Gas Gauge Ajustment
Thread Starter
Safety Car
Joined: Nov 2008
Posts: 3,720
Likes: 557
From: Seattle Washington
Gas Gauge Ajustment
Hello, I have the Gas Tank out of My 80 as I'm just about done installing a Bosch Fuel Pump. I'm replaceing an 82 Fuel Pump. Ever since I used the 82 Pump assembly with sender my Fuel Gauge has been off. The Gauge gets into the red but never quite all the way to Empty. The Low Fuel Light never comes on. Full is a Bit to Full. I always thought I just needed to ajust the Float but now I have a Dry Tank and its all the way down resting on the metal tab its not enough. Read my Shop Manual and it wasn't much help. Its there an Ajustment on the Gauge? Do I need to install a resistor or a 1980 Sender?? Thanx....
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Gary,
You don’t need anything drastic just yet!
You need to bend the float arm until you can reach zero ohms on the output wire. The float can reach the bottom of the tank and not send zero ohms if the arm is bent toward the bottom to far. This will not allow the potentiometer on the gauge to reach the bottom of its stroke which is zero ohms.
Move around the lever and tweak it until you have zero ohms when the float is all the way down in the bottom. From what you describe this will require you to bend the float lever upward a tiny bit. Try this, measure the output and then if needed move it again.
Willcox Inc.
You don’t need anything drastic just yet!
You need to bend the float arm until you can reach zero ohms on the output wire. The float can reach the bottom of the tank and not send zero ohms if the arm is bent toward the bottom to far. This will not allow the potentiometer on the gauge to reach the bottom of its stroke which is zero ohms.
Move around the lever and tweak it until you have zero ohms when the float is all the way down in the bottom. From what you describe this will require you to bend the float lever upward a tiny bit. Try this, measure the output and then if needed move it again.
Willcox Inc.
Race Director
Joined: May 2006
Posts: 16,528
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From: Dayton, Ohio
I agree with Wilcox.Make sure when the float arm is all the way down that you have zero ohms.If the dash gauge is still not low enough you will have to check how the gauge is installed.First thing I would do is to do the standard gauge test.Key on-pull the sender wire off from tank unit=needle on dash should peg towards full.
Next ground the tank sender wire to the tank=needle should peg towards empty,if it doesnt go completely to empty reground the wire with a wire connected to the negative term of the battery.If the needle still doesnt go all the way to empty you need to check the resistance of the sender wire and then move to the gauge,its installation particularly the connections and the resistor across the back of the gauge.Changing the resistor on the back of the gauge will change the position of the needle.
Note-adding resistance to the sender wire can only move the needle towards full.
Next ground the tank sender wire to the tank=needle should peg towards empty,if it doesnt go completely to empty reground the wire with a wire connected to the negative term of the battery.If the needle still doesnt go all the way to empty you need to check the resistance of the sender wire and then move to the gauge,its installation particularly the connections and the resistor across the back of the gauge.Changing the resistor on the back of the gauge will change the position of the needle.
Note-adding resistance to the sender wire can only move the needle towards full.
Thread Starter
Safety Car
Joined: Nov 2008
Posts: 3,720
Likes: 557
From: Seattle Washington
I agree with Wilcox.Make sure when the float arm is all the way down that you have zero ohms.If the dash gauge is still not low enough you will have to check how the gauge is installed.First thing I would do is to do the standard gauge test.Key on-pull the sender wire off from tank unit=needle on dash should peg towards full.
Next ground the tank sender wire to the tank=needle should peg towards empty,if it doesnt go completely to empty reground the wire with a wire connected to the negative term of the battery.If the needle still doesnt go all the way to empty you need to check the resistance of the sender wire and then move to the gauge,its installation particularly the connections and the resistor across the back of the gauge.Changing the resistor on the back of the gauge will change the position of the needle.
Note-adding resistance to the sender wire can only move the needle towards full.
Next ground the tank sender wire to the tank=needle should peg towards empty,if it doesnt go completely to empty reground the wire with a wire connected to the negative term of the battery.If the needle still doesnt go all the way to empty you need to check the resistance of the sender wire and then move to the gauge,its installation particularly the connections and the resistor across the back of the gauge.Changing the resistor on the back of the gauge will change the position of the needle.
Note-adding resistance to the sender wire can only move the needle towards full.
Drifting
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Melting Slicks
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Thread Starter
Safety Car
Joined: Nov 2008
Posts: 3,720
Likes: 557
From: Seattle Washington
Simple enough, with the Fuel Gauge Sender wire Grounded the Gauge goe's to the exact same spot where it dose when the Float is all the way down and touching the stop. With the Wire Disconected it Goes way past Full. So there is nothing to be done with the Sender and I can reasemble. I either have to much resistance in the Wire or I have a Gauge starting to go bad. Thanx...
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
With the ohms wire grounded the gauge should peg full! <<<<<----- Wrong, When the Ohms wire is grounded the gauge goes to empty, when the ohms wire is off the sender it goes to full. (I've never tested one this way until yesterday). This is not like the temp sender which if grounded pegs to full.
You should test the sender with the wires off it and see if empty is 0 ohms and 90 = full.
If you have this on the sending unit, then the problem is in the wiring. If you don't get this reading on the sender you do have one going bad.
You can take apart the potentiometer, there are three tangs holding the cover on. The contact that runs the wire could have an issue and you can check this and even file it down if needed.
Willcox
You should test the sender with the wires off it and see if empty is 0 ohms and 90 = full.
If you have this on the sending unit, then the problem is in the wiring. If you don't get this reading on the sender you do have one going bad.
You can take apart the potentiometer, there are three tangs holding the cover on. The contact that runs the wire could have an issue and you can check this and even file it down if needed.
Willcox
Last edited by Willcox Corvette; Jan 9, 2009 at 02:46 PM.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Edit-Here is something I posted awhile back and a story of how I remember which direction the gauges go during testing.
Temp gauge wire falls off of sender = needle goes to cold (grounding=hot)
Oil gauge wire falls off of sender = needle goes to high press (grounding=zero)
Fuel gauge wire falls off of sender = needle goes to full (grounding=empty)
Does anyone notice the false sense of security ?
Every time the wire "falls" off we have
“cool” coolant temps,
”great” oil pressure and a
“full” tank of fuel.
I remember this because it is just opposite of the way I wish it was.
I ran out of gas out in the boonies once because the wire fell off
the tank sender and my tank kept showing a full tank.
Last edited by ...Roger...; Jan 3, 2009 at 10:52 PM.
Thread Starter
Safety Car
Joined: Nov 2008
Posts: 3,720
Likes: 557
From: Seattle Washington
Somebody has been doing there homework! And yes you were right, When the Wire falls off and is disconected it reads Full, or in my case to full, and when the Wire is grounded it reads Empty, or in my case not empty enough. Thanx...
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Where did you go for dinner tonight ?
Edit-Here is something I posted awhile back and a story of how I remember which direction the gauges go during testing.
Temp gauge wire falls off of sender = needle goes to cold (grounding=hot)
Oil gauge wire falls off of sender = needle goes to high press (grounding=zero)
Fuel gauge wire falls off of sender = needle goes to full (grounding=empty)
Does anyone notice the false sense of security ?
Every time the wire "falls" off we have
“cool” coolant temps,
”great” oil pressure and a
“full” tank of fuel.
I remember this because it is just opposite of the way I wish it was.
I ran out of gas out in the boonies once because the wire fell off
the tank sender and my tank kept showing a full tank.
Edit-Here is something I posted awhile back and a story of how I remember which direction the gauges go during testing.
Temp gauge wire falls off of sender = needle goes to cold (grounding=hot)
Oil gauge wire falls off of sender = needle goes to high press (grounding=zero)
Fuel gauge wire falls off of sender = needle goes to full (grounding=empty)
Does anyone notice the false sense of security ?
Every time the wire "falls" off we have
“cool” coolant temps,
”great” oil pressure and a
“full” tank of fuel.
I remember this because it is just opposite of the way I wish it was.
I ran out of gas out in the boonies once because the wire fell off
the tank sender and my tank kept showing a full tank.
Willcox Inc.
Last edited by Willcox Corvette; Jan 8, 2009 at 07:13 PM.
