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Where to order a fuel level sender for my 66, 16 gallon tank, 5/16 fuel line? I see NDP sells a Scott Drake brand and I find Dorman elsewhere with similar price and shipping. Dorman has a 1 year guarantee. Does anyone have a preference?
 

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Buy the NPD house brand for $20. The others are no better. Regardless of what you buy, odds are it will be less than accurate. Care should be taken to adjust the sender so that it reads 70 ohms when installed in an empty tank. You should also confirm, before installing in the tank, that it reads about 10 ohms in the full position. These are NOT just drop in an expect it to be close devices.

When you buy the new tank, be sure to get one with a drain plug.
 

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The Barn did some work a few years ago with ACP to produce a more accurate version. Should still be available.
 

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Discussion Starter #4
...Care should be taken to adjust the sender so that it reads 70 ohms when installed in an empty tank...
Just by bending the float arm? I have a new tank with a drain plug.
 

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The Barn did some work a few years ago with ACP to produce a more accurate version. Should still be available.
NPD sells that one as the "improved" sending unit but I think it has a 3/8" outlet. The purchaser will have to reduce from 3/8" to 5/16".
 

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NPD sells that one as the "improved" sending unit but I think it has a 3/8" outlet. The purchaser will have to reduce from 3/8" to 5/16".
I just bought one of the "calibrated" NPD units. After making sure it was 70 ohms on an empty tank I filled up. I was less than pleased when I filled up with the gauge showing about 1/8th tank and it only took 8 1/2 gallons. Sadly the world that can create an iPhone more powerful than the computer that put a man on the moon cannot re-create a variable resistor.
 
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Had the same problem with the improved NPD one also. When I am at 1/4, I still have about 6-7 gallons. I just go by the milage anymore - its getting old working on my back at 70.
 

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The important question is if there's a repro sender with a correct "progressive" resistor, similar to those used by Ford? The main problem with the repro senders are not ohm at full and empty, but that the resistors used are of a fundamentally wrong design. Woodchuck mentioned it like 5 years ago in a post and I have later meassured on an old Ford vs. an improved NPD sender, only to find his info was correct. The stock fuel gauge will never be able to show correct connected to one of these repro senders.
 

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Given Ford made millions of the original senders to be installed at incredible speed on an assembly line and expected to be reasonably accurate the question still begs, why cannot anyone seem to make an equivalent aftermarket part? It's not like it was some special technology that no longer exists.

Hey NPD, take a factory sender apart, see how it is made and copy it. Make sender that actually functions like factory and people will pay twice the price of the current crap that is being sold (including the so-called "calibrated" unit).
 

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Just by bending the float arm? I have a new tank with a drain plug.
No. The only reason to bend the arm is if it is already bent from mishandling. The float should physically go from the bottom of the tank to the top. Bending the arm so it does not do one or the other only makes it worse.
Given Ford made millions of the original senders to be installed at incredible speed on an assembly line and expected to be reasonably accurate the question still begs, why cannot anyone seem to make an equivalent aftermarket part? It's not like it was some special technology that no longer exists.

Hey NPD, take a factory sender apart, see how it is made and copy it. Make sender that actually functions like factory and people will pay twice the price of the current crap that is being sold.
OK, second first. Other than perhaps including a tapered rheostat to follow closely the shape of the tank, even the crappy repros already do that. The upgraded ACP unit was specifically made with tighter electrical tolerances.

Now for the Ford comment. Ford had the advantage. They were making a whole new car. The sender, wiring, gauge, and CVR were all new.

What you can do is accurize the system. New sender in hand, make sure the float travels to the proper full and empty position. Attach to the rear of the car, using jump wires.

Remove the instrument cluster from the dash, remove the fuel gauge from the cluster, connect the fuel gauge using jump wires, and reconnect the cluster to the car wiring harness.

With the power on, using a small Torx tool, adjust the position of the needle with the float at the E and F positions. There are small gear teeth visible through the back of the gauge for this purpose.

761079


Reassemble the car. This will pretty much shoot a Saturday, but you'll have a surprisingly accurate gauge, especially at the E and F. That's about the best you can hope for. My daily driver, an Outback, very accurately shows the E and F levels of fuel, but half a tank is about at the 3/4 mark on the gauge. Due to the odd shape of the tank, not surprising.
 
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The upgraded ACP unit was specifically made with tighter electrical tolerances.
But tolerances are not the main problem with the repro senders, it's that the resistors used are of a completely wrong design. Meaning that even if you get them to measure absolutely perfect in the ends, they will still be way of in the middle. They are using liniear resistors, Ford used a progressive resistor that gave the gauge a liniear move.
 

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Not so far off as you think, once the F and E are correct. And I have taken these apart. The originals weren't perfect, either. The best I have seen was the OEM sender in my "other" car. The windings tapered about halfway through the travel, just like the tank did. It was almost right from top to bottom. Sadly, the smoke came out of it in 1987, and I replaced it with a sender from a Chevy pickup truck, identical except perfectly linear. So now, 1/2 means 3/8. Which really doesn't matter, since the OEM one was about 10% off anyway, and even if the repro now available is that good, I don't think $110 and a whole day to install is worth it.

I have never owned a car where 1/2 was actually 1/2.
 

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One other possibility, is to have your original rebuilt.

 

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Not so far off as you think, once the F and E are correct. And I have taken these apart.
I don't think, I have measured on a perfect working sender from '64. Measured the ohms while moving the arm in several small steps. Did the same with a new NPD sender. Plotted the numbers in a diagram and draw lines. The NPD made a stright line, while the original Ford made a smooth arc, hitting the NPD line in top and bottom. The gauge will show to little in the middle, and will be most off between 1/2 and 1/4 actual in the tank. Exactly what the old repro sender in my tank did. But I brought a MeterMatch and now my gauge are probably more correct that it have ever been. 😎
 

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Well, there you go, we agree on the function of these replacements. The tank tapers as it goes down, which means the rheostat, like the original one in my other car, did. But it's harder to make them that way.

I also pointed out that you could have an original rebuilt. That would also solve the problem.

The only thing that really matters, though, is that the E is actually where it runs out of gas, in my case the low side of the line at the E. It's also nice if the F is where the needle goes when it's full.
 

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I just bought one of the "calibrated" NPD units. After making sure it was 70 ohms on an empty tank I filled up. I was less than pleased when I filled up with the gauge showing about 1/8th tank and it only took 8 1/2 gallons. Sadly the world that can create an iPhone more powerful than the computer that put a man on the moon cannot re-create a variable resistor.
As I eluded to earlier, it's almost certainly a cost item. Harder to make a tapered rheostat than a straight one. And most buyers don't care how accurate the 1/2 tick is.
 

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No. The only reason to bend the arm is if it is already bent from mishandling. The float should physically go from the bottom of the tank to the top. Bending the arm so it does not do one or the other only makes it worse.
I beg to differ. I had a recent post with two sending units. One, a deluxe stainless steel unit from CJPP and one the "calibrated" NPD part. The two parts arrived in undamaged packaging and were unmolested. I posted pictures of them here:

Inaccurate fuel gauge

The CJPP part did not seem to be bent far enough to reach the bottom of the tank. The NPD part was bent too much and the pickup filter would hit the tank before the mounting plate would seat on the tank. To get the NPD part to "work" the pickup tube had to be bent. Then when installed the empty resistance 65 ohms, not the 70 ohms it read when bench tested outside the tank. That told me the arm needed to be bent to get to 70 ohms, installed and empty.

As as far as the benefit of "new" goes, sorry I am not buying it. On the assembly line these cars were slapped together at the rate of about 1,000 per day per plant. No one was calibrating the sending unit to a gauge on the line. My factory sender and gauge combo worked fine for 50 years until the filter became clogged.


I agree that the only real concern is that the gauge show full when full and empty when empty. Neither the CJPP or NPD parts can manage to do that. I only bought the new NPD part due to the claims that it was calibrated as the CJPP was new. It was only marginally better. (I am not talking mid range accuracy here, rather just tell me when my damn tank is empty accuracy) Looks like I am stuck dropping $70 for a Meter Match gizmo since no one can spend the extra $2 to manufacture a sending unit with a factory style rheostat. Seriously, who would not spend $60 for a factory correct sending unit vs what is offered today?
 

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I hate to sound cynical, the the vast majority of buyers shop price, price, and price.

I once thought as you do, but I used to work with an online catalog, and if there was a left-hand framistat for a 65 Mustang from one supplier that was pretty usable, and for $2 less another maker had a piece of crap, we'd sell the more expensive one. But people would buy the crap from another dealer, then call us to find out how to make it fit. We'd ask them why they were calling us, they'd say they called the seller already, and the seller had no idea.

So yes, cutting $2 off the price is an effective marketing strategy for the vast majority of buyers.
 
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