[needtocamp]

I moved this to “Ask PRevost” and will alert them of the question.

[Archived]

Ed,

They need the last 8 digits of your Vin number and is it a 40 or 45?

[Archived]

Hello Ed,

This is my second attempt to answer your question, first one went who knows where, so this time I will copy and paste prior to posting it.

The fuel gauge works off a varied ground from the sending unit. You will find 3 wires on the sending unit:

Circuit OW- this is chassis ground, disconnect it from the sending unit ohm it out to be sure this is not the issue before you start to troubleshoot the system.

Do the following with the ignition on,, all done at the sending unit with all 3 wires disconnected from the sender. The gauge should read empty and low fuel lamp off at this point.

Circuit 76L- this is for the tell tail lamp, disconect it and touch it to OW and the low fuel lamp should come on. If it does then the circuit and lamp are good.

Circuit 76- this is your sender wire to the gauge , touch it to OW, your gauge should go to full.

If it does replace the sender.

If not we ground the sender wire at the gauge, if it does not go to full we replace the gauge.

if it goes to full we have a wiring issue. This circuit is also connected to terminal stud 68 in the FJB And the issue could be there.

We do not post resistance values for this sending unit as this is not how we troubleshoot the circuit.

Hope this answers your question,

Best regards ,

Hittman

[Rick & Denise]

The Hittman is with Prevost in case you were wondering.

[gary]

Thanks Hittman,

That information looks perfect. We are on the road now but will use your procedure and report the results. I checked terminal stud 68 in the FJB and that looked fine. I may start the diagnosis at the gauge because access is easier.

BTW, our coach is a 1998 Royale, 1997 45′ chassis, VIN V1026170.

Thanks,

Ed Roelle

Grand Blanc, MI

[Jerry]

Good trouble shooting dialogue, now all I have to do is find my sending unit. At just below 1/2 tank today on level surface, took 98 gal and I do not have the celebrated Jon Aux Tank. Any one?

1990 conversion, 89 chassis, last 4 is L1001530

[Archived]

Ed,

Robert Hitt’s explanantion is exactly how to checkt o see whether it is the gauge, sender or connetions. One other item that you need to know is that Prrevost always skews the value of what is in the tank. We have it set so that if you should choose to run the gauge down to empty you will still have 40-50 gallons left in the tank. We have always done this to prevent you from getting so low on fuel that the pickup in the tank can come out of the fuel and suck air, which is bad for any diesel engine.

Plus the senders are always in the fuel tank. They are mounted through the plate bolted to the top of the tank with the fuel pickups and returns.

[Rick & Denise]

Rodger,

If the last 8 digits of your VIN are as you note then the chassis is a 1990. The “L” denotes that in the VIN.

If yoiu have n auxilary tank mounted in this shell it will be in the midle of the bay to the front fot he fuel tank bay. If yo can get under the vehicle you will see the hose connection between the main tank and the auxilary. If not then you should have the standard 160 gallon tank.

[Archived]

Is that skewing of the gauge only at empty? We just reported a gas station to the State because we were between 1/4-1/2 tank and put in 120 gallons.

[Archived]

Interesting… I have long range fuel, 250 gallons and today just off the empty mark it took 136 to fill. The second tank must contribute to the inaccuracy and it’s good to know when I’m empty on the gauge, there is still about 100+ gallons remaining.

I use the pro driver and mileage to determine my fuel and don’t rely completely on the gauge. The other thing to consider is if your down to a certain level on fuel, say 1/4, the general rule is the generator will run out of fuel because the pickup tube is at a higher level so as not to run the bus dry. So, sounds like empty on the gauge will still have enough to keep the gen running.

Bottom line, do whatever it takes to NOT run out of fuel.

[Michael]

All the pilots here will understand this and it is how I determine when I need fuel. To make the significance of this greater, everyone should understand I minimize fuel stops and take advantage of my fuel capacity.

I have the 208 gallon standard tank with the 90 galllon auxiliary for a total of 298 gallons. Depending on circumstances I have gone as far as 1900 miles with the fuel gauge showing near empty. My fuel consumption has never gone above or below 7 to 8 miles per gallon so I have a theoretical 2100 to 2400 mile range.

I just simply set the trip odometer at each refueling to zero and I just never go further than 1800 to 1900 miles before refueling. Routinely with typical trips our round trip distance falls around 1300 to 1400 miles so I fill up upon returning home. I treat the fuel gauge as nothing more than the suggested fuel level, with the trip odometer being the more accurate fuel level indicator. It just requires me to know my average MPG and a minimum amount of fuel on board that I want to have when I fuel up.

When I get the new coach I will fuel frequently until I learn the average MPG the coach delivers and then I will aim for a minimum fuel on board at refueling like 40 gallons, allowing me whatever range 168 gallons will get me. The new coach has 208 gallons of fuel capacity. My guess is the new range will be 1000 miles.

In the plane there was no odometer, so refueling was based on hours. My time until dry tanks was 6 hours, so I set 4 hours as my maximum time of operation since topping the tanks. Same concept and it worked very well.

[Archived]

Not as much time behind the wheel on the Prevost as you Jon, but around the 1000 mile rule is where we start looking for more fuel. When I fuel I note the mileage on a small travel book next to me.

Another method I know is using the 1/4 tank rule . At that position on the gauge start looking for fuel. Doing this you are trusting the gauge to be accurate and this might sometimes not be the case.

On our Country Coach Affinity, two tank sending units failed in under 10 years. I learned to trust the mileage rather then the gauge. Looking down at the fuel gauge and seeing the needle peged at empty will raise your blood pressure. Then looking in the rear view mirror to check for a trail of diesel fuel behind you.

The last thing I want to happen is run out of fuel.

[Dale]

Jon: I think you will have the same dash as I do. I reset the fuel used segment of the display (fuel used and MPG) at each fuel stop and between that and the gauge, I find it is pretty accurate. It does not, of course, add the generator useage, but that is insignificant compared to the engine so I don’t worry about that.

I know you will miss the long range fuel, but at your stated speed, you should still do pretty good for fuel mileage.

[Archived]

Tom, I also carry 250 gallons. Main tank is 160 gallons and an attached 90 gallon aux tank. They act as one tank since they are connected all the time. The gauge is in the back of the main tank.

I have always noticed that when driving up hills my fuel gauge rises and the opposit is true when declining. When driving or sitting in a level posision, I have a true reading on fuel. Believe me with the price of fuel, I never have enough.

[Larry & Diane]

I opened this thread, and now can report the results after returning home.

I followed Hittman’s procedure. Everything checked-out OK except
the sending unit. This made sense after going throught the procedure. I ordered a replacement from Prevost Parts, replaced the sender, and all is
good. BTW, the sender is accessible behind a cover in passenger
side, Bay 3. The plate on the tank must be removed and tilted
to remove the sender. Pretty straight forward though. I
think I will disassemble the old sender to find out why it failed – when I
get some time.

I will also track mileage so as not to run out of fuel.

Thanks for the help.

Ed Roelle

Grand Blanc, MI