[TR] Fuel gauge troubles

Randall tr3driver at ca.rr.com
Sat Aug 17 18:24:38 MDT 2019

Quick and dirty test : Remove the wire from the sender, turn the key on, and ground the wire while watching the gauge.  If the gauge starts to climb towards full, then the gauge & wiring to it are probably OK.  Probably best to not leave it this way for long, but a few minutes won’t hurt.

My next suspect (especially since it worked before restoration) would be the grounding for the sender.  IIRC the TR4 grounds the same as TR3, meaning not very well.  I like to add a ground wire from the stud on the sender to one of the tank mounting bolts.

Use an ohmmeter to check the sender.  I don’t recall the exact numbers offhand, but it’s something like 100 ohms empty and 10 ohms full.  If it seems to work backwards (low resistance empty and high resistance full), you’ve got a TR3 sender instead of TR4.

Also worth checking the temp gauge if the first test above doesn’t work.  Do the same thing, pull the wire off the sender and ground it.  If temp gauge doesn’t respond either, it’s probably the voltage stabilizer.  Seems like maybe it’s mounted over in the passenger footwell on a TR4, but honestly I don’t recall for sure.

-- Randall

Sent from Mail for Windows 10

From: Jim Henningsen
Sent: Saturday, August 17, 2019 6:54 PM
To: 'Triumphs'
Subject: [TR] Fuel gauge troubles

Help, I'm calling the TR bat phone again.  Switching projects to get my car
ready for AACC southeastern fall nationals on Mobile AL.  1962 TR4 CT5212LO.
Fuel gauge worked prior to restoration but not after.  Car is switched to
neg ground.  Orig fuel sender float was sunk in tank.  Removed it and
verified there is gas in it.  Hoping there is a way to rebuild it since orig
part.  Put in a new sending unit from TRF this morning and added 7 gallons
of gas and it still doesn't work but float rises.  The needle moved ever so
slightly right above E then dropped back down with ignition on.  I even used
a coat hanger to manually raise the float in the gas tank to "full" with
ignition on but needle still didn't work.  Ignition in "On" position, but
not running.  

My thoughts.
1. Bad gauge?
2. Wires reversed on fuel gauge from resto impacting since it is neg not
original positive ground.  Running generator that has been polarized to neg
3. connections at new sending unit not secure. Neg is to ground and positive
to pos on sending unit
4. new sender bad

Any thoughts on the possible easy fix before going through the list
tomorrow.  Also, if anyone is looking for a nice 73 Stag with hardtop,
manual tran, that has been owned by a TR owner of 60+ tyears and avid VTR
member, it is for sale in Tally.  I am trying to help the family find a home
for it.  Email me offline if you would like pics and contact info.

Many thanks,
Jim Henningsen
Ocala, FL
60 TR3A
61 TR3A
62 TR4
75 TR6

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