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EL fuel gauge reading over-full always - ideas? 

 

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 Post subject: EL fuel gauge reading over-full always - ideas?
Posted: Wed Dec 12, 2007 10:29 pm 
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Ride: EL 97

Location: Perth
WA, Australia

I have a Dec 97 EL Futura 4 litre with a misbehaving fuel gauge. The gauge mostly shows over-full, regardless of the tank contents, but occasionally also drops under zero for short periods (which appears to be the symptom of an open circuit in the sender connections). It never shows anything other than over-full and under zero.
I’ve confirmed that the sender leads are connected and that the resistance of the sender is roughly around 120 ohms. I also ran the EL diagnostics on the odometer which showed:
Mode 1: Petrol in litres=63, petrol sender resistance=183 ohms
Mode 7: Buffered fuel tank level in litres=58; buffered fuel tank level resistance=8.5 ohms
Some notes:
1. I reckon I must have used about ten litres off a full tank, so it should be have ~58 litres left, so the buffered level reading sounds right.
2. I’m a bit confused about the two resistance levels – they look wrong.
3. I note that in some US motor forums there’s a lot mentioned about fuel “slosh” modules between the sender and the gauge going bad with the symptoms I’ve described….but does the EL Falcon have such a module, and if so where is it?
Does anyone have any thoughts about the right way to fix this. At $179, I’m a bit reluctant to buy a replacement sender if the sender might still be OK! Thanks!
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Posted: Wed Dec 12, 2007 10:34 pm 
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Ride: 2.0 Turbo VW

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Have you checked the needle? It may be getting caught or too close to the dail/face.

Second hand sender?

Slosh module, no this is where the buffer comes in. it reads an average of resistance and displays whats calculated.

 

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Posted: Wed Dec 12, 2007 11:07 pm 
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Hi Krytox,
Tks for quick response.

The needle is completely free - when it goes to zero occasionally or if ignition turned off, it drops like a stone - no interference with the meter housing.

If the average of the buffer and normal resistances are taken for the gauge driver, that may explain why the needle stays in one place....the two readings are 183 ohms and 8.5 ohms according to the diagnostic report - which is quite inconsistent. If one of these is open or shorted and the other is roughly OK, then the average will always be a stuffed-up reading...

A s/h sender may be the go - just a bit nervous about opening up the tank...!

Ian
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Posted: Thu Dec 13, 2007 12:22 am 
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the tanks a piece of piss, use a 5/16th spanner to remove the large hose clamp,

http://www.fordmods.com/forums/viewtopic.php?t=38649

Obviously you have removed the plate to get to the unit to measure the resistance.

Im was sure on some late EL's the inspection plate was tacked in, not screwed. so removal of the tank was the nicest way to replace pump/sender?
or butchering the cover?

either way, when you get to the pump, its a 5 minute change.

 

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Posted: Sun Dec 23, 2007 6:22 pm 
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Well, replacing the sender with a $40 used part solved the problem. But in fact I had two problems: a) loose contact on sender connector resulting in gauge randomly dropping to zero, and b) either a stuck float or a dud sender resulting in the gauge always showing over-full.

Here are some notes for anyone else going this job:

1. The two resistance measurements from the fuel tank sender that are shown in the EL diagnostic displays (on the odometer) are quite different on a correctly functioning sender, so don't think i's a clue that they're quite different.

2. To get the sender out of the tank required me to make a simple tool. I couldn't budge the plastic castellated 'nut' from the plastic tank. After few attempts at moving it I mimic-ed the tool shown in the car manuals. In my case a short piece of one inch square steel tube, drilled at the appropriate width to thread two long 3/8 inch bolds through and have them lock into the two opposite sides of the plastic nut securing the sender unit. Then place hand on tube and spin. It was remarkable how much easier it was with the crude tool :-)

3. It's very easy to get the sender float stuck if you don't orient it perfectly. In fact in retrospect, I reckon the old sender might just have been spun around in the tank a little too much and jammed the float. But that thought occured after I had got the new sender in, so I didn't want to stuff around with the old one any more to try out the theory!

4. The connectors on the sender that go to the gauge were very dirty and also loose - hence the gauge randomly dropping to below empty...that's what happens when the connector is loose. I RP7-ed them and also crimped the clips a little to make them hold better.

5. I had to drop the tank a little to give me more room to undo the pipe clamp around the castellated plastic nut. Rotten job even so, I think that was the longest part of the whole process, undoing the clamp, and then doing it up again afterwards!

Cheers

Ian
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