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Thread: Fuel sending unit/Cell question

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    Default Fuel sending unit/Cell question

    Aight,

    As most of you know, electricity is my downfall when it comes to figuring shit out. I just have a problem with electrical stuff. So let me start by telling you what I want to do, and the issue I am up against.

    I am planning on putting a fuel cell in Smokey, I have all of the rest of the fuel system, just havent pulled the trigger on a cell yet. I want to be able to maintain a fuel level gauge in the dash, so I looked up the factory empty/full ohm ratings on the sender. Here is the info that I found...

    Empty 220 Ohms Full 20 Ohms. Both are +- 6 ohms.

    Now, thats VERY close to the "aftermarket gauge" style senders, that read

    Empty 240 Ohms Full 33 Ohms.


    If I can drop 13 Ohms of resistance off of the system somehow, once the cell is installed, then the factory gauge cluster will read correctly.

    Can this be done? If so, how?

    Thanks for your electrical help guys

    99 DA RC To Be Discovered AKA Smokey
    98 DA CC 11.59@118 AKA Barney

    [Duner] : I was afraid I was going to go too fast and scare myself. Lucky for me - the DA rose up to save me.

    [Kotta390] : Oh that's right! Well FML.....Looks like I am getting shafted because of my bore size

    [BlakDak71] : I don't run oil, I run a special blend consisting of Hellman's mayo and the tears of a pregnant mermaid

    [Kotta390] : My electric water pump puts out too much fuel at idle and is not a variable pump which makes it overheat in the summer at idle if I sit too long

    [KotaRT] : Ed, you can have cake, as long as I get something in return

  2. #2

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    with that range, 13 ohms is only about 5% off. I'm pretty sure it would function fine and be about as accurate as the factory sender anyway- mygauge goes way past full when I fill up and will run on empty for a week- not exacxtly scietific test instruments..

    As far as removing resistance from the system, I'm not really aware of any ways to accomplish that. It might be possible to isolate the gauge's power supply/input reference from the senders power supply and install a resistor in the gauge wire to fool the guage into seeing a higher voltage from the sender just like it would have with a lower ohm reading. But that seems like a bunch of unnecessary work for perfect accuracy on a somewhat non-vital gauge.

    Drops panties faster than any R/T

  3. #3

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    You can put a resistor in parallel that would get you close but its not linear so my advice if you want to do it is to get the 33 on the empty side down to 20. The gauge may not read correct on FULL but it would be correct on empty which is what you are probably most concerned with.

    There is some formula to figure out the resistor value, I would have to research it.


    "The journey is more fun than the destination"

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    Danno's Avatar
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    Quote Originally Posted by wyotech_cuda440 View Post
    with that range, 13 ohms is only about 5% off. I'm pretty sure it would function fine and be about as accurate as the factory sender anyway- mygauge goes way past full when I fill up and will run on empty for a week- not exacxtly scietific test instruments..

    As far as removing resistance from the system, I'm not really aware of any ways to accomplish that. It might be possible to isolate the gauge's power supply/input reference from the senders power supply and install a resistor in the gauge wire to fool the guage into seeing a higher voltage from the sender just like it would have with a lower ohm reading. But that seems like a bunch of unnecessary work for perfect accuracy on a somewhat non-vital gauge.
    Wow, yours is WAY off. None of mine have been that bad. Admittedly, the last 1/4 of a tank seems to go MUCH quicker than the first 1/4... lol.

    Yeah I thought about leaving it as is and giving it a shot, but if there is a fairly easy way to make this happen, Id just rather do it correctly the first time. If not, then 240-33 will have to do the trick

    99 DA RC To Be Discovered AKA Smokey
    98 DA CC 11.59@118 AKA Barney

    [Duner] : I was afraid I was going to go too fast and scare myself. Lucky for me - the DA rose up to save me.

    [Kotta390] : Oh that's right! Well FML.....Looks like I am getting shafted because of my bore size

    [BlakDak71] : I don't run oil, I run a special blend consisting of Hellman's mayo and the tears of a pregnant mermaid

    [Kotta390] : My electric water pump puts out too much fuel at idle and is not a variable pump which makes it overheat in the summer at idle if I sit too long

    [KotaRT] : Ed, you can have cake, as long as I get something in return

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    Danno's Avatar
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    Quote Originally Posted by WhiteRT View Post
    You can put a resistor in parallel that would get you close but its not linear so my advice if you want to do it is to get the 33 on the empty side down to 20. The gauge may not read correct on FULL but it would be correct on empty which is what you are probably most concerned with.

    There is some formula to figure out the resistor value, I would have to research it.
    I was thinking the 33 to 20 would be the way to go. Just not sure how to get from point A to point B in the problem lol. I am sure that someone else has had to go down this path at some point....

    Any help/direction you could toss my way would be appreciated Todd.

    99 DA RC To Be Discovered AKA Smokey
    98 DA CC 11.59@118 AKA Barney

    [Duner] : I was afraid I was going to go too fast and scare myself. Lucky for me - the DA rose up to save me.

    [Kotta390] : Oh that's right! Well FML.....Looks like I am getting shafted because of my bore size

    [BlakDak71] : I don't run oil, I run a special blend consisting of Hellman's mayo and the tears of a pregnant mermaid

    [Kotta390] : My electric water pump puts out too much fuel at idle and is not a variable pump which makes it overheat in the summer at idle if I sit too long

    [KotaRT] : Ed, you can have cake, as long as I get something in return

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    You're fine. Don't make a mountain out of a mole hill.

    I used an aftermarket gauge with factory sender. Instead of having that 'window of error' where I could drive for 100 miles after it read empty like everyone knows you can do with stock tanks/gauges. I was on empty and about to stall when the gauge read zero, and when I filled up, it showed way past fuel.
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  7. #7

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    Quote Originally Posted by Danno View Post
    Wow, yours is WAY off. None of mine have been that bad. Admittedly, the last 1/4 of a tank seems to go MUCH quicker than the first 1/4... lol.

    Yeah I thought about leaving it as is and giving it a shot, but if there is a fairly easy way to make this happen, Id just rather do it correctly the first time. If not, then 240-33 will have to do the trick
    Yeah, when I fill up the needle goes about 1/8" past the full mark, the first half of the tank lasts way longer than the second half, and the gas light turns on when I've used 15.5 gallons

    The parralel resistor that White mentioned would let you dial in the empty or full, but it will be off at one end of the spectrum. You could pick up a 0-50 ohm potentiometer from radio shack and use it as an adjustable resistor to calibrate it how you want and make it very easy to figure out- with an empty tank, just turn the potentiometer till the gauge reads empty too.

    Like tom said it will still function as-is, just opposite of how his factory sender/ aftermarket gauge did. You will see almost full when you fill up, and still have a little reserve when the gauge reads empty.

    Drops panties faster than any R/T

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    Quote Originally Posted by Filthy Filbert View Post
    You're fine. Don't make a mountain out of a mole hill.

    I used an aftermarket gauge with factory sender. Instead of having that 'window of error' where I could drive for 100 miles after it read empty like everyone knows you can do with stock tanks/gauges. I was on empty and about to stall when the gauge read zero, and when I filled up, it showed way past fuel.
    Thanks Tom

    I just like to make sure I have my duckies in a row before I pull the trigger on anything.

    99 DA RC To Be Discovered AKA Smokey
    98 DA CC 11.59@118 AKA Barney

    [Duner] : I was afraid I was going to go too fast and scare myself. Lucky for me - the DA rose up to save me.

    [Kotta390] : Oh that's right! Well FML.....Looks like I am getting shafted because of my bore size

    [BlakDak71] : I don't run oil, I run a special blend consisting of Hellman's mayo and the tears of a pregnant mermaid

    [Kotta390] : My electric water pump puts out too much fuel at idle and is not a variable pump which makes it overheat in the summer at idle if I sit too long

    [KotaRT] : Ed, you can have cake, as long as I get something in return

  9. #9

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    I agree with just run it and figure out when/where the gauge reads for different levels in the tank.

    It is a small difference as you are not trying to use a GM type sender with a 0-90 sender vs 20-220. The 33-240 should be close enough to gauge when you need fuel or not.

    I will see if I can find the formula though to determine the resistor you will need if you want to "calibrate" the empty side of it. But as stated by me and garrett your gauge will be off in the rest of the sweep by just a tad but the most important point in a fuel gauge readout is the E imo.


    "The journey is more fun than the destination"

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    Danno's Avatar
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    Quote Originally Posted by WhiteRT View Post
    I agree with just run it and figure out when/where the gauge reads for different levels in the tank.

    It is a small difference as you are not trying to use a GM type sender with a 0-90 sender vs 20-220. The 33-240 should be close enough to gauge when you need fuel or not.

    I will see if I can find the formula though to determine the resistor you will need if you want to "calibrate" the empty side of it. But as stated by me and garrett your gauge will be off in the rest of the sweep by just a tad but the most important point in a fuel gauge readout is the E imo.

    Yessir!

    And thanks for checking that formula out.

    99 DA RC To Be Discovered AKA Smokey
    98 DA CC 11.59@118 AKA Barney

    [Duner] : I was afraid I was going to go too fast and scare myself. Lucky for me - the DA rose up to save me.

    [Kotta390] : Oh that's right! Well FML.....Looks like I am getting shafted because of my bore size

    [BlakDak71] : I don't run oil, I run a special blend consisting of Hellman's mayo and the tears of a pregnant mermaid

    [Kotta390] : My electric water pump puts out too much fuel at idle and is not a variable pump which makes it overheat in the summer at idle if I sit too long

    [KotaRT] : Ed, you can have cake, as long as I get something in return

  11. #11

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    Quote Originally Posted by Danno View Post
    Yessir!

    And thanks for checking that formula out.
    Ok back on a computer lol - ohms law states that a 50 ohm 1 watt resistor should work...

    1/33+1/x=1/20


    "The journey is more fun than the destination"

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    Quote Originally Posted by Joskanner View Post
    Danno, I agree that there is no need in worrying about getting it exact. No two senders are going to be exactly the same, also resistance is the result of many factors including the length and conducting material of wires and the connectors. So the end resistance will vary a little.
    Thats probably why the factory specs are +- 6 ohms

    Thanks!

    99 DA RC To Be Discovered AKA Smokey
    98 DA CC 11.59@118 AKA Barney

    [Duner] : I was afraid I was going to go too fast and scare myself. Lucky for me - the DA rose up to save me.

    [Kotta390] : Oh that's right! Well FML.....Looks like I am getting shafted because of my bore size

    [BlakDak71] : I don't run oil, I run a special blend consisting of Hellman's mayo and the tears of a pregnant mermaid

    [Kotta390] : My electric water pump puts out too much fuel at idle and is not a variable pump which makes it overheat in the summer at idle if I sit too long

    [KotaRT] : Ed, you can have cake, as long as I get something in return

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    Quote Originally Posted by WhiteRT View Post
    Ok back on a computer lol - ohms law states that a 50 ohm 1 watt resistor should work...

    1/33+1/x=1/20
    And that basically just goes inline correct?

    99 DA RC To Be Discovered AKA Smokey
    98 DA CC 11.59@118 AKA Barney

    [Duner] : I was afraid I was going to go too fast and scare myself. Lucky for me - the DA rose up to save me.

    [Kotta390] : Oh that's right! Well FML.....Looks like I am getting shafted because of my bore size

    [BlakDak71] : I don't run oil, I run a special blend consisting of Hellman's mayo and the tears of a pregnant mermaid

    [Kotta390] : My electric water pump puts out too much fuel at idle and is not a variable pump which makes it overheat in the summer at idle if I sit too long

    [KotaRT] : Ed, you can have cake, as long as I get something in return

  14. #14

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    Quote Originally Posted by Danno View Post
    And that basically just goes inline correct?
    It goes parallel- hook it to the + and - on top of the sender along with the two wires from the gauge.

    Drops panties faster than any R/T

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    ^^^^this!!


    "The journey is more fun than the destination"

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    Quote Originally Posted by wyotech_cuda440 View Post
    It goes parallel- hook it to the + and - on top of the sender along with the two wires from the gauge.
    Aight! Thanks guys!

    99 DA RC To Be Discovered AKA Smokey
    98 DA CC 11.59@118 AKA Barney

    [Duner] : I was afraid I was going to go too fast and scare myself. Lucky for me - the DA rose up to save me.

    [Kotta390] : Oh that's right! Well FML.....Looks like I am getting shafted because of my bore size

    [BlakDak71] : I don't run oil, I run a special blend consisting of Hellman's mayo and the tears of a pregnant mermaid

    [Kotta390] : My electric water pump puts out too much fuel at idle and is not a variable pump which makes it overheat in the summer at idle if I sit too long

    [KotaRT] : Ed, you can have cake, as long as I get something in return

  17. #17

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    Something else to keep in mind. Depth of cell, length/angle of gauge arm. You may find you are only using 150-50ohms range. You may have to "customize" by altering arm length/angles, etc anyway. Adding a cell is coming up soon for me as well. I have everything but rails(ordered) and cell here as well. Hopefully you will have it all figured out by then

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    Most of the units I have found are specific to cell depth

    99 DA RC To Be Discovered AKA Smokey
    98 DA CC 11.59@118 AKA Barney

    [Duner] : I was afraid I was going to go too fast and scare myself. Lucky for me - the DA rose up to save me.

    [Kotta390] : Oh that's right! Well FML.....Looks like I am getting shafted because of my bore size

    [BlakDak71] : I don't run oil, I run a special blend consisting of Hellman's mayo and the tears of a pregnant mermaid

    [Kotta390] : My electric water pump puts out too much fuel at idle and is not a variable pump which makes it overheat in the summer at idle if I sit too long

    [KotaRT] : Ed, you can have cake, as long as I get something in return

  19. #19

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    I should have known better
    Share a link or two?

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    Danno's Avatar
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    Quote Originally Posted by FLRT View Post
    I should have known better
    Share a link or two?
    What are you looking for in a cell? I have finally found specifically what I want, but not everyone needs the same thing

    Jaz seems to offer the most cells with the correct sending unit, but most of them with sumps are plastic cells. There are a couple of aluminum ones out there too, but none as large as I wanted.

    I finally found a 20 Gallon, 240-33 sender, Alum cell, with at least a -10 outlet, and 2 -8 top return/vent provisions.

    http://www.rhodesracecars.com/Pro-Se...l_p_11399.html

    99 DA RC To Be Discovered AKA Smokey
    98 DA CC 11.59@118 AKA Barney

    [Duner] : I was afraid I was going to go too fast and scare myself. Lucky for me - the DA rose up to save me.

    [Kotta390] : Oh that's right! Well FML.....Looks like I am getting shafted because of my bore size

    [BlakDak71] : I don't run oil, I run a special blend consisting of Hellman's mayo and the tears of a pregnant mermaid

    [Kotta390] : My electric water pump puts out too much fuel at idle and is not a variable pump which makes it overheat in the summer at idle if I sit too long

    [KotaRT] : Ed, you can have cake, as long as I get something in return

  21. #21

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    That is a good find! Looked at so many sites I lost track but never ran across that one. Mine is going to be street driven so decided to go in-tank vs sump, back and forth many times, but right or wrong went in-tank pump. Looking at using 1" square tubing to build cage for cell, then adding 1" above tank for vents and lines, meant 10" cell would be 12" down. Got concerned about being so low and vulnerable to rear end hit. Pretty much decided to go 8" cell depth. At that depth everything was plastic or custom. Have finally found a local fabricator that does really nice work, reasonably. As soon as a I can finish the projects that are already in progress will be going back for final price to have cell fabricated. I have figured out what I (think) I need for baffling hole sizes, just have to clean up drawing.

  22. #22

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    Have a Fuel cell question, I just installed my fuel cell finally and I am using the 10AN feed and 8AN return that are at the bottom in the front of the cell. I have two more 8AN ports on the top of the cell and one is marked tip over valve and there is a ball in there, so I assume that is a check valve. Question is the vent that returns to the EGR vacuum system on the truck should be connected to the Tip over valve and cap the other 8AN port as it is not used? Hopefully I am not over thinking this.
    I did use a 240-33ohm sender from Summit racing and it has alot of vertical and float swing adjustments that can be done.

    Thanks,

  23. #23



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    Quote Originally Posted by Electrical Tech View Post
    Have a Fuel cell question, I just installed my fuel cell finally and I am using the 10AN feed and 8AN return that are at the bottom in the front of the cell. I have two more 8AN ports on the top of the cell and one is marked tip over valve and there is a ball in there, so I assume that is a check valve. Question is the vent that returns to the EGR vacuum system on the truck should be connected to the Tip over valve and cap the other 8AN port as it is not used? Hopefully I am not over thinking this.
    I did use a 240-33ohm sender from Summit racing and it has alot of vertical and float swing adjustments that can be done.

    Thanks,
    The 8AN return should be one the fittings on top of the tank, I put a filter on the tip over valve...You have to vent the tank.
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  24. #24

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    Quote Originally Posted by Adobedude View Post
    The 8AN return should be one the fittings on top of the tank, I put a filter on the tip over valve...You have to vent the tank.
    Same here. Though I am about to run the vent out under the truck so fumes don't collect when I put a bed cover on.
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  25. #25

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    OK, finally got my cell fabricated. Using an Autometer #3262 sending unit and adjusting the arm until when it rests on the bottom of the tank the in dash gauge reads with needle just touching bottom edge of red line for empty. With arm fully extended just missing top of tank gauge reads with needle just touching far side of full mark.
    Looking at the wiring diagram it appears that this must go through the PCM (2001) (also the way I tested). Once the tank is installed and grounded I will need a separate, sealed, insulated terminal to attach the "return" side of wire back to PCM. I called Autometer but they will not sell the terminal that comes with the sending unit separately (2nd pic). I have found these terminals before, but now that I "need" one I am unable to find one. Does anyone know where I can buy one separately?
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