Well, I had a good weekend going to 3 cruise-ins, Hoover, Decatur, and Gurley, Al trying to get flyers out for our Ardmore Car Show in August. I probably put about 400 miles on my truck with no problems until Sunday morning when I was carrying her to put her up in the stable in town. The truck died on me at a local watering hole(I was just passing by but a great place to break down at he he) and I have just fought with the cheapo 12v in line fuel pump saga over the last month and I assumed that was my problem again. Well, I did check the gas in my tank and I could and hear gas in there (my tank is in the back and filler thru the bed). I again assumed that the dern pump went out but it was pumping. Well no worries, after the last time ole dad here had a spare. I flopped under the truck and changed her out and celebrated the victory(assumed) with a cool pop(in the local watering hole and it was after 12 o'clock). So after I quinched my thrist, I tried to get on down the road well it would not crank, still no gas. Getting hot now, so here I flopped back under there this time checking the gas supply line to the pump and no gas. What the heck? I gave it a blow test and nothing but air. I was out of gas. I felt like I didn't deserve the joy of driving that day. I just so happened put a gas tank in the bed to go and cut grass later that day so I was covered. The crowd that converged by that time was very amused and vocal at me (drunk idiots). Well I learned a lesson don't trust what you assumed and check everything under the trunk when your there.

Now, a question. I am running a new 1970 mustang tank and sending unit to VDO gauges on the truck. My gas gauge has never worked properly. I verified I have proper ground and voltage with no shorts to the gauge and sending unit. When I install the sender in the tank, I again assumed that I put it in right, but I have been wrong before. Has anyone dealt with this type of tank and gauge before and did you experience any issues? Thanks for any help.

 

I am running the 70 mustang tank and the VDO 240-33 sender. I haven't connected a gauge yet, but I don't expect problems..

what gauge are you running, and does it match the sender range?

We had this problem on my sons 66 chevy, we 'assumed' the under bed tank sender matched the gauge.. (we ordered it from one of the top chevy truck places, so you'd a thouhght!) uh, no..

Sam

 

not to put salt in a wound, but being married to an English teacher, it's actually:
"I am an idiot."
in case you're concerned with such particulars...

I too plan to do this tank and am taking notes. thanks for the segway into a tech question; it was a nice scenic route.

JML

if you can't laugh at yourself, who can you laugh at?

 

ALL of us have worn that hat at one time or another . last week i ran outta gas as my gauge quit working a while ago and it and the speedo are waitng till i park it to rewire . well i carry a yardstick for a gauge and i didnt check it like i should and ran out just as i pulled into the lot at work ........... thank god noone was there yet .........

 

Recognition is the first step towards recovery.

 

In the words of Carl Childress "Ain't got no gas in it"

Seriously, we've ALL been there

 

If the VDO gauge is for a Mustang and the sending unit is 70 Mustang it should work fine but if the sender is Mustang and gauge is for something else (like Sam's 240-33) it won't work. The sender and gauge HAVE to match...

 

First, don't feel bad, we've all done something like that. I spent all the time I could afford on the panel chasing an overheating problem. I visited every board looking for advice, following most of it. I flush the engine three times, change radiators, checked timing a few times, everything I could think of. Turns out the sending unit were shot. Put in after market mechanical gauges and the engine doesn't overheat, imagine that.

Second, I also am running a mixture of gas guage and sending unit. The gauge is '48-50 stock and the tank/sending unit is out of early '90s diesel big Ford truck. When I first hooked up the gauge it pegged out pass "Full". Did a lot of asking, here and an electrical engineer friend. It turns out I had to install a resistor in the wire going from the gauge to the sending unit and another shunt resistor across the two posts on the gauge. It might not be exactly accurate but at least I know about how much fuel I have in the tank and know to play it safe I need to get gas when it gets around a 1/4 tank.

 

Ford makes 2 different fuel sending units that I know of. A 73-10 ohms and 20-150 ohms. The first number being the resistance of the sender when empty and the second when full.

Rick

 

This might be some help:

 

Bob,

Do you mind sharing what exact resistors you put in?

 

I'll have to crawl under the dash to measure them. I forgot what I used.

 

Here we go again with all the electrical calculus on gas gauge sending units.

Long frustrating story short: The sending unit has to be made by and be matched to the gauge - period. Even if you find something with electrical values that are close, it will not be accurate.

Also, you need check to make sure the swing of the float arm has full range of motion. For example: is it sitting on the bottom of the dry tank in the quarter full position.

Try this. Take the sending unit out. Measure the depth of the tank from the sending unit opening to the bottom. Cover the hole in the tank where it was. Get a cardboard box. Draw a line on the vertical face of the of the box that is the distance of the depth of the tank . Tape the sending unit in place with masking tape on the top of the box with the float hanging over the edge as though it were mounted on the top of the tank.

Now, turn on your ignition and position the float arm to it's uppermost limit. Does the float go above the top of the box, or stay below? What does the gauge read. Next draw a line half way between the other top of th ebox and the line that is simulating th ebottom of your tank. Move the center of the float onto that line and read the gauge. It should read half full. Next move the float so th efloat arm rests on its lower stop. Will it go all the way down or does the float hit the ground before the arm gets to the stop? What does the gauge read - should be on empty.

If the float hits th eground before the arm gets to the lower stop, it's sitting on the empty tank bottom and reading there is still gas in the tank. Adjust this by CAREFULLY bending the arm up slightly until the float is 1" above the ground when at the lower stop. That will give you a 2 gallon reserve when the gauge reads empty. After adjusting the arm, try the readings in the various positions a few times. Be sure to let the gauge settle when moving the arm - may take up to 2-3 minutes.

If the gauge does not read "Full," "Half Full," and "Empty" on the when at the upper stop, midway line, or lower stop (respectively), the sending unit IS NOT compatible with the gauge and you have to buy one that is. Get it directly from the manufacturer of the gauge. If the mounting plate is different, there are, or you can make, adaptors. You can also shorten or lengthen the float arm if necessary.

Trust me - it will take less time, and cause a lot less heart ache (and drunken laughter from the side of the road) than trying to use resistors, phases of the moon, Voodo, and other units you are trying to MAKE WORK - they won't.

A fellow "A Idiot" (tee hee)

J!

 

Cardboard box!... Sheesh, such a simple idea..

thanks.. another tool..

Sam

 

I did measure the depth of my tank. I laid the sending unit on it's side, marked the top even with the plate of the sending unit, and made a mark representing the bottom of the tank. I then moved the float through the entire range, E, 1/4,1/2,3/4,F and watched the reaction of the gage. It took some time but I was able to get it to register pretty close. I also would position the float in the above increments and left it sit in each position for 15 minutes to make sure it wouldn't creep up or down. I am very satisfied with the results. It might not be 100% correct but at least I know I have gas in the tank.

I would have used the original type sending unit but when I moved the holes and filler neck in the tank to fit the truck I didn't realize the sending unit wouldn't easily work with the stock gage. I would have also made an adapter but the tank sending unit had a smaller hole and I couldn't get the stock float through. I couldn't see a way of combining the two sending units together to make one that would work.