Yet another fuel gauge thread...but different

[Billccm]

The USB specifications is 5V.

Ground your DMM to a good chassis ground, like the cigarette lighter outer shell, or ashtray case. Measure the voltage on your cluster grounds. If you measure more than 100mV your cluster PCB is not grounded.

 

[383man]

Just thought I would throw something in here which wont apply to most if any here but maybe some of your family members cars. And that is that GM cars use a different type of gauge then our Mopars and Fords did back in the 60's and 70's. GM used what is called a Magnetic type gauge as they don't use a 5 volt IVR (Instrument voltage regulator) as they work on a full 12 volts and they use two coil windings in their gauges. The two windings work against each other as one goes to the sending unit. They don't need a constant 5 volts because if their voltage fluctuates any from the charging system it effects both coil windings the same so the gauge is not effected like the Mopar and Ford gauges that use the bi-metal strip and needs a constant non changing voltage feed.

I figure if someone works on a family members car that may be a GM its good to know. Ron

 

[CoronetDarter]

A few weeks ago I decided to send out the cluster for refurb. Based on FBBO members posts I went with JC Auto Resto in Seattle. Jeff the owner and Lyle their gauge tech were the best; spent a lot of time going over a game plan with me. I sent the repro sending unit with the cluster so Lyle could calibrate it to the fuel gauge. While at the shop I had them refurb the speedo, paint the gauges, solder all the pin connectors and polish the bezel. The cluster looks brand new.
It's been said before: repro sending units follow a linear resistance arc from full to empty while the OEM was non-linear. So the gauge can't be precisely calibrated to the sending unit, however Lyle was able calibrate to almost OEM needle sweep from F to 1/2 and from 1/2 to E the needle will drop more rapidly. The gauge will read E when there's still 1 - 2 gallons left.

BTW, if you have an OEM sending unit that you believe is faulty, it can be rebuilt. It's pricier than buying a rebop, but your gauge will remain accurate.

Dropped the sending unit in earlier this week and installed the cluster and dash pad today. Tomorrow morning the switch plate.

 

[XMAN JR]

Here is on for ya. When my dad & I restored the 67 gtx we bench tested all the gauges. Every thing worked good. Put in a new fuel sending unit in. Tested all the wires. Since dad had passed I only driven the car a hand full of times. No matter how much gas you put in it only would read between a 1/4 & a 1/2. Now I took it for a ride today & has I was driving I noticed the gas gauge was pegged all the way over pass the full line. Anyone have any ideas ?

 

[bigmanjbmopar]

It pegs past full wirh a full tank or?

Here is on for ya. When my dad & I restored the 67 gtx we bench tested all the gauges. Every thing worked good. Put in a new fuel sending unit in. Tested all the wires. Since dad had passed I only driven the car a hand full of times. No matter how much gas you put in it only would read between a 1/4 & a 1/2. Now I took it for a ride today & has I was driving I noticed the gas gauge was pegged all the way over pass the full line. Anyone have any ideas ?

 

[themechanic]

This video talks about E body gauges. So, adapt for your gauges and this should help.

 

[XMAN JR]

It pegs past full wirh a full tank or?

doesn't matter how much is in the tank when it does it

 

[dadsbee]

Sender wire is shorted out to the frame somewhere...

 

[XMAN JR]

I tested the gauge with an old sending unit. Ran a jumper wire from sending unit wire to an old sending unit. Then a ground wire from the old sending unit to a spot on the car. When the old sending unit was on empty the gauge read a 1/4 So the gauge in the car reads a 1/4 when the tank is empty. Question is is the gauge bad or is it the new sending unit.

 

[CoronetDarter]

The answer could be neither. Could be the calibration. My gauge even after a professional rebuild isn't accurate. It's a little unnerving but when the gauge reads E there's still 2-3 gallons left. I go by the odometer reading.

 

[CoronetDarter]

Here's a little irony. Went with a Tanks Inc. FI tank with in-tank pump to support the FiTech TBI. Had to buy their fuel sending unit because the stock sending unit won't work with all the tank baffles. It requires measuring and cutting the float in order to fit, but now my fuel gauge is dead-on accurate!

 

[themechanic]

Here's a little irony. Went with a Tanks Inc. FI tank with in-tank pump to support the FiTech TBI. Had to buy their fuel sending unit because the stock sending unit won't work with all the tank baffles. It requires measuring and cutting the float in order to fit, but now my fuel gauge is dead-on accurate!
View attachment 885841

That is what @Dennis H told me about his recently but he uses Rick's Tanks. So, I guess one answer is buy a new tank to get an accurate reading on the fuel gauge.

 

[Ron H]

what is the correct reading for a voltage limiter?

 

[Beekeeper]

It puts out a pulsed 5 volt reference unless it a newer solid state one then it’s a constant 5 volts

 

[CoronetDarter]

Here's a little irony. Went with a Tanks Inc. FI tank with in-tank pump to support the FiTech TBI. Had to buy their fuel sending unit because the stock sending unit won't work with all the tank baffles. It requires measuring and cutting the float in order to fit, but now my fuel gauge is dead-on accurate!
View attachment 885841

I just got an alert that someone "Thanked" my original post so I need to update. For the first several fill ups the gauge read very accurately but it's degraded over time. The gauge now reads consistently low throughout the range. Better than the other way; I haven't run out of gas yet (just can't afford it anymore).

 

[RM23M9A]

I just got an alert that someone "Thanked" my original post so I need to update. For the first several fill ups the gauge read very accurately but it's degraded over time. The gauge now reads consistently low throughout the range. Better than the other way; I haven't run out of gas yet (just can't afford it anymore).

Yeah I installed a new one from Yr One or Classic, cant remember its been 1 year ago.. Worked great at first, now after setting a few months? Damnned thing wont come up Past the E. Guage works I know that. I just posted same thing further down... Many say theyre TRASH. Looking for a rebuilt unit seems to be Only choice. Pleaze keep us informed if you find someone that does this??

Thanks & good luck..
69 A12 Bee

 

[RM23M9A]

A few weeks ago I decided to send out the cluster for refurb. Based on FBBO members posts I went with JC Auto Resto in Seattle. Jeff the owner and Lyle their gauge tech were the best; spent a lot of time going over a game plan with me. I sent the repro sending unit with the cluster so Lyle could calibrate it to the fuel gauge. While at the shop I had them refurb the speedo, paint the gauges, solder all the pin connectors and polish the bezel. The cluster looks brand new.
It's been said before: repro sending units follow a linear resistance arc from full to empty while the OEM was non-linear. So the gauge can't be precisely calibrated to the sending unit, however Lyle was able calibrate to almost OEM needle sweep from F to 1/2 and from 1/2 to E the needle will drop more rapidly. The gauge will read E when there's still 1 - 2 gallons left.

BTW, if you have an OEM sending unit that you believe is faulty, it can be rebuilt. It's pricier than buying a rebop, but your gauge will remain accurate.

Dropped the sending unit in earlier this week and installed the cluster and dash pad today. Tomorrow morning the switch plate.

View attachment 572791 View attachment 572792 View attachment 572795

How did it last, or work out 4 years later??

 

[RM23M9A]

Yes, i do understand what you are saying,but the 5v has to get to the sending unit in order for it to "dim" it, correct? So what does no juice at the fuel gauge pin on the gauge harness tell me?

NO voltage TO circuit board short in BLACK wire to the pin pigtail, corrosion there?

 

[CoronetDarter]

How did it last, or work out 4 years later??

The gauges are all still good. The inaccurate gas gauge is the sending unit not the gauge.

 

[RM23M9A]

How did it last, or work out 4 years later??

Low quality sending unit from either Year One or Classic.. I wont buy ANY electrical parts from Classic Ind especially DIMMER SWITCHES.. Might just bee my bad luck? But 4 have went bad within a year, as well as the fuel tank send unit.
I dont know if they ALL buy from same vendor? But this is what they look like-