Fuel Sending Unit Trouble Shooting

tengland

Need a few ideas on trouble shooting Fuel Sending Unit Wiring on
2009 26' Venture. I believe the fuel sending unit is Model 9300 Rochester gauges.

Issue: Wires going to the starboard side gas fuel level sending unit on the rear fuel tank were all burnt. The insulation on the wires was melted and bare wires were showing.

What should I do? Run new wires to the front console?

BrentB · Posted: Sun Jan 11, 2015 9:42 pm Post subject:

You will need a DVM digital volt meter (Fluke, Radio Shack, Sears, Home Depot, etc) to check voltage and resistance (OHM)

http://www.rochestergauges.com/pdfs/DS_953.pdf

and contact the company for the manual

Here is one for 953 model

http://www.rochestergauges.com/pdfs/DS_953.pdf

should help guide you

One is hot 12 V and other wire is a ground

tengland · Posted: Mon Jan 12, 2015 6:08 am Post subject:

Thank you for the reply. It gives me a start point.

Todd England

BrentB · Posted: Mon Jan 12, 2015 9:31 am Post subject:

Can you post some pics of the wires and connections?

I would try to determine the root cause first before making
repairs. off the top of my head, bad grounds, over-voltage, incorrect wire type not marine grade, poor crimping of the connections, poor mechanical connection to the electrical items (fittings not tight), incorrect fusing, circuit breaker panel issues, breaks in wire exposing bare wire, ......

Have you checked other connections? Are they loose? have bare wire exposed? What is the wire gauge?

I would check the entire electrical system including the OB, something is amiss and posting some pics would be useful for us to help you.
I would invest in a good DVM. I have an old Fluke and entry level one from Sears. Both are fine.

Any additional information and pics you can provide would be useful

AstoriaDave · Posted: Mon Jan 12, 2015 10:43 am Post subject:

Tengland,

Burnt wires and melted insulation strongly suggest that a hot wire was abraded and the insulation touched a grounded point, perhaps the fuel tank if it is aluminum. If you can, identify where that point of abrasion is likely to be, and when you run new wires to the sending unit, enclose the wires in split loom or other chafe protection. If you are lucky, the gage is undamaged, but the wires are shot.

Also inspect the rest of the wiring for other chafe points and protect the wiring. It is possible, though unlikely, that an exposed hot wire, perhaps at a connection point, was immersed in salt water, forming a conducting path to ground, which could also fry the wiring. All wiring should be above where bilge water might lie, except for whatever powers your bilge pumps.

tengland · Posted: Tue Jan 13, 2015 6:43 pm Post subject:

Brent B:

I just posted a picture of the fuel tank sending unit wiring -Located in "LIL Sis". The fuel tank trouble is on my dad's 26ft- SheSayNo. The black/red wires were in a nylon loom. the connections looked tight and there was nothing obvious.

I did follow the fuel sending unit wires all the way to the rear cabin and the insulation was melted at least 8ft from the fuel tank.

salt water...Boat was only exposed to salt water for the first time last spring for 2 months down in Florida. The home base for SheSayNO is on the Mississippi in Winona, MN.

Thank you for the replies!

T.England

AstoriaDave · Posted: Tue Jan 13, 2015 7:02 pm Post subject:

Tengland,

Hard to tell for sure, but it appears the black wire was the one that has the destroyed insulation? Also appears that there is a chafe hazard where the black wire passes across the large tab coming off the tank.

When you say the insulation on the wire is destroyed 8 feet from the tank, do you mean from the sender to that point?

Again, can not tell for sure, but from the green corrosion on the sender install plate, I would guess salt water has been on top of the tank, perhaps not for long, but long enough to leave a residue.

Looks like a wholesale replacement of both the black and red wire systems would be in order.

BrentB · Posted: Tue Jan 13, 2015 8:10 pm Post subject:

Thanks

After you replace both wires check them for bad spots

thataway · Posted: Tue Jan 13, 2015 8:19 pm Post subject:

Looking at the black wire, it looks as if it got hot--perhaps a connection with a positive, hot wire, and that lead to a short--not fuse protected. The insulation looks burned off. This does not look typical of rodent or corrosion damage.

Look for a short some where. I agree that a rewire job the entire way is in order. The ground tab is also connected to the ground screw on the sender. There looks lake an illusion that the ground wire stops at the "tab", or is spliced to the wire…which goes to the ground screw on the sender.

tengland · Posted: Wed Jan 14, 2015 6:33 am Post subject:

Great ideas...I will keep you posted on the progress this spring.

Right now, this is a good winter project with 6" of snow and 10°F outside. I still have a few weeks.

TEngland