Fuel Sender

Hi everyone..hope all is well.

Does anyone have or know of where I can source a replacement fuel level sender? Removed you can hear the float move and the resistance is correct with 8ohms min and 380ohms max. With the sender back in the tank and 3/4's full the resistance is only 11ohms. It would seem that the sender is working when forced, but the fuel isn't moving the float, can these be repaired?

Any help would be much appreciated, if a known good 2nd hand or new is available, please let me know.

Thanks in advance, much appreciated....

Hi Matt

Can I take it your Alp is pre 1990 as there was a change of sensors then ?
Firstly ..... have you done a Full Computer Reset ? ........ just in case you have not,.... with sensor back in Alp and connected up ..... Disconnect Battery ... Press and hold the reset button for 20 secs (reset button is at bottom of Rev Counter) ... Reconnect battery .... press reset button momentarily once more ..... see if that cures your problem.
If you want to check the sensor, ...... having removed the sensor, make sure the float is at the bottom .... connect your meter to the sensor and slowly lower into tank and see if the resistance changes as you do so.
Let us know how you get on

Hi John,

Thanks for your reply. Yeah I've already removed the sender from the tank and measured the resistance as above - so tipped it upside down over 300ohms, right way up (empty) 5-10ohms. I've not completed a computer reset as the sender is still under range with the computer/field wiring disconnected. I think I have fuel guage issues also (separate issue really) as with a 250ohm resistor connected across the female connector the LCD fuel level is still only 4 gallons.....Oh and yes pre-90, its a 1988.

Cheers and any thoughts let me know

Matt ...... apart from the computer reset ... which is a must each time you do anything to the instrument panel .... the sensor can be taken apart .... I have not opened a pre 1990 type, but others have and from what I remember, there is a spring like coil of wire linking the float to the top, that often gets detached from the float .... not in your case, as you are getting varying readings, but the float should be checked .... again I am not too sure what the float is made of, but if it is hollow, there might be a pin hole in it which has let fuel in and as a consequence it might not be floating where it should .... worth a look. If it is similar to the post 1990 type, there should be a small nut at the bottom of the sensor which once removed, the whole tube can be slid off.

I have had my pre 90 one apart as it didn't work at all after being laid up for six years or however long it was, John is correct in that it is a long (brass looking) spring that coils down and connects to the float making contact with the central variable 'rheostaty' bit.
I have found that basically the float gets stuck when below 4 gallons, well sticks.........if I keep it above that perhaps 6 six gallons plus it works great and is pretty accurate, below that level and it's a bit hit and miss and if I let it drop below 4 then it will go haywire and it'll take a proper filling up and a day or so for it to get back into its groove.

When I took it to Dieppe, I was brimming it as soon as it dropped to 6ish gallons and had no issues, but now it's back home, not racking up miles and with other thirsty tanks to feed I've let it slip down to 3 gallons, so you can bet if I put £30 in or so it wouldn't move until I'd run it round and then all of a sudden it'll jump up to 6 or 7 gallons and I wouldn't be sure what was really in it.
Ahh......... joy

In a long winded way I'm saying bite the bullet and brim it, and see what happens, It'll improve the handing if nowt else.

The Spring is a wire that connects to the float, they often break with age.
Seperate and check inside, you can resolder! (But it does make you think, being submerged in fuel, not for the faint hearted)

Dave

This may be of interest to some owners. I drew this out some time ago showing the difference between the pre 1990 and post 1990 fuel sensors.
It is interesting to note that they both work in different ways ..... one has highest resistance when full, and the other has highest resistance when empty.
With both of these, due to them working with relatively low resistances, the end resistance readings are not set in stone ..... expect them to be slightly plus or minus the shown readings .... even the resistance of the meter leads can add as much as an ohm with digital meters.
Anyway, for what its worth, here is the drawing.

as with a 250ohm resistor connected across the female connector the LCD fuel level is still only 4 gallons.....

Matt - I'm not sure if you're aware, but the way the GTA computer calculates the fuel uses an odd logic. The gauge will only read a new increased value when it sees the predicted level of fuel in the tank go up - e.g. you've put extra fuel in.
The rest of the time it uses the flow meter on the atmo (correct me if I'm wrong JohnC) and the maths from the Renix ECU (in the case of the turbo). Basically it works out how much fuel is being used and subtracts it from the number it last registered when the ignition is switched on. Even if the level is lower, that won't be taken into account as the system sees that as spurious - where else can the fuel go other than normal use.

Hence why JohnC's comments about a reset are important in the context of fuel and the computer.

There is a diagnostic mode that allows the system to constantly register the fuel used (until you re-start from memory). I'll see if I can find the thread. Hope that helps...?

Hi guys, thanks for your replies. Interesting info and much appreciated. The 250ohm resistor was used only to mimic a circa 3/4 tank of fuel, must admit I didn't think of the reset. Will try the reset with the resistor in place, please have patience with me, time is tight especially with juggling work/family life (I know I'm not alone with this!).

The fuel sender definitely needs to be repaired/replaced, but I'm also aware that the trip computer has issues, so one step at a time...interesting the things you find out about a car after you buy it - broken dip stick tube springs to mind

Just as an example, I set off for RATS on Saturday morning, which is a 40-50 mile round trip from home with the gauge reading about 3.6 gallons and by the time I got home I was down to 2.2 I was only bimbling along with a bit of a blast nearer home, so about right.

Thought I ought to put some juice in later that night so I put twenty quid in, which by my rough calculations is about four gallons.
Gauge never budged...........until this morning it had gone up to 9.2!

Battery off and reset and it now reads 6.3 which would be about right from what the gauge read before filling up, looking in the tank I would say it's about half full at that and If I remember correctly about 13 is full?

My car spends a lot of time with the battery off, and then back on ( I don't like leaving cars for a week or more connected) and don't always reset the computer.
But under constant use after resetting it and keeping the tank half full or more, it seems reliable and accurate enough.
I always reset the trip after fueling any car or bike and then I get an idea how far I can go anyway, but also if any of them get thirsty without hammering them it highlights a possible issue that has yet to cause a breakdown or mishap, but could indicate something is going south.......