NO FUEL error on 802a/803a when there is actually fuel in the tank

[zarathustra]

There have been a few questions on how to solve this problem.

I got into it today a little more, and here are some tips.

First, the NO FUEL light circuits are not electrically connected or in common with the fuel gauge. They even have separate sending units..

NO FUEL as well as AUX FUEL PUMP are controlled by the liquid level sensor which is located in the left top of the fuel tank. Note that the fuel gauge sensor is in the right rear top of the tank.

The liquid level sensor has two floats on one unit; each float controls either NO FUEL or AUX PUMP. Each float controls a switch internal to the sensor, and the switch is either open or closed. In the case that the tank is halfway filled the switch for the AUX PUMP is closed; it opens and shuts off the pump when the float determines that the tank is full.

Same condition as above but the NO FUEL switch is normally open; it will close when the tank is empty.

So, if one has a NO FUEL error light when there is actually fuel in the tank, an easy way to test the sensor without removing it is to (unfortunately) remove the rear panel. Disconnect the connector coming out of the sensor -- it'll be two red wires and two black wires running through a white connector.

It will be a four pin connector. The top of the connector has a point on it-- sorta like a roof, and the bottom of the connector is flat. That makes the connector "murphy proof". The top two pins (near the angled edge) are 1 and 2 and are the output of the AUX PUMP switch. The bottom two are 3 and 4 (naturally) and are the switch output for NO FUEL. This can be tested with a continuity tester. 1 and 2 should be normally closed and 3 and 4 should be normally open if the tank is, say half full.

If you don't have a continuity tester -- no problem. Simply disconnect that connector and crank the engine. By disconnecting the connector you simulate an open switch which indicates fuel in the tank. If it cranks over then the liquid level sensor is bad.

Now, just because it is bad doesn't mean it can't be fixed. You'd have to remove the sensor and chances are you will find some sort of corruption or corrosion that is not letting the float move freely.

Note that the switches are inside the aluminum tube on which the floats are mounted, so you can't see the switches when looking at the sensor.

Note that while the liquid level sensor works identically in the 802a and 803a, the sensor itself is not the same for both units.

Hope this helps ----

zarathustra

 

[CDR]

So what's easiest way to remove it from the tank

 

[zarathustra]

If one looks at the liquid sensor, it's an aluminum tube with four wires coming out. Further down there is a nut and at the point where it goes into the tank there is a flange with phillips screws. Loosen the nut first -- that nut is a locking nut that holds the sensor in place. With the nut very very loose the sensor will move up and down somewhat. Move the sensor up maybe an inch or so. Retest the sensor to see if it is now working properly. It could just be badly adjusted.

If it still is bad, remove the phillips screws and pop off the flange from the tank. There's a gasket there, so try not to damage it or you may have to make one. As I remember, I think that the holes in the gasket are not evenly spaced, so the gasket has to be at the right clocking position for all holes to align -- a tip for replacing later.

Between lifting the unit out and moving the flange the sensor should come out with some wiggling.

Once out, the upper float controls the aux pump and lower controls the no fuel. By placing the continuity tester on pins 3 and 4 and moving the lower float you should get continuity when the float is at its bottommost position. By lifting the bottom float a little the switch should open.

There are several locking rings on the sensor. They look a little like "C" clamps, but they're not, they are just tight fitting and clamp on to the sensor body. Those locking rings can be moved up or down. Try to leave them alone if possible, however you might try raising the bottom locking ring just a little bit and re-test the unit. It is possible that the locking ring got moved by jostling around or some previous maintenance.

Since it is apart I'd check the AUX pump float as well. Keep in mind that the two floats perform differently when fully up and alike when fully down.


When replacing, fasten the flange first. Then adjust the depth of the sensor. That is more feel than anything else. I kinda try to not have the sensor resting on the bottom of the tank, but it doesn't want to be too far off the bottom either. Once you get it in the position you want, fasten down the locking nut.

zarathustra

 

[CDR]

This is great info thanks so much

 

[dav5]

My auxiliary pump doesn't shut off. How do I adjust the C clip. Should the upper clip be move up? Or down? Thanks Ted

 

[Guyfang]

Do you still have this problem?

 

[dav5]

Do you still have this problem?[/QUOTe

Guyfang sorry for the delay I haven't had a chance to test it. I just got home and will be leaving again Saturday for a month. If I can't get to it tomorrow it will be awhile before I can get back to you with an answer. I really appreciate your interest and help. Ted

 

[Guyfang]

Ted,

No problemo! When you get around to it, is about fast enough.

 

[dav5]

Since you are nice enough to follow up I thought i better get my ass in gear and go test it. I filled the tank, started the unit and then switched to the auxiliary fuel position. I siphoned fuel out of the tank as it ran to save time and it cycles perfectly. It shuts off at about 80% full. I repeated it 3 or 4 times. Guyfang Thank You so much for your help.

Ted

 

[Guyfang]

You did all the work. All I did is nag.