I have the bed off for repainting and while I was there I thought I'd fix the fuel gauge that never worked since I've owned it. I ordered a new Fuel Sending unit and put it in but the gauge was still buried.

So tonight I spent a little time looking at the Haynes manual to see if I could figure it out, but only got so far. I checked the sending unit itself, it measures roughly 70 ohms when fully down (Empty) and 10 ohms when fully up (Full). Even if that range was off slightly it should give me some reading as with the gas in the tank now its reading about 50 ohms.

I checked between the Yellow lead and chassis and got a good ground. Measure the blue lead though I get a waivering voltage between 5.6 and 6.5V and it jumps around. I thought it may be the connector so I tried to clean it out with no results. Where should I go from here? I assume I should see 12V there and its ground through the resitance which translates to some gauge level, but looking at the Haynes wiring its hard to chase. It looks like that blue wire travels to the engine bay, through firewall connector and directly into the gauge package. Is it possible I have a bad connection at the firewall or in the cluster itself preventing good voltage?

Thanks,
Ryan

 

did you try the hooking the sending unit up before putting it in the tank? voltage is a bit high but almost sounds like the gauge might be the issue. you could try this first tho if you want. pretty simple
https://www.allpar.com/history/mopar/electrical2.html

 

Because I have the bed off I took it right out and ran the float through its range and the gauge didn't so much as twitch off its fully bottomed below empty state. I have to assume the issue is in the dash, so at least I am fairly confident I can put the bed back on and fix it elsewhere. That link was great, thanks. I would lean towards the gauge itself reading that, even though my voltage is off slightly, even off a bit it should have moved the gauge somewhat. Now to find gauge parts ack.

 

you could try contacting this company if you want but might be cheaper to find someone parting out a truck and get the whole instrument cluster and swap out what you want. any 81-87 truck should have the right gauges.
https://mrheaterbox.com/

 

Generally, when you have a bad ground, it will read empty regardless of fuel level. If it reads full all the time, you have a short somewhere between the gauge and the fuel sensor. I'd check the wire for a pinch or worn spot.

 

this is a test

 

Are you positive??????

 

Would the best way to test that be to find the blue wire closer to the gauge cluster and physically ground it there, or just put a ground right at the tank.

 

Thanks for that. Turns out he is about 10 mins from my house, so at least he could look over the gauge package if he's still open during all of this.

 

you live in Ontario? your location says Vancouver. if you live close enough to just go and get them to check it out that definitely may be the best option. if you had to pay shipping both ways plus repairs it would have got expensive quick.