Multimeter Idiot
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Joined: Mar 2012
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Does the ohms of your sending unit match the ohms on your gauges? This sounds like your problem in the beginning.
I am guessing, but I'd think you would check for DC voltage on the lead wire to your sending unit, with the truck on. I'd do this by placing the meter on DC(Line with dashes below) and putting the red probe on the lead wire of the sending unit. A good place would be where it screw on or plugs in. These places are naturally exposed a little bit. Then placing the black probe to your frame. Should read 6 or 12 volts. If you mix the probes up its not a big deal it would just read negative. If you have no voltage at the sending unit Id check up the wire at the control panel. If you have voltage at the sending unit Id would think your problem lies there.
I'm not good with electricity either, Someone may come along and affirm that this isn't a good idea. This is just how I check electrical components on copy machines. Which obviously aren't trucks.
I am guessing, but I'd think you would check for DC voltage on the lead wire to your sending unit, with the truck on. I'd do this by placing the meter on DC(Line with dashes below) and putting the red probe on the lead wire of the sending unit. A good place would be where it screw on or plugs in. These places are naturally exposed a little bit. Then placing the black probe to your frame. Should read 6 or 12 volts. If you mix the probes up its not a big deal it would just read negative. If you have no voltage at the sending unit Id check up the wire at the control panel. If you have voltage at the sending unit Id would think your problem lies there.
I'm not good with electricity either, Someone may come along and affirm that this isn't a good idea. This is just how I check electrical components on copy machines. Which obviously aren't trucks.
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Logistics Pro
Joined: May 2010
Posts: 3,793
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From: Austin
Thanks Aaron,
My son Zack shows from college this afternoon & we'll start working our way through this one. It's frustrating not knowing how much gas you really have in the tank - seems pretty basic. I obviously know what type of gauges we have & their ohm requirement but I don't know what type of sending unit was installed in the tank. I'll probably have more questions as we jump into this one. I'd at least like to get back to the gauge reading half full - that would feel like some sort of victory.
Ben in Austin
My son Zack shows from college this afternoon & we'll start working our way through this one. It's frustrating not knowing how much gas you really have in the tank - seems pretty basic. I obviously know what type of gauges we have & their ohm requirement but I don't know what type of sending unit was installed in the tank. I'll probably have more questions as we jump into this one. I'd at least like to get back to the gauge reading half full - that would feel like some sort of victory.
Ben in Austin
Tuned
Joined: Sep 2011
Posts: 309
Likes: 9
From: Northern IL
Hey Ben
Looking at that yellow tap splice in your picture that may be your issue. I believe the yellow is for larger gauge wire ( red is for smallest guage and blue for middle) than your probably running from your wire harness. In turn the two sides of the "teeth" inside the splice may not be close enough together to cut the outside of the wire and touch copper. I'd take that out like mentioned, and solder, heat shrink like said earlier, then test your gauge out again. If it was working before and this is the only thing that changed it might be the problem area. Of course you will still have to change the ohms like you we're looking at so the guage works properly.
Good luck today
Looking at that yellow tap splice in your picture that may be your issue. I believe the yellow is for larger gauge wire ( red is for smallest guage and blue for middle) than your probably running from your wire harness. In turn the two sides of the "teeth" inside the splice may not be close enough together to cut the outside of the wire and touch copper. I'd take that out like mentioned, and solder, heat shrink like said earlier, then test your gauge out again. If it was working before and this is the only thing that changed it might be the problem area. Of course you will still have to change the ohms like you we're looking at so the guage works properly.
Good luck today
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Logistics Pro
Joined: May 2010
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From: Austin
Ok - We've been at this for a bit so far today. Some progress - We
have tested the gauge per Dmack's instruction & we get needle at Empty with the sender wire & ground hooked up. The Gauge goes to Full when Ground is taken off - So..... That would leave me to believe that the Gauge is good?
I read somewhere on FTE that Autometer Ford Gauges require
the 3262 Sender Unit. I don't know what type of sender unit we have.
Will be back shortly with an Ohm reading from the sender unit to see if we can figure out if that's the issue.
It was nice to see the guage move into Full territory - haven't seen that ever on this truck.
Ben in Austin
have tested the gauge per Dmack's instruction & we get needle at Empty with the sender wire & ground hooked up. The Gauge goes to Full when Ground is taken off - So..... That would leave me to believe that the Gauge is good?
I read somewhere on FTE that Autometer Ford Gauges require
the 3262 Sender Unit. I don't know what type of sender unit we have.
Will be back shortly with an Ohm reading from the sender unit to see if we can figure out if that's the issue.
It was nice to see the guage move into Full territory - haven't seen that ever on this truck.
Ben in Austin
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Logistics Pro
Joined: May 2010
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From: Austin
Ok - Our Fuel Tank Sending unit read 188 ohms coming from the sender unit. Hmmm..
From everything I've been able to read this is what's out there for possible gas tank sending units..
Pre'87 bimetallic sending unit 10 Empty 70 Full
Ford '87 & later F Series Magnetic 15 Empty 160 Full.
Modern Aftermarket Senders 240 Empty 33 Full.
Hmmmm.. A head scratcher - My guess is that the 188 ohm reading rules out all older senders because it only falls in the range of the modern aftermarket sender units. The confusion is that I know the tank is full so it should be sending somewhere around 33 Ohms for Full.
My guess is that the guys may have installed it upside down?
Or the Float sank to the bottom of the tank?
I've ordered a new Modern Sending Unit as the solution - it should be here in a few days. Have I missed something? Any better ideas?
I'm guessing I've got to drain out 22 gallons of gas to put the sending unit in - That doesn't sound like too much fun but ok. I'm also hoping the modern aftermarket sender will fit into the 1970 tank.
Ben in Austin
1950 F1 351W/AOD
From everything I've been able to read this is what's out there for possible gas tank sending units..
Pre'87 bimetallic sending unit 10 Empty 70 Full
Ford '87 & later F Series Magnetic 15 Empty 160 Full.
Modern Aftermarket Senders 240 Empty 33 Full.
Hmmmm.. A head scratcher - My guess is that the 188 ohm reading rules out all older senders because it only falls in the range of the modern aftermarket sender units. The confusion is that I know the tank is full so it should be sending somewhere around 33 Ohms for Full.
My guess is that the guys may have installed it upside down?
Or the Float sank to the bottom of the tank?
I've ordered a new Modern Sending Unit as the solution - it should be here in a few days. Have I missed something? Any better ideas?
I'm guessing I've got to drain out 22 gallons of gas to put the sending unit in - That doesn't sound like too much fun but ok. I'm also hoping the modern aftermarket sender will fit into the 1970 tank.
Ben in Austin
1950 F1 351W/AOD
Elder User
Joined: Feb 2012
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From: Central Oregon
Ben,
The sender should be mounted in the top of the tank. I have never had to drain one to pull the sender. Just make sure the level of fuel is below the sending unit opening.
I would pull the sender and check to see if the float has a hole in it, causing it to sink to the bottom of the tank. Or, it could just be stuck on something.
Once out, you can check it by cycling it through it's range of motion while the ohm meter is hooked up and see what it is doing. All the sender is is a coil of wire with the float arm moving a wiper along the coils. As it moves over a differing number of coils, the resistance changes.
Good luck,
Dave
The sender should be mounted in the top of the tank. I have never had to drain one to pull the sender. Just make sure the level of fuel is below the sending unit opening.
I would pull the sender and check to see if the float has a hole in it, causing it to sink to the bottom of the tank. Or, it could just be stuck on something.
Once out, you can check it by cycling it through it's range of motion while the ohm meter is hooked up and see what it is doing. All the sender is is a coil of wire with the float arm moving a wiper along the coils. As it moves over a differing number of coils, the resistance changes.
Good luck,
Dave
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Logistics Pro
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From: Austin
Hey Dave,
Thanks a lot for your help - we used your approach to check to see if the gauge was ok - it worked great. The head scratcher is just that I know the tank is full but the sender is reading near empty. Just decided to
replace the thing & install it ourselves. As with most projects it spills into next weekend but that's ok.
Here is a picture of my son, Zack - enjoying himself checking & re-checking wires to the fuel gauge. He stayed home from a big concert here in Austin this weekend to work on the truck - though he'd like it all to work after the first shot - patience grasshopper...
The 1970 Mustang tank has the sender entering from lower in the back so we'll have to drain a lot of the gas out of the tank.
Thanks again.
Ben in Austin
1950 F1 351W/AOD
Thanks a lot for your help - we used your approach to check to see if the gauge was ok - it worked great. The head scratcher is just that I know the tank is full but the sender is reading near empty. Just decided to
replace the thing & install it ourselves. As with most projects it spills into next weekend but that's ok.
Here is a picture of my son, Zack - enjoying himself checking & re-checking wires to the fuel gauge. He stayed home from a big concert here in Austin this weekend to work on the truck - though he'd like it all to work after the first shot - patience grasshopper...
The 1970 Mustang tank has the sender entering from lower in the back so we'll have to drain a lot of the gas out of the tank.
Thanks again.
Ben in Austin
1950 F1 351W/AOD
Elder User
Joined: Feb 2012
Posts: 948
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From: Central Oregon
Nice to have a son around to help. Mine is much stronger than I am, which helps alot (plus I take longer to heal). He is in Nepal right now on a Habitat for Humanity build right now. I think he is learning to appreciate what we have compared to much of the world.
Best of luck on it.
Best of luck on it.
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Joe Kucinski
Fleet Owner
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From: NM
Modern gas frequently forms varnishes on the tanks and other parts, right at the fuel level where evaporation is taking place. The varnish prevents good electrical contact from there up. A good blast with carb cleaner will usually restore function.
If you have an electric fuel pump, it takes no time at all to transfer your gas to another vehicle.
If you have an electric fuel pump, it takes no time at all to transfer your gas to another vehicle.
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Logistics Pro
Joined: May 2010
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From: Austin
Hi Ross,
Thanks - We do have an electric fuel pump with a manual switch in the cab. That's a much smarter way to get the gas out of the tank than what I was working on... So.. - just disconnect it up by the carb & run it over to another vehicle?
Ben in Austin
1950 F1
Thanks - We do have an electric fuel pump with a manual switch in the cab. That's a much smarter way to get the gas out of the tank than what I was working on... So.. - just disconnect it up by the carb & run it over to another vehicle?
Ben in Austin
1950 F1
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Logistics Pro
Joined: May 2010
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From: Austin
Hey Jeff,
We spent some time on this one looking at different alternatives.
Our challenge was we had aftermarket gauges that require a 240ohms empty to 33 ohms full sender. You won't find one that fits the 1970 mustang gas tank's existing sender "opening" - not happening. It's a unique screw in deal.
The solution is - You get a 1970 mustang sender unit ($35) & install it in the standard opening - this is just for the fuel line. You then have to cut a hole in the top of the tank for the after market 240/33 sender unit.
You wire up this sending unit & not the 1970 one.
This is our Christmas project. Need to find a safe way to drill a circular hole in the top of the tank. We'll drain out the gas but there will be fumes. I'm thinking we'll fill it with water then drill the hole.
How close are you getting over there Jeff?
Ben in Austin
1950 F1
We spent some time on this one looking at different alternatives.
Our challenge was we had aftermarket gauges that require a 240ohms empty to 33 ohms full sender. You won't find one that fits the 1970 mustang gas tank's existing sender "opening" - not happening. It's a unique screw in deal.
The solution is - You get a 1970 mustang sender unit ($35) & install it in the standard opening - this is just for the fuel line. You then have to cut a hole in the top of the tank for the after market 240/33 sender unit.
You wire up this sending unit & not the 1970 one.
This is our Christmas project. Need to find a safe way to drill a circular hole in the top of the tank. We'll drain out the gas but there will be fumes. I'm thinking we'll fill it with water then drill the hole.
How close are you getting over there Jeff?
Ben in Austin
1950 F1
Logistics Pro
Joined: Apr 2010
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From: Pekin, IL
Not even anywhere close enough to see any light at the end of any tunnel...
But I just keep pickin away!
Thanks buddy!
But I just keep pickin away!
Thanks buddy!
Senior User
Joined: Sep 2006
Posts: 198
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To get my 6 volt instrument panel to talk to the gas gauge I got a voltage regulator off ebay:
1pc x L7806 LM7806 Three Terminal Voltage Regulator Module 6V Voltage Regulator | eBay
And ran the main power lead for the panel through the regulator and then to the panel, dropping the power to the panel down to 6 volts.
Then to get the gas gauge from the 1970 Mustang tank and sender to read close (close enough), I connected a 10 ohm 2 watt resistor on the lead from the sender. Radio Shack can set you up with one of those.
As I say, it's close enough.
1pc x L7806 LM7806 Three Terminal Voltage Regulator Module 6V Voltage Regulator | eBay
And ran the main power lead for the panel through the regulator and then to the panel, dropping the power to the panel down to 6 volts.
Then to get the gas gauge from the 1970 Mustang tank and sender to read close (close enough), I connected a 10 ohm 2 watt resistor on the lead from the sender. Radio Shack can set you up with one of those.
As I say, it's close enough.