Aftermarket Fuel Level Sending Unit Problems

[47heaven]

Just purchased the Sunpro CP7583 Fuel Level Sender unit to replace the previous aftermarket one I had that was failing. It, to, was a Sunpro. Anyway, went to test it (connected it tightly and grounded it) and the reading wasn't a precise as it was with the one before it. When I moved the float to 1/2, it registered a little below 1/2 on the gauge. When I moved it to full, it registered almost full on the gauge. When I moved it to empty, it registered 1/4 on the gauge. I thought that it was going to be an easy "hook up and go," but it doesn't seem that way. I don't have an Ohm meter with me, but I'm not sure if testing ohms would matter in this case or not.

Anyone have any suggestions on what could be causing this and what troubleshooting can I do to make the reading accurate? How would I calibrate a unit like this?


http://www.amazon.com/Sunpro-CP7583-Fuel-Level-Sender/dp/B00029JXMU 

 

Edited April 22, 2013 by 47heaven

[TodFitch]

There are a number of different "standards" on the impedance (ohm) range for different dash gauges and you need to match what that needs. The sending unit you linked to shows a range of 33 to 240 ohms. Thats the typical range for Stewart-Warner units. Mopar (starting in 49 or 50) and Ford are typically 78 to 10 ohms. GM is usually 0 to 90 ohms. And VDO is 10 to 180.

[47heaven]

There are a number of different "standards" on the impedance (ohm) range for different dash gauges and you need to match what that needs. The sending unit you linked to shows a range of 33 to 240 ohms. Thats the typical range for Stewart-Warner units. Mopar (starting in 49 or 50) and Ford are typically 78 to 10 ohms. GM is usually 0 to 90 ohms. And VDO is 10 to 180.

Tod...the fuel gauge is also an aftermarket one as well...fabricated to look like the original. So, it's no longer a two-wire system.

How is the adjustment made?

Edited April 22, 2013 by 47heaven

[TodFitch]

Tod...the fuel gauge is also an aftermarket one as well...fabricated to look like the original. So, it's no longer a two-wire system.

How is the adjustment made?

 

What is the designed resistance range of the aftermarket gauge? You need to get a sender that matches it. . .

[47heaven]

What is the designed resistance range of the aftermarket gauge? You need to get a sender that matches it. . .

 

What is the designed resistance range of the aftermarket gauge? You need to get a sender that matches it. . .

Have no idea. It was a  non-Sunpro marine gauge, but worked fine with the other Sunpro fuel level sending unit before.

[Alshere59]

Are you testing the unit in or out of the tank? I think out but....

 

If it is inside the tank. You probably need to shorten the arm to allow it to read the full range of the unit.The instructions that came with it will tell you how to do it.

 

If it is outside the tank. Check the ohms to see if it reads correctly for the sender. New doesn't mean working. If it does you will need to find out what range your gauge needs or get a different one. Adjusting either of them would be difficult at best.

[Robert Horne]

My fuel tank is 8 inch deep.      I bench tested several fuel gauges, and sending units to get a match.

I used a Ford fuel gauge with my 38 Plymouth gauge face attached.    I believe I used a Datson fuel

sender, can not remember the ohms, but I dropped the voltage to 9 volt, and then again to 6 volt to

get the fuel gauge to match the readings of the sender.      The 6 volt reducer did the trick.    I used

a $3 resistor to go to 6 volt.      I moved the setup from the bench to the fuel tank, and all is working

good so far.....

[47heaven]

I just confirmed that the fuel gauge is also the same brand as the sender, so they should be compatible. I'm going to test it again, but make sure that the grounding is better. Yes, Al, I am testing outside of the tank. It may be just a grounding issue that's causing this because the previous sender, which I believe was the same as this one, sent accurate readings. I will check back with my findings. Thanks again for your advice, and if it turns out that's not a grounding issue, then I will refer back to the info.

[DJ194950]

I just confirmed that the fuel gauge is also the same brand as the sender, so they should be compatible. I'm going to test it again, but make sure that the grounding is better. Yes, Al, I am testing outside of the tank. It may be just a grounding issue that's causing this because the previous sender, which I believe was the same as this one, sent accurate readings. I will check back with my findings. Thanks again for your advice, and if it turns out that's not a grounding issue, then I will refer back to the info.

 

Checking  sunpro.com it seems they use  a Empty =240 ohm, Full = 33ohm ,sender for all of their newer gauges (now the standard for all aftermarket sets not made for special apps. ie.stock gauges).

 

If your problem is not solved by testing the way it's been suggested, you can either (1) buy a new sunpro gauge avail at summitracing.com- $19-$30,or 

(2) Find a friend thats into electronics and has pieces at his house and borrow a variable ohm potentometer to check what your current gauge uses ohm wise to see what it requires to read correctly. Matches your sender? Ask that friend how to hook up the wires and will require an ohm mter to read your findings. Maybe your old gauge is bad?

 

Best to ya,

 

Doug

[47heaven]

Doug, thanks for your input. The gauge should be good. I can't see how it would break between the changing of the senders, but then again anything is possible.

 

Unfortunately, I have no friend who's into electronics; my grandfather was, but he's long gone. I'm going to do some ground testing and see if that fixes it, and if not, then start troubleshooting with the advice that you and the others have given me. Was going to do it yesterday, but had to work late. Thanks, again.

Darin
 

[desoto1939]

I have a 39 Desoto and the fuel gage that is in the dash can also be adjusted.  This type of guage in my car fluctuates between two contact point behinf the face of the gage. You loosen the bolts on the back of the gage and also adjyst the gage to work to get correct results. 

 

If you have a service manual for your car check to see if there was any thing onthe old gage setup  Mabe the old gage is stilluseable.

 

Just my two cents. Not sure if this helps.

 

Rich Hartung

desoto1939@aol.com

[47heaven]

I have a 39 Desoto and the fuel gage that is in the dash can also be adjusted.  This type of guage in my car fluctuates between two contact point behinf the face of the gage. You loosen the bolts on the back of the gage and also adjyst the gage to work to get correct results. 

 

If you have a service manual for your car check to see if there was any thing onthe old gage setup  Mabe the old gage is stilluseable.

 

Just my two cents. Not sure if this helps.

 

Rich Hartung

desoto1939@aol.com

Rich, thanks for your input, but I'm not running an original P15 gauge. Would this advice you give also work with new, aftermarket gauges as well? How does loosening the nuts on the back of the bolts adjust it?