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CMC MGTD kit fuel tank

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  • #232674
    John McDermon
    Participant

    @hawk521

    My Chevette based MG TD arrived last October partly assembled by the prior three owners who collectively had held it and/or worked on it for some 25 years.  It was a semi-basket case.  I completed the install (including a LOT of re-work) and it is finally on the road with pretty much everything is working.

    My first fill-up (on a dead empty tank) took only about 7 gallons.  And even part of that spilled out of the vent tube.  The fuel gauge now reads about 3/8 full.  I do not yet know if the gauge is anywhere close to being calibrated properly, but the tank sure appears to be larger than 7 gallons.

    Does anyone know the capacity of the standard fuel tank that was supplied with these kits in the mid 80s?  It appears to be a rectangular galvanized steel box attached between two rear frame members.  I will measure it this weekend and calculate capacity but was thinking one of you guys would know this off the top of your head.  I’m hoping my problem is simply that the rubber vent tube was poorly placed and/or misrouted and is somehow allowing fuel to dump through it even though the tank is only partially full.

    Sunny day forecast for tomorrow.  I’ve only got 10 miles logged so far, but that’s going to change!  Might venture as far as the Blue Ridge Parkway if she keeps purring along.

    John McDermon, Rural Hall, North Carolina

     

     

     

     

     

     

    #239199
    Mel Zeiger
    Participant

    @luvmytd

    My ’85 CMC ford only hold about 9 gallons. luvmytd40004.6484722222

    #239200
    James Cochran
    Participant

    @jascochran

    I am not for sure the capacity of mine, but I have been putting in about 5 gallons when mine gets just below a quarter of a tank.

    #239201
    Rob Baker
    Participant

    @robbaker

    My gas guage is not reading properly so I’m filling up every hundred miles.

    #239202
    Steve Crites
    Participant

    @ringo

    John

    Welcome to the group!

    Since you describe the tank as rectangular, I really doubt it’s a stock tank. Chevette and Pinto tanks are flatter than what I would call rectangular, so the only way to be sure of capacity is to measure dimensions.

     You might want to test the sender with an OHM meter to see if it’s in spec.  My experience says replace it if in doubt.  (Nothing seems to work for me when tryin to fix the old ones). 

    Ringo

    #239203
    Montie Henderson
    Participant

    @montie

    Guess I’ll join the pack too and put my 2 cents in.  My gas gauge dosen’t work either, one of the things I’ve been wanting to fix.  I’ve just been doing like Rob and filling up about every hundred miles.  It takes about 5.5 to 6.5 gal each time.  Sounds as though the gauges aren’t too reliable.   

    #239204
    Mark Hendrickson
    Participant

    @pink-mg

    The senders in these cars are usually the culprit. Today’s gasoline eats up everything. The older stuff was not made to withstand the additives, especially the ethanol, in today’s fuel. Letting our cars sit for long periods of time with today’s fuel in them doesn’t help either.

    Measure your tank’s dimensions, get the cubic inches and convert that to gallons or litres to determine the tank’s capacity. My Ford based CMC tank was aluminum and held 8.2 gallons.

    A quick test for the gauge or sender is to disconnect the wire at the sender. The gauge should read below empty. With the ignition switch turned to “on” touch the wire you just connected to ground (away from the fumes please) and if the gauge reads over full, the sender is bad. If it just stays below empty on the gauge, it’s the gauge.

    Most gauge/sender set ups work on two different ohms range values. GM had one and Ford used another. Aftermarket gauge companies usually offer fuel level gauges based on this too. Or in some cases, they have their own senders that usually operate on the GM ohms range values.

    #239205
    Rich Bellefeuille
    Participant

    @richbelfay

    All,

    This was driving me nuts. My gage seems to work fine. It read just below 1/2 when I filled it a few minutes ago. It took 6.39 Gallons. That would put the capacity at around 12. So not leaving things to chance and applying a little math, I came up with the following:

    My tank is 15″X20″X9.25″ which = 2775 Cubic Inches

    There are 1728 Cubic inches in a Cubic Foot

    2775/1728= 1.605 Cubic Feet in the Tank

    1 Cubic Foot = 7.48051945 Gallons of Liquid

    1.605 X 7.48051945 = 12.0129 Gallons in the Tank

    So, I think mine is a 12 Gallon Tank. Any Questions?

    Rich

    #239206
    Steve Crites
    Participant

    @ringo

    Rich

    So did the gauge go all the way to full after filling?  If so, you can’t beat perfect!

    Ringo

    #239207
    Rich Bellefeuille
    Participant

    @richbelfay

    Ringo,

    Yup, gage went all the way to F. By the way, my wife still thinks E means “Enough”

    Rich

    RichBelfay40009.8656481481

    #239208
    Dan Rosa
    Participant

    @dan-r

    Hawk I have had the same trouble with many cars that sat for a long time ,remove the sending unit ,wire it to the guage, sending unit out of the car, where you can watch the guage, move the float up and down and see if you have dead spots you can clean them with sand paper . at the same time you will see if your ground is at falt , after setting a long time things tend go bad I had to solder 2 holes in my float __________Good Luck DanR

    #239209
    Mark Hendrickson
    Participant

    @pink-mg

    I love math wizards!

    My ’74 Beetle has a screwy gauge. If it’s totally full, the gauges reads fine. When it hits 3/4 tank the needle disappears below empty. So, last night I disconnected the sender wire and the needle stayed below empty. I touched the wire to ground and the needle went beyond full.

    We tried the same thing on my buddy’s ’87 Pontiac. When the sender was disconnected, it read beyond full. Grounded, it read below empty. So the wiring is the opposite of the VW.

    I’ll be ordering a new float/sender for the VW today.

    #239210
    John McDermon
    Participant

    @hawk521

    Measured my tank today and it is the same size as Rich’s tank.  12 gallons.

    My gauge was not initially wired and the gauge read below empty.  When I hooked up the gauge it read about 1/4 tank.  But after a fillup it still reads 1/4 tank. 

    This car sat for many years in a semi-finished condition.  The seller I dealt with said the tank had never had fuel in it.  It smelled like gas though – so I take his comment with a grain of salt.

    Most likely the sending unit is gunked up.  I may get to it one day – but am enjoying driving it too much to drop the tank out of it just now.

    Thanks for the discussion.  I learn something every time I spend a little time out here reading.

    Hawk

     

     

     

    #239211
    Dan Rosa
    Participant

    @dan-r

    Hawk ; You do not have to drop the tank, remove the spair and the cover it will be on the top  with 6 screws about 8 min . to get at it GOOD LUCK Dan R

    #239212
    Paul Mossberg
    Keymaster

    @pmossberg

    At full, my gas gauge reads full.

    With half a tank, it’s basically on empty.

    My more reliable gas gauge is the odometer. I follow three simple rules:

    Always fill the tank
    Always reset the trip meter
    Always start looking for a station at about 200 miles.

    Paul Mossberg
    Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
    2005 Intermeccanica Roadster

    If you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)

    #239213
    John McDermon
    Participant

    @hawk521

    Dan,

    Unfortunately for me, a prior builder of this car sealed up the spare tire cover with fiberglass.  It makes it tight – but certainly inhibits access to the things under that cover.

    I’ll sort it out sooner or later.  And meanwhile I’ll use the trip odometer to handle fuel needs.

    Thanks to all who’ve contributed.

     

     

     

    #239214
    Mel Zeiger
    Participant

    @luvmytd

    Hawk:

    FYI

    Moss sells a stick which you put down into the tank and it approximates the amount of fuel in there

    Mel

    #239215
    Rob Baker
    Participant

    @robbaker

    Did some investigation on my fuel system gauge not working this weekend.  It appears the sender has failed.  Just ordered a new sender Auto Meter part number 3262, 240 OHM, $39.  I’ll have it to install this weekend.  My tank is the same size as Rich’s and I have the Vintage Reproductions gauges so hopefully the original sender which is marked as 240 OHMS will work with the original gauges.  Install is pretty easy as I had the old one out to trouble shoot my problem.

    #239216
    Greg Stickney
    Participant

    @stickney

    Rich has the formula exactly right, and those are the same dimensions I have in my car. I figure 12 gallons is just about right, and my gas gauge seems to be accurate, although I need to test it to be sure.

    Greg

    #239217
    Rich Bellefeuille
    Participant

    @richbelfay

    All,

    Wow! You know math was never one of my best subjects, but as time has moved on I have developed a much better understanding and appreciation of it. Good to know I got the answer right. Take THAT elementary school math teacher, whoever you were!

    Oh yeah, and just to be absolutely sure, we shoud all fill ’em up and run ’em till they’re empty over and over again until we have a solid statistical sample  Enjoy the Ride!

    Rich (aka Math Wizard)

    RichBelfay40016.3298726852

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