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Russell H.
Russell H., Service Tech
Category: Marine Electronics
Satisfied Customers: 11046
Experience:  8+ years of professional experience
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I have the Garmin 1020XS and have fitted the GFS10 flow

Customer Question

Hi , I have the Garmin 1020XS and have fitted the GFS10 flow sensor connected to the NMEA 2000 NETWORK and connected to my fuel gauge.
Running this on the weekend I found that the fuel flow level varied greatly running at steady RPM.
The unit did originally detect the gauge and asked for setup (1 coil/2 coil) but from this point it now doesn't recognize the gauge.
This was before the test run.
I have checked the wiring and its all as per the manual.
Any ideas why it wont sense the gauge and varies greatly on fuel flow running ?
This variance can be from 5 l/hr - 15l/hr running steady on 3000rpm.
Submitted: 2 years ago.
Category: Marine Electronics
Expert:  Russell H. replied 2 years ago.

Hi, thank you for contacting My name is Russell. I will do my best to provide the right answer to your question.

Is it possible that you have an irregular fuel flow rate in reality? such as, owing to pinching (intermittently or varyingly) of the fuel line somewhere, or clogging of the fuel filter ?

That's my though on this matter - unless, of course, you have either loose connection, corroded connection / wire-ends, or an unreliable ground on the fuel gauge or on the Garmin, or an unreliable GFS10 flow sensor - how new is the GFS10 ?

Customer: replied 2 years ago.
Thanks Russel,
The GFS10 is Brand new , along with the NMEA network and the Garmin 1020XS.
This is a complete new install, so can count out loose connections / corroded etc.
However before the install the fuel gauge, when powered down, did always read about half tank, with now power. Since the install this drops back to beyond empty , as i would expect.
It could possibly be a bad neutral connection, but this is direct from the battery bank to the neutral terminal bar.
Its just strange that when the meter read half tank, the 1020XS did recognise that it was connected to a fuel gauge , but now doesn't.
The fuel tubes/pipe and filters are all good so think can count out the irregular flow, it varies rapidly by a large amount.
I disconnected the flow meter from the NMEA then ran it again , and reconnected , it didn't vary as much , but at a good steady running 3000rpm with the engine running nicely it still varied by approx. 5-10 l/hr. flow rate.Thanks again
Expert:  Russell H. replied 2 years ago.

If the meter read half tank but the 1020XS recognized the fuel gauge, then that's closer to the right hookup. (Is reading half tank, the middle position on the gauge?)

Varying rapidly by a large amount signifies a loose connection of some sort, normally.

Customer: replied 2 years ago.
Hi , Yes the meter is at half way point , or used to be at first, but since the install it drops back to zero with no power.
When it was originally installed and the meter at Half way the 1020 did recognise the gauge.
I will double check the connections but am certain they are not loose, I will also check the neutral connections.
Expert:  Russell H. replied 2 years ago.

In a three-prong power outlet, the three prongs are



& Ground.

The Neutral is *not* equal to Ground.

What is the 'neutral' that your wiring is using, please? since it is on shipboard, it is not the same as three-prong house current/outlets I presume!

I suspect you should wire the meter back to the way it was when it went to half-way with no power.

A connection can be 'loose' esp. on shipboard, even when mechanically tight, if there is corrosion or dirt inside the connection, blocking it. So I advise disconnecting every connection, using a clean dry brush on the metal of each side, then wiping down each side's metal with a clean dry rag cloth, then re-connecting. That will make sure corrosion is eliminated.