After market fuel tank sending unit

[ROKuberski]

When I got my car, the fuel tank and fuel sending unit were so rusty as to be unusable.  I bought a new gas tank and a new sending unit from Concours Parts.  The first sending unit gave erratic ohm readings and they sent a replacement. About this same time, I replaced the voltage regulator for the instruments.  It's a 5 volt unit mounted on the back of the instrument panel and it works properly and the temp gage works properly. 

Problem is that I can't get a correct reading on the fuel gage.  The gage on the instrument panel works properly, I tested it per the instructions in the original service manual.  When I called Concours Parts and told them that the sending unit had the wrong ohm range, they replied that the ohm range had nothing to do with a correct reading on the gage.  Well, that's pure BS, it has everything to do with getting a correct reading.  By adding a resistor, I've got my gage to give me a correct reading for an empty tank, but it is still wrong for a full tank. 

By using resistors, I have determined that to get an exact full reading it takes 3 ohms and an empty reading takes 21 ohms.  I know that it is not unusual for a gage to show more than F with a full tank and less than E for an empty tank.  I just recorded the readings for when the needle was exactly on the E & F.  The sending unit I have runs from 15 - 106 ohms.  Am I the only person with this problem?  Does anyone know of a source of a "correct" gas tank sending unit?

Thanks,

Rich

[RICH MUISE]

Mine appears to be working correctly, however I have not wanted to fill the tank yet. I haven't known exactly how much gas was left at the times I added fuel, but it can't be far off. The problem I have noticed is when I come to a stop, the gas gage needle waves back and forth at me from the gas sloshing back and forth. I'm not sure I should call it a problem, just something I've never encountered before.
The welding I did on the tank and the fact I'm not positive I have a non vented (it's a locking cap) gas cap is the reason I'm reluctant to fill it until after it's made it's rounds of the shops in the next few weeks for alighnment, etc.
Anyway, that was a long answer for a short question.  I got the sending unit I used from Tanks Inc to match the OHMS range of my gage.  YES, Concourse' comment about ohms not making a difference IS total bs, but I guess thinking about his answer, which ohms range it is doesn't make a difference.....as long as it has a matching gage.
The Tanks Inc sending unit's screw down mounting ring, btw, will not fit the oem tank with the locking ring. You will need to sacrafice an old sending unit that has a good top plate and merge that with the lower (inside the tank) components from the Tanks inc sending unit.

http://www.tanksinc.com/index.cfm/page/ptype=product/product_id=276/category_id=62/mode=prod/prd276.htm
Be sure to click on the "for more info click here"....just after the descriptive paragraphs.
According to their info, ford up to '86 used 73-10 ohms
I'm not sure why you have the 15-106 sending unit mentioned...do you have an aftermarket gage?
Rich

[ROKuberski]

Rich,

Thanks for the information.  My gage is original and seems to be working fine.  However, I don't thing it would give an accurate reading with73-10 ohm sending unit.  I guess I'll craw under the dash and do the test described in the service manual again.  They apply three volts directly to the meter and that should show about 1/2 tank.

I measured the depth of the tank and then made a minor bend in the arm to make sure that it would be laying on the bottom of the tank at the lower end of its range.  That may not be the right way to do this either.  When the fuel pump is sucking air, I'm sure that there is still some gas in the tank.  I'm going to stick a 10 ohm and 73 ohm resistor in the circuit and see what the meter shows.

I still have the defective sending unit and I could harvest the metal parts to mount another gage if that's what it takes.  I'll check into your link.

It sounds like you are driving your car?  Are you close to completion?

As to the needle moving when you come to a stop.  That seems odd.  The response time on the gas gage is pretty slow and I would think that it would not be able to respond quickly to a change in fuel float position.  I mounted my sending unit so that the arm of the float points to the side of the car, not towards the front or back.  My logic was that it would not have as much movement because of the slosh factor.   

Rich

[RICH MUISE]

Completion..no, but driving? yes. I've circled my neighborhood many times in the last few days. Tommorrow it's going into the alignment shop. He's an old school mechanic/alignment guy...gonna align it, get the R & P checked out/adjusted..kinda look around for anything that doesn't look right under there. I sure envy guys with lifts...just too hard anymore crawling under the car. Hopefully within the next week or so I'll have it in the exhaust shop. I was going to attempt the rest of the exhaust, but as I mentioned...too old. The mufflers are held on with baling wire at the back, just so I could drive it around. lol
I'm still needing back brakes also and shocks. limited funds available means probably into early next year before what I mentioned is done.
Rich...read the extra info on the Tanks inc site. It talks about things like if the float arm is mounted backwards, the gage will read backwards, in other words 0-100 is not the same as 100-0

[ROKuberski]

Rich,

My gage reads in the right direction, but I just don't have the correct ohm range.  I will work on that some more today.  If I can get a sending unit that is closer to what I need than the one I have, I will do that.  There are other things that you can do to.  For example, on a universal unit, you can use an arm on the float that is too long.  That will restrict the size of the arc that the float will travel, in effect changing the range.  You can only reduce the arc, that would decrease the ohms on the empty side and increase it on the full side.  And, by bending the arm, you can change where the reduced arc is in the modified range.  Something that I have thought about, but not done.  What I have done is to put a resistor in parallel with the gage and that decreases the ohms on the empty side of the range.  That way I could get an accurate reading for empty.  I will always know it is full when I leave the gas station.  I am also keeping a log of the mileage when I fill up and using a conservative number for MPG to estimate when I need to fill up.  Once, I put in 17.9 gallons in my 19 gallon tank.  That was very close to having to walk home.

Congratulations on being able to move under your own power.  That's a big step forward.  It sounds like you are really close.  We all look forward to a new batch of pictures.

Rich

[BWhitmore]

Several years ago I sent the original stock sending unit from my Ranchero to be rebuilt by John Wolf & Co in Willoughby, Ohio.  They asked me to send my gauge and gauge voltage regulator along with the sending unit so that when the sending unit was rebuilt thry could calibrate the sending unit with the gauge.  Worked out great and my gauge was accurate.  All these guys do is rebuild gauges and sending units.  Might be worth a try. 

[RICH MUISE]

I didn't word what I was trying to say very well. If Ford gages are in fact 73-10, yours may be working in the correct direction because your float arm is on backwards, in effect making it a
106-15 rather than the intended 15-106. That would put the higher ohms on the end where they needed to be, just not quite the right value.

[ROKuberski]

Rich,

The unit I bought was not a universal unit.  The arm was mounted and could not be changed.  See the picture.  The arm is not mounted in this photo.  As you can see, it is not a wirewound unit as the original ones were.  I assume that all the new ones are made like this one, but I haven't seen any other replacement units.

Rich