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BJ8 Fuel gauge help



I'm having some trouble with an erratic fuel gauge. I'm pretty sure it's the gauge and not the sender. Is there any information out there on the fuel gauge operation. It appears there are to nuts on the back that when loosened allow some adjustment. I'm just not clear on how to go about making the adjustments.



Country flag
Hi Ed,
First thing I'd look at is the ground wire, make sure the metal is clean on the wire's terminal and where it attaches to the gauge. It is not uncommon that the sending unit suffers from poor grounding also. A fix for that is to run an additional ground wire to one of the 6 screws on the sending unit.

P.S. Welcome to the Forum


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Obi Wan
Country flag
Hi Ed,
Yeah, what Darth Vader said above.

Unless your a qualified fuel gauge tech, don't move the two small bolts/nuts. I've seen what's in there. Maybe you have too. There is a very very small wire that runs across those two bolts. Also, the placement of the two units are critical. If the nuts are lose, that may be the problem. Maybe they have moved. If that is the case, the gauge should be sent out for recalibration. If your asking how to calibrate, maybe some others will chime in on that topic.

If it were me, I'd do what Greg says first. (I always do what Greg says, he's all knowing). If it solves your problem, then.... I would carefully tighten the two small nuts on the back of the fuel gauge. Making sure to keep their position intact.

Good luck and welcome to BCF!
Happy motoring!

Dave Russell

Yoda - R.I.P
Hi Ed,
Welcome to the forum.

If you want to see how to do it go here:
Scroll down to FG-101, 102, 103, 104.

The MGA gage is very similar to the Healey gages. I believe that the main difference is that the BJ8 has a bit different resistance in the sending unit.

Good grounds on both the dash & tank units are important.

If you loosen the two adjusting nuts on the back of the gage, be prepared to go through the entire calibration procedure.

It's possible to do the job, I've done it, but if you are not comfortable working on small delicate parts it can drive you up the wall.


Well I'll certainly check the grounds first and then the sender and hope that's the problem.


Country flag
Thank you Roger. I think it would be more accurate to say I'm some knowing, or know-enough-to-be-dangerous knowing. My first car was a '67 Mustang that my dad helped (showed) me how to rebuild the motor. We added some goodies like a Holley carb and Mallory dizzy. It wound up being too much for the tired old rear end and I sheared the pinion yoke in half, boy was that loud. Junkyard wouldn’t sell just the yoke so I bought an entire axle. I inspected the gears and determined that the ring gear on the original axle and the pinion gear on the newer axle were in the best shape so I did some swapping and installed the hybrid. Car made strange whining noise though, turned out my original axle was a 3.2 ratio and the new one was 3.07. The next axle went straight in with no alterations. :blush:
edscripps, if you do remove the sending unit youll be putting in a new seal/gasket, dont over tighten the six screws just snug them down well in a cross patern, the tendency is to over tighten the screws thinking it will help seal, not so in this case, Ive never used any kind of gasket sealer on them and never had a leak.


Jedi Warrior
Country flag
There are small tabs on the coil holders inside the gauge that fit in the slots on the back of the gauge where the posts slide for adjustment. If you loosen the nuts on the T and B posts and are not careful to prevent the tabs from coming out of the slots, you'll break the internal coil wire when you tighten the nuts (the tabs prevent the coils from spinning when you tighten the nuts).

The MGA Guru website is a great explanation for how the gauges work and the general principals of adjustment. But the data given is for an MGA and the Jaeger gauge, not the Healey and Smiths gauge. Circuit resistances are not exactly the same. These gauges are very difficult to calibrate correctly.

EdScripps: do I have your BJ8 listed in the BJ8 Registry?


I have repaired/calibrated some fuel gauges and senders for some sprites and midgets for folks. That sender looks the same as the bugeye and I imagine the guage works the same too. Let me know if I can help.
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