[TR] Fuel gauge troubles

Jim Henningsen trguy75 at gmail.com
Sun Aug 18 09:40:23 MDT 2019

Thanks all for the feedback.  I’m heading out this afternoon for some tinkering.  I didn’t mention this since I didn’t think related, but the temp gauge is also not working, and didn’t realize it might be the voltage stabilizer unit.  Hmmmnn.

Jim Henningsen 


From: Randall <tr3driver at ca.rr.com> 
Sent: Saturday, August 17, 2019 8:25 PM
To: Jim Henningsen <trguy75 at gmail.com>; 'Triumphs' <triumphs at autox.team.net>
Subject: RE: [TR] Fuel gauge troubles


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 <https://go.microsoft.com/fwlink/?LinkId=550986>  for Windows 10


From: Jim Henningsen <mailto:trguy75 at gmail.com> 
Sent: Saturday, August 17, 2019 6:54 PM
To: 'Triumphs' <mailto:triumphs at autox.team.net> 
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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