View Full Version : Filling the Tank
12-20-2014, 12:52 AM
Is it common for fuel to come spray back out of the fill tube opening when filling up with fuel? I think best described as a burp of extra air escaping from the tank as fuel is taking up the space in the tank and the air inside the tank is trying to get out
Also, the gauge never shows a full tank. The sending unit is a replacement from the original sending unit.
12-20-2014, 02:48 AM
Fuel tanks with low filler necks tend to splash back IF you pump too fast. Normally it is not a problem because the filler neck IS above the tank. Of course, if you're parked on an incline where the front is pointing up, that exacerbates the condition.
Your fuel gauge should work properly under these conditions:
* The tank must be properly grounded. If you depend on 60 yr-old rusty spot welds to return six volts, you're shakin' dice. I recommend you drill a hole in the corner of your tank in an area safely away from the seam weld. Then use a #8-32 brass or stainless screw and nut to fasten a jumper wire. Connect the other end of your jumper to a frame channel with a sheet metal screw.
* After determining your ground is solid, see if the gauge goes to 'full' when you turn the key on and you ground the sending unit wire. If it does, pull the sending unit out and make sure the float isn't full of gas. If it's clear, bend the arm so it has full range of motion. Some aftermarket arms are too long.
* If your gauge does not go to 'full' when the sending unit is jumpered to solid ground, you need a Constant Voltage Regulator. I retrofit original CVRs with solid state components that output rock-steady six volts.
Run those tests and let us know what you found. - Dave
12-23-2014, 12:03 AM
Great information Sir. I will run these test and see what happens.
03-08-2015, 09:39 PM
So finally today it was warm enough to work with the fuel gauge issue i've been having. I set me up a ground wire from the edge of tank to frame work that the bumper attaches to. That did not seem to change anything to the gauge reading.
03-09-2015, 05:25 AM
Ha! It depends on how much gas you have.
With a full tank, the gauge passes the most current and the needle goes all the way up.
With a half tank, the gauge should read 'half'.
With NO gas, the gauge is electrically open and it passes zero current.
It's all about current. Assuming your grounds are good now and your power supply is actually outputting six volts (average), your gauge stands a good chance of telling the truth.
OEM CVRs are mechanical and they go bad in a few different ways:
They get erratic instead of transitioning on-off in equal intervals. (We call this 50% duty cycle.) Sometimes the same CVR will go faster then go slower, then whatever... They go all over the map.
A CVR can open, short or lose part of it's ground.
What is your concern with your gauges? What is it doing or not doing? - Dave
03-09-2015, 07:51 PM
I guess my concern is that the gauge is not telling me how much fuel I really have in the tank. With a full and I mean to the brim when I take the sending unit out it is not reading full. I have also seen the gauge bounce for no real reason moving back and forth. The current unit is a replacement from original (Taiwan) so maybe it is not a good replacement.
03-09-2015, 08:02 PM
I just realized you said "you ground the sending unit wire". I am not sure what you mean here. I did ground the nut that is just under the connector terminal and the gauge read past full. But without that connection the gauge did not read a true full tank level.
03-09-2015, 08:13 PM
If you remove the wire from the sender and ground the wire to the body the gauge should go to full. If it doesn't then your wire, gauge or CVR is defective. If it goes all the way to full then either the sender is bad, the float is bad or it's not grounding.
03-10-2015, 05:58 AM
...* After determining your ground is solid, see if the gauge goes to 'full' when you turn the key on and you ground the sending unit wire. If it does, pull the sending unit out and make sure the float isn't full of gas. If it's clear, bend the arm so it has full range of motion. Some aftermarket arms are too long...
Did you do this? Many of our members found the float either missing (detached) or full of liquid. Either way, the float sinks like a bomb and your gauge reports an empty tank.
After thinking about your situation I felt you need more info. Please read this a few times. Your gauge needle deflects from heating a bi-metal strip, much the same as old thermostats in your house. Because this heating process takes a little time, your needle is slow to react (on purpose). If you have seen the needle waving back and forth that is a real problem. Either your CVR is becoming erratic, as they often do, or the float sending unit is faulty.
If you have a replacement sending unit, check the range of motion and bend the arm so the float nearly hits the bottom when empty. Some have an arm that is too long, giving false readings. I would use a troubleshooting jumper wire with alligator clips on both sides. Connect one end to ground and the other end to the sending unit flange while you have the nut wire connected and the unit out of the tank. Turn the key on and slowly raise the float while you watch the gauge. If you need a helper, ok. Again, when the sending unit is connected with the wire AND your jumper ground, the gauge doesn't know whether it's in the tank or not.
You may find 'dead spots' in the range of motion which will send the needle back down to empty. If so, a new sending unit is in your future. eBay has them for $40.
If you find the sending unit is ok, look me up and I'll give you a deal on a new solid state CVR unit with a Squarebirds.org membership for a year. - Dave
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