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TR2/3/3A TR3 fuel sending unit

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Re: TR3 fuel sending unit

In the event TR3 folks are still following this thread, i was wondering if anyone had advise on a related TR3 fuel sending unit question. I just bought a 59 TR3 that had been tucked away for the last 35 years. The shop that found it and cleaned it up for me put in a new fuel tank. He also changed it over from Pos to Neg ground. I picked it up last week and have been running it to see what issues it has. The fuel gauge read 1/2 when I got it although I know it had to be pretty low, and after filling it up and turning it on, it went to E, actually past E, and just quivers there. Maybe a polarization issue or does the sending unit sound like more of the problem? The other gauges seem to work within reason.
 
Re: TR3 fuel sending unit

BanzaiRat said:
The fuel gauge read 1/2 when I got it although I know it had to be pretty low, and after filling it up and turning it on, it went to E, actually past E, and just quivers there. Maybe a polarization issue or does the sending unit sound like more of the problem?
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Either the gauge or the sending unit is from a TR4. Neither design "cares" about polarity but the gauge mechanisms are different even though the early TR4 gauge looks nearly identical to the TR3 unit.

One way to determine which is which is to temporarily jumper the sender post to ground (or the gauge post that goes to the sender). With a TR3 gauge, the gauge should go to empty. With a TR4 gauge, it will go to full. (If it does go towards full, turn the key off promptly. The TR4 gauge is designed to run on 10v, so putting a full 12v across the gauge for very long may overheat and damage it. A few seconds won't hurt but don't leave it for several minutes.)

Doesn't sound like your problem, but one other thing to watch for : The TR3 gauge needs to have a ground. The factory relied on the mounting to the panel to ground the gauge but I've had lots of problems with that in the past. Adding a short ground wire, with a ring terminal for the gauge mounting post and the other end in the tie point on the back of the panel helped a lot.

But without the ground, the gauge will just snap to one side or the other and stay stuck there. Can't get a reading in the middle without a ground.
 
Re: TR3 fuel sending unit

Much obliged! Thanks for the reply. That gives me something to think about. The gauges on my 75TR6 work quite differently with the voltage stabilizer. I haven't been under the dash of this car yet so I'll take a look.
 
Re: TR3 fuel sending unit

<span style="font-size: 11pt"><span style="color: #003300">A real easy way to tell which gauge you have is by the part number located just above the needle. If it is a TR3 gauge, the part # is FG2530/20 or X.49422/220. PG.163 If it is an early TR4 gauge, the part # is BF2301/00 The faces look almost identical but the gauge and the tank sending unit have to match in order to get a correct reading. Since the tank itself was replaced, who knows what you have back there !!
Frank </span></span>
 
Re: TR3 fuel sending unit

6TTR3A said:
[size:11pt][color:#003300]A real easy way to tell which gauge you have is by the part number located just above the needle.
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Easy for you, maybe. I'd forget my name if people didn't yell it at me all day long!

:laugh:
 
Re: TR3 fuel sending unit

I agree with whats-his-names. I have what I believe to be a fuel gauge from an early TR4 with the curved face, and it functions the opposite as a TR3 gauge, like the TR4. It has on it's face "BF2301/00". Your sending unit needs to match your gauge.

The TR4 ones need the voltage regulator so the imput is around 10v. According to my notes, 214 ohms is the reading with the float at the bottom (empty) and 12 ohms is the top (full) reading. -Note these readings aren't exact, but your sending unit should be somewhat close. The TR3 sending unit is something like 90 ohms full, and 0 empty.

Looking at that relationship, I could see you with something swapped.

Welcome to the TR party.

Jer
 
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