Author Topic: pegged fuel gauge  (Read 4649 times)

Cloyd Robinson

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pegged fuel gauge
« on: February 06, 2020, 09:22:07 PM »
So here I am getting everything ready for my first trip in the coach. Right after I purchased it, I topped off the fuel tank. The gauge had been working perfectly. The gauge immediately pegged and that is where it has stayed. I have read about algae in fuel and am wondering if this could have something to do with this problem.
Cloyd Robinson
2006 Monterey C9
Bend, OR

Joel Ashley

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Re: pegged fuel gauge
« Reply #1 on: February 06, 2020, 10:05:39 PM »
Not sure algae would foul the gauge, but it takes a good number of miles before mine shows a drop after a fill-up.  Then it’s accurate enough for me to estimate how many gallons I‘ll need to refill, usually best practice at the half-tank point.

Algae grows at the interface between fuel and any water it’s floating on.  Keeping the tank full during storage or long camps is your best defense, especially in humid regions and/or cold weather.  I use Power Service products, and might suggest their Bio Kleen (a pint is adequate, added according to directions) and then perhaps regular use of one of their other additives.  If algae is in the tank from a previous owner’s neglect, it may show as dark particles in the clear water-separator bowl at the bottom of the Primary fuel filter.
https://powerservice.com/products/
Many Power Service products can be found at hardware and auto parts stores, but Bio Kleen can be harder to come across.

https://www.bellperformance.com/bell-performs-blog/recognizing-diesel-fuel-algae

Joel
« Last Edit: February 06, 2020, 10:22:34 PM by Joel Ashley »
Joel and Lee Rae Ashley
Clackamas, Oregon
36.9 ft. 2006 Monterey Ventura IV, aka"Monty Rae"
C9 400HP Cat

Gerald Farris

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Re: pegged fuel gauge
« Reply #2 on: February 07, 2020, 03:35:50 AM »
Cloyd,
There is virtually no chance that microbial growth that is commonly called diesel algae, is causing a problem with your fuel gauge. Microbial growth in fuel is a common cause for frequent fuel filter restrictions in humid areas, but it does not cause gauge malfunctions.

If you can give me the readings for your fuel gauge at different levels, and the ohms for your fuel tank unit at different levels, I can tell you where to look to correct your problem, or if you actually have one.

Gerald

Larry Fisk

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Re: pegged fuel gauge
« Reply #3 on: February 07, 2020, 04:28:30 PM »
My gauge did the same thing. The problem was one of the sensor wires had become loose. I simply pushed the wire connector on all the way and then tightened it to the slip on connection with needle nose pliers. Gauge once again shows level perfectly. My level gauge is located on the drivers side of the fuel tank and is mounted on the side of the tank. I had to slide under the coach to access it. Yours may be located differently.
Best regards,
Larry Fisk
Larry Fisk
2005 Patriot Thunder 40 ft.
525 (C-13) CAT Engine

Al Anderson

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Re: pegged fuel gauge
« Reply #4 on: February 10, 2020, 11:50:47 PM »
I had a similar problem with mine and I found corrosion not only on the wire coming from the gauge but also on the ground wire.  After a year of the gauge reading erratic, I replaced the end on the guage wire and replaced the ground wire with a new one. 

I have now driven 20K miles and it has worked flawlessly.

Ray Bendle

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Re: pegged fuel gauge
« Reply #5 on: March 26, 2020, 10:44:01 PM »
Just got our coach last year. Had same issue needle pegged on bouncy section of I 90 between Erie and Buffalo.  Assumed it was going to be a wiring or sender issue. Was actually needle on gauge stuck against glass of gauge. Gave it a couple of raps with my knuckle and it returned to normal. 
2001 Marquis Emerald 42 X Edition 500 Cat
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Cloyd Robinson

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Re: pegg?ed fuel gauge
« Reply #6 on: April 06, 2020, 11:04:46 PM »
I have checked everything about the wiring connectors from the gauge end and the tank end. Everything feels tight and not corroded. Gerald, I am ready to try your suggestions of ohm readings. Which connections should I be checking between? I haven't undertaken a continuity check between the sender and gauge but might start there. I notice on the sender there are 3 wires, send, positive and negative. I assume the positive goes to the nearest 12 v and the negative is ground and the send goes to the gauge? I keep wondering why it worked fine until I first topped of the tank.

Gerald Farris

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Re: pegged fuel gauge
« Reply #7 on: April 07, 2020, 05:41:17 PM »
Cloyd,
The sender (tank unit) should have two wires, a positive (signal wire) from the dash gauge, and a ground wire assuming that the sender does not depend on the tank as the ground. The dash gauge should have three wires, a positive to the battery, a signal wire to the sender (tank unit), and a wire to the gauge light. In some cases there may even be a fourth wire to the dash gauge to ground the light if the gauge is not case grounded. 

Most of my experience has been on SMC era coaches and the automotive industry, and that is how they were wired. The only three wire senders that I am familiar with have an in-tank fuel pump and the third wire was the pump power supply. However, since your coach does not have an in-tank fuel pump, I do not know why you would have a third wire unless Monaco wired the fuel gauge backwards and grounded the circuit at the dash gauge. You will have to check the circuit to determine if this is your case.

Normally a fuel gauge is diagnosed with a variable resistor. The dash gauge should read full with the maximum resistance for the system and that can be from about 30 to 250 ohms depending on the dash gauge design, and empty at 0 to 10 ohms depending on design. A variable resistor is required when diagnosing an operational but inaccurate fuel gauge. For a problem like you expressed, I normally just disconnect the sender wire at the tank unit and see if the dash gauge goes to max full reading and ground it to see if the dash gauge goes to max empty reading. That will tell you that the gauge wiring is OK, and if the sender ground is good, your issue is not wiring related. Then you need to take an ohm meter and check the resistance in the sender (tank unit). If the sender shows an open circuit, it is bad an your dash gauge will be pegged to max full. Since you did not say which way your gauge was pegged, I am assuming to max full, but if it is at max empty, that would require a shorted sender or wire. If this did not make sense to you, just call me, and I will walk you through the process 713-254-4156

Gerald

Bill Lampkin

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Re: pegged fuel gauge
« Reply #8 on: April 07, 2020, 07:00:16 PM »
I've read that Monaco used Centroid senders. See troubleshooting

http://www.centroidproducts.com/zTroubleshootingMonaco.pdf

2005 Patriot Thunder Lexington, 3 slides
40' tag axle (short wheelbase)
525 hp C13

"Goin where the weather suits my clothes..."
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Bill Lampkin

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Re: pegged fuel gauge
« Reply #9 on: April 07, 2020, 07:04:14 PM »
Tip: if it is a Centroid sender, with 5 mounting screws, make sure to paint an index mark on sender and tank before removing sender, to make sure you re-install in the same orientation. The 5 screw pattern can be forced in at least two ways, the wrong way (ask me how I know this) and the correct way. The wrong way? I filled up my boat's bilge with fuel!
2005 Patriot Thunder Lexington, 3 slides
40' tag axle (short wheelbase)
525 hp C13

"Goin where the weather suits my clothes..."
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