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MG MGA - Gauge Wizard

I fitted a new fuel sender unit a year or 2 ago which was a vast improvement on the old unit because its resistance range was almost correct.
Its resistance range is 0.5 to 72 ohms which is really close to the correct range according to MGA Guru) of 0 to 70 ohms.

The old sender unit had a resistance range of 15 to 98 ohms which meant that the gauge showed full most of the time and dropped to about 1/3rd full when the tank was empty.

The new sender unit was much better in that the gauge did drop to about 1/8th full but would never quite drop to empty.

The trouble was that I started to trust the gauge a lot more than I did before which was a mistake, I normally keep an eye on the odometer to see how many miles I have driven since refilling the tank and doing this combined with an eye on the gauge has worked fine.

However, if you have ever attended any of the MGCCs MGA Weekend Tours or similar, you are often told to zero your trip at a certain points so that you can follow the route.
This meant that it is really easy to lose track of your actual mileage and this meant that I ran out of fuel on the way home from 2 of these events!


So a few months ago I bought Gauge Wizard (From Spyda) to see if its digital processor would let me correct the gauge so that it read correctly.

I had read about it in Safety Fast Magazine when the MGA Scribe Mr Edward Van Dyke wrote about the Gauge Wizard by Spyda. He had arranged with Spyda to include the MGAs sender unit (0 to 70 ohms) to be included in its range of built in pre-programmed range (or Pre-Sets)
This means that you install the gauge wizard, select the MGA pre-set and off you go.

Well, its no surprise to know that using the pre-set, my gauge didnt work any better than it did before!

So I had to then go through the Spyda recommended procedure of filling the tank in 2 1/2 gallon steps and programming the gauge wizard each step of the way.
You start with an empty tank and work your way up to the tank being full.

It is a bit tedious and I must admit that I was not totally comfortable with the process as you have to handle a lot of fuel to do this. (In did keep a couple of heavy duty fire extinguishers handy.)

You have to input the sender units output to the gauge wizard in 1/4 steps, from empty through to full so that it remembers each setting.

Then you programme the gauge wizard to move the gauge needle to match the newly memorised settings from the sender unit.
This means that when the sender unit sends empty, the needle also shows empty and when the sender unit send full, the gauge then also shows full. etc

At first I was unsure if there was any real improvement, the gauge showed full for longer than I expected. But this was because when I checked the resistance reading of the sender unit on the 3/4 full mark, there wasn't so much difference from the full resistance reading.

However, once the fuel level dropped, the gauge began to show much more accurate readings.
I found that when the gauge showed 1/2 full there were exactly 5 gallons remaining in the tank and when the gauge showed 1/4 full there were exactly two and a half gallons remaining.

I have also installed the warning light option to act as a low fuel warning light, this illuminates continually when the needle drops to the 1/4 level and then flashes when the needle drops to 1/8 full.

It is a refreshing change to be able to look at the fuel gauge and know that what you see is what you have really got!

Cheers
Colyn
Colyn Firth

My old broom handle is graduated in litres..LOL
Gary Lock

Colyn
You had the chance to make a standby graduated stick, i hope you availed!
Mike
Mike Ellsmore

Colyn

Very interesting. I am currently having an extreme version of your MGCC event issue as I am setting up Scottish MGA day. Multiple zeroing the trip.

My question though is what is your source of the fairly accurate sender unit, is it the MGOC one? Found Gauge Wizard on web.

Several years ago I had a similar experience but not in my MG. I ran out of fuel on north end of M6. Walking back to car after calling RAC (pre mobile days) a police car stopped. Slightly worried at first he said hop in and he ran me back to my car and family in high speed reverse down hard shoulder. Then he said I am not very busy so he ran me to Southwaite Services at 100mph telling me about a training exercise the police did with 3 cars in parallel doing 130mph. Used the private road to get across motorway. Another fast drive back but he didn’t wait for a junction to turn round but put his blue flasher on and he did a u turn through small gap in barrier. I did wonder what would have happened if he had received a real emergency call! Quite an experience.

Paul
Paul Dean

Mike I never gave it any thought but it would have been the ideal time to make a fuel dipstick.

To be honest there was so much other stuff to do in the calibration process it would have taken me all day to sort through it.

I even made a note of the sender units resistance readings at all of the 5 points (ie. Empty,1/4, 1/2, 3/4, Full ).
This was so that if I ever had to do this again I could use the resistance readings to calibrate the unit instead of repeat having to refill the tank in stages.

Paul, I got my "almost perfect" sender unit from NTG Services.

A couple of tips.
1 If you do fit a Gauge Wizard unit, wire it with an extra long loom so that you can pull it down to be able to re programme it easily. It saves you from having to assume the usual undignified (but surprisingly comfortable) upside-down MGA position, head and shoulders under the dash, legs hanging over the tonneau!

2 I fitted the optional LED low fuel light which works a treat, but you have to select the maximum "Anti-slosh" setting. Otherwise, the light will occasionally flash even if the tank is only half empty, because of the movement of the fuel in the tank.
(If you are like me, a flashing low fuel light is difficult to ignore)

The anti slosh feature tells the gauge to ignore any sudden needle movements.

Hope that helps
Colyn
Colyn Firth

This thread was discussed between 13/07/2018 and 14/07/2018

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