank feeding into a tee and going to the motor. Run either one dry and just flip the switch to the other tank.
Am I thinking right at all?
How have you done it? Help, I want to get this done today.

 

I had an 78 Chevy K20 p/u with stock dual tanks. It used the stock pump on the motor, and an electrically operated switch valve under the truck that was fed by both tanks. Flip the switch and the fuel gauge would read the other tank and draw fuel from it. Always worked flawlessly. That was in high school and I was always flipping between tanks with a 1/8 fuel level!! If a guy could find one of those swithc valves I bet it could be adapted, and I would even bet the gauge could be made to work off between 2 senders as long as they were the same ohms.

 

I set this same thing up in the M715 last year when I put in two 19-gallon poly tanks. You can get the switch/valve at NAPA or JC Whitney. Seems to work well and is simple to plumb. Getting the gauge to work off both tanks takes a DPDT switch (as I recall). NAPA has those too. And yes, your senders would have to match the gauge requirements.

Stan