Inaccurate Fuel Gauge

[StoopKid]

Hello all!

As per my previous post, I believe my issues were caused by my inaccurate fuel gage. I think I ran my tank empty without realizing it. 10gal in the tank and bleeding the lines and it ran good as new. Couple months later, I’ve flushed and replaced all the fluids, and have redone my front and rear brakes, replaced a couple minor parts and straight piped my exhaust (old muffler fell off LOL). Planning to begin tackling a front end rebuild soon, once Christmas shopping is over.

I was wondering if anyone may have any ideas what may cause the fuel gauge to read incorrectly. The tank was empty when it read just above 1/2 on the gauge. When I fill it up, the gauge reads above F until I am at about half a tank, then it starts reading from F to 1/2. I usually fill up once a week regardless and have gotten pretty good at estimating fuel consumption based on miles driven but I’d like to fix the gauge. Any tips on where to start. From preliminary research it seems it’s either an issue with the fuel sending unit, the float, or the gauge cluster. Wondering if anyone had any tips?

2000 Dodge Ram 2500 24V 5.9L Cummins Turbodiesel

 

[BarryG]

That era of dodge ctd’s were notorious for sending unit failures. If you search on here you should be able to find a lot of threads about it as they used to come up somewhat frequently. There were some diy fixes such as sanding the contacts, using a screw to adjust or along those lines. You used to be able to buy just the sending unit assembly. In fact I just checked genos garage and they have just the sending unit as well as the whole fuel canister assembly if you go that route.

Not that the cluster can’t be the culprit but it was usually the least common issue . Same with the float they did sometimes disintegrate and were the cause. You can check the resistance readings on the sending unit though I don’t recall the range off the top of my head I do remember that they were different than many am thinking 20/220 +or- 5 or 6 ohms but that is vague memory

 

[NIsaacs]

I had to change the sender on my '01. The float wore out on the arm, slid down the arm and just floated up and down the arm.

https://www.genosgarage.com/product/04897669ab/fuel-tank-components

 

[Matt42]

The Gen 2 sending units are notorious for being unreliable and short-lived. (The sender float on my 1996 wasn't as bad as the one on Nick's 2001, though.) I replaced both sending units (OEM tank and Transfer Flow Aft Axle tank) about 5 years ago in a week-long ordeal. The replacement (from Geno's) was dead accurate for about two years. Then it began to show 7/8 full when full. Even that is a vast improvement from it not working at all and relying on a guesstimate of fuel mileage.

When the original OEM tank sender failed, that's where the failure began. It eventually got to the point where the best it reported when full was 1/8 tank. When the low fuel warning light was illuminated at a full tank was when I replaced the sender.

It's an unpleasant job, but do-able. If you perform it yourself, here are some suggestions:

• Lengthen the wires that go to the pump and sender by about 12 inches. I recommend solder and heat shrink tube. This will make it way easier to reinstall the tank, and also to drop it again in the future if you need to.
• If you need to bend the tank straps to get the tank out, it is OK. They bend back into shape if they are not badly rusted. Replacement straps are easily available.
• Buy both a new tank seal and screw-on ring. I only bought the seal. The screw-on ring was OK, but it's iffy.
• Look closely at the fuel lines that are attached to the frame adjacent to the tank. Many miles of tank vibration may have squashed them a little. Or a lot. The hard plastic lines are especially prone to squashing, but even the steel lines will deform. I replaced both with rubber lines and galvanized steel brake tube that I formed and half-bubble flared.
  
• I used the least expensive Harbor Freight transmission jack to lower and raise the tank. I bolted a sheet of plywood to the top of the jack. The jack uses a 1/2 inch drive ratchet for raising and lowering, so it is simple to use. It's on small casters, so it'll roll well on casters.
• Consider buying a replacement fuel filler neck hose. Your OEM hose may have vulcanized itself to the filler neck and tank, and you may ruin it to get it off. That was the situation I faced. So I had the part on hand.
  
• This is also a good time to inspect and maybe replace the fuel return line from the injector pump.

All of this is for what it's worth.