Help with fuel guage PLEASE!

-
Cornernfool

Cornernfool

Well-Known Member
Joined
Nov 12, 2012
Messages
59
Reaction score
17
Location
Arizona
1975 Plymouth Valiant, 318, auto. Purchased for my Daughter 12 years ago, gauge was reading incorrectly, put in a aftermarket sender, worked for a while. Gauge started showing empty at aprx. 1/2 tank. Took it to a few shops (she lives 800 miles away) replaced float, replaced sender, same thing. Sent the car home to me, I replaced the sender with an e-bay new unit. Gauge would not read full and again read empty at 1/2 tank. Pulled the dash, replaced the gauge with 1 from Classic Industries, replaced the voltage controller behind the dash, cleaned everything, scotch brighted the circuit board, replaced all dash lights and checked continuity of all circuits. Found the sender wire in the dash plug and checked the ohms of it. I new the tank was low and got a reading of 63. Cleaned the dash where it grounds, used new screws and reinstalled the dash. Turned on the key and the needle went up and dropped back to under a 1/4 tank. Went and filled the tank and it took 8 gallons and did not read all the way full. Ordered a new sender from Classic Industries, installed it, filled the tank again and still not a full reading. Drove aprx. 25 miles and its reading 1/2 a tank. Also, when I first turn on the key the gauge goes up hi, then drops back about a 1/4 of a tank reading. I'm lost, please help. Thank you, Mike
 
I've posted this stuff until I'm blue in the face

Check your wiring, the ENTIRE PATH from ignition switch........to cluster.......to the IVR.......to the gauge.......back to the sender...

and check the gauge WITH KNOWN RESISTANCES. Do a search. Hundreds of posts on here about this

Hey Del, Look what I found!!! An original Miller Gauge tester!!!

c-3826-jpg.jpg
 
All aftermarket sending units are linear, so they won't read right. Also some of them have the pickup tube either too high or too low (if too low the sending unit won't seal). Only way to know for sure is to pull the tank and check. It's a pain. It sounds like having the fuel gauge read correctly is very important to you. To achieve that you need to search on here, ebay, etc for an OEM or NOS sending unit.

You can get floats and screen/sock for them on Amazon or take them off an aftermarket sending unit.

Here's 3 places that rebuilds them in case you have an OEM one you can rebuild, or maybe they have some rebuild OEM ones in stock:

Fuel tank sending unit rebuild service

Fuel Senders

Home

Rebuilt Fuel Sending Unit Specialist
 
Had the same problem put a set of aftermarket gauges in the car now everything works right. Drove the car to 1/16th just to tezt the gauge.
 
Yes, very important to me to know fuel level. Travel a lot of back roads and down to Mexico. I'll dig around and see if I have the oem unit. Also seen an item while searching called a Meter match. Anybody have any feedback on these? Thanks, Mike.
 
Cornernfool said:
Yes, very important to me to know fuel level. Travel a lot of back roads and down to Mexico. I'll dig around and see if I have the oem unit. Also seen an item while searching called a Meter match. Anybody have any feedback on these? Thanks, Mike.
Click to expand...

I should have mentioned that. YES!! I bought one just to try it out. Don't have "feedback" on how their longivity might be but they do work.

My advice? Install a small (additional) fuel cell in the trunk
 
I had the same issue on my 1967 Dodge Dart, stock gauge, aftermarket sender.

Do you have the ground strap on the fuel sender to fuel line ( I assume it is still used in 75)

My aftermarket sender's pickup was almost an inch farther above the gas tank floor than the OEM unit, which would indicate the tank empty sooner than OEM, I saw a Chrysler TSB regarding fuel senders on a different car needing their pickup tubes bent to get it closer to the floor of the tank. might apply here as well.

I know this is not alot of help here but I feel your pain.

I also know the below info does not solve your issue but it does shed light on the linear vs non linear aspect of things.

I found an OEM NOS sender (04051004 latest replacement number from Mopar) Now my gauge reads much better. I Filled the tank full, then I attached a multimeter to the sender output and outlet tube on sender, then I siphoned out one gallon at a time shook the car and let it settle. Then I measured and recorded the resistance. I did this with the aftermarket sender installed then when the tank was empty (I could only get 17.5 gallons out. I have a dented area in the tank BUT I don't think it accounts for 1/2 gallon). I changed the sender to the OEM Mopar unit and added one gallon at a time and measured the resistance the same as before. ( yes the car was on a flat garage floor and it is not jacked up and sits very flat) The measurements are from the senders ONLY no chassis wiring involved. The first is the chart of resistances and the second is the graph of those values.

I have not worked out the resistance values for the dash gauge yet but if you take the 74 = empty, 23 = 1/2, and 10 = full the mopar unit comes MUCH closer to reading proper resistance values per gallon than the aftermarket.

I am building a resister bridge to chart the fuel gauge including the chassis wiring. I'm going to change the resistance by one ohm at a time, wait a length of time and take a photo of the gauge from a fixed location than using CAD determine the angle of the needle. (I do this type of data acquisition for a living)

Once I gather that I'll post my findings

Sender resistance data.JPG
Sender resistance chart.JPG
 
fuel gauge1.jpg
I found something interesting in my 66 Dart fuel gauge. There are adjustment slots for the high and low limits and holes is the gauge body to adjust when installed in the cluster
 
Dana67Dart said:
I had the same issue on my 1967 Dodge Dart, stock gauge, aftermarket sender.

Do you have the ground strap on the fuel sender to fuel line ( I assume it is still used in 75)

My aftermarket sender's pickup was almost an inch farther above the gas tank floor than the OEM unit, which would indicate the tank empty sooner than OEM, I saw a Chrysler TSB regarding fuel senders on a different car needing their pickup tubes bent to get it closer to the floor of the tank. might apply here as well.

I know this is not alot of help here but I feel your pain.

I also know the below info does not solve your issue but it does shed light on the linear vs non linear aspect of things.

I found an OEM NOS sender (04051004 latest replacement number from Mopar) Now my gauge reads much better. I Filled the tank full, then I attached a multimeter to the sender output and outlet tube on sender, then I siphoned out one gallon at a time shook the car and let it settle. Then I measured and recorded the resistance. I did this with the aftermarket sender installed then when the tank was empty (I could only get 17.5 gallons out. I have a dented area in the tank BUT I don't think it accounts for 1/2 gallon). I changed the sender to the OEM Mopar unit and added one gallon at a time and measured the resistance the same as before. ( yes the car was on a flat garage floor and it is not jacked up and sits very flat) The measurements are from the senders ONLY no chassis wiring involved. The first is the chart of resistances and the second is the graph of those values.

I have not worked out the resistance values for the dash gauge yet but if you take the 74 = empty, 23 = 1/2, and 10 = full the mopar unit comes MUCH closer to reading proper resistance values per gallon than the aftermarket.

I am building a resister bridge to chart the fuel gauge including the chassis wiring. I'm going to change the resistance by one ohm at a time, wait a length of time and take a photo of the gauge from a fixed location than using CAD determine the angle of the needle. (I do this type of data acquisition for a living)

Once I gather that I'll post my findings

View attachment 1715098450 View attachment 1715098451
Click to expand...

This might be incredibly useful for troubleshooting "all factory" gauge setups, meaning, IVR, gauge and sender all to factory specs

But there are almost NO factory senders.......something the OP is dealing with.

Nevertheless I encourage you to post your findings.
 
Dana67Dart said:
I had the same issue on my 1967 Dodge Dart, stock gauge, aftermarket sender.

Do you have the ground strap on the fuel sender to fuel line ( I assume it is still used in 75)

My aftermarket sender's pickup was almost an inch farther above the gas tank floor than the OEM unit, which would indicate the tank empty sooner than OEM, I saw a Chrysler TSB regarding fuel senders on a different car needing their pickup tubes bent to get it closer to the floor of the tank. might apply here as well.

I know this is not alot of help here but I feel your pain.

I also know the below info does not solve your issue but it does shed light on the linear vs non linear aspect of things.

I found an OEM NOS sender (04051004 latest replacement number from Mopar) Now my gauge reads much better. I Filled the tank full, then I attached a multimeter to the sender output and outlet tube on sender, then I siphoned out one gallon at a time shook the car and let it settle. Then I measured and recorded the resistance. I did this with the aftermarket sender installed then when the tank was empty (I could only get 17.5 gallons out. I have a dented area in the tank BUT I don't think it accounts for 1/2 gallon). I changed the sender to the OEM Mopar unit and added one gallon at a time and measured the resistance the same as before. ( yes the car was on a flat garage floor and it is not jacked up and sits very flat) The measurements are from the senders ONLY no chassis wiring involved. The first is the chart of resistances and the second is the graph of those values.

I have not worked out the resistance values for the dash gauge yet but if you take the 74 = empty, 23 = 1/2, and 10 = full the mopar unit comes MUCH closer to reading proper resistance values per gallon than the aftermarket.

I am building a resister bridge to chart the fuel gauge including the chassis wiring. I'm going to change the resistance by one ohm at a time, wait a length of time and take a photo of the gauge from a fixed location than using CAD determine the angle of the needle. (I do this type of data acquisition for a living)

Once I gather that I'll post my findings

View attachment 1715098450 View attachment 1715098451
Click to expand...
To the thread starter... What instrument voltage regulator did you install? A reproduction mechanical limiter may very well be a piece of crap. That based on your comment that needle races toward full at switch on then drops back again. That's what bad mechanical limiters do.
And this chart shows just how wrong the aftermarket linear senders are.
OEM gauges have a resistor wire with a ohms per inch rating AT ROOM TEMPERATURE. Then there are 2 different gauges in these cars ( although they do function the same ). First the 20 ohm gauges. These have larger heavier needles mounted on a pivot post at 2 places. This one contains approx' 13.5 inches of wire rated at 1.5 ohms per inch. Then the 13 ohm gauge with its extremely light needle hooked in triangles. This one contains approx' 13 inches of wire rated at 1 ohm per inch. Hell everything about them is different, yet they function the same, and that's not my point.
In any and all cases, the per inch resistance changes as the resistor wire heats up. That's why 23 ohms equals centered/half tank needle position of both types. Do the math. Half of a 80-10 range is 35 ohms. Half of a 18 gallon fill is 9 gallons. 9 gallons absolutely cannot be 35 ohms and half tank needle position on a OEM gauge. That is without adding the meter match module to alter it.
9 gallons isn't 23 ohms on that chart but 28 is close. Might we attribute that difference to the shape of the tank? Half the sender float arm swing isn't exactly half the tank volume either. The non linear OEM sender will provide 23 ohms at about half of the float arm swing. And 1/4 tank should be close 35 ohms, so test results are a few ohms wrong there also. I could question the voltage supplied and all relative conditions during the test but... who cares ?
What we call a instrument is a simple range indicator, Engineered to be fairly accurate when new. Age and other factors render them less accurate. Aftermarket junk parts are to blame for waaaaay wrong. After some years past we shouldn't expect the aftermarket to ever produce a proper sender, or a instrument that matches their sender. At least we do have the meter match module solution. Good luck to all.
 
I had the same issue on my Demon, I tried a few sending units and gauges. Last year I just got fed up and bought a meter match. Well not knowing how far the pickup was from the bottom of the tank. So I ran the car until I thought I was down to @ 4 gal. by milage. So I hooked an elect pump up to the sending unit and pumped it till empty. Now starting with a "empty tank" I put one gal. in the tank " kind of a reserve " and set that as empty. I then added 4 more Gal. in and set that to 1/4 tank. I added 8 more gal. and set that as 3/4 tank. Then I filled the tank @ 3 more gal. and set that as full. Well it's been over a year now and still working fine. It's not perfect but pretty darn close.
Good Luck!
 
Mr.FT said:
I had the same issue on my Demon, I tried a few sending units and gauges. Last year I just got fed up and bought a meter match. Well not knowing how far the pickup was from the bottom of the tank. So I ran the car until I thought I was down to @ 4 gal. by milage. So I hooked an elect pump up to the sending unit and pumped it till empty. Now starting with a "empty tank" I put one gal. in the tank " kind of a reserve " and set that as empty. I then added 4 more Gal. in and set that to 1/4 tank. I added 8 more gal. and set that as 3/4 tank. Then I filled the tank @ 3 more gal. and set that as full. Well it's been over a year now and still working fine. It's not perfect but pretty darn close.
Good Luck!
Click to expand...

Mr.Ft, I read that post of yours a few days ago. I did some research on the meter match and ordered one 3 hours ago. I just hate thinking about pulling the cluster out again. Car has A/C and I'm recovering from shoulder surgery from a bad motorcycle accident. But I'll get it done again. I'll pull fuel from the outlet and calibrate it just like you did.

Thank you all for responding and I'll let you know how it works out.

Thanks again, Mike.
 
Mike,
If your car has the same layout as my Demon you won't have to pull out the cluster to install the meter match. On my Demon the sending unit wire ran up the drivers side on the inside of the kick panel. I mounted the meter match under the kick panel with velcro. then I ran the power wire to a switched fuse and connected it with a fuse tap. I cut the sender wire and hooked the two ends to the meter match as er Instructions. Then the only other wire was a ground. I extended the wires enough so I could sit in the car to make adjustments, then just tucked them neatly back in the kick panel. Remember when you make a change give the Gauge a few minutes to fully change needle position.

PS: if it is easier than reaching under to the sending unit, we just pulled the fuel hose off at the feed side of the Mech. Pump. Don't forget to "pinch" the fuel line before you pull it off, This will prevent a mess, Trust me.
Hope this helps you solve your issue.
Let me know how you make out.
Tom
 
There is still the reported needle swing issue. Wild needle swing at switch on is not normal. It's more commonly seen in temp gauges when restarting a heated engine too. Anyway... If this is excessive voltage from a faulty limiter/regulator, Meter Match wont prevent it.
 
Last edited:
Mr.FT said:
RedFish, you are correct, meter match won't help that.
Click to expand...
Temp gauge works fine. I bought the meter match vr just to be sure. Ordered the plastic isolators to. So cluster will come out of the car and out of the system.
 
I just refilled the tank after my OEM NOS sender (04051004 latest replacement number from Mopar) installation. Gauge read a needles width over 1/4 tank, put 13.48 gallons in to the tank to make it full. 0.25 x 18 = 4.5, 18 - 4.5 = 13.5 I think my gauge is accurate enough! (I only got 17.5 gallons into the tank from siphon hose empty and the tank has a crushed area. Assuming 17.5 = max tank will hold 0.25 x 17.5 = 4.375, 18 - 4.375 = 13.625. ) All of the values are within 1% I'm good! Not bragging just VERY happy with my NOS sender!
 
Dana67Dart said:
I just refilled the tank after my OEM NOS sender (04051004 latest replacement number from Mopar) installation. Gauge read a needles width over 1/4 tank, put 13.48 gallons in to the tank to make it full. 0.25 x 18 = 4.5, 18 - 4.5 = 13.5 I think my gauge is accurate enough! (I only got 17.5 gallons into the tank from siphon hose empty and the tank has a crushed area. Assuming 17.5 = max tank will hold 0.25 x 17.5 = 4.375, 18 - 4.375 = 13.625. ) All of the values are within 1% I'm good! Not bragging just VERY happy with my NOS sender!
Click to expand...

Where did you score the NOS sender?
 
I called the local Dodge dealer and he referred me to another dealer who had old books and was able to confirm the PN I had PNs from original parts book from 67. and found other PNs for the latest replacement part from Chrysler. From there he searched the Chrysler national parts system and came up with what he said was the last one the system in Georgia. I called them and they had it on the shelf best 150.00 I have spent. If I was to do it again I would scour the wrecking yards for an OE 1967 unit and have it rebuilt by one of the sources above. someone posted an OE 1967 dart pickup tube (Fuel sending units) and the shape of the pickup tube and the sender on the tube is much different then the one I have. But it works!

Progression of sender part numbers 2421493 (OE 67) is superseded by 3621615 which is superseded by 4051004
 
Last edited:
Have not pulled the dash out yet. Spent a few days in Mexico on the Targa Baja California rally. Running the Plymouth with the Porsche's and Alphas.
 
You must log in or register to reply here.
-

Back
Top