Fuel Tank Airlock or Guage Faulty ?

[Badger]

I just tried to fill up the fuel tank on my new boat which according to the guage was 1/3rd full when I took delivery. It only took about £7.00 worth of diesel and is now showing 2/3rd full. It is 13 gallon tank. is the guage faulty or do I have some sort of airlockas its all new ? Any suggestions welcome.

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[jimh]

I might have the maths completely wrong - but isn't 13 gallons 61 liters and at 30p per liter isn't that £18 for a full tank ?? If so - suggest that you neither have airlock or faulty gauge -

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[byron]

<font color=blue>Huh? Am I missing something? If it was 1/3 full thats about 4 gallons, you stick in about 4 gallons that takes you to about 2/3 full.

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[Badger]

Let me clarify. The diesel is spraying out of the filler and I cannot physically get anymore in the tank but the guage is telling me it is only 2/3rds full. Why ?

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[johnsomerhausen]

In this Internet age, one's never sure which unit the correspondent is using
the US gallons equates 3.8 litres whilst the Imperial one is 4.5 litres
so that 13 US gallons makes 49.4 litres and 13 Imp gallons give you 58.5 litres.
One way to check whether the fuel gauge is working correctly is using a multimeter connected between the wire that goes from the sender unit in the tank and ground. The readings will differ according to the brand of gauge and sender unit, but with the Stewart-Warner it is 330 ohms for full and 40 ohms for empty (or is it the reverse ? memory playing tricks...)
john

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[byron]

<font color=blue> Ah! I see, misread what you were saying, apologies. Tank guages are notoriously unreliable. If yours is a float system it could be the float isn't moving up past the 2/3 mark.

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[Freebee]

its mostly likely the cheap gauge thats been fitted it probaly wont ever show full because the float cant rise far enough or maybe its the way its been mounted.

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[happychap]

Re: Fuel Tank Guages ?

I've also just bought a boat with a 'duff' fuel guage, reads zero I think. The seller suggested forgetting the guage and keep a log based on hours-run. At the time I took it as a 'sellers comment', was he talking common sense
1 - Just how notoriously bad are diesel fuel guages??
2 - Is there an obvious starting point for the fault?

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[Viking]

Probably the gauge. I've had to remark (collobrate) my gauge. Waited until the gauge was down low or showing empty. Then add fuel in 5 or 10 lites amounts marking of the gauge until no more fuel could be added.

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[Badger]

I think you could be right. Obviously the tank must be full. I will look at the float mechanism. Thanks.

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[Badger]

It's all British kit but thanks for the tip on the multimeter Ohms reading.

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