Fuel sender question.

[Huicho417]

I have some problems with my fuel gauge reading correctly, and have finally decided to take care of this annoying issue. It is an aftermarket sender and original fuel gauge. Knowing that the new senders do not really send correct ohm readings I added a meter match to help.

My issue is that after I calibrate the gauge with the meter match device. A full tank will only read at about 3/4 full. I do have a new grounding strap from sender to steel fuel line. But will add a grounding strap screwed to frame and see if that helps.

Here’s the question. My insulated connector that goes over the sender stud was very brittle and cracked. I replaced it with a ring connector with nut. Any chance this may be adding to the issue?

 

[ruffcut]

The different connector isn't the problem. In my experience with the new senders, a 3/4 reading at full is probably the best you're going to achieve.
I have the same thing with my Roadrunner. Doesn't give you much confidence about how much fuel you really have, does it? Good luck. Hope to see how you remedy this. ruffcut

 

[pnora]

I would add the ground. With a poor ground you may of calibrated it incorrectly. What I do is start with an empty tank. Add 3 gallons and calibrate it to read dead on empty. You should leave the key on for a couple minutes and tap on the gauge before locking the empty setting. Then I fill it right to the brim and set the full setting to a needles width above the full mark. Procedure same as the empty setting. Once done they work excellent. There are more settings you can use but the empty and full as I described seem to have a very accurate reading throughout the full sweep of the gauge.

 

[zyzzyx]

I always add a stainless steel internal star washer on all of my ground connections anywhere on
the body to "bite in" and make a positive connection. Just screwing down a connector to a rusty
are won't do. You may have continuity, but some resistance.

 

[R413]

What is grounding that sending unit? It needs a reliable ground, it sends a ground to the gauge.

You familiar with the strap that clips on each line.

OER MF290 1962-76 MOPAR FUEL TANK SENDING UNIT GROUND STRAP- STEEL | eBay

 

[dadsbee]

What is grounding that sending unit?

I do have a new grounding strap from sender to steel fuel line

 

[Geoff 2]

Most likely sender 'adjustment'. When full, the sender float needs to be at the top of the tank. The fix to getting the sender to read correctly is to bend the float arm.

 

[pnora]

Most likely sender 'adjustment'. When full, the sender float needs to be at the top of the tank. The fix to getting the sender to read correctly is to bend the float arm.

Most senders are made with the incorrect resistance. The readings stop to stop are not in the correct range 70-10 for the gauge.

 

[Cincy Kid]

The different connector isn't the problem. In my experience with the new senders, a 3/4 reading at full is probably the best you're going to achieve.
I have the same thing with my Roadrunner. Doesn't give you much confidence about how much fuel you really have, does it? Good luck. Hope to see how you remedy this. ruffcut

My experience is the same, new sending unit, old gauge 5/8 when fuel & 1/2 tank when its on E, not a lot of confidence after the E reading. Wondered about leaving the original gauge intact & somehow putting on an after market fuel gauge, has anyone done this, or can it even be done?

 

[pnora]

My experience is the same, new sending unit, old gauge 5/8 when fuel & 1/2 tank when its on E, not a lot of confidence after the E reading. Wondered about leaving the original gauge intact & somehow putting on an after market fuel gauge, has anyone done this, or can it even be done?

Just install a meter match and dont look back.

 

[ruffcut]

Im curious what a meter match device is? ruffcut

 

[pnora]

Im curious what a meter match device is? ruffcut

MeterMatch Fuel Gauge Interface Module

 

[Geoff 2]

A lot of bad info here. Problem is most likely a very simple one....that I described in post #7.

If the resistance of the sender is incorrect, the sender needs to be removed from the tank to check the resistance. There is no way it can be done in situ. Sure, in situ you can get a resistance reading, but there is no way of knowing if the float arm is touching the stop.
If res measures correctly, then the problem is adjustment of the sender float arm, gauge it self or wiring. Messing around with i'face modules should be a 'if all else fails' fix.

 

[dadsbee]

There is Zero reason you can't check stroke, stop to stop and ohm readings IN the tank with a '68/69/70 with rear filler tube! Now that said, the OP didn't even state a year, but going by his avatar I'm guessing he's working on a '66/67 side filler.. so yah. Still easy enough to make a diagram of tank depth, sender location and preadjust your up and down float before installing.

 

[pnora]

A lot of bad info here. Problem is most likely a very simple one....that I described in post #7.

If the resistance of the sender is incorrect, the sender needs to be removed from the tank to check the resistance. There is no way it can be done in situ. Sure, in situ you can get a resistance reading, but there is no way of knowing if the float arm is touching the stop.
If res measures correctly, then the problem is adjustment of the sender float arm, gauge it self or wiring. Messing around with i'face modules should be a 'if all else fails' fix.

The problem is a lot of these senders swing stop to stop in the tank. Out of the tank the same and the OHM's are off due to all the junk being sold. The resistance windings are incorrect. The unit swings stop to stop so there is a full to empty ohm range. The range is not suited for the gauge. That's where the meter match comes in. It allows the senders ohm readings and different levels to be read and then calibrating the gauge. Very effective and end of problem. At this point this is not bad information. This is only for incorrect readings. If you have other issues they need to be sorted out. In a perfect world these replacement senders should have the correct 70 to 10 ohm range which they do not.

 

[dadsbee]

^^^^ new **** is linear on the sweep and not proportionally compensated like the OE resistance rheostats. Another, why can't they just make it correct issue. You're making a rheostat board and wrapping wire, just do it correctly. I was going to get my *** in gear on this a few years ago, but... too many things to work on, and that's not a bad thing I guess! LOL

 

[Geoff 2]

Post #14.
It might be a bit hard to see with any accuracy if the float arm is hitting the stops.....just peering through the filler opening. With or without fuel in the tank....

 

[dadsbee]

Post #14.
It might be a bit hard to see with any accuracy if the float arm is hitting the stops.....just peering through the filler opening. With or without fuel in the tank....

That was shot with a normal camera through the hole before the filler neck went in. No reason you can use todays technology and an inspection camera and a yard stick to lift the float... a meter stick to you.

 

[Geoff 2]

I get the impression from the pic in post #1 [ the deteriorating insulating material between tank & trunk ] & the description that the fuel tank is an existing tank, still in the car & has not been removed to fit the sender.

 

[Huicho417]

Update on this issue.

First to answer a few questions in the previous comments. The car is a 1967 coronet 440 with 318 and 727. The fuel tank is new and was installed about a year ago at the same time the sender was.

I went under the car and added a proper ground strap from fuel line to frame. I did sand the area where the ground fastener screwed in and added a star washer for assurance. Secondly I also purchased a solid state RTE IVR/Limiter to replace the existing one, which I had purchased online.

I immediately noticed a difference specially in the temp gauge. The needle reaches temp much faster and responds as it should as the car drives versus sitting in traffic. I added five gallons of fuel and the fuel gauge seems to be reading correctly.

Now to see if the empty setting will be correct. Thank you all for your feedback.