Gas Gauge not working

[Jennifer "water-wolf"]

It's not exacly engine and outdrive but it IS related...1994 model, V6 with Alpha One. I have the original factory install manual that Mercruiser gave the OEM boat manufacturer, and the electric harness and gauges are exactly what is described in the Mercruiser install manual. I suspect that my boat builder [ Blue Water Boats, then in Springfield Oregon] just got complete power/out-drive/electric packages from Mercury, but that is just an assumption on my part....

After spending the winter in a heated warehouse we took 'er out a few days ago on the first outing of the season,:joyous: and found the gas gauge not reading.:grumpy: We motored from the marina to a gas dock and added over half a tank worth of gas just to make sure we had some...and still no movement of the gauge. Anyone got any ideas where I should look first? It was functioning fine when last out in October, with about 1/4 tank remaining on last use. The boat has been quietly waiting in a heated warehouse, not subject to rain or freezing temps....If there is typical failure mode, is what I am looking for advice on....next week I can put 'er out on a work platform and trace everthing out with a volt/ohm meter, but if there is some advise as to what to check first, it might save me some time or frustration. Also of interest would the typical ohmage that I should read from the sending wire to ground through the sending unit, at empty and at full..... . I have had trouble with the trim gauge not working too....and that was traced once to a faulty install of the sending unit on the out-drive, after a service we had done, and the second time to a bad splice someone had made in the sending unit wire under the dash....and it is out again too, but I am quite familiar with how to trace that circut now. I have very long extension test leads for my multimeter, so I can connect right at the sending unit and go all the way up to under the dash if I need to. Thanks for any help in advance. Sure hope I don't have to spend big bucks on a new sending unit, which is also hard to get to for removal and replacement. I can reach it easily to clip on test leads, but to replace it, I would probably have to remove the entire rear seat bulkhead.
Jennifer

 

[tpenfield]

Re: Gas Gauge not working

First thing would be to check the connections at the gauge and at the sender unit to see if they have come loose or corroded, etc.

Next would be to see if you are getting voltage to the gauge.

There are a variety of fuel senders, but generally they should have maximum resistance in the 90-240 ohm range.

A word of caution with working around the fuel tank, etc. make sure there are no fumes present and you are not making sparks, etc.

Here is a typical schematic for a fuel gauge:

 

[Jennifer "water-wolf"]

Re: Gas Gauge not working

Schematic is VERY useful..., with this I can check it out very quickly...THANKS for helping, I just LOVE THIS FORUM!!..

 

[Don S]

Re: Gas Gauge not working

You should check out the stickies at the top of this forum. There are detailed troubleshooting for the gas gauges.

 

[Jennifer "water-wolf"]

Re: Gas Gauge not working

I missed the 'stickies'.......going to look at them now...Thanks- I'll make a mental note to look in that section first in the future.
Jennifer

 

[achris]

Re: Gas Gauge not working

The most common problem I see with fuel gauges (after loose/dirty/broken wires) is the float arm falls off the sender. Unfortunately you'll need to pull the sender out for that. Sometimes you can retrieve the arm and float, sometimes not.

A new sender is not that expensive, but can be a pain to set up and install. To test the system, just pull the wire off the sender and ground it. The gauge should peg 'FULL'... If it does, the sender is the issue... If you want to put a meter on the sender, it should measure between 33 ohm (FULL) and 240 ohms (EMPTY)....

Chris....

 

[rabristol]

Re: Gas Gauge not working

Quick tip: Rusted rheostat on fuel sender, soak it in vinegar and looks and works like new.