Wedge TR7 Gas Gauge

[ObiRichKanobi]

I just purchased a 1980 TR7 that overall is in good shape (found receipts in the trunk for a major overhaul in 1999).

However, one of the more irritating faults it has is a fuel gauge that's not working.

Being a rather novice at maintaining cars, I'm guessing it's either the sending unit, the gauge itself, or the wiring in between, as all the other gauges work (except for the clock). I have a couple of the maintenance manuals, but none of them tell how to troubleshoot this, and I'd hate to replace parts unnecessarily. If anyone can help, I'd sure appreciate it. I'd hate to run out of gas due to a malfunctioning gauge!

 

[Steve]

Welcome to the forum, and congratulations on your find !

The sender is the most likely suspect. Check the connections to the sending unit just in case, but the sender has probably had it. Was the fuel tank replaced? If so, the wiring may have been switched, or not connected properly. Always check the daft stuff first!

 

[MDCanaday]

Steve forgot to mention that this is the most famous area of total lucas failure. Since they never figured out how electrons flowed, Lucas could never make a gage that meant anything.The best most people do is to cleanup all the connections, then get a good idea what 1/2 a tank on the gage means. this could be 5 gallons or .5 gallons. As long as you can read it for what it is.I have read articals on how to add resistors to compensate for the errors but as long as you know how to read the gage then you're OK. Unless you jump in the wife's tr, and forget to adjust to the different error, then you had better have a cellphone.........
Md(mad dog)

 

[Gary Pope]

Take the colored wire going to the sender unit on the tank and place the end on a good ground point.
With ignition on the gauge needle will go to Full position. If it does, sender is faulty if not then most likely gauge is faulty or of course a break in that wire. It's a good place to start.

 

[ObiRichKanobi]

Thanks guys!!! I'll check this out as soon as I get a chance. There's a few other things wrong with the car, such as a gas smell without any apparent leaks, and a heater that doesn't put out heat that I'll be working on as well.

 

[Dale]

Welcome to the forum and greetings from a fellow TR7 owner.
The sender unit is probably the culprit as the sliding element tends to wear out over time. Does your low fuel warning light work? It will come on somewhere between full and empty usually at 1/4. That segment is a seperate contact in the sender and doesn't wear out as fast as the other. I can't remember what diagnostic procedures I used to determine that my sender needed replacing, but that's what fixed it. New ones are available from the usual suspects I got mine from VB. Again welcome and stay in touch and post, post, post.

 

[BOXoROCKS]

Hi,
Used to have the same problem with my 76 TR7. Amongst other problems. I considered pulling the drain plug out of the gas tank, and replacing with a fresh champion spark plug, with a long jumper wire running to the center of the coil.Nothing will happen until you run out of gas, then you will have a definate warning blast that you are out of gas. But never quite got around to it. Finally sold it to a friend of mine in the club.

 

[ObiRichKanobi]

Actually, the fuel gauge shows bone dry empty...even with a full tank.

 

[Dale]

Hello Again,
The check in Gary Pope's post should verify that the sender is bad. The clock is easily replaced and not worth having repaired. All the gauges can be replaced from the front. Don't remove the entire cluster. Access is fairly easy once you take the dash top cover off and slide the clear lens up. Have seen new clocks on E-bay for much less than factory suppliers prices. Don't buy a used one even if the seller swears it was working when removed from the parts car. The TR7 heater is a good one and shouldn't be too hard to fix. Be sure and check the coolant level in the header tank often, though the level light on mine is pretty good yours may not be working. Hope your 7 gives you the enjoyment I get from mine. I drive mine to work at least 2 days a week and every day when I can't ride my scooter. Yours is a later build than those early ones that gave them the bad rep and am assuming it's a convertible which is much fun.

 

[MDCanaday]

OBIRICH,I forgot to mention fuses(sorry) they corrode and resist voltage. My 7 required the fuse contacts to be clean and fresh or weird stuff started to happen. You can check these with a test lite, but a voltmeter detects the voltage drops more easily. 600 sand paper rolled into a fuse sized tube and lots of patients is needed to clean these little rascals.
Good luck!!
MD(mad dog)

 

[ObiRichKanobi]

Just a quick update...While tinkering with the dash, I pulled the fuel gauge and hot wired it to the batttery. The needle moved up off it's "permanent" empty, so that's working. Has to be the sending unit or the wiring. Will be ordering a sending unit on my next order. Appreciate the help!