Fuel gauge reading and sender

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MoparBrit

HillingdonDart
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Okay, considering putting in an aftermarket fuel level gauge. Stock one works when it wants too. Temp and everything else works okay all the time, but fuel sometimes works and sometimes does not.

I am going to ground the lead and see if it isn't just a factory sender problem, but the thought came to me that I might add a three gauge panel and put a fuel level gauge in it.

So, my question. I tried to look up on the net what the ohm reading should be for the sender. Found a place that listed Chrysler at 0 - 2 ohm empty and 70 to 73 ohm full.

Well, go to look at gauges and I find some Ford/Mopar ones that are saying that Mopar should be about 73 ohm empty and 10 -13 ohm full. Different reading and opposite.

Can someone confirm what is supposed to be correct for a '71 Dart?

Also, has anyone run one of these 73 ohm empty and 10 ohm or so full gauges on their car? How accurate is it?

Thanks for any help.

Cheers
 
According to Stewart Warner a Ford/Chrysler sender is zero ohms empty and 73 ohms full so I would think that their gauges would match this and not the opposite.

Chuck
 
Yes. The more resistance the less current goes through the gage. The less it heats up and the less fuel it shows. (Think I got that right)
That is why your gages pegs full is the regulator fails closed.
There are variable other than differences between sending units.
You voltage limiter is one.
Your gage is another. That is why places offer "calibration".
See the link below. I didn't know abou the electronic conversion till today.
http://www.forabodiesonly.com/mopar/showthread.php?t=22457
 
I'll have to look at SW. Been looking at Autometer. They have an ATM4315 listed for Mopar, but the spec given is that 73 ohm empty and 8 to 12 ohm full??? Makes for confusion for sure. Their 2315 is listed that way too! Says early Ford and most Chrysler. Maybe they are not for quite so early Mopar perhaps.

Just looked at the SW page in the tech section and sure enough they say the opposite from Autometer.
 
Now on the link of a link off of adrivers post and it is saying the sender should read 61 to 85 ohms empty and 8.6 to 10.6 full.

The fun goes on. I guess '71 still had that 5 volt regulator deal. I'd like to do the conversion, but tough for me to get the dash out as I can't (physical thing) currently lay twisted under the dash to try and get everything disconnected to get the gauges out. As the temp gauge works all the time that is part of the reason I thought about testing by grounding the sender and see what the gauge does. If it is a bad sender then I'll get a new one put in. If not then thought it might be easier at the moment to get an aftermarket gauge for the tank and go from there for a while. A pain to be driving along with the fuel gauge showing empty all the time and then about the 5th time you start the car the gauge reads finally.

Anyone put an aftermarket gauge in and if so how accurate is it?

Thanks for the posts everyone.

Cheers
 
If you are going to use an aftermarket gauge it doesn't matter what voltage limiter is used on the stock gauge because you are going to go direct to the sender with the aftermarket gauge.

Also are you sure it is the gauge that is bad and not the sender. It's been my experiance that the senders go bad before the gauges do. I have found that the cycling of the fuel level going up and down wears the resistor and contact portion of the sender and sometimes doesn't make good contact.


Chuck
 
That was my thought. As the limited deal would be nice if it was possible for me to get the gauge panel out, as I'm not right now an aftermarket wired direct I thought might fit the bill.

Thanks for the post!
 
I think the Stewart Warner site is a mis-print. I believe the 73 ohm empty and 0-13 full is correct because when we ground out the sender wire it goes to full (grounding has basically no ohm reading) and as the ohms go up the gauge goes down towards empty.


Chuck
 
Yep. Open is infinity resistance. So gage shows empty.
Less resistance means the gage metal heats up and it goes full.
I too can only assume 71 used this set up.
I think they even used it on 86s because when the parts counter had to find one for me they used a book with pictures and that is what it said.

The wiper in the sending unit is what fails.
It is a little stainless arm with a brass grommet that runs back and forth on a wound wire(rheostat).
The brass grommet wears off and so does the arm from running back and forth as fuel sloshes.
If you have to work under a dash for any amount of time, try taking the front seat out. Makes laying down a lot easier.
 
i had a problem with my fuel guage as well now if i remember correctly the fuel guage works off the temp guage (i think). now the magazine mopar action had a fix for it that was in the guage cluster it seemed to work for my 65 though the fix was for the 70's cluster. i'll see if i can dig up the copy of the mag i think that i still have it around here and at least post the year/month of the copy. though it could also be the sender but i will see what i can find out.
 
Agree that it's usually (in my case always) the sending unit or the ground that causes the problem. Seems every A I've owned has experienced this one. Luckily, years back, a 67 cuda I was driving had the issue, because the kids that stole it from in front of my house didn't know there was an almost full tank of gas. Living in a small town at the time, they only drove it far enough that they could walk home I presume. They logged 50+ miles on her, but left it two blocks from my house. Sometimes procrastination is not a bad thing!

Grant
 
Hi, Thanks for all the replies. I'm going to see about getting under the car and testing the sender wire by grounding it this weekend. I hope that the gauge works to full (340Mopar, if I'd been thinking.....a rare thing for me....I'd have realized just what you said about the SW site. Makes perfect sense now) as the sender would be an easier change for me.

I've already tried the ground on the sender and that did not make a difference. Operation of the gauge seems to just want to work by a fluke off and on. Temp etc. all work fine so hope it is just a sticking or worn sender.

Car is a /6 so will probably replace with the 5/16ths line stock sender. Think I got that size right. I found some listed on Ebay by vansautosalvage for a decent looking price. Anyone bought one of these? Are they okay or junk?

Thanks for the help all!

Cheers
 
I purchased the 5/16 sender from vansauto (ebay username) for 51 dollars about a year ago, and yes it appears to be a quality reproduction. It's not stainless.Those are twice the price. OEM wasn't stainless either.
No it didn't fix my problem but may fix yours. The altered fuel gauge and solid state regulator from www.demonivr.com did fix mine. My oil and temp gauge were working before. They all work much better now.
 
Glad the board is back up to reply. Thanks for your response on the sender. I'm still looking at them. Put quite a bit a fuel in the tank, not full, but quite a bit and the gauge worked somewhat (went to about 3/4) so I'm thinking that it is probably the sender. Looks like I'll probably give the sender a go. Just had a look on Ebay and the seller is still selling them. Now $60 plus ship, but that is less than the others out there and much more affordable for me. Just did not want the thing to be so naff that it would fall apart or something or not work any better than what is in the car now.
Cheers
 
Sender R&R is easier than panel R&R on these cars since you dont need to drop the tank. That explains sales volume of senders too. If sneder dont fix it , a gauge will. Good luck
 
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