Tanks Inc or Holley EFI fuel tank sender not reading right

[smh00n 87]

I have the Holley Sniper EFI 22 gallon fuel tank which is actually made by Tanks Inc.

The sender does not read full when in the tank. I currently have roughly 2/3 of a tank of fuel in it but the sender is reading 1/3 and is dropping as you'd expect with consumption.

I checked the numbers and its reading more than the 73-10 Ohms it needs. Full is well over 90 Ohms and empty is close to zero. So I'm unsure if this will affect the operation. Out of the tank, putting the rheostat to highest point the gauge just reads well over full. Empty, is well, empty.

Now here's the problem - I test the gauge out of the tank with the float fitted. Full on the sender gives full on the gauge. Empty gives empty. Halfway, roughly half.But when I install it it reads 1/3 tank with the 2/3 tank fuel level. I've driven it and as above it is dropping as gas is guzzled.

I don't know why it is reading so low when installed in the tank.

So far I have:

• Checked tank height and adjusted the float to min and max on the bench using a ruler
• Full reads 10.5 Ohms
• about 3/4" below the tank bottom I have 73 Ohms so I have some reserve gas when the gauge says empty
• The fuel tank is 9" deep, I have 3" gap to fuel level = 2/3 tank of fuel
• Rheostat is fitted correctly
• the float floats, both by itself and on the sender arm
• I tested the sender in a bucket of water. Floats, Ohms change as the sender moves

I emailed Tanks Inc about it. Their reply was quote Ford using 2 different kinds of 73 - 10 Ohm scales, one was linear where the scales changed equally across the sender range and the other was non-linear where the sending unit worked at 10 Ohms full, half tank was 25 Ohms and empty was 50 Ohms with everything else than 50 moving the gauge further below the E unquote.

He has a linear sender https://www.tanksinc.com/index.cfm/page/ptype=product/product_id=346/category_id=-1/mode=prod/prd346.htm which is a non-linear sender but it costs 98 bucks. Plus shipping, plus exchange rate for us, etc.

So, has anyone come across this and whats the fix? I see the logic in the quote above, but surely not every 1970 Mustang had 2 different fuel senders/gauges fitted depending on where they were built?

[Midlife 814]

That's BS.  No change in Ford gauge and sending unit resistance until well after 1973.

[smh00n 87]

Thanks. I was hoping you'd pop in.

So is there an answer? It's just got me beat why it reads fine out of the tank but not in the tank. 

No obstruction I can see, floating and it is dropping so something is happening

[Midlife 814]

Is the sender correct for a 22 gallon tank?  Is your gauge a factory Ford gauge?

[smh00n 87]

No, its a full Tanks Inc tank. So it is a 22 gal tank with the universal style sender that you adjust for height, pictured below.

The only thing I can figure is that somehow I have not assembled the sender correctly but I have checked 3 times, watched videos, scratched myself and I am sure it is correct.

The gauge is OEM. I've never driven the car a lot so I don't know if it works proper, BUT when manually moving the float the gauge shows full to empty and points in between.

[aslanefe 333]

2 hours ago, smh00n said:

22 gal tank with universal style sender that you adjust for height

No experience with that specific tank and sender but; you adjusted the height of the sender,  does the length of the float arm need adjustment too? It looks to me that if it is  universal, the float arm also needs to have the right length for that tank to read correct.

[smh00n 87]

Thats an unknown I am considering. All the videos I have seen cut them short.

But, I have set the sender up so that the float has the correct Ohms according to the specs; 10 at full and 73 at empty. So regardless of the length now it is reading correct.

 

[aslanefe 333]

21 minutes ago, smh00n said:

Thats an unknown I am considering. All the videos I have seen cut them short.

But, I have set the sender up so that the float has the correct Ohms according to the specs; 10 at full and 73 at empty. So regardless of the length now it is reading correct.

 

But if the arm is too long, it is not going to 10 ohms when the tank is full, if it s too short, it is going to 10 ohms before the tank is full; same thing for low fuel. The float is going to hit top or bottom of the tank but the rheostat is not going to reach the limits. When you move the float on the bench, you are hitting the limits of the rheostat because the top and bottom of the tank is not stopping the float and preventing the rheostat reaching it's limits. Does that make sense?  I am just thinking out loud.

[smh00n 87]

makes sense. But, I have set the float arm and the rheostat to where it reads the correct full and empty Ohm readings based on the interior height of the tank. I did this using a ruler so it's not perfect but close.So at where I estimate the full level would be it reads correct Ohms. Maybe I am an inch out, but that should still show over 1/2 tank, not 1/3.

I will try moving the rheostat one way and another see what it does. I can't figure out why it only shows 1/3 tank when it has 2/3 of fuel in it. I work this out using a 9 3/4" deep tank, fuel level is currently 3" down from top = 2/3 tank of gas.

[aslanefe 333]

13 minutes ago, smh00n said:

makes sense. But, I have set the float arm and the rheostat to where it reads the correct full and empty Ohm readings based on the interior height of the tank. I did this using a ruler so it's not perfect but close.So at where I estimate the full level would be it reads correct Ohms. Maybe I am an inch out, but that should still show over 1/2 tank, not 1/3.

I will try moving the rheostat one way and another see what it does. I can't figure out why it only shows 1/3 tank when it has 2/3 of fuel in it. I work this out using a 9 3/4" deep tank, fuel level is currently 3" down from top = 2/3 tank of gas.

Is the cross section of the tank rectangle? If not 3" down from top of a 9" deep tank may not be 2/3 full.

[smh00n 87]

the float actually goes across the tank so I am working with a 9 3/4" height.

So the float is at the deepest part of the tank. My assumption is that this is correct. And no video/guides point out anything as a watchout.

[Mach1 Driver 560]

 

 

If Gauge is:	Ohms Empty	Ohms Full	Use Classic Sender:
GMC 1964 or earlier	0	30	Sender SN36
GMC 1966 and later	0	90	Sender SN38
Ford - 1987-later (Unleaded Fuel only)	16	158	Not Available at this time
Ford (pre-1987); AMC	73	10	Sender SN39
Toyota-Nissan 1985 and later	90	0	Sender SN38 - mount movement Upside-Down
Stewart-Warner	240	33	Sender SN33 or SN35
Auto-Meter	240	33	Sender SN33 or SN35

[det0326 179]

I used a tanks inc tank in mine. I seem to remember instructions saying to cut the float arm to a specific length for a certain depth tank.  Even tho i cut it to there spec's mine always seem to read high (opposite from yours).