Interesting fuel problem - 67 Coronet

[TekHousE]

HI again..

Seems like I am going through a series of small challenges on this 67 Corrie.

OK..Latest thing.

Has anyone heard of a problem where the tank cannot take the full capacity of fuel? I am assuming (probably my first mistake) that what I am looking at under my 67 is the factory fuel tank. So if that IS the case it should be 19 gallons. Well we are metric over here, so that means 71 liters!

But.when the gauge shows nearly empty (gauge could be wrong too??), and I fill it, I get maximum 26 or 27 liters in it! Now I suspect the gauge is wrong, as there is no way this tank I am looking at can be only 27 liters capacity. It is huge!

Has this happened to anyone else? DO you all think that the Gauge is faulty? And if so, HOW can I check that? Because, if it's not, and I keep driving, I will ruin out of fuel. I have never seen this on all the mopars I have ever had. SO it's new to me at least.

Help and thoughts would be much appreciated.

 

[eagleone1983]

The fuel sending unit has a check in the factory service manual (FSM) that you can do. You'll have to remove the sending unit though, then you can check the resistance by moving the float arm and see how that matches to what the FSM says it should be.

 

[70redbee]

Carry a small container of gas with you and drive it till it runs out. Put just enough in it to get you to a station, fill it up and see how much it takes. Or you can empty the tank, then fill it to see how much it takes. Good luck in your search.

 

[TekHousE]

OK both good ideas. I have the service manual. I will check that.

To empty the tank I would have to pump the fuel out right? There is no other way of emptying it..other than driving it??

 

[pinkpanthr]

Is this a rebuild or restoration project. Is the tank original. If it sat for a while before being rebuilt as mine did. It could have mouse wadding in the tank. That is only if it sat empty and with the cap off though. Even mice won't go into a tank with old gas in it! Just an outside the box thought.

 

[67 coronet]

ohms reading on the sender should be from about 10 to 75 for a full flow reading.move the arm slowly and watch for dead spots while you do it.bad contacts in your wiring to the tank can cause the problem you stated as well.

 

[terzmo]

carry a couple gallons/litres in a can and see when it runs out then how much it takes....

 

[TekHousE]

This is NOT a restoration or rebuild the car is running and I am trying to sort out these few things to get it perfect.

The tank has not been replaced, nor has it been sitting open anywhere.

I think I have no choice but to try and run it out.

 

[kb67mopar]

its pretty easy to remove the sending unit. I would advise just replacing it as the floats get pin holes and fill with gas, they corrode and go bad. also the contacts on the float in the tank wear down and read improperly over time. These fuel systems are really simple so there is very little to actually prevent gas from filling the tank. I suspect your issue is the sending unit and not the tank.

If you want to drain the tank you can siphon the gas out through the filler, there is no anti-siphon in these.

That reminds me, I should get a locking cap.

 

[eagleone1983]

Tek, also depending on how full your tank is you can remove the sender even if there is some gas in the tank. Do not use anything but a brass punch to get that ring off. I don't want your next post to be one from the hospital on how you blew yourself up.

If you do get a new sender keep your old ring the new ones are shiz and don't seal well. You'll also have to make sure that ring and rubber gasket are dead center on the tank or you're going to have a leak when you reinstall the sender.

 

[TekHousE]

Great advice guys!

So my plan now is this..Since the tank is now full..

Drive it until it stops. Put a MEASURED amount of fuel in it, i.e. 4 liters. (a gallon?)

Remove the sender unit, as 4 liters will not be a factor. Trying carefully NOT to blow myself up, wise words eagleone1983! ;)

Replace the sender..

I too suspect that there could in now way be anything large enough blocking my tank for being filled up to its normal capacity, so I too believe that the sender is to blame. So the way I have it figured I have about 70 odd liters at the moment to get through..So I will hit the road and get through that as soon as I can.

 

[eagleone1983]

Luckily it doesn't take long for our cars to burn through gas. Oh and it's 3.78 Liters to a Gallon

 

[TekHousE]

Thanks!

Pedal to the metal..71 liters might last me half an hour! 383 FTW!

 

[Speedbird]

There are three things in this circuit that have to “match up” to be accurate.
The fuel sending unit (a rheostat), the gage and the voltage supply (limiter)
Some cars, have the limiter built into the gage. I know a 67 Charger does.
There is a new electronic item that I haven't tried yet. But I know it exist.
http://rt-eng.com/rte/index.php/RTE_limiter
The gages get old and change from new, the old mechanical voltage limiter supply is a little off.
Well, you get the idea.
I drive a car with a “new” sending unit. That the fuel gage drops FAST from full to ¼ tank. Then it takes a long time to go to empty.
When it gets to 1/4, I know that I still have half a tank.
There are services to “calibrate” your sending unit to your gage.
But why bother?
I think driving it till empty is a good start to see what it is really doing.

 

[barracudadan]

If you take out the sending unit solder a thin copper wire from the swing arm to the body of the sending unit. This really helped the accuracy on mine. Defiantly use the old locking ring as well the new ones are too thin.

Good info here that explains what i`m talking about if you don`t know what I mean. http://www.cuda-challenger.com/cc/index.php?topic=67680.15

 

[ws27]

A couple of things to consider as well. I really like barracudadans' idea of soldering the thin wire on. You can remove the sender without taking the tank down. Someone already may have said this, just make sure you have the level below the hole. Also as someone else mentioned, use a brass punch and NEVER use a 110v light. Should you drop it and is smashes and sparks, we will be reading something else other than a successful repair.

As far as running the tank down, you really don't have to run the poor car out of gas. Fill the tank note the mileage, run it to the point you normally do, note the mileage and you will get an approximation of the MPG (or L), then run the car to 16 or 17 gallons used, and you won't be pulled over to the side of the road.

Then go after the sending unit. Note too, a new sending unit will most likely not be accurate either. So if you do replace it, calibrate it before you install it.

Good luck.