Matching fuel guage to sender

[keith_h]

Re: Matching fuel guage to sender

Hi Rob,

I like the look of your circuit but I have a slight problem. When I built the car I made the whole dash look like the Sierra instrument cluster (from a wiring point of view) and terminated everything into a single multi-plug which matched the socket on the Sierra loom. That in itself is not a problem to break into (although I am a little reluctant as everything worked first time and touch wood I have never had a problem in 15 years - there's tempting fate). The real problem is that the dash is a real pig to get out whereas the sender is just behind me and very accessible. Is your idea re-workable to do something at the sender end?

[ROBERT.JACKSON]

Re: Matching fuel guage to sender

Well I have been watching this thread with great intrest as I have a SWB Marlin with a Ford Escort MK2 van fuel tank and a fuel gauge from an MGB and it has always shown 1/2 full on the gauge when empty. When I got the car over four years ago it had a clothes peg wrapped in a fine wire sttched to the wire from the tank sender to the gauge and the previous owner told me it was to help the gauge to operate correctly. I removed this peg wire thing and it made no difference to the gauge settings, so I have just put up with untill today. I have removed the tank sender and adjusted the tank min stop position and bent the float rod and moved the float manually and it works a treat. Measured the fuel in the tank with a stick and compared it to the float position and the gauge and adjusted the float rod to match the gauge compared to the marking on the stick. Refitted the sender to the tank and it seems to work ok. So up to know I do need any fancy pots or resister things. I have read all the threads dated in 2005 also and a mate of mine says it is a common issue on the Robin Hood forum and the most common fix is to bend the float rod to match the gauge.

[robert]

Re: Matching fuel guage to sender

Nice one Bob - the simplest ideas are usually the best! You could, of course, ignore the gauge altogether and just use the dipstick :-)

Keith, if you have a 10V regulator in the circuit already then something like this might work for you (see image). However it's not adjustable so to get it right we would need to know a)is there a voltage regulator in the circuit already or is the gauge fed directly from 12V? If you're not sure, disconnect the wire from the sender and measure the voltage on the wire (but what happens if it's a bi-metal reg? - does anyone know how fast they switch?). b) what is the resistance of the gauge? If you can't get to it, measure the resistance of the sender with the wire disconnected then measure the voltage on the sender with the wire connected.

Alternatively, my original circuit from 2005 should work from the sender end. Thanks to Patrick, this is available at http://www.msportster.co.uk/files/FuelGuage.pdf
along with the calibration spreadsheet at http://www.msportster.co.uk/files/FuelGauge.xls

Have you made any progress with the resistance wire?

[jon_cox]

Re: Matching fuel guage to sender

For those of us who use the Escort Van petrol tank then the easiest and most cost effective method is to use the gauges from the old Ford Cortina. I have these and the petrol gauge matches the sender perfectly. There are a couple of sets on eBay at the moment 280159905394 or 320164733450 but they seem to come up quite often.

[robert]

Re: Matching fuel guage to sender

Just in case there's anyone out there who hasn't had enough of all this, here is yet another circuit for your consideration.
It's a bit simpler than my previous effort but does rely on there being an electronic 10V regulator feeding the gauge (the bi-metal one will upset it). This is because the output is a voltage rather than a current as on the 2005 one.
The values shown are for the 10-180 ohm sender and the smiths 60 ohm, 20-120mA gauge. Best of all, R2 adjusts the empty end and R3 adjusts the full end with very little interaction between the two (we could make R3 a pot also in which case I would suggest a 200R pot in parallel with a fixed 15R resistor - this would probably need some experimentation). The total cost of the components should be about £2 - £3.

Keith, this should work for your setup too, but we would need those gauge measurements. Incidently, I am wondering if your SW gauge has the regulator built in - it would make a lot of sense.

Finally, I should point out that I have not actually built this circuit so I cannot guarantee that it will work - it is intended as a basis for experiment. The spreadsheet simulation looks promising though.

Anyone still awake?

[keith_h]

Re: Matching fuel guage to sender

Hi Rob,

I'm coming to the conclusion that I am going to have to delve into the back of my dashboard but that will have to wait as I am off on hols. on Sunday