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TR2/3/3A How to test fuel gauge & sending unit?

toysrrus

Yoda
Offline
Hi Folks,

My fuel guage suddenly decided to read "Empty" even when fuel tank is full?? My '61TR3 is a positive ground system. How do I check the guage & sending unit to see if either one is faulty?

Thanx for responding quickly, in advance, as I'll be in the shop 9:30AM today EST.

Thanx, Russ
 

TR3driver

Great Pumpkin - R.I.P
Offline
First make sure the gauge is grounded. If you haven't added a ground wire for it, temporarily connect a test lead from the mounting post to a good ground.
Then disconnect the wire from the gauge that goes to the sender. If the gauge goes to full, the gauge is working. Reconnect at the gauge and disconnect it at the sender. If the gauge still goes to full, the sender is bad. If the gauge stays at empty, there is a short between the wire and ground.
 
OP
toysrrus

toysrrus

Yoda
Offline
First make sure the gauge is grounded. If you haven't added a ground wire for it, temporarily connect a test lead from the mounting post to a good ground.
Then disconnect the wire from the gauge that goes to the sender. If the gauge goes to full, the gauge is working. Reconnect at the gauge and disconnect it at the sender. If the gauge still goes to full, the sender is bad. If the gauge stays at empty, there is a short between the wire and ground.

Thanx Folks for the "QUICK" replies.

My problem turned out to be a loose wire on the fuse box! No wonder I was blowing fuses & non-working gauge!! What "Amp" size fuses should be there; On both sides?

Thanx Again,

Russ
 

Gliderman8

Yoda
Gold
Country flag
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Glad you found the problem. I had the same problem on my 6 a couple of years ago. Turned out that the plastic float was full of fuel so it read empty. I replaced it with a brass float and it's been fine ever since.
 

6TTR3A

Jedi Warrior
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Russ, 9 out of 10 times it's a ground problem..Yours was #10 !!
re: the fuses. Haynes says 25 amp but that's the British 25 amp.
The US equivalent is AGC 15 amp.
Frank
 
OP
toysrrus

toysrrus

Yoda
Offline
Thanx Frank,

I'll be contacting you soon relative to my center gauge cluster.

Regards, Russ
 

GTP1960

Jedi Knight
Offline
I suggest you start by reading through Barney Gaylord's MGA Guru web pages on the magnetic fuel gauges. Once you have an understanding of how the gauge system works it will be easier to troubleshoot.

https://mgaguru.com/mgtech/electric/fg_01.htm

on a different note:
Barney was a guest speaker at our local British Car Club mtg. a couple weeks ago.
He is a very interesting free spirit.

He travels the country with his son, in his MGA, pulling a small trailer.
camps out or stays with LBC'ers. Works on MGA's mostly, but knows his way around the usual suspects.
has traveled about 300k, (I think) since he retired & hit the road a few years ago.
 

TR3driver

Great Pumpkin - R.I.P
Offline
on a different note:
Barney was a guest speaker at our local British Car Club mtg. a couple weeks ago.
He is a very interesting free spirit.

He travels the country with his son, in his MGA, pulling a small trailer.
camps out or stays with LBC'ers. Works on MGA's mostly, but knows his way around the usual suspects.
has traveled about 300k, (I think) since he retired & hit the road a few years ago.
Man, that sounds like fun! I had hoped to do something similar in a TR3, but it seems events have conspired against me for the moment. Maybe some day.
 

TomMull

Luke Skywalker
Silver
Country flag
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Thanks for the link, Guy. Almost makes me want an MG. Tom
 

dklawson

Yoda
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I wanted to just say a quick hello to Barney but he started a story about his trip in the Chesapeake Bay area and how he had to deal with a broken con rod on the trip. I could have listened as long as he talked... but I had left my wife waiting for me and had to excuse myself. He is indeed colorful.
 
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