When key is turned to run position but not started the gauge moves a tiny bit but still shows empty, idk If it's a short or grounded to chassis some where or just a bad sending unit if anybody can shed some light on diagnosis or help it's greatly appreciated

 

The Sender is the Ground for the gauge, it will have 16 OHMS when float is down all the way, EMPTY
160 OHMS when float is all the way up, FULL

There is a Yellow/white stripe wire that runs from the dash to the gas tank
And a Black-white stripe wire that runs from the gas tank to a Ground

If there was a short to Ground, 0 OHMS, then gauge would show empty all the time.
Or if float had a hole in it or if the sender has failed, so..................

Best thing would be to get under the truck, find the Yellow wire and use an OHM meter to see if sender is working, you can rock the truck and watch ohms change as gas sloshes in the tank and float moves up and down.

 

Thanks for that I had a pretty good idea about how the system works just was clueless about wiring colors and ohm specs I'm gonna crawl under the truck and test it with an ohms meter and get back with you

 

I carved out a 1" section of that yellow wire and put both leads of an ohm meter on that yellow/white wire and ohms were jumping around from 0.04 to 19.36 was the highest I saw but only for a second couldn't get a solid reading other than a 0.04 the truck was sitting still on level ground didn't have anybody to shake it,

I never got a 0 ohms reading, I will re test with a better multimeter tommarow i also got a p0460 fuel level sensor circuit a code

 

"put both leads of an ohm meter on that yellow/white wire and ohms were jumping around"

One lead on yellow wire the other on a Ground(like the frame), that measures the OHMs thru the sender in the tank

Ohm meter-------------(yellow wire)------------sender--------(black wire)---------Ground--ohm meter(on Ground)

Should see 16 to 160 ohms, steady, but will vary when you slosh the gas in the tank

If your ohm meter has ohm settings pick the lowest one, like 200 ohms or 1k ohms(1,000 ohms)

To test ohm meter touch leads together, should see 0 ohms

 

Okay I'm gonna test it tommarow by doing what you said,

where would we go after we check ohms if they are somewhere between 16-160 ohms would that mean the sender is good?

And then we would be looking at a hole in the float, since the gauge moves a little bit when the key is turned to run position or started does that rule that out as good?

 

When I test the circuit should the key be on? Or battery disconnected? Just wanna make sure that it's being tested right when I tested it yesterday key was in run position idk if that's how your supposed to seat that circuit as Ik your not supposed to test ohms on a powered circuit

 

I've also got a check engine light on as well as the p0460 code have yet to have it code read to see what the check engine light is on for

 

Key off, no need to unhook battery, unless you are pulling out the instrument cluster

The float sets the OHMs of the sender
16 OHMS or less means float is at the bottom of tank or sender is shorted to Ground
160 OHM or higher means float is at the top of the tank or sender is "open" not grounded

In between 16-160 is good usually means sender and Float are OK, but rock truck to make sure OHMs change a bit as gas sloshes around

 

Ive had the cluster out to Change bulbs and never unhooked battery just didn't touch any wires together was cautious about it and nothing has changed there.

I put positive lead of ohm meter on yellow/white wire and was getting 15.9-16.0 ohms so I kicked tank to slosh fuel and ohms jumped up to around 22-28 or more ohms.

so based on what you said in previous post that means sender and float are GOOD do I look at replacing gauge next, can you even replace just the gauge, or just get a whole cluster?

In between 16-160 is good usually means sender and Float are OK, but rock truck to make sure OHMs change a bit as gas sloshes around[/QUOTE]

 

I just filled up tank and ohms are steady around 16-18 occasionally they will jump up past 100 or up to 80ish so idk if float has a hole or if sender is junk I'll have somebody shake truck and see what they do then but a fuel pump is 280$ and I'm hoping it's not that

 

Either way fuel pump has to come out. Can I pull pump out leave it plugged in and just move float to see if gauge moves or ohms go up? They guys at the auto part store said I'd have to get the whole pump assembly instead of just a sender

 

Yes, float has a hole or sender is bad with 16ohms and a full tank.

Pulling the bed back is best way to get access to fuel pump assembly.

The access is just behind the cab so bed only needs to go back enough to work between the two.

If you have a second vehicle you could pull out the current assembly and find out the problem first, then decide what to buy at parts store, OR wrecking yard

 

I'll let you know what happens with it when I get around to fixing it