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  Repairing Fuel Flow Transducer Cable

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Author Topic:   Repairing Fuel Flow Transducer Cable
Buckda posted 04-08-2011 02:20 PM ET (US)   Profile for Buckda   Send Email to Buckda  
I have a Navman 2100 Fuel flow meter. The transducer cable was split about 10 feet down from the connection to the meter. I would like to repair/patch this broken section.

Stripping the cable back reveals that the transducer cable is made up of a very thin white and black wire surrounded by a sleeve of copper strand wiring, some insulation material and the outer cable jacket.

If I solder the white cables and black cables, and then solder the copper stranded wiring and wrap each in heat-shrink tubing to protect the patch, should this work?

It does not appear that there are replacement transducers available as this product is out of production.

Thanks in advance.

jimh posted 04-08-2011 08:41 PM ET (US)     Profile for jimh  Send Email to jimh     
Dave--It should be possible to repair the cable as you described. The data flowing on the cable is very low-frequency data, and it should be easy to make a repair that will be essentially unnoticeable to the signal flowing on the cable.
Buckda posted 04-08-2011 08:54 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Follow up:

When bench testing the unit, if you blow through the transducer, the paddle spins - if the splice is made correctly, would this be an adequate test to make sure the head is receiving signal?

The head unit works fine when attached to the battery, but I cannot get the unit to display a flow rate by blowing into the transducer.

I am currently interpreting this as a faulty splice.

Bulldog posted 04-09-2011 09:24 AM ET (US)     Profile for Bulldog  Send Email to Bulldog     
Dave, was the unit working when you got the boat? When you said the cable was split, if it was cut while turned on there could be damage or a protective data input fuse blown in the head unit. I trust your ability to make simple splice, as long as it was color for color and no way to cross connect the wires. Go back and check your splice again the shield that was soldered last, could have had an impact on the other splices. I think if the shield was not even hooked up, you would still get some signal....jack
Jefecinco posted 04-09-2011 10:10 AM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     
Is the transducer directional?

Butch

Buckda posted 04-09-2011 11:17 AM ET (US)     Profile for Buckda  Send Email to Buckda     
Butch - If you're speaking about the direction the fuel needs to flow through the transducer, then yes - and that is the direction in which I'm blowing.

The unit is designed to measure up to 36 GPH...I'm wondering if my breath allows the paddle wheel to spin much faster than it would at 36 GPH of fluid flowing through...my thinking is that the answer to that question is "yes".

...so I'll test it quickly on the boat later today with the engine idling on muffs.

Jack - the unit was working the last time it was used - on my 18. When I repowered with twins, I pulled it from the boat because it is designed for use with a single engine only. I am hoping to use this transducer with a used fuel flow head unit I'm considering buying (a Fuel 3100, which will accommodate two transducers, but is being sold with only one transducer).

The transducer had some gunk in it, but I soaked it in fuel yesterday and was able to get the paddle spinning freely again.

Peter posted 04-09-2011 06:33 PM ET (US)     Profile for Peter  Send Email to Peter     
I believe the transducer is merely a pulse transmitter (1 pulse per revolution) and the head unit is merely measuring the number of pulses received per time and thus is not directional. However, the shape of the turbine blades are what cause it to be directional. My recollection is that there is an arrow on the transducer to indicate flow direction and the potted wire coming out of the transducer is on the outlet side.
Buckda posted 04-09-2011 06:56 PM ET (US)     Profile for Buckda  Send Email to Buckda     
This is true. I ran the motor today with the transducer in the fuel line. I got 0.0 readings, so something is wrong. Either I haven't spliced the cable correctly or there is another problem.

Jefecinco posted 04-09-2011 06:57 PM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     
Dave,

Yes, I was tactfully asking if you were blowing in the right end of the tube. If my math is correct, always questionable, @36 GPH the flow would be about .04 quarts per second which should not be a problem for most people. Of course air and liquids act differently but your methodology sounds right to me. When you blow through the tube can you tell if the turbine is turning? Maybe use of a mirror could provide the answer for sure. Another test method could be to fill your mouth with water.

The splice you made sounds good to me. The darn thing should operate.

Butch

6992WHALER posted 04-09-2011 09:11 PM ET (US)     Profile for 6992WHALER  Send Email to 6992WHALER     
I did not install my Navman myself but my guy had to cut the cable to get it to fit through the hard top supports. He reconnected them and the connection has not been a problem. So there is no reason to believe you should have an issue.
I am moving the unit this spring so I will have to cut and re-splice them again, I hope I can just copy what was done before.
Buckda posted 04-09-2011 09:26 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Something else must be wrong then.

I can hear the paddle in the transducer spinning when I blow on it (which is the recommended "diagnostic" mentioned in the manual).

I ran an engine for 15 minutes today and it neither registered any flow, or tallied any total flow (trip setting).

I guess next step is to put a multimeter on the cable?

Frustrating.

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