Fuel Sending Unit

[7212Mopar]

When I was putting my car back together a few years back, I replaced the fuel tank, clean up the fuel lines and got replacement fuel sending unit from Mancinni Racing. It never worked right from the start. It will read full and then close to empty after about 5 or six gallons used. Last week the fuel gauge pegged past full when I switch the car on. I checked all the connections and wiring and everything seems to be good. After reading some posts thinking the blue wire got grounded, I disconnected the connector behind the side kick panel and ran a new wire to the sending unit. When connected, fuel gauge get past full. Gauge will sweep to empty if I disconnect the wire. I think my wiring and fuel gauge are ok and most likely something wrong with my sending unit. May be it got hung up but not sure how. May be it is time to fix the problem hopefully this time by going with with Mopar NOS sender. I found this site selling NOS unit, a bit pricey and I have no experience with this vendor. Anyone deal with them before and if you like to your experience?

http://www.bradsnosmopar.com/nosmop70ebfu.html

[Joegrapes]

That seems like a good price. About 6 months ago I bought an NOS sending unit from a different vender and I paid $250 for it. I know it was to much considering you can get an aftermarket one for a third of that. I got sick of screwing with the aftermarket sending units over the years never reading right. I bit the bullet and bought an NOS unit and couldn't be happier. I works great.  Get it, you won't be sorry you spent the money.

[floorit426]

Check to see how many volts are going to your blue wire. I just went through a similar issue. It was my voltage limiter. You should NOT have a reading of 12 volts. It should be a pulsating reading, around 5 volts. How is your stock temp gauge functioning? It may have the same issue, as the two are linked together. Be careful. If the gauge gets a full 12 volts, for very long, it will toast the gauge.

[7212Mopar]

I have the solid state RT Engineering limiter in the dash. My other gauges seem to be working so should be fine but checking voltage is easy.

[7212Mopar]

Well, I placed the order for the NOS fuel sending unit. A few minutes later got an email from the vendor saying they no longer have them in stock. Then they ask me if I want a repro unit for a few dollars less. So I replied and said only if it can read the fuel level same as a NOS unit. Waiting for reply. This ain't exactly rocket science and I just don't understand why they can't make a proper replacement unit.

[anlauto]

Well, I placed the order for the NOS fuel sending unit. A few minutes later got an email from the vendor saying they no longer have them in stock. Then they ask me if I want a repro unit for a few dollars less. So I replied and said only if it can read the fuel level same as a NOS unit. Waiting for reply. This ain't exactly rocket science and I just don't understand why they can't make a proper replacement unit.

At least they didn't send you a repro calling it NOS 

[Scooter]

Well, I placed the order for the NOS fuel sending unit. A few minutes later got an email from the vendor saying they no longer have them in stock. Then they ask me if I want a repro unit for a few dollars less. So I replied and said only if it can read the fuel level same as a NOS unit. Waiting for reply. This ain't exactly rocket science and I just don't understand why they can't make a proper replacement unit.

At least they didn't send you a repro calling it NOS 

^^^ This.

[Brads70]

Just discovered this....?

https://www.holley.com/products/fuel_systems/fuel_pumps_regulators_and_filters/fuel_pumps/muscle_car_efi_modules/parts/12-318

[7212Mopar]

That is a neat setup for folks switching to EFI. I am running EFI using Fitech with the second gen Fuel Commander. So really no need for another electric fuel pump. I dug up my other inaccurate sender I got from Yearone or may be from CI. I am going to test it next week. Thinking to try the Tanks Inc module that you can adjust and set the gauge by modifying the resistance signal off the sender.

[1 Wild R/T]

I followed the link to Brads NOS... I say be thankful they are sold out... The sending unit in the picture is not true NOS, it may have been sold by Chrysler, likely as an "Authorized Reproduction" but it's not what was used back when these cars were new.... That shiny plating is a dead giveaway... I bought & installed enough true NOS units back in the 70's/80's & 90's to know the real NOS stuff was a dull metallic gray finish, possibly galvanized... I remember Mopar selling reproduction senders in the early 2000 time frame, they were just as bad as an other vendors repo sending units....

[73chalngr]

I bought a reproduction sending unit when swapping out my fuel tank figured my old one was a 50-year-old part that was the time to upgrade never read right put the original one back in problem solved .

[Cratos]

i have two from tanks Inc neither reads correct in the tank but reads right out of the tank ? with 10 gallons it reads 1/8 tank or less both are the same tried 2nd ground still no joy so I put the 5/16 one back in and it reads correct. go figure.

[7212Mopar]

I pulled the old fuel sending unit out and found the problem. The design of this aftermarket unit had a metal strap with insulation that connects the float rheostat to the output terminal. The strap normally has a curve to it and not touching any other part of the sender. It looks like the ethanol gas ate up the insulation and wrinkled it up twisting the strap out of shape where it is touching the fuel tube and grounding it. That explains why my fuel gauge peak at full all the time. My other unit that is sitting around is of the same design. I check the resistance through its range on a multimeter and also connected to the fuel gauge. Moving the float arm, the resistance read around 75 ohms empty, 61.6 at 1/4, 36.6 at midpoint, 18.7 at 3/4 and 9.8 at full. All of these readings are relative of the float arm against the rheostat housing. But connect to the gauge, 9.8 is a little past F and 75 is a little past E. I suppose the resistance is not linear so I bent the arm down toward empty so when arm drops from full, level moves more before resistance goes up. I also bent the stop tabs at both ends a little so that E is about 75.7 ohms and F is about 8 ohms. I figure this should help and after inserted into the gas tank, gauge reads just a smudge past E and I think I have at least 6 to 7 gallons of fuel in tank (not sure). Very likely that it is still not quite reading correct. I have not try to fill the tank up yet so not sure about the other end. Like others had noticed, the resistance readings outside the tank might not be the same as it is installed in the tank.

Next thing to do is to add the Tanks Inc Meter Match (resistance manipulator) that I just received from Summit today. I will see if I have time to install it this coming weekend (too many wife assignments). The plan is to cut the blue wire before the connector at the kick panel and tie to the Meter Match unit. I will be using the sender that I pulled out last week to do the initial setting (four points). I will also check the ohms readings first to see how that compare to the one installed in the tank now. Will update again after I get it together. I am hoping this will do the trick. If not I just rely on the odometer since I know my car get around 7 mpg.

[RUNCHARGER]

7MPG? I had to drive my Hemis hard to get that bad of mileage.

[Scooter]

I filled up before our drive last weekend, let the gauge drop all the way to empty for the first time.

Filled up the next day and I still had over 6 gallons in the tank.

it's pretty consistent and I don't really feel like messing with trying to replace the float assembly as they are sooo hit-or-miss.

Will likely go the Meter Match route so let us know how the install goes.

Good news is after all the carb tweaking and ignition work my lil 360 is up to nearly 15mpg under normal mixed city/hwy driving conditions. Drops predictably if I'm just rodding around town.