Simple but IMPORTANT ? about fuel sender

[Print Dad 58]

Hello ALL,

ONce again I turn to the PROS here on a somewhat simple but VERY important couple of questions

regarding our fuel sender 

As a reminder - car is a 70 MAch - gauges all work - BUT

The fuel gauge reads FULL when only about 3/4 FULL.

I had changed the sender several years ago.

 

SO here are my 4? questions - -I should know the answers but OLD age has me questioning everything

1. - Will the sender PULL out while the tank is in the car - I had changed the tank several years ago.

Not sure if there is room between the tank and rear pumpkin - - I wish I could remember,  I think I installed the sender when the tank was new and out

2. - Should I simply bend the arm - - for a rough adjust or  OR

3. - Should I replace the sender and if so - - what brand seems BEST.

I think the once I purchased was a quality unit from CANADA - I just can't remember

4. - Are the S DRAKE units reliable and accurate 

 

I know this should be simple but I always seek advice of MANY here

 

Thanks - -Sam

[69RavenConv 286]

Hi Sam,

The fuel sender is really just a variable resistor that reads something like 73 ohms on empty and 12 ohms on full. The voltage from your CVR across this resistance determines how far the needle deflects.

I hear bending the arm can work , I've read about people using an old tank with water in it to calibrate the bend prior to install. Or you can just use trial and error which doesn't seem like fun to me. I suspect all replacement senders will be less than perfect out of the box. 

I do believe the sender can be removed with the tank in the car.

Some people claim replacing the OEM CVR can help. The OEM is a bimetallic device that delivers a weird pulse width modulated average voltage around 6VDC while modern solid state devices give you a solid 5VDC. 

Good luck and let us know what you find. Others who know more about this will undoubtedly have more/better advice. I always fill up above a quarter tank and am not too concerned about accuracy beyond "not empty/empty"

[TexasEd 188]

My replacement sender did as you say.  3/4 was showed as full on the gauge and it showed close to empty with a 1/4 tank.  I recently had my tank out to do some welding and I bent the arm up a little to see if that makes a difference but I have not put gas back in yet and my dash is out now.

 

[mauleta 10]

You can always use this to match the gauge to the sending unit:

https://www.technoversions.com/MeterMatch.html

[danno 128]

Yes, you need to work on the fuel sender with an empty tank of gas. 

There is one brand of newer floats that can have an issue with leaking. If the float leaks, it will collect gas inside and not float very well.  So after you remove the sensor, the first thing to check is to see if the float has fuel in it.   Your problem is the sensor is reading too high, which cannot be a float with fuel in it. Your problem is it reads too high, so this needs to be fixed by bending the arm to the float.  

Adjusting the arm to the float is a trial and error process that can take a lot of time because you need to fill the tank to check it, and empty the tank to adjust it.  Get the existing angle measured by tracing the arm with a piece of cardboard so you know how much you move it.  This will give you a reference of a starting place.  Then bend the arm and check with your reference to see how far you bent it. 

[Mach1 Driver 560]

f the other gauges work, then replacing the IVR with an aftermarket replacement won't help, and actually slows down the gauges at start-up. As said previously, if the float isn't full of gas, then bending the float arm or MeterMatch is probably the solution. If you need to buy a new sender go with NPDs best (call them). None of the replacement senders match the OEM according to Rick , the owner of NPD. The following may be of interest:

Edit: I removed the diagram and data from below, because with further testing done today, I found that both the OEM and aftermarket IVRs bring the gauges up to their operating ranges in about the same time. That was unexpected given the higher voltage for the OEM version just after start-up. What I found interesting was that the aftermarket IVR gave lower values when on high- about two needle widths lower. This may take a bit more investigation, because the OEM version of the IVR was outputting 5v continuous on high, but I'm not yet certain if the aftermarket IVR got loaded down and dropped it's output when on high, because it was also 5v ...when on low.