Fuel Gauge Question

-
1969VADart

1969VADart

Well-Known Member
Joined
Aug 19, 2013
Messages
2,498
Reaction score
813
Location
Fredericksburg, VA
So ever since I reassembled my Dart, which included a new fuel tank, lines and sending unit (everything in the fuel system), the fuel gauge only reads 3/4 full when I have filled the tank all the way up (nearly to overflowing). My question is, when the gauge is down almost to "Empty (E)" (I have not passed the E line yet) and I fill it up, it only takes 9-10 gallons. So I am safe to keep driving for awhile even after it hits E since the car presumably still has 8-9 gallons in the tank, or am I risking running out of fuel (or at least reaching a point where it does not pick up any more fuel)? Would appreciate any thoughts you guys might have on the subject.
 
1969VADart said:
So ever since I reassembled my Dart, which included a new fuel tank, lines and sending unit (everything in the fuel system), the fuel gauge only reads 3/4 full when I have filled the tank all the way up (nearly to overflowing). My question is, when the gauge is down almost to "Empty (E)" (I have not passed the E line yet) and I fill it up, it only takes 9-10 gallons. So I am safe to keep driving for awhile even after it hits E since the car presumably still has 8-9 gallons in the tank, or am I risking running out of fuel (or at least reaching a point where it does not pick up any more fuel)? Would appreciate any thoughts you guys might have on the subject.
Click to expand...
You have an aftermarket sending unit. All aftermarket sending units are linear so they don't read correctly. See this thread on the drawbacks of aftermarket sending units, as well as how to make them work properly:

Fuel tank sending unit for 1966 Dart?

By chance when you installed the aftermarket sending unit did you ensure the pickup tube reaches all the way to the bottom of the tank?
 
kiss said:
By chance when you installed the aftermarket sending unit did you ensure the pickup tube reaches all the way to the bottom of the tank?
Click to expand...

That is an excellent question, and the answer is I have no idea. Perhaps I could check it if I have to drop the tank to fix the leaking grommet issue anyway.
 
1969VADart said:
That is an excellent question, and the answer is I have no idea. Perhaps I could check it if I have to drop the tank to fix the leaking grommet issue anyway.
Click to expand...
That would be a good idea. Every aftermarket sending unit I've seen doesn't reach the bottom of the tank. With the tank out you can look through the filler neck hole and tweak it accordingly.

Just to expand a bit more than on the thread I linked you, it sounds like you will need to bend the float arm down a bit too. That way it reads the full range of travel. I've had to bend the arm down a bit on each aftermarket sending unit I've dealt with.

At that point you can either "get used to" the way your fuel gauge reads, or get a Meter Match.

As far as the grommet if you need a new one I pointed out a good quality new one to the guy in this thread:
Fuel Filler Neck Grommet Replacement
 
This seems to be a universal inaccuracy--my factory gauge/factory sender/factory pickup work together to read 3/4 when tank is very full. We all have been cursed by the same hex.
 
dibbons said:
This seems to be a universal inaccuracy--my factory gauge/factory sender/factory pickup work together to read 3/4 when tank is very full. We all have been cursed by the same hex.
Click to expand...
Please don't assume the gas gauge didn't read correctly when new. Although your fault could be as simple as a small amount of fuel inside the float ( we hope its that simple ), there are several other possibilities too. A failing limiter can cause all the thermal instruments to read below accurate. And compromised chassis ground path of that limiter does the same.
I've opened and renewed a few hundred of these instruments so I've seen the affections they get with old age. This is most typical of the fuel gauges simply because of their duty. They spend a lot more of their life at the high end of their range.
So... Agreeing that the aftermarket senders aren't proper, at 9 to 10 ohms the gauge should still go to full even if its inaccurate at the lower levels.
Measure your sender resistance at full tank. Approx' 14 ohms would be approx' 3/4 hash mark on the gauge screen.
 
Or you could do what I did... With an empty tank, add 1 or 2 gallons at a time, and record the readings on the gauge. I found out exactly how much my tank held (16.5 gallons), and how much is in the tank at various gauge readings. 4 gallons: right on the E line, 7 gallons: between 1/4 and E, 10 gallons: just over 1/4, 12 gallons: just under 1/2, 14 gallons: just below the F line, 16.5 gallons: right on the F line. Crazy stuff.
 
kiss said:
That would be a good idea. Every aftermarket sending unit I've seen doesn't reach the bottom of the tank. With the tank out you can look through the filler neck hole and tweak it accordingly.

Just to expand a bit more than on the thread I linked you, it sounds like you will need to bend the float arm down a bit too. That way it reads the full range of travel. I've had to bend the arm down a bit on each aftermarket sending unit I've dealt with.

At that point you can either "get used to" the way your fuel gauge reads, or get a Meter Match.

As far as the grommet if you need a new one I pointed out a good quality new one to the guy in this thread:
Fuel Filler Neck Grommet Replacement
Click to expand...

I bought this exact grommet you mentioned previously. If all goes as planned, I am going to swap it out this weekend, so that I will be all set for Carlisle next week.

As for the sender, how difficult is it to bend the fuel pickup? Seems that it is on the opposite side of the tank from the entry point for the filler neck and would have to be removed from the tank completely in order to bend it. The gauge issue does not bother me all that much. Until my fuel leak started, I would just fill it up when it got basically to Empty. It would take about 10 gallons approximately to fill the tank up from E (gauge still reading only 3/4 full though). I believe my tank is an 18 gallon tank, but it has been almost four years since I bought it, so I don't really remember.
 
1969VADart said:
I bought this exact grommet you mentioned previously. If all goes as planned, I am going to swap it out this weekend, so that I will be all set for Carlisle next week.

As for the sender, how difficult is it to bend the fuel pickup? Seems that it is on the opposite side of the tank from the entry point for the filler neck and would have to be removed from the tank completely in order to bend it. The gauge issue does not bother me all that much. Until my fuel leak started, I would just fill it up when it got basically to Empty. It would take about 10 gallons approximately to fill the tank up from E (gauge still reading only 3/4 full though). I believe my tank is an 18 gallon tank, but it has been almost four years since I bought it, so I don't really remember.
Click to expand...

After you drop the tank just look through the filler neck hole at the sending unit. If the sending unit is touching the bottom of the tank you're good to go. If not remove the sending unit, bend the pickup tube down a little bit (remove the strainer first) and re-install. Small adjustments only. I was able to bend it with my hands. I think I put a screwdriver in the end of the pickup tube to make it a little easier when first bending it. Might take a few times of removing/reinstalling/checking but it shouldn't take long.
 
If the grommet doesn't get here before this weekend, I guess I will be making the Carlisle run without a full tank of gas to prevent the leak. Not my preferred option, but it looks like the grommet may be delayed in arrival.
 
hope this is the right place 4 a fuel question.
have 64 val. g/gauge only moves 1/8 of inch I've ground tank ,cleaned connection. any suggestions.gauge worked until car sat in pole barn 4 a year.thanks packerman
 
My gauge worked until a week after getting back from a road trip. Pulled the sending unit out only to find the brass float had a pinhole and filled with fuel, lost its buoyancy (gauge was reading empty).
 
The float I need is for a '72 BBody, according to Amazon database, the above float does not fit (but it looks the same).
 
You must log in or register to reply here.
-

Back
Top