Community Forums

edmount · 03-24-2025, 02:32 PM

I have a 2004 HR Scepter PDQ diesel with a 100 gal. tank. The fuel gauge is stuck on all the way past full when the ignition is on and driving. When the ignition is off, the gauge shows almost to the left of the left side of the "F" mark.
Does anyone have any suggestions as to what the fix might be or how to troubleshoot the problem?

ED

jacwjames · 03-24-2025, 06:24 PM

Your fuel sender in the tank is probably a Centroid unit, they have a trouble shooting guide.

https://www.centroidproducts.com/
Scroll down the page and download/print the guide.

You will have to use a voltmeter and take some readings and then email the page to Centroid,

Mine was doing similar and the unit was bad. I decided to replace with a Holly Easyread sender. Had to go through a calibration process but it does work.

Lowflyer1 · 03-25-2025, 01:48 AM

With that age Centroid, I would not mess with trouble shooting. Not much anything you can do about it anyway. Just get a new sender.
The previous owner of mine had the same issue and replaced the sender.

jacwjames · 03-25-2025, 07:20 AM

If you are new to a diesel pusher I'd suggest you look at buying a Bluefire engine monitor system. This plugs into the diagnostic port under the dash left side of the steering column.
Information is sent via Bluetooth to your phone or tablet.

Bluefire will display all the critical info you'd need to monitor the health of your engine. It will also monitor fuel consumption and you can create both a tank level monitor and fuel gauge.

edmount · 03-25-2025, 11:59 AM

Where did you get your bluefire engine monitor?

jacwjames · 03-25-2025, 03:30 PM

Quote:

Originally Posted by edmount

Where did you get your bluefire engine monitor?

I use a Silverleaf VMSpc for engine monitor. It is no longer made though.

https://bluefire-llc.com/store/motorhomes

https://bluefire-llc.com/store/500k-...08-ios-adapter

You probably have a 6 pin diagnostic port so you will have to get an adapter to make it a 9 pin.

There is a forum on IRV2 that discusses Bluefire and has many templates that you can use

edmount · 03-26-2025, 01:45 PM

I'm getting somewhat confused. I saw a video yesterday that showed a sender that used lidar where you didn't need a tube on the sender. Seems far-fetched but you wouldn't have to drop the tank. Just measure the depth and calibrate it on a flat surface with a solid surface as the bottom. So far I haven't been able to find that video but I think it was made by Centroid.

edmount · 03-26-2025, 03:54 PM

Now I do remember where the video came from. It was the Holley easy level fuel sender. the new one uses LiDAR instead of the in-tank tube. eliminating the need for dropping the tank.

jacwjames · 03-26-2025, 05:41 PM

I installed a Holly Easy Level.

Calibration wasn't as simple as the video showed. I muddled through it and followed the video/instructions, but wasn't confident that it was right.

So I came up with my own method. I took a piece of 3" PVC pipe, cut to the the length of the old sender unit ~19". I didn't The top ~4" of the tank wasn't usable because of the fill necks so I cut the pipe off that long but save that piece, also wanted a little reserve so I held back a couple inches.

So I stacked the pipe 2" ~13" ~4".

The holly sender was smaller then 3" so I cut a piece of card board with a hole in it. I had another piece of paper to put between the pieces of pipe.

I let the sender set at a slow rate.

So I put the piece of paper at 2" and calibrated for empty there, I left that sit and watched the fuel gauge need go to empty. Then pressed the appropriate button to register that.

Then moved the piece of paper to the 4" mark, let the sender sit there and I went and watched the gauge move to full. Then pressed the button to recognize it as full.

It seemed to work so as a test I cut the long piece in ~1/2 and tested the sender, set it on the pipe and watched the gauge slowly go to ~1/2 full

When I finally got to go on a trip the fuel gauge appeared to work, much better then the Centroid did.

edmount · 03-27-2025, 04:57 PM

Seems way too complicated even though you did a good job explaining the process. Should I decide to give it a try, would you be willing to discuss on the phone?

jacwjames · 03-27-2025, 06:09 PM

Download the instructions from the Holley site and watch the video.

In the video they do the calibration on a table.

By using the pipe cut to the lengths it made it pretty easy.

If you decide to try the Holly, if you have trouble post again.

bobkat11208 · 03-28-2025, 11:25 AM

Quote:

Originally Posted by edmount

Seems way too complicated even though you did a good job explaining the process. Should I decide to give it a try, would you be willing to discuss on the phone?

When I installed mine, I didn’t have any PVC pipe and being ‘frugal’

and the fact my wires weren’t extremely long, I ran painters tape on the side of the coach, but using the correct measurements for my tank, similar but a bit different than Jim. I was able to still calibrate the unit and I’m always within 3-5 gallons of the calculation I get from my BlueFire.
It actually sounds harder, regardless of method you use, than it really is, be it hooking up to 12v on a tabletop, using PVC, or tape on the side. They all achieve the same result.