Low Fuel Light

[MKII]

Hi everybody:

As you may have read from my introduction or my transmission thread, I am new to Mark II's, so I have an extra doubt with my car.

If I understand correctly when the ignition switch is turned on, the red arrow on the instrument cluster lights up. Once the car starts and has oil pressure, it quits lighting. My car did that, until last night, when it lighted up when I stopped the car, and everytime I opened the switch and started the engine. I feared oil pressure problem and not tried it again, but then again, this morning the light just didn't went on any more, prior to or when starting the engine but the engine made not a sign of any problem (I used it carefully watching for noises). So apparently, my light is not working any more. I suspect I have no oil pressure real problems as it made no noise at all and used it for about 15 miles (I guess I could have broke the engine if there really was an oil pressure problem).

One other thing. When I open the switch the needle in the oil pressure gage automatically goes up, well past the 80 mark, and stays there for the whole time the engine is running.

Any suggestions as to where should I start looking for the cause of the problem?

Thanks,
victor

[Barry Wolk]

The arrow is a low fuel indicator. Be glad yours works, most don't.

[Barry Wolk]

The oil pressure gauge sending unit is probably at fault. It's probably shorted. Disconnect it and see if the gauge goes to 0. Sending units are cheap. Gauges are not.

I'll post the schematic soon.

[Shelly Harris]

I haven't had guts enough to ride on "E" and see if the red light goes on. Someday I'll put a filled gallon can in the trunk and see if it ever lights up. Anyother way to test it?

[Barry Wolk]

You can probably test it by disconnecting the sending unit. There an access hatch in the floor of the trunk.

I'm having trouble with my scanner right now. The schematic should tell us what we need to know.

[Mad Scientist]

When you first turn on ignition the arrow is suppose to light up for 2-3 seconds telling you the light bulb is OK.
If it stays on then you are low on fuel.

Mine lights up with key on but goes out even with a completely dry tank.:(

Looking at the schematic there is an "S.I.P. relay" in the fuse box that controls this function. It and the fuel gage are reading the signal from the tank sender. If the fuel gage is reading OK then the problem with this relay.

[Barry Wolk]

http://i244.photobucket.com/albums/gg18/barry2952/1%20Mark%20II%20docs/sc02c5db2f.jpg

[Barry Wolk]

I blew up the schematic for the SIP relay. Are they depicting relay coils or bi-metal switches, like blinkers?

http://i244.photobucket.com/albums/gg18/barry2952/1%20Mark%20II%20docs/sc02c5db2f-1.jpg

[Mad Scientist]

I have not taken mine apart but I would assume they are bi-metal. However I did take the tank sender apart to clean it and it was a bi-metal unit, thus I would expect the entire circuit would work using the same system.

[MKII]

I am embarassed to be asking such dumb questions. So, the light that I assumed was from oil pressure is really the low fuel warning light, and it was working on my car, lighting up for 2 or 3 seconds when opening the ignition switch. My gas gage isn't working, so far, and it is one of the last details I need to correct.

I will check on the oil pressure sender or change it, and that should solve my problem.

On the fuel light, thanks a lot for the diagrams! I will try to see if I can make it work again, together with the fuel gage.

Victor

[linmk2]

One area that is rather easy to check is the wire attached to the sending unit. Remove the trunk carpeting and you will find the access cover on the trunk floor. Remove the cover and there is the sending unit. You will see a wire held in place with the screw. Remove the screw and clean the wire connection and the top of the sending unit where the wire connects. I would use contact cleaner rather than sand paper or other abrasive. No use to temp fate with sparks. While you have the wire off, get a friend and have them sit in the car. Turn the key to the 'on' position and ground the wire to a non painted body part. If the gauge is working, your friend should see it. The gauge should start to move when the wire is grounded. As soon as the gauge starts to move, if it does at all, remove the wire from the ground quickly. I would be very surprised if your low fuel light works correctly. Mine does turn on for a few seconds, then off, but that is as far as it goes. If the gauge works when grounded, you at least know the gauge and associated wiring is working correctly. That would leave the problem with the sending unit. Hope this helps. Good luck

[MKII]

Howard and all:

Thanks for the descriptions and for the diagrams!

I did it as described and luckily, my fuel gauge in the dashboard is working fine, and there is no problem with the electrical harness. Problem turned out to be a tiny hole in the sending unit float, which filled itself with gas, so it was stuck to the bottom of the tank for who knows how long.

Probably that did it with the SIP relay, which we also checked. It is completely fried now. It did work when I started using the car, at least the red light going on for 2-3 seconds, but old age or the gas tank sending unit problem may have had to do with it's demise.

We are in the process of cleaning sending unit, patching the float, and should have the gas gage working fine in a few hours.

Anybody has a SIP relay they would be willing to sell?

Otherwise, I can live with no red light in the dashboard for a few seconds, but it sure looks nice when you open the ignition. I'd love to get the system running again. In the meantime, since apparently it does need the SIP relay to be in place for the gas gauge to work, we are doing a direct conection between the two cables needed (black and yellow-red).

thanks,
Victor