MK1 fuel gauge.

Post technical questions here.
Post Reply
1970 cortina GT
Posts: 311
Joined: Thu Dec 05, 2013 7:19 pm
Location: Saskatoon, Saskatchewan

MK1 fuel gauge.

Post by 1970 cortina GT » Thu Mar 21, 2019 7:27 am

I've started another post on my fuel gauge woes, don't want to get booted off the forum for the longest thread ever............... It's that time of year again where I can get some work done on the car. Planning on taking the sender and gauge out again and trying to find out what's not right. I'll be looking to start from basics, lots of replies and suggestions which I am very grateful for. What's the best step by step way to check and determine where the fault lies. Thanks.
Life isn't complete until you have a pair of twin cams in the garage...

Bob_S
Posts: 398
Joined: Fri Nov 27, 2009 8:22 pm
Location: Michigan, USA

Post by Bob_S » Thu Mar 21, 2019 12:53 pm

I think you should be booted off the forum for having the longest thread in the history of the world..... Just kidding! :D

Since you have gone through all the parts individually is there a chance of taking all the parts off the car and set then up on the bench and test them as a system? Meaning the fuel gauge, voltage regulator and sending unit. If they all worked on the bench it would point to the wiring in the car as the problem.
Bob_S
First car 70 Cortina GT

1970 cortina GT
Posts: 311
Joined: Thu Dec 05, 2013 7:19 pm
Location: Saskatoon, Saskatchewan

Post by 1970 cortina GT » Thu Mar 21, 2019 1:19 pm

Thanks Bob, it's worth a try, I guess running a new wire from the sender to the gauge is essentially the same thing. I'm building up the motivation to swallow a litre of gas again and strip it down :cry:
Life isn't complete until you have a pair of twin cams in the garage...

Bob_S
Posts: 398
Joined: Fri Nov 27, 2009 8:22 pm
Location: Michigan, USA

Post by Bob_S » Thu Mar 21, 2019 2:07 pm

The advantage of bench testing is that you eliminate any possible bad grounds, corroded wires and connectors. You can also swap in and out components much easier. Clean the connectors on the components with a wire brush or small file prior to testing.

I would also soak the sending unit float in gasoline overnight. Then check it to see if you hear any gas sloshing around in it. Solder seams are known to leak over time due to temperature changes causing expansion/contraction of the metal.

You may want to use dielectric grease when you reassembly the part in the car.
Bob_S
First car 70 Cortina GT

1970 cortina GT
Posts: 311
Joined: Thu Dec 05, 2013 7:19 pm
Location: Saskatoon, Saskatchewan

Post by 1970 cortina GT » Thu Mar 21, 2019 3:22 pm

Sound advice, thank you.
Life isn't complete until you have a pair of twin cams in the garage...

1970 cortina GT
Posts: 311
Joined: Thu Dec 05, 2013 7:19 pm
Location: Saskatoon, Saskatchewan

Post by 1970 cortina GT » Sun Mar 24, 2019 3:50 pm

Here is what we found with the sending unit, voltage stabilizer, and fuel gauge on the bench. The voltage stabilizer turns down the voltage from 12v to a steady 5v. The sender unit reads 20 ohms full and 200 ohms empty. The fuel gauge gives a 12 ohm reading when empty. We hooked it all up and had the same half a tank on the gauge when the sender float position is giving out 20 ohms and should read full. We did available voltage readings, coming out of the voltage stabilizer was 5 volts, going into gauge 5 volts still. Coming out of gauge 3.3 volts ( remaining voltage eaten up by sender unit). We verified that by supplying 5 volts to the gauge it ran past full.
So the sender gives the correct ohms readings between empty and full, the gauge appears to work yet the sender unit is only leaving 1.7 volts for my gauge to read full when it appears it's not enough. So is it the sender even though it has the correct range? Or does the sender need to go down to 10 ohms ? If this is the case can the current one be converted?
Appreciate anyone's thoughts
Life isn't complete until you have a pair of twin cams in the garage...

1970 cortina GT
Posts: 311
Joined: Thu Dec 05, 2013 7:19 pm
Location: Saskatoon, Saskatchewan

Post by 1970 cortina GT » Mon Mar 25, 2019 5:20 pm

Last post on my fuel gauge..... honest. It’s now working correctly , it turns out the gauge needs 10 ohms to read full. Gauge is new but the range is 20 to 200 ohms so I had to bend the max level tab on the sender slightly to give me that extra 10 ohms, well 10 ohms less. Not sure how 10 ohms gives me an extra half tank reading but it’s a fact. Hopefully someone else will benefit from these posts at some point. Thanks again to everyone for suggestions.
Life isn't complete until you have a pair of twin cams in the garage...

Bob_S
Posts: 398
Joined: Fri Nov 27, 2009 8:22 pm
Location: Michigan, USA

Post by Bob_S » Mon Mar 25, 2019 5:51 pm

THANK GOD! Just kidding🤣

Glad you figured it out and it’s working the way it should. The littlest things can take the longest to figure out.
Bob_S
First car 70 Cortina GT

Post Reply