Still fighting fuel gauge issues...

[OneEyed]

So as much as I love beating on this dead horse...

67 Newport base, 383, auto.

The car came with a new sending unit installed but the gauge never read full. I had another, supposedly better sending unit installed just over a year ago and it worked great for about 2 tanks of gas and now it has the same issue.

It reads almost half when really it's full.

I can ground the wire from the sending unit and the gauge will go all the way up.
I sink tested the "old" unit and it works fine. I hung that under the car and hooked it up, moved the float but same result, only about 1/2 on gauge when it should be full.

I've got the gauge in my hand and I can put 4.5v across it and it goes full.

I'm trying to test the voltage limiter that is tacked on behind the gauge but not sure how. I assume 12v goes in and 5 out?

If I put my 4.5v in I get 4.5 out. 12v in and nonsense readings out.

How do I test the condenser?

Really getting tired of the same old horse....I've got $300 into now...and many of my own hours now too..

 

[OneEyed]

 

[OneEyed]

I tested the wire from the tank to the gauge and that is good. The shop put in a $180 unit w/plastic float. The "old" one looks like the cheap ebay special. Does the gauge want to see resistance? Since I'm grounding it basically like a dead short w/ no resistance..

 

[Big_John]

I've got the gauge in my hand and I can put 4.5v across it and it goes full.

You may have ruined the gauge by doing that. It's meant to measure the resistance of the sender, not voltage.

I'm trying to test the voltage limiter that is tacked on behind the gauge but not sure how. I assume 12v goes in and 5 out?

If I put my 4.5v in I get 4.5 out. 12v in and nonsense readings out.

The voltage limiter won't show a constant 5 volts on your voltmeter when you put in 12 volts. To simply explain it, it has a coil and contacts that turn off and on and keep the average voltage to the gauge at 5 volts.

Really, the problem isn't in the gauge... It's the sender and it's typical of all the replacements out there.

I'm working on putting one of these in my car right now as I have the same issue.

TechnoVersions - MeterMatch for Analog Gauge Correction

You could use their Mopar version with the built in voltage regulator.

I'm going to write up what I did for a thread here... Just gotta work out a couple more things and take a couple more pics.

 

[Big_John]

I tested the wire from the tank to the gauge and that is good. The shop put in a $180 unit w/plastic float. The "old" one looks like the cheap ebay special. Does the gauge want to see resistance? Since I'm grounding it basically like a dead short w/ no resistance..

The gauge measures resistance to ground.

Short the sender wire to ground and your gauge should go to full. If it doesn't the gauge is faulty.

 

[OneEyed]

The sender I sink tested is in spec for resistance according to the FSM though...

 

[OneEyed]

The sender I sink tested is in spec for resistance according to the FSM though...

But maybe I have messed up the gauge..

 

[Davea Lux]

I tested the wire from the tank to the gauge and that is good. The shop put in a $180 unit w/plastic float. The "old" one looks like the cheap ebay special. Does the gauge want to see resistance? Since I'm grounding it basically like a dead short w/ no resistance..

Did you try checking to see if the tank has a proper ground? The exterior of the tank can corrode over time and lead to a poor ground. Take a set of alligator clips and ground the tank to to a frame rail and see if that helps.

Dave

 

[OneEyed]

Did you try checking to see if the tank has a proper ground? The exterior of the tank can corrode over time and lead to a poor ground. Take a set of alligator clips and ground the tank to to a frame rail and see if that helps.

Dave

Yes, did that as well. Ground "strap" is in place too.

 

[Big_John]

The sender I sink tested is in spec for resistance according to the FSM though...

Yes, but testing it in the sink is going to be different than the tank. The sender might not be traveling as far as it needs to when mounted in the tank.

 

[OneEyed]

I feel like the car isn't giving proper voltage or the gauge isn't putting out proper resistance, if that makes sense. I dont have another $180 for a sending unit again that can't guarantee it'll work either. Shop said "90 day warranty, sorry..."

 

[OneEyed]

Yes, but testing it in the sink is going to be different than the tank. The sender might not be traveling as far as it needs to when mounted in the tank.

True. I guess I'll have to pull that unit again as well. Will it come out without dropping the tank? Just put 10 gallons in to see if it would work..

 

[Big_John]

I feel like the car isn't giving proper voltage or the gauge isn't putting out proper resistance, if that makes sense. I dont have another $180 for a sending unit again that can't guarantee it'll work either. Shop said "90 day warranty, sorry..."

The voltage limiters seem to either work or not. They are simple to replace and I would use a new electronic unit if it were me.

The gauge doesn't "put out" resistance. It measures it. You can check it with some resistors to mimic the sender if you want. That's the way the FSM checks it.

Full =10 ohms
Med =23 ohms
Empty=74 ohms

 

[OneEyed]

The voltage limiters seem to either work or not. They are simple to replace and I would use a new electronic unit if it were me.

The gauge doesn't "put out" resistance. It measures it. You can check it with some resistors to mimic the sender if you want. That's the way the FSM checks it.

Full =10 ohms
Med =23 ohms
Empty=74 ohms

So I'd replace the sending unit with said resistors?

 

[OneEyed]

The gauge measures resistance to ground.

Short the sender wire to ground and your gauge should go to full. If it doesn't the gauge is faulty.

Shorting that wire to ground does make the gauge read full.

 

[Big_John]

So I'd replace the sending unit with said resistors?

Yes.

I was just thinking about it... putting voltage across the gauge shouldn't have hurt it.

 

[OneEyed]

Yes.

I was just thinking about it... putting voltage across the gauge shouldn't have hurt it.

The way I look at it is, every wire has voltage of some sort. If i put 12v across it, then yeah, that would be bad, lol.

 

[Big_John]

I'll tell ya though... I think the MeterMatch is the way to go. Read a couple of the links on their website.

It's a simple solution.. It corrects for the errors in the sender and/or the gauge. I put one in my car and adjusted it to where I think it should read. I gotta fill the tank and set it for the full mark.

 

[OneEyed]

I'll tell ya though... I think the MeterMatch is the way to go. Read a couple of the links on their website.

It's a simple solution.. It corrects for the errors in the sender and/or the gauge. I put one in my car and adjusted it to where I think it should read. I gotta fill the tank and set it for the full mark.

I just might have to if I can't figure this out, it's been a pain since I bought the car 4 years ago.

 

[rags]

check for ground on the sender housing itself when installed in tank. run a jumper from the battery just to prove it out absolutely.