Fuel Gauge woes

B

Badfish888

New Member
Jul 18, 2015
85
Va beach
Boat Info
175
Engines
3.0
So here's the run down, 1998 search 175. 3.0 merc. Out yesterday with a half tank of fuel. I look down and notice the gauge is buried under empty. ( topped tank off, no change). I brought boat home today. And pulled sending unit to check. With a multi meter set to ohms I meaured around 240- 30 through the whole swing on the float. So that checked out for me. So on to the gauge now. The gauge has 4 wires. Black-center, red purple and another one.
The tank also has a red and black.
i can't find any combination on the back of the gauge where I get the same ohm reading. So it is hard for me to say the sending unit is bad. When it's reads a resistance difference, And I can't say the gauge is bad if I can't even read the input to it. I disconnected the wires on the gauge and checked no still nothing.

need help. As I don't think my gauge or sender is bad. Which wired are I out for the gauge, And if I bought new wire. Could I just run them from gauge to tank. Again. Not sure. I'm a diesel mechanic. Not an electrician
 
How are all the connections? Anything loose or corroded?
 
1 make sure 12v is at the gauge
2 using a jumper, ground the sender lead at the dash , should go full scale
3 hook the gauge back up and go to the tank, hook the jumper to the neg battery and touch the (red/pink) wire, gauge should go full scale
4 short the red/pink wire to the black wire at the tank, gauge should go full scale.
report your findings
most gauges have 4 studs, 12v, sender, ground, panel light. panel light feed is sometimes combined with the 12v
feed
 
Last edited:
I had a similar problem last season. Is frustrating when you cannot tell how much fuel you have onboard. The members on this forum told me to check my connections. Turns out I had a loose ground wire on one of my fuel senders. I simply tightened it down and my problem went away.

Good Luck!
 
So i rechecked the sender. And have good ohm reading. I replaced the grownd wire at tank. Under console. I ran a new ground to gauge, ran a new wire from tank to gauge, Made a jumper from a working gauge to fuel gauge for power.
so I have 12v At gauge. A good ohm reading at gauge, and a good ground at gauge

turn the key And the gauge dont do ****.

is my gauge bad?
 
Sounds to me as if that is your next step.
 
Bad fish did you touch the ground to positive? If you did and the gauge did not go "full" it is your gauge.


Sent from my iPhone using Tapatalk
 
I did The guage does nothing. To cover my steps I re wired every thing.
New gauge light connection, new gauge ground, New power jumper from a working gauge, And ran a completley new sending wire. Gauge light comes on But no gauge movement.
 
If no movement when grounded. Time for a new gauge. If it deflects to full, time for a new sending unit.


Sent from my iPhone using Tapatalk
 
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