Dead fuel gauge

[Atcmcc]

Hi, I have a 2001 dodge 3500

Cummins diesel.I have a dead fuel gauge issue that doesn't seem quite like the others that I have researched,so I could use some help. It reads empty at all times, UNLESS I unplug the batteries for 15-20 minutes and let the truck reset. At this time the fuel gauge will read full for about 15 mins, before it slowly drops to empty again and stays there permenantly. Here is what I have done. I have dropped the tank and I have replaced the entire canister/float/fuel level sending unit. I used an volt meter on the new sending unit and as I moved the float up and down I watched the resistance change. I have done the gauge test and watched the gauge move through its full range of motion. I have also looked at the wiring harness underneath the front driver wheel well where the wires are exposed before they enter the harness, and the wires above the fuel tank to look for any breaks in the connection. I have a fass fuel pump and fuel pressure gauge and everthing reads normal as far as that is concerned.  Any ideas? Thanks for your time. 

[notlimah]

Sounds to me like wiring might be fried. Maybe a bad sender at the fuel module?

[Mopar1973Man]

The only thing I can think off would be do a AC noise test on the alternator verify there is no excessive AC noise beating up the PCM. Beyond that I would say replace the sender in the tank which is about $80 bucks or so. It could be you have a weak spot in the rheostat still. Like on my 1996 Dodge Ram 1500 the range around 3/4 to 7/8 of a tank the gauge needle drops to Empty and trips the light. As you consume fuel and get below 3/4 of a tank it pops right back up. Like on my 2002 when the sender failed it was running out of fuel at 1/2 tank to 3/8 of a tank. So fuel sender weirdness does occur with age so I wouls start there first.

[JAG1]

He did say that he replaced the senderalready you guys

 

 

Could be the gauge on the dash.

 

 What does the overhead say? Does it reflect MPG and miles left before it needs refueling like my overhead display does?

[notlimah]

3 minutes ago, JAG1 said:

He did say that he replaced the senderalready you guys

 

 

Could be the gauge on the dash.

 

 What does the overhead say? Does it reflect MPG and miles left before it needs refueling like my overhead display does?

 

Whhhooooppppssseeeee!

 

Was there any resistance on the float? Did you reinstall it away from the sides so it could actually move?

 

Sorry if you've done these but not sure what else it could be.

[Mopar1973Man]

3 hours ago, Atcmcc said:

I have replaced the entire canister/float/fuel level sending unit. I used an volt meter on the new sending unit and as I moved the float up and down I watched the resistance change.

 

 

 

Opps I missed that... 

 

So did you center the sender in the tank? So the float isn't hung up on the walls? Loosen the ring and turn the sender slowly left to right listening for the arm to strike the tank. Split it half and tighten again. 

 

[Atcmcc]

I will do the test and get back to you, but I tried plugging in another brand new fuel level sending unit that I had when the tank was out and that one didn't do anything either

[Mopar1973Man]

Just now, Atcmcc said:

I will do the test and get back to you, but I tried plugging in another brand new fuel level sending unit that I had when the tank was out and that one didn't do anything either

 

 

Check the resistance at the PCM plugs to verify the signal is making it to the PCM. Also you might check the plug there at the driver side fender it might be corroded from mud and water making weak connection. 

[Atcmcc]

Yes The overhead display reads correctly, it's what's been keeping me from running out of gas this long!?. And yeah the float isn't stuck on the side of the tank,  I hooked up everything outside of the tank first and it never worked correctly even then. I just had to put it all back together becUse I needed he truck back that weekend and I have no concern of any of the parts inside the tank being the culprit since every single piece is brands new. Haha it's ok moparman, we all miss things Once in awhile??

Oh and yes the new float had  resistance on the voltmeter and it changed as I moved the float. Every now and then the overhead display reads "ccd" for a minute or so and then fixes it's self, but this is something it has done for years.

[Mopar1973Man]

Hmmm... If the overhead is working that means the PCM is working and sending out data of the fuel level. 

 

 

But the cluster check works fine. But only displays for a short time nad the fall to empty again. I'm stumped if there is a module that is partly failed. This really got my head scratching going. Have you checked the interior cab ground in the driver side kick panel?

 

I'll keep thinking on it. 

[Atcmcc]

Correct, however the the gauge only reads full after unplugging the batteries, the gauge check takes it through the parameters but it immediately reverts to empty when that test is finished.

Kick panel ground looks good 

[Atcmcc]

New development, if I unplug the pcm harness closest to the passenger fender I get a full reading for the typical 10 minutes and then straight back to empty. Same thing happens if I reflash the ECM with a smarty ( the truck doesn't have any smarty programming I just used my brothers to try the reflash 

Edited July 24, 2016 by Atcmcc

[JAG1]

Since the overhead is unaffected and shows correct wouldn't the problem exist with the gauge or it's wiring then?

[Atcmcc]

But the gauge test works, it reads quarter,half,three quarter, full.

[Mopar1973Man]

Well here is how it works. The PCM looks to the fuel sender for resistance value for remaining fuel. Then the PCM converts this information into digital message on the CCD bus. Now it up to the Cluster or the Central Timer to receive these messages and convert the data into the information required. So the fuel gauge is stepper motor and told where to place the needle in respect to the digital information. Then the Central Timer tells the overhead computer how much fuel is left and calculates DTE (Distance To Empty) by using existing MPG data. So The weird part is the CCD data is correct because other than that the overhead would be providing false data to you. So that leaves me pointing my finger at the cluster. At least what I can think my way through.   

[JAG1]

Atc, you are very good about getting right after this and the way you describe what you've done is very clear. There must be , and I'm guessing here, some connection near the gauge being sent by the test phase that shows it's good but then when on actual gauge use there may be a different conductor that has  a bad connection possibly.

 

If I had this problem I would wonder about bypassing/ trying to bypass the gauge only and wire up my own gauge so the overhead still works.

[Me78569]

I am gonna guess cluster also.  The gauge test proves what you already know, that the gauge works for the first 10 minutes.  I would pull apart the cluster and reflow the joints around the fuel level gauge. 

[Atcmcc]

Ok guys, thanks so much for the help, I will get after taking a look at the wiring for the gauge cluster or try to rig up my own gauge as a test sometime during this week. Thanks for the compliment jag! Btw do you guys think that the overhead display flashing "ccd" at me every once in awhile could have anything to do with it? It seems to be doing it more frequently lately, but like I said before it has done it since I've owned the truck and the fuel gauge problem is a recent issue. 

[JAG1]

It's my guess that it could be. I'd like to know what the 'ccd' means. Is it in the owners manual?

[Mopar1973Man]

9 minutes ago, JAG1 said:

I'd like to know what the 'ccd' means.

 

Chrysler Crash Detection

 

This isn't like vehicle crash but data crash. It's built on the same design as ethernet cable networks.