Fuel Tank Sender ..

Post by **JustinMinor1000** » Fri Nov 28, 2003 7:19 pm

I bought a new fuel tank sender and fitted it into the car in exactly the same place as the old one had been. The guage only ever read to 3/4 full.

Now as much of an idiot as I am it looks to me as if the float should actually rise above the level of the sender but if I want to put it that way there appears to be something in the way and the book does not seem to give me any indication as to how to fit it.

Can anyone let me know for sure ?

Post by **Willie** » Sat Nov 29, 2003 2:24 pm

Yes,there will be something in the way if you try to fit it
the wrong way round!! ( It will go in ok but the float will be prevented from risingand it will only ever read less than
full. It is important to fit the correct sender unit to match
the fuel gauge. what year is your Minor, what colour the
speedo face,and what was the original terminal on the sender
unit? i.e. a nut or a Lucar push on connector? The terminal
should be on the left hand side looking from the rear of the
car.

Post by **JustinMinor1000** » Sat Nov 29, 2003 9:48 pm

Willie wrote:Yes,there will be something in the way if you try to fit it
the wrong way round!! ( It will go in ok but the float will be prevented from risingand it will only ever read less than
full. It is important to fit the correct sender unit to match
the fuel gauge. what year is your Minor, what colour the
speedo face,and what was the original terminal on the sender
unit? i.e. a nut or a Lucar push on connector? The terminal
should be on the left hand side looking from the rear of the
car.

Willie,

Thanks very much for the reply, it's a 69 car and the sender unit has a Lucar connector on it. It would read correctly if I could fit it (Looking from the back of the car) with the float going to the left (Ie to the Fuel cap) However there is a baffle in the way. What sort of different speedo's are fitted to moggies ?

Post by **Matt** » Sat Nov 29, 2003 9:55 pm

there are ones with a black face - and ones with light coloured faces (dont know which colour)

Post by **elainemr** » Sat Nov 29, 2003 10:40 pm

Matt, I think "opposite the Albert Hall" has to be one of the best locations on this website!

Post by **Gareth** » Sun Nov 30, 2003 9:32 am

The light coloured faces are a sort of silver / goldish colour. Some refer to them as the "bronze speedo" cars - they look fab!

Post by **Willie** » Sun Nov 30, 2003 9:54 am

Your '69 car should have a black faced speedo, if you give me
the chassis number I can tell you what the serial number on
the face should be. The only time I have heard of a gauge
only reading 3/4 full maximum was when the sender unit had
been fitted 180 degrees out. Is the arm carrying the float
straight?

Post by **Willie** » Sun Nov 30, 2003 10:07 am

JUSTIN...CORRECTION. I have just removed the spare wheel
to check and I have given you wrong info. looking from the
rear the Lucar connector should be slightly to the RIGHT of
centre on the sender plate, sorry about that.

Post by **Willie** » Sun Nov 30, 2003 12:41 pm

Another thought, did the gauge EVER read correctly or did
you fit a new one to try to get a full reading? You could try
removing the lead from the sender unit and shorting it to the
tank metal. With the ignition on the fuel gauge should read full,
if it does not then short the lead direct to the chassis,not the
tank, and see if it now reads ok. That would indicate that the
tank is not in good contact with the chassis(corrosion)?

Post by **JustinMinor1000** » Sun Nov 30, 2003 9:01 pm

Yes, it does read full in "short" condition. No it never (in our ownership) read full and I origionally refitted the new sender in the same orientation as the old one. But it seems wrong to me .. if there wasn't a baffle on the way it would make sense to fit the guage 180 degrees around from where it is now.

Willie wrote:Another thought, did the gauge EVER read correctly or did
you fit a new one to try to get a full reading? You could try
removing the lead from the sender unit and shorting it to the
tank metal. With the ignition on the fuel gauge should read full,
if it does not then short the lead direct to the chassis,not the
tank, and see if it now reads ok. That would indicate that the
tank is not in good contact with the chassis(corrosion)?

Post by **Willie** » Mon Dec 01, 2003 7:48 pm

One other question, does the top of the petrol tank stick up
through the boot floor by about an inch or so? I ask because
the earlier (5 gallon) tanks were not as tall. This could give a
wrong reading BUT I am not sure if they are interchangeable
anyway. If you have fitted the sender with the Lucar terminal
slightly to the right of centre on the sender plate and with the
float swinging in the same plane as from one rear wheel to
the other and it still reads 3/4 full max then compare the
angle of the rods which hold the float. If you think about it
you only have to bend the rod carefully, as a last resort, so that
the float sits a bit LOWER to give a 'Higher' reading on the gauge
at the same level of petrol! BUT if that is not the actual problem
then you will not get an accurate 'empty' reading so you would
have to do a careful check. Can't think of any other suggestions.

Post by **Matt** » Mon Dec 01, 2003 11:57 pm

thanks elainemr, i am i uni halls of residence, it is about 150 yards from my kitchen!

Post by **Willie** » Tue Dec 02, 2003 3:25 pm

Geoff, if his sender has a Lucar connector and fits the Minor
tank then it IS the correct unit, there are no alternatives
at least,as far as I am aware,
The other Minor type has a nutted terminal and makes the
later fuel gauges read BACKWARDS.

Post by **Willie** » Wed Dec 03, 2003 7:15 pm

Yes Geoff i am fully conversant with the workings of the sender
unit,but i doubt that Justin has access to an AVO or the equivalent.
Your suggestion of trying it out of the tank is much more practical,
so we are waiting for some feedback aren't we?

Post by **JustinMinor1000** » Wed Dec 03, 2003 8:36 pm

Electrically they are both exactly the same. What I need to do is to post some photo's here so that we are all sure we are talking about the same thing.

It might be worth running the tank out, and measureing the resistance with the Float "Down" and compareing it with the other unit at full travel. If it's lower then assuming all other thing's to be equal then simply bending the arm should simply bring it all back in line. The danger I could see with the "Bend the arm" answer is that it could read 1/4 full when in fact it's bone dry which is one heck of alot more dangerous than reading 3/4 full when it's full.

Geoffb wrote:Yes Willie I hear that, I was after getting him to check the electrical characteristics of the sender, not the physical one. A sender (electrically) is nothing more than a variable resistor, one end goes to Earth, and the other end goes to the guage. The float arm moves a slider that runs up and down the resistance wire which is (usually connected to earth. hence the resistance varies dependent upon the level in the tank. It may be for example be 0 ohms for empty 1K ohm for 1/2 and 10K ohms for full dependent on the guage (or vica versa). I will get the decade box out at lunch time and post some real values off my 4 door, which has a Gold/Bronze faced guage with black lettering. If there is some resistance in the wiring between the sender and the guage that could account for the problem, If the instrumentation (and I'll check) runs off a voltage regulator that could be faulty and could also give similar effects, any of these things being at fault, bending the "arm" will not fix the problem !!

Post by **57traveller** » Thu Dec 04, 2003 4:10 pm

Had this same problem some months ago, fuel gauge only showing 3/4 full with a full tank.
Don't know if this has been mentioned earlier in this thread but the voltage stabiliser, attached to the rear of the speedo, had fried. Fitted another 2nd hand unit and all was well. It could be that simple!

Post by **Willie** » Thu Dec 04, 2003 5:01 pm

That's some useful data Geoff but, is not applicable to Justins'
sender as he has the Lucar connector type with a black faced
speedo. Your 'Nutted' sender unit is for the earlier 948 fuel
gauge and will not work on a later1098 type. In fact it will make
the fuel gauge read backwards! I fancy '57's suggestion
because Justin says it was the same 3/4 reading on his original
sender unit as on the replacement so perhaps he ought to take
his speedo out and check the voltage at the Light Green wire
on the gauge? Are you watching Justin? What may be the
answer is that Geoff says his float points towards the REAR
of the car! Without removing my sender I cannot say where
my LUCAR type unit points but reaffirm that the lucar terminal
should be just to the right of centre on the mounting flange
looking from the rear......you have not confirmed that Justin?

Morris Minor Owners Club

Fuel Tank Sender ..

Fuel Tank Sender ..

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Re: sender

speedo

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3/4 full

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