60 BE Fuel gage issue

Synopsis
60 Bug Eye
New Sending unit installed in 16 with new gas tank. Such a pain to get at sending unit in BE so replaced the original unit when installing new tank. Separate ground wire for sending unit
Last summer gage working fine.
Took out for first run this year, gage fine with engine not running and during warming up. Tank 1/2-3/4 full
Driving gage was jumping from 1/2- full. Came in, gage read correctly with engine off. Tightened ground to gage a little
Yesterday gage is stuck on full with both engine off and running.
Gage goes from 0 - full when removing the ground. I cannot remember which way the sending unit works. Full volts when full or empty??
I know this has been discussed before.
Any thoughts on this?? Most likely the sending unit??. Shorted wire(s) from sending unit?
I really don't want to have to drop the tank and replace the sending unit unless I really have to

I’ve had nothing but trouble with the replacement sending units. After the third one went bad in 18 months I sent the original sending unit and gauge to West Valley Instruments for rebuild. I haven’t had a problem since.
My symptoms were similar to yours so I would start at the sending unit.
Replacement units can’t be rebuilt so if you have the original Smith’s sending unit it might be worth it to send that and gauge out for rebuild.
West Valley wanted both my gauge and sending unit so they could verify both worked together and the gauge was adjusted properly.

Sending units don't "send", they are variable resistors to ground.

The early, magnetic gauge system is different from the bimetallic system introduced in the mid-1960s. On the magnetic gauges they will read FULL when the sending unit is disconnected and when the gauge itself looses its ground. Visit the MGA Guru website and read up on the magnetic gauges. You will find additional troubleshooting and calibration information there.

I suggest spending a little time under the dash of your car. You should see two wires going to the terminals on your fuel gauge, dark green to the gauge's "B" terminal, green/black to the "T" terminal. There is probably a black wire connected to one of the gauge's mounting studs. Clean all the gauge terminals and make sure the black wire is providing a good clean ground. See if that fixes your car's problem.

If that doesn't help, replace the green/black wire at the gauge with a jumper wire. With the ignition on, touch the other end of the jumper wire to a good grounding point on the dash, then remove it from ground. If the gauge goes from EMPTY to FULL when you disconnect the wire, this suggests your green/black wire to the tank is broken or the sending unit has lost its ground. Lastly, if with your sending unit the gauge works fine until the float drops below some critical level, that suggests a break in the internal resistance wire windings of the sending unit.

Doug
Thanks for the info.
I think I have a broken wire (green black) from the sending unit close to the gage. The voltage across the power (green) and the GB wire goes from almost 0 to 8-9 volts as I move the wire around.
I will jumper it out today to make sure and put everything back together

Doud
t appears to be either a bad wire back where I cannot get at it or the sending unit died. I found the Green Black in the harness on the passenger side dash and jumped it with no luck. Although I may give it a second try tomorrow.

I hope this doesn't turn out to be a problem that dictates dropping the tank. Keep at it as you can and let us know what you find.

Joe,

I just went through this while waking up my sister's '59 Bugeye - a car that had been stored in a basement for 23 years. Sure looks like you are getting great advice here however there is one thing I have not seen mentioned.

There is one of those Lucas bullet connectors in the green w/black wire to the sending unit in rear of the car just inside the car body. Pulling and cleaning that connector and cleaning the actual bullet connectors on the wires cured my problem. I also use dielectric grease inside these Lucas bullet connectors to protect from dirt and corrosion for a long time to come.

Access inside the boot area can be a real issue. I am 6' and 285 pounds. Luckily for me the seats were already unbolted. (car came to me that way) I simply lifted the seats out in order to get back there.

Hope this helps.

Tim
Thanks for the info. I was not looking forward to going into the boot, however, I have exhausted everything else.
I found the green Black wire under the dash and it appears to be on an open circuit. Either the wire is NG somewhere back to the sending unit or the sending unit packed it in.
I am betting that it is the unit as the gage was jumping from 1/2 to full before going full. I tried a spare gage and I get the same no ground symptom with it.
I guess I will give it a try to find that connector before I pump out the tank and replace the sending unit.
I see you are from Waterford. I visited a friend with an Alpha that ran at that track way back 25 plus years back. Interesting place.
Do you still run your FP car??

Hello Joe,

I recognized your name when reading your first post about the fuel gauge issue. You used to post quite regularly over on the Prod board, right? I joined the Prod board in 2002 (fourth name on the first page of the member list) and was also a member of the predescessor to the current Prod board. You won't find many postings by me over there even though I read it daily, I seldom post. I guess you could say the same thing here. Love the people and the things they post but tend to stay quiet myself.

I had replaced both the tank and the sender with new items on my sister's Bugeye so I really suspected the new sender and went after it first. As noted above the problem turned out to be the bullet connector.

Waterford? Lived here since 2000. Moved here because of the Waterford Hills track and all the beautiful lakes in the area. Generally quiet and peaceful too. My Dad used to take me and my brother to the races back in the late 1960's and early 1970's when I was a teen myself so that was my initial exposure to Waterford Hills. I loved watching the Bugeyes and the Lotus Sevens/Super Sevens! (My first car was a Bugeye Sprite my Dad sold me for the grand total of $1.00!)

I raced first in HP for a few years starting in 2000 or 2001. Then I bought an FP engine from Peter Morton and changed to FP. I was the HP champ one year and the FP champ later. Of course I can't claim large fields and oodles of competition but...

Unfortunately 2005 was my last year on the track. Life was happening (teen issues and working midnight shift with lots of overtime in a high stress position at Ford's Dearborn Stamping Plant) and I just had to give up something -- at least for a while. Then in 2007 we bought our cabin in the upper peninsula and that consumed me for a few years. Also intended to get back on the track but have not made it yet. Last December we bought acreage in the upper peninsula and intend to move up there eventually. I am hoping to be back out next year but I've said that a lot of years in the last decade. I do still have the car though it needs a complete end to end going through. With my sister's Bugeye now back to her, I have the room to get the old race car into the garage!

The fuel gauge in my BE isn't working either.
It reads full constantly. I took it out of the dash, supplied 12V power to the B terminal and jumped the T terminal to ground. Needle doesn't budge form Full. So it must be the gauge.
Any thoughts on how to trouble shoot the gauge, or should I just send it off for a rebuild?

Fred,
Thats the only gauge I sent to Nisonger for a rebuild and I’m glad I did.
Rut

TulsaFred said:

The fuel gauge in my BE isn't working either.
It reads full constantly. I took it out of the dash, supplied 12V power to the B terminal and jumped the T terminal to ground. Needle doesn't budge form Full. So it must be the gauge.
Any thoughts on how to trouble shoot the gauge, or should I just send it off for a rebuild?

Click to expand...

Run a jumper wire from the gauge case to ground and repeat your test. The gauge MUST have a good ground connection to work correctly.

For info on the magnetic fuel gauge, visit the MGA Guru website. Barney has sections there that explain the gauge system and how to calibrate it. Link below.

https://www.mgaguru.com/mgtech/electric/fg_01.htm

Yes, Barney has more information than you will ever need about fuel gauges and sending units. Make sure you have a matched set of gauge and sending unit (early Sprite). As Doug said, make sure the case of the gauge is grounded. Battery power goes to the "B" terminal. Sending unit wire is on the "T" terminal. Make sure the sending unit is grounded (I run an extra wire from the sending unit to ground). The gauge should read from about 70 ohms (full) to zero ohms (empty). If the sending unit wire is grounded momentarily, gauge should read empty. If the sending unit wire is removed, gauge should read full. Good luck. BTW: I have had nothing but trouble with BE sending units.....next time I will send an original one out for repair. Scott in CA

Yup fuel gauges a on going saga
a friend of mine has a mini moke from the Catalina auction years and years ago.
the only cure was to send it and the sender to be rebuilt .
hate full little bit of kit. As Richard called it.

I read the material at MGA guru. Very detailed. The internet is amazing. So I now have the confidence to begin disassembly and testing of my gauge. I suppose if I bugger it up, I can always send it off to Nisonger, so its worth a go. After studying the "course" on MGA Guru I have an odd confidence. In the past that has been an ominous sign, so wish me luck.

I would NOT disassemble the gauge if you do not have to. The tiny magnet wires inside are VERY easy to break. There is also an insulated mandrel inside which is wrapped with magnet wire. That mandrel is VERY easy to break and once broken... that will render the gauge useless.

Confirm the resistance readings of the windings to make sure the gauge is OK, then check how it behaves with resistors between the T terminal and the grounded gauge case.

Again, do NOT take the gauge apart if you don't have to.

Thanks Doug. I do plan to test the resistances first prior to any disassembly.
One odd thing is that the gauge stays on "F" at all times, including when removed from dash and all power. Based on the diagrams on MGA guru, the gauge should fall to "E" based on gravity when there is no electricity applied (and thus no magnetic force). Seems like it must be mechanically "stuck" in some manner.

My alternative to my own investigation of the internals is simply to send it off for a rebuild. If I open it and damage a wire, am I really any worse off - ie. I'd have to send it for a pro rebuild anyway?

My Prefect has the same gauge but in 6 volt and nobody wanted to mess with it. Anyway, one of those "tiny" wires inside broke. It was quite "fiddly" but I was able to resolder it. So it can be done but certainly not trivial or even easy. And yes it should fall to E with no electricity so something is physically stuck inside. You should be able to fix that but do be careful of the wiring.

I applied my ohm meter and get the following readings:
Between "B" and "T" terminal posts: 67 Ohms
Between "T" and ground posts: 104 Ohms

Based on the information on the MGA Guru site, I interpret this as correct/good.
Do why does my needle stay on "F" no matter what?
I think it must be mechanically stuck.