fuel gauge or sender??

[s2gots]

Yesterday I got stuck on the water--out of fuel

Luckily it was close to the dock, and a friendly boater gave me a tow..
I usually always fill up the tank before I head out, but yesterday i didnt, dont know why, I just didnt...
I didnt know my gauge/sender was not working since I always filled up the tank, so you can say yesterdays insidents were somewhat of a good thing!!
My question is if there is a way to test to find out which part is bad?
While im at it, replacing senders or gauges, I believe the fuel tank was replaced by the prior owner, and installed a bigger tank..how do I determine how much fuel it holds, and how do I get the correct parts for the tank? There is no writting on the tank to determine what it is.. Its an aluminum tank, rectangle in shape..


TIA

 

[scutly]

Re: fuel gauge or sender??

Yesterday I got stuck on the water--out of fuel

so did I. ok this is from my Merc manual so here goes. to test the gauge (water temp, fuel or oil pressure)

1-turn ignition to off.
2-remove the "S" sending terminal wire from back of gauge. (light pink for fuel)
3-turn ignition to run, gauge must read empty for fuel, cold for temp or zero for oil. basically the gauge must be pinned to the left with the key on and the sender wire removed.
4-turn ignition to off.
5-connect a jumper wire from the sender terminal "S" to the ground terminal "GND" on the back of the gauge.
6-turn ignition to run. gauge should be pegged to the right this time with the jumper installed. if not replace gauge.

ok this is for the sending unit now.

1. Disconnect wire from terminal on sending unit and ground wire from sending unit mounting screw.
2. Remove sending unit from fuel tank.
3. Connect ohmmeter between sending unit terminal and sending unit housing.
4. With float arm in FULL position (arm horizontal), ohmmeter should read 30 ohms (+/- 5 ohms).
5. With float arm in EMPTY position (arm vertical) meter should read 240 ohms (+/- 5 ohms). Sender is defective if not within specifications

i replaced both for about $30 each. the sending unit i bought is a Moeller adjustable replacement unit with a standard 5 bolt flange. now as far as telling how much fuel your tank holds, there's only one way. now that she's empty, fill her up!

 

[Solittle]

Re: fuel gauge or sender??

Most tank manufacturers put a data plate somewhere close to the sending unit. It will have the tank capacity.

 

[Silvertip]

Re: fuel gauge or sender??

The other way is to measure it. LxWxH = cubic inches. 61 cubic inches = 1 liter or .264 gallons.

 

[s2gots]

Re: fuel gauge or sender??

good info thanks!!

If the sending unit is bad, Im obviously going to replace it..I thought the capacity of the tank was important when ordering a new sending unit..

Im gonna go check them out, hopefully find the faulry unit..thanks again

 

[scutly]

Re: fuel gauge or sender??

nah. the new sending unit is determined by the length of the old one. there adjustable.

 

[s2gots]

Re: fuel gauge or sender??

Looks like it's an easy fix, the gauge is bad. How can I find out if the ohms listed above are correct for my unit? Unfortunatelly I don't have a user manual...

 

[scutly]

Re: fuel gauge or sender??

the ohm readings are universal to all merc fuel sender applications i believe. both my 5.7 and 7.4 manual give the same information. what are you running?

 

[s2gots]

Re: fuel gauge or sender??

It's an 88 omc cobra with chevy 350

 

[62 pipestone]

Re: fuel gauge or sender??

i got a new boat and i checked it over with a fine tooth comb. one thing i notaced is the gauge was inop, i tested the gauge good so i pulled out the sinder and found nothing..... I MEAN NO SINDER! it was just a plate with the 2 wires going to it, WTF!

 

[scutly]

Re: fuel gauge or sender??

maybe it broke off and is sitting in the bottom of the tank?

 

[62 pipestone]

Re: fuel gauge or sender??

maybe it broke off and is sitting in the bottom of the tank?

checked that. think it may have broke off at 1 point and someone fished it out.
o well ,its on my list