How to test fuel sender

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gdizzle

gdizzle

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66 ddart \6 225. Ok fuel gauge has been tested when I removed the dash. It appears to function. I have replaced the old Voltage Limiter with a new one. I have replaced the old PCB board with a new one.
Fuel gauge does nothing when car is turned on/started. doesnt flinch.

The fuel tank has a huge dent in it like someone hit a huge rock.

How can I trace that voltage is getting all the way to the tank?
If that is good, then how can I test the Fuel Sending unit which is inside the tank?

I am thinking the huge dent could have broken the sender unit? Or also there may not even be a sender inside. The previous owner said he replaced the tank, and the gauge did not work.

Any ideas? I see new tank CR11A for $170 from Amazon,. New sender unit FG69A for $53 from Rockauto.

If I disconnect the sender wire at the tank (I think I can get at it) how do I ground it out? without exploding
 
The only way I know how to test the sender is out of the tank and ohm test. With the wire going back to the tank ground it with a test light. If you get a on off repeating signal then your wire is good. But your sending unit is not. Ground the sending unit and it should work.
 
You can pull the wire off this sender and check everything just like the temp sender. Remember how the first sender test was ohms, one probe where wire attaches, other on body of sender. Assuming you have half tank of fuel resistance should be 23 ohms. Anything between 78 and 10 is good ( although you may not see any needle movement beyond 73 ohms. Then wire the lead kept at sender wire terminal, move the other lead onto fuel line, chassis ( knowing you don't have leads long enough to reach back to the battery neg like at the temp sender ). We're confirming the chassis ground path of the sender through the ground jumper and to the chassis, ohms reading staying consistent.
 
Well got the tank out and sender. pretty rusty. I have to assume it is so rusty that it dont work. I tried to test Ohms on the sender but not sure how to touch body of sender because it has rubber around it. unless I can just touch it anywhere else other than the stem?
Also the new sender has a wire that is wrapped around? there was no wire wrapped on the old sender.

Also I assume the older sender is trash, right?
 

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It's already been mentioned above, but I'll put it a different more direct way if it helps.

Take the wire off your current sender and ground it to the body or frame.
The gauge should read full when you do.
 
Replacement senders are built differently so there is a short wire from external contact to internal resistor. No fault there.
 
gdizzle said:
Well got the tank out and sender. pretty rusty. I have to assume it is so rusty that it dont work. I tried to test Ohms on the sender but not sure how to touch body of sender because it has rubber around it. unless I can just touch it anywhere else other than the stem?
Also the new sender has a wire that is wrapped around? there was no wire wrapped on the old sender.

Also I assume the older sender is trash, right?
Click to expand...




thats a factory sender,i would repair it.
 
ok reinstalled new sender into brand new tank. Filled tank. Turn key on and the gas gauge (and temp gauge?) starts to creep up to 1/4 full, 2 seconds pause, then gauge goes back down to beyond empty, like all the way to the left. remains dead while I drive. If i turn off car for a few seconds, then turn key back on, the gauges do the same thing as above.

Any idea what this means? I had tested the Gas gauge off the car using 3 D batteries and I was able to get the gauge to move to 3/4 full.


Recap: New cluster board, new voltage limiter, new Fuel sender unit.

Is it possible that the voltage limiter is wrong or bad or would bad limiter also effect other things?
 
gdizzle said:
ok reinstalled new sender into brand new tank. Filled tank. Turn key on and the gas gauge (and temp gauge?) starts to creep up to 1/4 full, 2 seconds pause, then gauge goes back down to beyond empty, like all the way to the left. remains dead while I drive. If i turn off car for a few seconds, then turn key back on, the gauges do the same thing as above.

Any idea what this means? I had tested the Gas gauge off the car using 3 D batteries and I was able to get the gauge to move to 3/4 full.


Recap: New cluster board, new voltage limiter, new Fuel sender unit.

Is it possible that the voltage limiter is wrong or bad or would bad limiter also effect other things?
Click to expand...



repair factory sender,dont know about temp though
 
Temp gauge should not move. I don't know what limiter you have but, there is a short or crossed circuit somewhere that causes that limiter to shut down.
Could you possibly post some pics of the inst' panel, its wiring, etc...?
 
gdizzle said:
ok reinstalled new sender into brand new tank. Filled tank. Turn key on and the gas gauge (and temp gauge?) starts to creep up to 1/4 full, 2 seconds pause, then gauge goes back down to beyond empty, like all the way to the left. remains dead while I drive. If i turn off car for a few seconds, then turn key back on, the gauges do the same thing as above.

Any idea what this means? I had tested the Gas gauge off the car using 3 D batteries and I was able to get the gauge to move to 3/4 full.


Recap: New cluster board, new voltage limiter, new Fuel sender unit.

Is it possible that the voltage limiter is wrong or bad or would bad limiter also effect other things?
Click to expand...

Don't take this as a jab at you or anything, but doing what I said in post #6 would have pointed that out before you replaced all that stuff. :D
 
Ha ha dont worry, I don't take anything as a Jab, only as constructive crit. Wanted to update this thread, I had installed new sender and new tank and a new gauge. It is working. Gauge is about 1/4 tank off, but better than no gauge. I noticed when I installed the sender the buoy and fuel tube are about 1 in from the bottom of the new tank. I guess I could have bent it down a little.

Anyhow, I thought it was good, then I looked under and saw a real nice gas leak puddle. Coming out of the sender seal. Yes I used the new lock ring that came with the tank. So I had to drop the tank again, remove the sender and used a new gasket and the old original lock ring. Tapped it into place (i put a little grease on the gasket this time). Reinstall and seems to be leak free at the moment. I put in about 6 gallons and the gauge says I am just below 1/4 tank.

So people reading or searching this thread, DO NOT TRY TO USE THE NICE NEW SHINEY lock ring that comes with the sender or the tank.. Use the old crusty one instead.:banghead:
 
Very similar situation. Compared resistance on both old and new sending units. Full was about 9.5 ohms and empty was 76. Not too far off what was posted above. New one was purchased because old one was suspected as reason for gauge not working. Hmmmmm

Installed the new one and it does the same as the old one - with key on, the needle barely reaches the empty mark. Using the gauge checking methods posted earlier, found that grounding the gauge wire pegs the needle to full as described. Placed test light in line to terminal on sending unit. When key is turned on, tester lights up for about 3 seconds and goes out, and needle does not move on gauge.

What am I looking at here, a problem with the gauge, or maybe the voltage limiter? Although, the temp gauge appears to be functioning properly.
 
'74 Sport said:
Very similar situation. Compared resistance on both old and new sending units. Full was about 9.5 ohms and empty was 76. Not too far off what was posted above. New one was purchased because old one was suspected as reason for gauge not working. Hmmmmm

Installed the new one and it does the same as the old one - with key on, the needle barely reaches the empty mark. Using the gauge checking methods posted earlier, found that grounding the gauge wire pegs the needle to full as described. Placed test light in line to terminal on sending unit. When key is turned on, tester lights up for about 3 seconds and goes out, and needle does not move on gauge.

What am I looking at here, a problem with the gauge, or maybe the voltage limiter? Although, the temp gauge appears to be functioning properly.
Click to expand...

You should have started your own thread. Sounds like no fuel in the tank
 
I usually get decent results by joining ongoing conversations along the same vein as my issues, rather than reinventing the wheel. We drained the tank and removed it because the sending unit would not clear the 8-3/4" rear end. The sender was replaced, fuel tank reinstalled, and at least 8 gallons of gas were put back in. The ground strap was tight and a secondary ground was added just for good measure. With continuity of the gauge wire confirmed, and the resistance range of the sender within reasonable tolerance, what else could be the problem other than the gauge or voltage limiter?
 
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