69 b body sending unit fuel in tank question

Posted By: mikemee1331

69 b body sending unit fuel in tank question - 03/26/15 11:17 PM

my tank has 10 gallons in it right now. can the sending unit be removed without a flood? in looking at pictures it looks as though it would need to be 3/4 full to be a problem.

Posted By: edmopar440

Re: 69 b body sending unit fuel in tank question - 03/27/15 05:07 AM

GOING TO BE CLOSE

Posted By: MidPenMopar

Re: 69 b body sending unit fuel in tank question - 03/27/15 05:24 AM

If you are replacing the sending unit let me know if you ever get one that reads correctly. I have gotten two so far that read 1/4 tank off. No matter what i do to try to fix it i cant.

Posted By: RapidRobert

Re: 69 b body sending unit fuel in tank question - 03/27/15 05:30 AM

Michael, I'd do some more cruisin

Posted By: mikemee1331

Re: 69 b body sending unit fuel in tank question - 03/27/15 01:33 PM

Quote:

If you are replacing the sending unit let me know if you ever get one that reads correctly. I have gotten two so far that read 1/4 tank off. No matter what i do to try to fix it i cant.

yep that's what I've done and nope, it's a 1/4 off. it's one of the newer, new repro's. I won't get into the ohms and all but it appears the float position is off versus the working original. won't know until I pull it back out and hook up a meter outside of the tank.

Robert, then I won't know how much fuel is in the tank. right now I know it's 10 gallons which is a little over half full. new sender only shows under a 1/4. I have an electric pump so it's not a huge issue except i'm running out of vacation time

Posted By: Pynzo

Re: 69 b body sending unit fuel in tank question - 03/27/15 01:57 PM

Slide the filler tube out and peer inside with a flashlight. You'll see exactly where the fuel level is in relation to the sender. You can reach the float and raise it with a broomstick to measure ohms at different float levels while this sender is still installed.

Posted By: mikemee1331

Re: 69 b body sending unit fuel in tank question - 03/27/15 02:33 PM

Quote:

Slide the filler tube out and peer inside with a flashlight. You'll see exactly where the fuel level is in relation to the sender. You can reach the float and raise it with a broomstick to measure ohms at different float levels while this sender is still installed.

ah! we think alike! no dice on pulling the tube out without turning it into a major job. i'll just pump out half of what I put in. i'm re-plumbing anyway

Posted By: Pynzo

Re: 69 b body sending unit fuel in tank question - 03/27/15 04:13 PM

Has anyone tried readjustment of the gas gauge to tune it to these repop senders? I have a box of 68-70 B Rally gauges and they have small adjustment holes in the back to move the pointer.

Posted By: MidPenMopar

Re: 69 b body sending unit fuel in tank question - 03/27/15 04:33 PM

Quote:

Has anyone tried readjustment of the gas gauge to tune it to these repop senders? I have a box of 68-70 B Rally gauges and they have small adjustment holes in the back to move the pointer.

All i have tried is trying to change the position of the float arm. I had it cut down a little and that helped some but not much...I had no idea about the gauge adjustment though?

Posted By: Pynzo

Re: 69 b body sending unit fuel in tank question - 03/27/15 04:44 PM

I'll post some pics of these junk gauges tomorrow. Some have the faceplate removed so you'll be able to see what moves with the adjuster mechs.

Posted By: mikemee1331

Re: 69 b body sending unit fuel in tank question - 03/27/15 06:20 PM

Quote:

Has anyone tried readjustment of the gas gauge to tune it to these repop senders? I have a box of 68-70 B Rally gauges and they have small adjustment holes in the back to move the pointer.

interesting...
I just drained, pulled, and ohmed both units to get float positions and ohms as close to each other as possible. put the new sender back in, refilled with the 10 gallons and I only gained 1/2 a quarter of a tank. I went from being under a 1/4 to just over. doing this out in the cold on your back is no picnic!

I don't have a ralley cluster but I do have a spare non ralley cluster and i'll look at what you suggested.

Posted By: Pynzo

Re: 69 b body sending unit fuel in tank question - 03/28/15 04:05 PM

This gauge has seen better days- the thermal wire has burned due to a bad voltage limiter. The adjuster teeth are easily turned with a small blade and change the position of the pointer.
I figure that a gauge can be fine tuned to the sender prior to installation by hooking up a circuit with a 3 volt power source and enough 18 gauge wire to match what is in the vehicle. Set the sender for empty and adjust pointer to far edge of E mark on gauge, raise sender arm to full stop and adjust pointer to far edge of F mark, recheck E setting, and you should be done.
Unfortunately you'll need to remove the gauge from the cluster to do this.
Edit- this pic is of an Oil or Temp guage- Gas guage internals are slightly different but work the same way.

Attached picture 8473423-image.jpg

Posted By: Pynzo

Re: 69 b body sending unit fuel in tank question - 03/28/15 04:08 PM

Backside pic

Attached picture 8473426-image.jpg

Posted By: mikemee1331

Re: 69 b body sending unit fuel in tank question - 03/28/15 04:40 PM

thanks but like you pointed out, a whole lot of work in a together car. I looked at my spare non-ralley cluster and decided just taking THAT apart wasn't worth the effort let alone pulling mine out of the dash!

Posted By: NITROUSN

Re: 69 b body sending unit fuel in tank question - 03/28/15 05:32 PM

Quote:

I figure that a gauge can be fine tuned to the sender prior to installation by hooking up a circuit with a 3 volt power source

You need 5 volts. The gauges were calibrated in 3 different modes. E-1/2-F. There is a factory tool that allows you to do so. It is just a ground with resistance for each mode. I have that tester and I can measure each mode for anyone trying to tune your gauge. Then all you need is a resistor or resistors to equal that OHM for calibration. The factory manual should have a write up as I remember it instructing you how to do it. If you adjust it for just one mode as mentioned above it will or can affect the other gauge readings.

Posted By: Pynzo

Re: 69 b body sending unit fuel in tank question - 03/28/15 06:25 PM

Looking at a '70 Charger/Coronet FSM, it lists a tester, C-3826 for the gauges, with low medium and high settings. The section on Fuel Tank Sending Units has a figure of 73 ohms empty,+or- 12 ohms. Full setting 9.6ohms +or-1 ohm.
What are the values of the L,M, and H settings for the tester?

Posted By: NITROUSN

Re: 69 b body sending unit fuel in tank question - 03/28/15 06:27 PM

When I get out in the shop I will measure the OHM'S of each setting.

Posted By: mikemee1331

Re: 69 b body sending unit fuel in tank question - 03/28/15 06:43 PM

Quote:

Looking at a '70 Charger/Coronet FSM, it lists a tester, C-3826 for the gauges, with low medium and high settings. The section on Fuel Tank Sending Units has a figure of 73 ohms empty,+or- 12 ohms. Full setting 9.6ohms +or-1 ohm.
What are the values of the L,M, and H settings for the tester?

my original was 68 at E and 13 at full FWIW. E on the gauge was always below the line and full a little above.

Posted By: Pynzo

Re: 69 b body sending unit fuel in tank question - 03/28/15 06:59 PM

How about the readings for your new unit? By factory specs a range of 85-61 ohms would make a difference in gauge readings and who knows if your gauge ever recieved a voltage spike due to a faulty limiter. I've got a box full of burned gauges picked from junkyard crawls in the mid '80s. How old is your gauge? How's the voltage limiter and wiring/connections?
I installed what I was told was a "Premium Stainless Life Time Warranty Unit", it bench tested in specs and when installed and wet, has a dead spot right in the middle where the resistance values barely change between 1/4 and 1/2 tank. Haven't bothered to fill it yet, but lifting the float to full stop with a broom handle thru the filler opening,Full reads 3/4 on my old gauge.
I picked up a new Spectra unit and it too bench tests in range and will install it along with a modern gauge setup.

Posted By: mikemee1331

Re: 69 b body sending unit fuel in tank question - 03/28/15 07:14 PM

I don't really suspect my gauge. it's read the same for 30 years with the old unit and prior to this car I had another (non-ralley) and it too read the same.

i'm going to answer the rest of your question over in the other thread I started on the new unit to kinda corral the whole thing. a very un-moparts thing but......

https://board.moparts.org/ubbthreads/show...e=0#Post8406855

Posted By: Pynzo

Re: 69 b body sending unit fuel in tank question - 03/28/15 07:33 PM

That works for me having bought the Spectra unit myself to replace a junk Chinese Stainless unit. I had hoped that Dixie's group buy had worked out and seeing that these Spectra units were Mexico made had to figure they came from the same factory he was trying to deal with. I look forward to more feedback on the Spectras-

Posted By: NITROUSN

Re: 69 b body sending unit fuel in tank question - 03/29/15 03:30 AM

Quote:

Looking at a '70 Charger/Coronet FSM, it lists a tester, C-3826 for the gauges, with low medium and high settings. The section on Fuel Tank Sending Units has a figure of 73 ohms empty,+or- 12 ohms. Full setting 9.6ohms +or-1 ohm.
What are the values of the L,M, and H settings for the tester?

The tester uses E 1/2 F. The tester had the following OHM readings. E or L 77 ohms. 1/2 or M 24 ohms, F or H 11 ohms. On the tester it self the acceptable gauge range listed was E 0 to -3/32, 1/2 + or - 1/16 and F 0 to + 3/32.

Posted By: mikemee1331

Re: 69 b body sending unit fuel in tank question - 03/29/15 02:35 PM

NITRO - I copied this info over to the other thread

https://board.moparts.org/ubbthreads/newr...part=1&vc=1