I'm lost, gas gauge pegged passed full

[old guy rich]

Hi Guys, I researched gas gauge/ sending unit in the search engine. Seems everything points to a grounded wire. Most logical place to be would be above the tank between the trunk floor and the tank. I slid a split wire cover over the wire from the sending unit to where the wire goes thru the trunk floor. Gauge still pegs. I disconnected the wire from the sending unit and the gauge never moves, stays on empty. I bared a spot in the wire going to the sending unit at a point in the trunk and connected it to the sending, eliminating the wire between the tank and trunk floor, gauge pegs. If the wire is grounded between the trunk and gauge why wouldn't the gauge peg when I disconnect the wire at the sending unit? I took the sending unit out and measured the ohms, reads 11 to 100 from empty to full. Any ideas would be appreciated. Thanks rich.

[19Fordy]

Rich,
If you are dealing with the OEM King-Seally gas tank sending unit and gauge they DO NOT operate on the ohms principle. Does you gas tank sending unit look like the one below? If not, no need to keep reading.
If so, it the OEM King-Seally unit used in Fords and Mercurys up to 1953 or 1954.
Here's what I would suggest.
Remove your gas tank sending unit from the tank and set it on a piece of cardboard in your trunk to insulate it from the metal floor. Then connect the wire from your dash gauge to the top center screw of your gas tank sending unit. Then, using an alligator clip connect a ground wire from one of the screw holes in your sending unit top to a good ground on your car, like the frame or floor trunk latch.

Switch ON the ignition and move the float thru its range of motion to see if it registers on the gauge. If it doesn't register, you may have a defective sending unit or defective gauge. Check to see if your float is full of gas due to a hairline crack. That is very common.

It is also possible to carefully pry off the top of the gas tank sending unit and clean the internal points with 600 grit emory paper. BE VERY CAREFUL NOT TO DAMAGE ANY INTERNAL WIRES OR THE CARBON RESISTOR. Use a bench vise to hold the sending unit without crushing it.

Hope this helps.

[old guy rich]

Thank you 19Fordy, my sending unit does not look like the one pictured. It is stamped with "Bob Drake". The float is not full of gas. The sending unit is very clean, spotless on the inside. Bought the car in 2015 and the gauge worked flawlessly until I filled up last week. This is my 50 Merc, forgot to mention that. Again, thank you for all that info. rich.

[19Fordy]

Rich, Read about BOB DRAKE fuel sending unit here. Perhaps it will help. You might also want to send a PM to the folks posting about this for extra help on how they solved their problem.
https://www.google.com/search?q=bob+...hrome&ie=UTF-8

Could you post a photo of what your gas tank sending unit looks like?
Is your car still 6V or did you convert it to 12V?

[old guy rich]

Originally Posted by 19Fordy

Rich, Read about BOB DRAKE fuel sending unit here. Perhaps it will help. You might also want to send a PM to the folks posting about this for extra help on how they solved their problem.
https://www.google.com/search?q=bob+...hrome&ie=UTF-8

Could you post a photo of what your gas tank sending unit looks like?
Is your car still 6V or did you convert it to 12V?

19Fordy, car is stock, 6 volts. I made a new gasket and reinstalled the sending unit but a can take it out and take a pic. Would be tomorrow before I can take a pic. Thanks again and I will go the the link you posted. rich

[old guy rich]

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19Fordy, I read a few articles on that link. The arm that holds the float did move a bit harder than I thought it should. I will take the unit out, ground it and see if the gauge moves when I move the float by hand.

[old guy rich]

I'm really confused now. I took the sending unit out and wired it up with the same wires used when in the tank, the gauge follows the s/u arm to a tee. full is full, one half is one half and empty is empty. Put the unit back in the car and gauge pegs out. The arm will move from top to bottom by just turning the unit upside down and back. No gas in the float.
I tried to post some pics but can't. It says insert image, I click on that and says enter image URL, I don't know what that means, I click on my pic and it doesn't come to my post. How do I post a pic?

[TJ]

You may not be getting a good ground. Run a ground wire from the sender to a clean ground on the frame and see what happens. The aftermarket senders have never been known to be friendly to the stock gauges.

[old guy rich]

Originally Posted by TJ

You may not be getting a good ground. Run a ground wire from the sender to a clean ground on the frame and see what happens. The aftermarket senders have never been known to be friendly to the stock gauges.

TJ, I'll try that tomorrow. Thanks.

[19Fordy]

Rich, Be sure to let us know your results.

JIM

[old guy rich]

Originally Posted by 19Fordy

Rich, Be sure to let us know your results.

JIM

19Fordy, how do I post a picture, can you help me in there area
? Not sure what image URL is.

[VeryTangled]

Originally Posted by old guy rich

I tried to post some pics but can't. It says insert image, I click on that and says enter image URL, I don't know what that means, I click on my pic and it doesn't come to my post. How do I post a pic?

Photo posting in a video tutorial, about 8 minutes long. There are some other ways that aren't covered, but this should get you started.

https://youtu.be/CGijbl1bfnI

[old guy rich]

Originally Posted by VeryTangled

Photo posting in a video tutorial, about 8 minutes long. There are some other ways that aren't covered, but this should get you started.

https://youtu.be/CGijbl1bfnI

VeryTangled, thank you, I'll give it a try.

[oldskool]

could it be the wire coming from the gage to the sending unit be shorted/grounded if so run a new wire

[old guy rich]

Originally Posted by oldskool

could it be the wire coming from the gage to the sending unit be shorted/grounded if so run a new wire

oldskool, not sure at this time.What I did yesterday was took the sending unit out of the tank, stuffed a tee-shirt in the hole and covered it with a moving blanket.(don't want to get blown up). I used the two normal wires that it would use if it was in the tank. (feed wire and ground wire) I moved the sending unit arm to the empty position and the gauge went to empty, moved to full and gauge went to full, went to half way gauge went to half full. Installed the sending back in the tank and the gauge pegged. The float is empty and if it was full the gauge should read empty as it would be at the bottom of the tank.
Thanks for your interest, oldskool.
Posting a pic is more complicated than it use to be for me, but trying to get thru it.

[old guy rich]

Originally Posted by verytangled

photo posting in a video tutorial, about 8 minutes long. There are some other ways that aren't covered, but this should get you started.

https://youtu.be/cgijbl1bfni

IMG_4525sized.jpg

[old guy rich]

Originally Posted by 19fordy

rich, read about bob drake fuel sending unit here. Perhaps it will help. You might also want to send a pm to the folks posting about this for extra help on how they solved their problem.
https://www.google.com/search?q=bob+...hrome&ie=utf-8

could you post a photo of what your gas tank sending unit looks like?
Is your car still 6v or did you convert it to 12v?

IMG_4525sized.jpg

[19Fordy]

Rich, Thanks for posting the photo of your sender.
Based on what you say: "I used the two normal wires that it would use if it was in the tank. (feed wire and ground wire) I moved the sending unit arm to the empty position and the gauge went to empty, moved to full and gauge went to full, went to half way gauge went to half full. Installed the sending back in the tank and the gauge pegged. The float is empty and if it was full the gauge should read empty as it would be at the bottom of the tank."

I too am puzzled that the sending unit and gauge reads accurately when the sending unit is outside the tank but, inaccurately when reinstalled.

I don't have a solution. As a last resort I would run a new wire from the gauge to the sending unit and a new ground wire from the sending unit to the frame. But, before doing that, check the continuity of the original wires. Perhaps there is a short.

Also, loosen and clean the connects of any wires on the sending unit that are held by screws. Make sure the soldered joints are good.

I am still surprised that the after market gas tank sending unit gives correct readings on your OEM gauge.

[swedishsteel]

Are you sure the float is traveling up and down freely in the tank? Maybe turn it 90 or 180 degrees. Excuse my ignorance if the screw holes line up only one way.

[petehoovie]

old guy rich's sending unit >