Fuel Gauge

EBS

Well-known member
My fuel gauge is operating at half function. Full is full, and half full is empty. I was hoping it was something simple like a bad ground, but reading here and at d source seems to indicate it's more likely to be an issue with the sender. The tank was dropped a few weeks back to replace the rear cross member, and I think the issue started then. This is a '94 NAS. Has anyone seen this particular issue before and any tips on getting it straightened out? Thanks all.
 

JimC

Super Moderator
Staff member
I’ve got the problem right now with a new sender, new wiring, and a new gauge. I’ve even removed the sender and verified that it works when I manually move the float arm to the various locations on the resistor. Im to the point that I think I’ve got some physical interference in my tank.
 

Napalm00

Technical Excellence Contributor
the senders are soooo fragile. i went through 2 before i got one out of the box that worked. old you could remove it and check the little trace wiring on the sweep arm, make sure its contacting. at that point id just out in a new one...that also may not work lol
 

EBS

Well-known member
Thanks guys. Dropping the tank is not something I want to get involved with right now (or possibly ever), so I think this will be something I learn to live with until I can have someone who knows what they're doing take a look.
 

evilfij

Well-known member
I just use the trip odometer to known when I need to get gas. I don’t run her down to close to out of fuel anyway.
 

MountainD

Technical Excellence Contributor
I hate fuel systems. I probably went through 5 or 6 pumps in my NAS before I switched to the LS. I went through 3 gauges but I fixed the third and it has been perfect since. For mine, the flexible wire corroded and basically disintegrated. I used a piece of copper braided solder remover tape (if you know what that is) and it has worked perfectly since.
 

uc4me

Well-known member
I don't have your full/half full inconsistent reading issue but I do have the wavering fuel needle which may be related. Mine started when I had the binacle out to replace a rebuilt speedo from NHS and thought I may have unintentionally dislodged a wire somewhere.

But I just had my 97nas tank down to replace the faulty c113 connector at the pump (Big thanks to @WreckITFrank for making up a pigtail connector with the correct color wire!) and was hoping this might also fix my sender issue at that connector. I removed the pump, checked the internal wiring, trace arm and made sure the float was measuring relative to the gauge level reading.. which it was.

Re-installed the tank and I was rewarded with a working fuel pump but still have the sloppy fuel reading. Can't have it all with these rigs.
 

hillstrubl

Founding Member
So I noticed today that my fuel gauge isn't working (correctly). I filled up yesterday (and it show the level correctly as full) but this morning when I start it up the needle only moves the slightest bit. I guess that's the sender then?

Ignition off
1626190546472.png


Ignition on
1626190581813.png


I checked the level manually by peering down the filler next, yep, still full.
 

Napalm00

Technical Excellence Contributor
Depending on the year of the truck you can just pull the wires off the sender and ground them with the truck key in the on position.

Grounding one will turn on the idiot light grounding the other will cause the fuel gauge to peg all the way to full.

If this works on your truck then you know that the circuits and gauge/lamp are both good , sender bad. Also some early tanks require a ground wire to be added to the sender on the threaded post in the center. If you're missing this you can use a temporary jumper to see if it makes things work correctly.
 

hillstrubl

Founding Member
So today it woke up (pointing more to a ground issue) however hills tend to make the gauge change indicated level (its at ~60% in the tank now) from 25% (going up the hill) back to the correct ~60% indicated. I haven't had a chance to test the grounds yet but figured I'd report back that new development.
 
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