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 Posted: Jan 20, 2016 02:17PM
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Quote:
Originally Posted by dklawson

That's very interesting.

Since you are not running stock gauges, you have a couple of choices.  As you said, you can use the aligator clip gauge you have with your existing sender.  If you get tired of that, you could fit a later sender to your tank and use the new gauge you bought.  $50 from our host for the new 270-30 sender.

Right you are, Doug.  

There is one other option, though.  I need to get in touch with RCI and see if they offer a sending unit for this 4-gallon fuel cell that's been gathering dust here for the past couple of years. I really hope to get it installed sometime this year.  I've been holding off on that until I see what the SCCA is going to do with my car because the bulk of my ballast to achieve minimum weight is in the spare tire well in the boot and the fuel cell is going to have to mount above it.  I don't want to permanently mount the fuel cell until I know, for sure, what my required minimum weight is going to be.  Under the current Heritage Classic proposal that we sent to the Solo Events Board just before Christmas, I would have to weigh 1480. That's ten pounds more than I had to weigh in G-Prepared, before the SEB killed our class, but it's 50 pounds less than the Spridgets would have to weigh under our current proposal.    

 Posted: Jan 20, 2016 12:07PM
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CA
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Quote:
Originally Posted by Jemal

I've selected this thread as my "Post of the Week" for the "Classic Mini Blog" that I've recently taken over.... ...  I'll make a new post about it soon, but for you guys deep into Classic Mini details like the fuel gauge specs, consider this a sneak preview!  I can't get a screen grab to show you, but it's right there! 

Just for you, Jemal!

.

"Hang on a minute lads....I've got a great idea."

 Posted: Jan 20, 2016 11:01AM
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US

That's very interesting.

Since you are not running stock gauges, you have a couple of choices.  As you said, you can use the aligator clip gauge you have with your existing sender.  If you get tired of that, you could fit a later sender to your tank and use the new gauge you bought.  $50 from our host for the new 270-30 sender.

Doug L.
 Posted: Jan 20, 2016 10:26AM
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Quote:
Originally Posted by dklawson

Bayonet ring senders should be 270 to 30 Ohms empty to full.  If you get the fuel level lower than the hole in the side of the tank, it is pretty easy to remove the sender and bench test its resistance.  While it is out you can flush the sender with spray carb cleaner and work the float arm through its range several times to remove deposits.  If you are lucky that will be all you need to do. 

When putting the sender back in, remember the non-insulated spade lug spot welded to the sender flange is the ground connection and receives the black wire.  The other terminal will be attached to a nylon insulator.  It gets the green/black wire that goes to your gauge.

Let us know what you find.

And the verdict is -- I think I must have one of those "interim period" sending units.  It's bayonet mount but it measures 0-90 (or thereabouts).  On top of that, I think the 0-90 gauge that I bought a couple of years ago is either defective or they sent me the wrong one.  Either way, it's too late to return it.

As an additional test, I poked my wooden dowel "dipstick" down into the tank and it showed that I only had about 1/2-gallon of fuel left.  (It's a good thing that I completed all six of my AutoX runs Sunday before I ran out of fuel on-course)  At that point, the sender resistance measured 12.6 ohms.  I added one gallon of fuel and it read 26.5 ohms.  Given that my fuel quantity measurement isn't exact and the sending unit probably isn't linear, that would be about right.

In all of my messing around, I came across an old square fuel level gauge out of "something" in one of my parts boxes.  Just for the heck of it, I hooked it up and it showed 1/4-tank.  Well, whatta ya know -- 1-1/2 gallons would be 1/4 of a 6-gallon tank!  So now I've got a way to measure.  Instead of poking a stick in the tank I can just alligator clip that guage in and get a reading.

Thanks, everybody, for all of the help and advice.

 Posted: Jan 20, 2016 05:08AM
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US

Bayonet ring senders should be 270 to 30 Ohms empty to full.  If you get the fuel level lower than the hole in the side of the tank, it is pretty easy to remove the sender and bench test its resistance.  While it is out you can flush the sender with spray carb cleaner and work the float arm through its range several times to remove deposits.  If you are lucky that will be all you need to do. 

When putting the sender back in, remember the non-insulated spade lug spot welded to the sender flange is the ground connection and receives the black wire.  The other terminal will be attached to a nylon insulator.  It gets the green/black wire that goes to your gauge.

Let us know what you find.

Doug L.
 Posted: Jan 19, 2016 06:55PM
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Quote:
Originally Posted by dklawson

At some point in 1964 there was a transitional sending unit but I would think it unlikely to be on your 1965... unless your '65 is the year of first registration, not the year of build.  re-1965 senders will bolt to the fuel tank and they are the ones that read 0 Ohms = Empty to about 90 Ohms = Full.  The later senders mount to the tank with a locking bayonet ring.  They are the ones that read 270 Ohms = Empty to 30 Ohms = Full.  If I remember correctly, the transitional sender is supposed to bolt on to the early tank but have the resistance range of the later senders.  I have never seen one up close.

Does your sending unit bolt on or use the bayonet ring?

When the fuel level is down, disconnect the black and green/black wires from the sending unit.  Connect a multimeter across the sending unit terminals.  Note the resistance reading with the arm down.  Now use a coat hanger through the filler neck to lift the float arm and when it is at the top, record the "full" resistance reading again.  Let us know what you find.

This one has a bayonet mount sending unit.  If the weather warms up enough tomorrow, I plan to check the resistance across its entire range -- something I probably should have done a long time ago to eliminate the guess work.  

 Posted: Jan 19, 2016 05:15PM
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US

At some point in 1964 there was a transitional sending unit but I would think it unlikely to be on your 1965... unless your '65 is the year of first registration, not the year of build.  re-1965 senders will bolt to the fuel tank and they are the ones that read 0 Ohms = Empty to about 90 Ohms = Full.  The later senders mount to the tank with a locking bayonet ring.  They are the ones that read 270 Ohms = Empty to 30 Ohms = Full.  If I remember correctly, the transitional sender is supposed to bolt on to the early tank but have the resistance range of the later senders.  I have never seen one up close.

Does your sending unit bolt on or use the bayonet ring?

When the fuel level is down, disconnect the black and green/black wires from the sending unit.  Connect a multimeter across the sending unit terminals.  Note the resistance reading with the arm down.  Now use a coat hanger through the filler neck to lift the float arm and when it is at the top, record the "full" resistance reading again.  Let us know what you find.

Doug L.
 Posted: Jan 19, 2016 04:13PM
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Well, so much for that little experiment.  After hooking up the 240-33 gauge with clip leads, it still showed full with only about 2 gallons of fuel in the tank.  I measured the resistance from the sender to ground and it read 39 ohms.  After making 6 full-blast AutoX runs this past Sunday, I measured the resistance again today and it showed 8 ohms.  So that tells me the sender resistance is dropping along with the fuel level -- which takes me back to the 0-90 gauge and my belief that my sender is toast.    

 Posted: Jan 12, 2016 09:30PM
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Johnlee:

Your original post says you wanted an inexpensive gauge until you get around to installing a fuel cell.

That was why I answered your post.

A fuel gauge as used in MGB will work with the Mini tank unit.

Have fun,

Russ

 

 

 Posted: Jan 12, 2016 05:19PM
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Quote:
Originally Posted by CA2SBL1275

Johnlee:

If you had asked here, you could probably found someone with an old gauge that they would sell to you cheep.

That would have solved your problem but you would not have the learning experience.

Russ

I'm sure I could have, Russ -- IF I had wanted a factory-type gauge.  But I wanted another aftermarket gauge to match the others in my homemade dash.

 Posted: Jan 12, 2016 03:31PM
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Johnlee:

If you had asked here, you could probably found someone with an old gauge that they would sell to you cheep.

That would have solved your problem but you would not have the learning experience.

Russ

 Posted: Jan 12, 2016 01:58PM
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US

I've selected this thread as my "Post of the Week" for the "Classic Mini Blog" that I've recently taken over.... It is such useful info to have at your finger tips!    One of my goals with writing a regular blog is to capture useful current info that can easily be searched when needed.  The "Classic Mini Blog" is done on a simple wordpress, pretty much like my CooperRoadMini site, so I shouldn't get overwhelmed with too many buttons!

If you'd like to follow my rants and raves, or just my civilized discourse, you can get to the blog anytime just under the "Home" tab to the right of the "Mini Mania" logo.... hover over "Home" and click on "Classic Mini Blog".   I'll make a new post about it soon, but for you guys deep into Classic Mini details like the fuel gauge specs, consider this a sneak preview!  I can't get a screen grab to show you, but it's right there! 

 Posted: Jan 11, 2016 06:10PM
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Went to AutoZone today and ordered an Equus 7363 fuel level gauge with 240/33 range.  It's supposed to be here tomorrow afternoon.  I'll report back after I get it hooked it up.

You guys have been a great help.  Thanks a bunch

John

 Posted: Jan 10, 2016 07:18PM
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Thanks, guys.  That makes a whole lot more sense and helps explain why my gauge reads Full with only 2 gallons of fuel in the tank.  I guess I'd better start shopping for a 240-33 gauge and find somebody with an older Chebby or Mini equivalent who can use the 0-90 one.

BTW -- the one I have now is a Sunpro.  But, while searching for information about it, I learned that Sunpro gauges are now Bosch.  The numbers are the same but the prefix letters have changed.  For example, a Sunpro CP-xxxx is now a Bosch FST-xxxx.  It's the same gauge but with a different name and prefix letters.  And, as usual, they're all cheaply made in China!!!

 Posted: Jan 10, 2016 04:43PM
 Edited:  Jan 11, 2016 04:37AM
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Minis before late 1964 had the 0-90 Ohm (empty to full) range that you mentioned.  That is comprable to some GM guage systems.  

From 1965 on the classic Mini had a sending unit with a resistance range of about 270 Ohms = Empty to about 30 Ohms = full.  These are nominal values.  If you measure a Smiths sending unit it probably won't match these values exactly.

To use an aftermarket gauge with the Smiths bayonet mount sending unit you will need a gauge that works with the industry standard range of 240 Ohms = empty to 33 Ohms = full sending unit.  Your gauge will show empty a bit sooner than true empty but consider that a safety bonus to prevent you from running out of fuel.

Alternatively you can order the fuel gauge wizard from Spiyda Design in the U.K.  It will allow you to match almost any gauge with almost any sender.

Spiyda Design Link

Fuel Gauge Wizard Link

If you use an aftermarket (non-Smiths) fuel gauge you are not likely to need the voltage stabilizer.  Most modern aftermarket gauges have their own voltage stabilizer built inside.

 

Doug L.
 Posted: Jan 10, 2016 01:47PM
 Edited:  Jan 10, 2016 01:50PM
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The sender unit is the part with variable resistance. The gauge measures current based on the input voltage and the resistance of the sender unit. The original Mini gauge is powered by a 10v voltage stabilizer. You need a voltgae staibilizer oyherwise changes in the voltage would cause fluctuations in fuel levels. It would be a fluke if your after market gauge worked exactly like Smiths gauge and the original sender unit. A Mini sender unit has something like 30 ohms when the tank is full and 270 ohms when the tank is empty. The gauge you bought should have come with a specification list.

The power of accurate observation is commonly called cynicism by those who have not got it. G.B.S. Sarcasm is the lowest form of wit. Oscar Wilde

//www.cupcakecooper.ca/

 Posted: Jan 10, 2016 12:56PM
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Does anybody know the correct resistance range for an after-market fuel level gauge?  This would be installed in a '65 Mini Saloon with the factory (AHU1029) sending unit in the factory gas tank  Several people told me that it was the same as the early GM cars -- 0-90 ohms -- but when I bought and installed one of those gauges, it reads Full with just 2 gallons of fuel in the tank. So that, obviously, isn't the correct resistance range.  OR, my sending unit is frobbed!

I'm getting tired of poking a stick down into the tank to see how much fuel I've got left, or running out of fuel in the middle of an AutoX run, so I'd like to use an inexpensive gauge until I can get around to installing my RCI fuel cell.