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Fuel Sender Response [message #263150]

Thu, 02 October 2014 08:10

Jp Benson

Messages: 649
Registered: October 2011
Location: Fla

Karma: 2

Senior Member

I added fuel to one of my tanks in 1 quart increments to characterize the response of the sender to the fuel level in the tank. Initially the sender did not respond and then began to respond erratically. Apparently adding 1 qt of fuel is not enough to overcome the friction in the sender. After the tank was about half full I could tap the sender housing after adding each quart and it would respond. Here's the result:
http://www.gmcmhphotos.com/photos/fuel-supply/p56109-fuel-sender-response-curve.html

At 24.5 gallons there was 92.6 ohms resistance in the sender.
http://www.gmcmhphotos.com/photos/fuel-supply/p55982-fuel-level-ohm-meter.html

From 1/2 full to full the response appears nearly linear. Somewhere between empty and 1/2 full there has to be a bend in the curve. Has anyone done this before and published the results?

JP

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Re: Fuel Sender Response [message #263174 is a reply to message #263150]

Thu, 02 October 2014 14:42

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

Jp Benson wrote on Thu, 02 October 2014 09:10

I added fuel to one of my tanks in 1 quart increments to characterize the response of the sender to the fuel level in the tank. Initially the sender did not respond and then began to respond erratically. Apparently adding 1 qt of fuel is not enough to overcome the friction in the sender. After the tank was about half full I could tap the sender housing after adding each quart and it would respond. Here's the result:
http://www.gmcmhphotos.com/photos/fuel-supply/p56109-fuel-sender-response-curve.html

At 24.5 gallons there was 92.6 ohms resistance in the sender.
http://www.gmcmhphotos.com/photos/fuel-supply/p55982-fuel-level-ohm-meter.html

From 1/2 full to full the response appears nearly linear. Somewhere between empty and 1/2 full there has to be a bend in the curve. Has anyone done this before and published the results?

JP

JP,

You did about 17 times the amount of work I did when I was rebuilding my fuel senders. This was an operation I will never report on because there are replacements available that are much better than what I did and the only advantage to mine was minimal cash out of pocket.
My original were not linear - I worked in 5 gallon increments - and even then stiction was not overcome by the fuel level. But, with some banging, they would settle to the new level.
I also discovered that the OE readout was not linear. Unfortunately, I did not have the time to compare the readout to either the repaired OE sender or the replacement that I used a year later.

Matt

Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

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Re: Fuel Sender Response [message #263175 is a reply to message #263150]

Thu, 02 October 2014 14:48

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

Jp Benson wrote on Thu, 02 October 2014 09:10

I added fuel to one of my tanks in 1 quart increments to characterize the response of the sender to the fuel level in the tank. Initially the sender did not respond and then began to respond erratically. Apparently adding 1 qt of fuel is not enough to overcome the friction in the sender. After the tank was about half full I could tap the sender housing after adding each quart and it would respond. Here's the result:
http://www.gmcmhphotos.com/photos/fuel-supply/p56109-fuel-sender-response-curve.html

At 24.5 gallons there was 92.6 ohms resistance in the sender.
http://www.gmcmhphotos.com/photos/fuel-supply/p55982-fuel-level-ohm-meter.html

From 1/2 full to full the response appears nearly linear. Somewhere between empty and 1/2 full there has to be a bend in the curve. Has anyone done this before and published the results?

JP

JP,

You did about 17 times the amount of work I did when I was rebuilding my fuel senders. This was an operation I will never report on because there are replacements available that are much better than what I did and the only advantage to mine was minimal cash out of pocket.
My original were not linear - I worked in 5 gallon increments - and even then stiction was not overcome by the fuel level. But, with some banging, they would settle to the new level. I figured that the vehicle motion would supply at least enough motion to do that as required.
I also discovered that the OE readout was not linear. Unfortunately, I did not have the time to compare the readout to either the repaired OE sender or the replacement that I used a year later.

Matt - homebound from Chippewa Falls

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Re: [GMCnet] Fuel Sender Response [message #263176 is a reply to message #263175]

Thu, 02 October 2014 15:01

James Hupy

Messages: 6806
Registered: May 2010

Karma: -62

Senior Member

I only have one question. WHY? (Grin)
Jim Hupy
Jp Benson wrote on Thu, 02 October 2014 09:10
> I added fuel to one of my tanks in 1 quart increments to characterize the
response of the sender to the fuel level in the tank. Initially the
> sender did not respond and then began to respond erratically. Apparently
adding 1 qt of fuel is not enough to overcome the friction in the sender.
> After the tank was about half full I could tap the sender housing after
adding each quart and it would respond. Here's the result:
>
http://www.gmcmhphotos.com/photos/fuel-supply/p56109-fuel-sender-response-curve.html
>
> At 24.5 gallons there was 92.6 ohms resistance in the sender.
>
http://www.gmcmhphotos.com/photos/fuel-supply/p55982-fuel-level-ohm-meter.html
>
> From 1/2 full to full the response appears nearly linear. Somewhere
between empty and 1/2 full there has to be a bend in the curve. Has anyone
> done this before and published the results?
>
> JP

JP,

You did about 17 times the amount of work I did when I was rebuilding my
fuel senders. This was an operation I will never report on because there
are
replacements available that are much better than what I did and the only
advantage to mine was minimal cash out of pocket.
My original were not linear - I worked in 5 gallon increments - and even
then stiction was not overcome by the fuel level. But, with some banging,
they would settle to the new level. I figured that the vehicle motion
would supply at least enough motion to do that as required.
I also discovered that the OE readout was not linear. Unfortunately, I
did not have the time to compare the readout to either the repaired OE
sender
or the replacement that I used a year later.

Matt - homebound from Chippewa Falls
--
Matt & Mary Colie - Members GMCMI, GMCES
'73 Glacier 23 - Still Loving the Applied Rear Brake Control Arms
SE Michigan - Twixt A2 and Detroit
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Re: [GMCnet] Fuel Sender Response [message #263186 is a reply to message #263176]

Thu, 02 October 2014 18:01

Jp Benson

Messages: 649
Registered: October 2011
Location: Fla

Karma: 2

Senior Member

"I only have one question. WHY? (Grin)"
Jim Hupy

Well it may be overkill but... I do enjoy this sort of thing.

On the plus side, when filling the tanks I would not have to depend on the pumps automatic shutoff to know when the tanks are full. Now though I'm wondering how well it will work if the sender doesn't respond correctly when the vehicle is not moving. It did seem to work better when the tank is close to full. That's when the float lever is horizontal and the most torque is applied.

It also provides an opportunity to get better mileage estimates if the actual amount of fuel in the tank is known. Add in a micro-processor and one could calculate and display mpg on the fly.

JP

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Re: Fuel Sender Response [message #263324 is a reply to message #263150]

Sat, 04 October 2014 04:44

cbwoodsr

Messages: 1063
Registered: February 2004

Karma: 0

Senior Member

In a related manner, when your gauge show past full(all the way to the right), is it shorted or open??
Took out some regular electrical wire the PO had put in (like 6 ft long wrapped up) and even tho I was very carefull to make sure the wires were put back together the same, the ones for the fuel gauges wasnt...
thankx
CBW

CBWood
77 Kingslay
MWC OK
ONLINE PARTS PROGRAM
www.GMCMHParts.com

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Re: Fuel Sender Response [message #263332 is a reply to message #263150]

Sat, 04 October 2014 10:25

Jp Benson

Messages: 649
Registered: October 2011
Location: Fla

Karma: 2

Senior Member

"In a related manner, when your gauge show past full(all the way to the right), is it shorted or open??"

The sender operates from ~zero ohms (tank is empty) to ~90 ohms (tank is full). If the sender were shorted it would read zero ohms and a working gauge would read empty. If the sender was open circuit there would be no current and I don't think the gauge would respond at all. Bench testing my sender it ranged from 1.4 to 105 ohms. Maybe there is some other source of resistance in the circuit (perhaps a corroded connection) that is causing your gauge to read past full. If you can access it, check the sender with an ohm-meter.

JP

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Re: Fuel Sender Response [message #263355 is a reply to message #263332]

Sat, 04 October 2014 16:57

Loffen

Messages: 1087
Registered: August 2013
Location: Norway

Karma: 1

Senior Member

I think most GM fuel senders goes up to around 105 ohm and it is not unusual to see the needle go over the full mark and stay there for a a couple of gallons of gas.
The reason is that in some fuel tanks the float on the fuel sender will hit the travel limiter on the sender before the tank is full, I have no idea why except that it might be nice to drive with a full tank of gas for a while longer.

1973 23' # 1848 Sky Blue Glacier called Baby Blue and a 1973 26'-3 # 1460 Parrot green Seqouia Known as the Big Green, And sold my 1973 26'-2 # 581 White Canyon lands under the name Dobbelt trøbbel in Norway

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Re: Fuel Sender Response [message #263382 is a reply to message #263324]

Sat, 04 October 2014 22:00

A Hamilto

Messages: 4508
Registered: April 2011

Karma: 39

Senior Member

cbwoodsr wrote on Sat, 04 October 2014 04:44

In a related manner, when your gauge show past full(all the way to the right), is it shorted or open??
Took out some regular electrical wire the PO had put in (like 6 ft long wrapped up) and even tho I was very carefull to make sure the wires were put back together the same, the ones for the fuel gauges wasnt...
thankx
CBW

Open.

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Re: [GMCnet] Fuel Sender Response [message #263401 is a reply to message #263176]

Sun, 05 October 2014 08:00

Jim at the Co-op

Messages: 291
Registered: May 2014
Location: Orlando Florida

Karma: 2

Senior Member

An open circuit (disconnected) shows full.

Jim Bounds

Sent from my T-Mobile 4G LTE Device

-------- Original message --------
From: "A."
Date: 10/04/2014 8:00 PM (GMT-08:00)
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Fuel Sender Response

cbwoodsr wrote on Sat, 04 October 2014 04:44
> In a related manner, when your gauge show past full(all the way to the right), is it shorted or open??
> Took out some regular electrical wire the PO had put in (like 6 ft long wrapped up) and even tho I was very carefull to make sure the wires were
> put back together the same, the ones for the fuel gauges wasnt...
> thankx
> CBW
Open.

--
'73 23' Sequoia For Sale
'73 23' CanyonLands For Sale
Upper Alabama
Perpetually annoyed that "political correctness" and Secular Humanism control every aspect of American life
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