A 98 dodge diesel question

SGT FURY

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Any dodge diesel guys here?
I have a 98 Cummings 24 valve diesel.
It’s forever had a problem with fuel gauge.
It bounces back and forth making the dinging
low fuel sound. Empty/full/empty/full.
When it’s VERY full it will correct and work proper
At 3/4 tank it will start malfunctioning.
My question is this a gauge problem or a problem in the tank.
I’m changing the bed soon and will have access to tank sending unit and pump. I want to deal with
this problem while I have access with bed off.
Don’t want to dig in tank if it’s a gauge cluster problem.
Anybody here ever had this same problem?
 
It could well be an issue with a baffle which surrounds the fuel ending unit itself, in the tank. We had something possibly similar in the later '80s GM pickups and suburbans. The tanks were as they had been with the previous carb'd models, but for EFI, had a plastic baffle which was secured by a "U" tacked to the bottom of the tank, so that the baffle (cup shaped of sorts) kept fuel around the fuel inlet at all times.

In production, GM used only one speed nut to keep them attached, but after they got loose, they would move around with the fuel as it sloshed. Many times damaging the fuel pump module and sender. Imagine going over a speed hump at the mall and the vehicle dying! A TSB was generated and the fix was TWO speed nuts, one for each tang. Speed nuts with a clear anti-corrosion coating on them.

With the bed off, you should be able to remove the sending unit/module, I suspect. Then look into the tank for such a baffle and where it might attach and/or how securely it might be attached. Plus inspecting the sender for any damage.

Yes, this is "GM" information, but Chrysler vehicles might be similar.

Just some thoughts,
CBODY67
 
My 96 V10 did that under 1/3 of a tank it would just drop out and say empty. It didn't bounce back and forth. I just lived with it until the pump went bad and replaced the module. The tank on mine was a plastic tank and the baffles were made in so I don't know if one could come loose or not. My thought is if it it always does it around the same time it is probably the sending unit. Bad part about them is everything is made into one module, the pump and sending unit. Factory manual says it has to be changed as a unit but I have seen guys take them apart and just fix the pump. You could probably do that with the sending unit.
 
There is no baffle in the tank.
There is a way to test all the gauges in the cluster. It is simple but don't remember how to do it but I remember it will run the fuel gauge through the full sweep.
There is a plastic bushing on the float arm that is known to wear and give bad readings.
There is a plug behind the drivers side left wheel that can be seen under the truck that goes to the rear lights and fuel sender and you can get a reading with an ohm meter and take the dash gauge out of the equation.

Instrument Cluster Gauge Test - Cool! - DodgeForum.com
 
If you go to the truck forum someone there has probably experienced this.
 
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