How accurate are servo pumps?

**Offender90** · 2nd July 2008, 01:11 PM

A "tips on filling fuel in your vehicles" pdf was circulated by someone at my work recently (attached) Could it explain the observed discrepencies (if accurate)? Don't know, 10 litres is a bit much to disappear, maybe some of it overflowed? No guarantees on accuracy by the way, but thought I'd throw it out for comment from those in the industry. Or perhaps anyone with access to reliable info... EchiDna?

Cheers

**p38arover** · 2nd July 2008, 01:12 PM

Originally Posted by crump

I always wonder about whats left in the actual hose, especially with HI-Flo pumps.I've paid for it but its not in my tank unless I want to perform gymnastics with the hose to get the last bit out.By the way, does anyone do this???

Yes, but it only works when you have put in a set amount, e.g., $50 worth. Then you can hold the pump nozzle handle open whilst you manipulate the hose.

**Pedro_The_Swift** · 2nd July 2008, 01:16 PM

Originally Posted by crump

I always wonder about whats left in the actual hose, especially with HI-Flo pumps.I've paid for it but its not in my tank unless I want to perform gymnastics with the hose to get the last bit out.By the way, does anyone do this???

you do get the free bit left from the guy before---

d@rk51d3 · 2nd July 2008, 01:16 PM

Without trying to make it look obvious........ yes.

**B92 8NW** · 2nd July 2008, 01:20 PM

Originally Posted by crump

I always wonder about whats left in the actual hose, especially with HI-Flo pumps.I've paid for it but its not in my tank unless I want to perform gymnastics with the hose to get the last bit out.By the way, does anyone do this???

I don't think this is a problem as the hose would probably be full when you pick the thing up to stick in the tank. Would it not also be impossible to "drain the hose" because in squeezing the trigger, its only going to pump more?

Maybe, and I might try this, you could drain the contents of the hose if you placed your hand on the cradle thereby manually shutting the pump off and simultaneously squeezing the handle.

**paulthepilot_5** · 2nd July 2008, 03:39 PM

Originally Posted by B92 8NW

I don't think this is a problem as the hose would probably be full when you pick the thing up to stick in the tank. Would it not also be impossible to "drain the hose" because in squeezing the trigger, its only going to pump more?

Maybe, and I might try this, you could drain the contents of the hose if you placed your hand on the cradle thereby manually shutting the pump off and simultaneously squeezing the handle.

I like this idea

I reckon i i could just about fill my bike with the fuel left in the hose

**p38arover** · 2nd July 2008, 03:46 PM

Originally Posted by paulthepilot_5

I like this idea

I reckon i i could just about fill my bike with the fuel left in the hose

Wheeling it from pump to pump might be a bit obvious!

**hodgo** · 2nd July 2008, 04:19 PM

I had the same problem a couple of years ago at a Caltex in Beenleigh Qld. More fuel than the tank could hold according to Ford's spec's
I reported the matter to the weights and measure people who did a check and in formed me the pumps were correct. I did not except this finding and they proved to me it was my vehicle that was at fault .
Not only hadt the plastic fuel tank had saged between the two straps that held it in place but the hole fuel tank had changed shape which had increased the compacity by about 7 liters.

Hodgo

**p38arover** · 2nd July 2008, 04:59 PM

Originally Posted by hodgo

Not only had the plastic fuel tank had sagged between the two straps that held it in place but the whole fuel tank had changed shape which had increased the capacity by about 7 litres.

I suppose it's possible that's what has happened with our Disco.

**EchiDna** · 2nd July 2008, 05:01 PM

okay well here is the deal for service station meters - in the past (as surmised above) the weights and measures blokes used to bring out a prover tank (a proven volume tank) which measures the exact amount (+/- about 50mls) for 10 litres or gallons if you go far enough back

and measure what they get from the bowser. These days a primary meter (one calibrated with a prover tank) is used onsite to measure the accuracy of the bowser. These primary meters are 0.02% accurate, while the bowser itself must be 0.05% accorate or better to be in use.... in terms of variation in volume - higher temperature reduces the density of the fuel, going from a cool underground tank to a hot in vehicle tank can cause less to fit, with the reverse in winter... warm underground, cold above ground, more (by volume) in the tank. However fuels are not bought on volume, they are bought on energy content (e.g. RON 92, 95, 98 etc...), so if you buy your fuel on a hot day, expect to get a bit less bang for your buck as the fuel temp in the tank preceeding the meter will be hotter and hence less dense.

Of course none of this takes into account the variation in the scruples (sp?) of the petrol station owner in the first place who might just have a switch under the counter for just such circumstances.

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