Right, I've run in out of fuel twice in the silver car, about 10 miles or so after the reserve light comes on, when the needle is only just starting its descent town to the end of reserve. The gauge is not working like I expect it to so I have been messing in Tech 2.
The activation of the needle by Tech 2 correctly places its position
I understand there is a global adjustment, and then individual calibration adjustment at certain points.
Anybody know how the "increase" / "decrease" translate into the reading of the gauge, or how to interpret "Fuel level (ECM)" and "Fuel level (Calibrated)"
So in other words I can see where to make the adjustments, but am unable to observe a visible change in the fuel gauge, so don't know if I making things better or worse.
I am trying to avoid draining the tank to go through the WIS procedure ....... but in a sense that's a bit of a false objection as I have obviously already done this twice :-[
I have already read that there may be an issue with baffles coming loose, but these symptoms would not seem to fit with a physical blockage, as the point where the reserve light comes on would seem to be correct.
For reference I just looked at the green car and the settings there are 2 0 1 0 0, reading top to bottom.
Thoughts ?
If you know your mpg figure is accurate (on a couple of brim to brim fills) then you can start from a full tank and work out the fuel consumed, read the actual values at the theoretical set points and then set a suitable offset.
The problem is I don't understand which way the adjustment works.
If I was to set the adjustment to +5, which of these statements is true?
A, Resistance reading indicates there is 20 litres in the tank, +5 means show 25 litres on the gauge; or
B, Resistance reading indicates there is 20 litres in the tank, +5 means the gauge is over-reading by 5 so move the needle to where 15 litres should be
I was hoping I could just go to the extreme and see a difference, but that cunning plan has not worked ::)
Bright idea. Does ECM mean Engine Control Module ? (as I just think ECU), so ECM is the base reading from the resistance, and calibrated is where the needle should point to on the gauge ?
IIRC there are two values that you see on the "read" display- actual and filtered. So I guess you just try the offset plus or minus and see what it does to the filtered value (which is the one the display and DTE uses)
Messing about on a different car now, ignition on engine not running:
Starting point, set to -1, sender showing 3.0v
ECM: 62 litres
Filtered 62 litres
Changed from -1 to +3
ECM : 66 litres
Filtered 62 litres
Distance to empty did not change, unsurprisingly, at that part of the fuel gauge scale 4 litres is not visible.
My logic tells me that the MIU is getting a "filtered" value from the sender, and it is then telling the T7 ECU a different, bigger value, and also making consequential changes to the needle position. I expected DTE to change, as I see DTE as litres remaining x miles per litre. Looks like T7 does not.
That would seem to be the "wrong" way to go if you don't want to run out of fuel ?
Quote from: carrera on 17 April 2020, 03:24:56 PM
My logic tells me that the MIU is getting a "filtered" value from the sender, and it is then telling the T7 ECU a different, bigger value, and also making consequential changes to the needle position. I expected DTE to change, as I see DTE as litres remaining x miles per litre. Looks like T7 does not.
With T7 that the DTE is only calculated periodically when driving, the reason is that if the value changed constantly it would mean as you accelerated your DTE would drop massively and then if you went down a steep hill it would go to infinity. I can't remember the update interval though but did you actually take the car for a drive after changing the value and resetting the DTE?
It does drop massively when I boot it :Fawlty: :thumbsup:
Experience tells me that the DTE is updated fairly regularly, but with a smoothed recent average MPG, rather than instantaneous.
It's also fun to clear the calculation when you are doing say 60, then let the car coast and suddenly you can see 99.9 mpg on the SID. Little games :)
I didn't take the car out for a run as I didn't want to change the test conditions, as soon as the car was started the internal mpg would have started dropping DTE dropping and then would go up again as the engine got warm. Probably just an invalid expectation from me for the DTE to immediately change with the fuel level "change".
Maybe a bit of overthinking or logic overload :)
I was working on my car, and the engine had been ticking over for a while. I got in to turn the engine off when I saw a photo opportunity. It was not long after I bought the car. The mileage is over 150,000 miles higher now...
I did read the bit in WIS on the DTE. It's an accumulation of weighted averages. A bit of instant, a fairly large % of the last 10 mins, and other %ages of older consumption. Something like that.
Thanks for that.... fits with my gut feel too. However is this a start of a competition for the worst mpg on a car :)
Postie still hasn't been so I might end up doing a tank drain over the weekend after all
The post seems to be a mess at the moment. I ordered a new battery charger/conditioner on Good Friday. It was listed as "dispatched by First Class post" by the seller on Saturday. It's still not here. The sharkfin I ordered a week or so back took nearly a week to get here by First Class post.
The sharkfin seller has since posted that he leaves the packages at his local post office, but he found out that the Royal Mail are only collecting from the PO three times a week, rather than twice a day. Mine was left at lunchtime on a Friday, but not collected until the following Tuesday...
The package that is currently awaited, may have been left at a PO on Saturday, but due to Easter holidays, it may not have been collected from there until the following Wednesday...
I've found the DTE info from the WIS. It's not as I remember it.
The SID uses the following sources: Fuel level, Miles travelled, Fuel consumed (from ECU), Coolant temperature. It's updated every 16 seconds.
but... no update takes place when starting from cold or when the speed speed is below 5km/hr. When reset, the starting value is calculated using 1 litre/10 km.
Postman brought the package this morning. So a whole week from posting to arrival for First Class post. Battery is now on charge.
Postman brought two packages this morning
Power supply is in the car and does clear error P0826, so later TCM's can be used in a 2002 car with this mod.
I'm about to shuffle cars about and will look at the fuel gauge again, then it'll be a siren repair with the other package.
I decided to drain the fuel off.
Believe it or not, the first time I tried this on a 9-5 I managed to syphon it off. no luck this time, so as I don't have the tool to disconnect the fuel lines easily I decided to remove the pump to put the drain pipe in.
Wise choice !
Someone has been in here before, and the pump body was no longer attached to the cover plate by the spring plate. So, resting on the botton of the tank probably, and probably stopping the float moving fully down.
I cleaned the contacts and it has a nice full range from 50 ohms to 425 ohms.
Now I just have to try and reassemble it, and hope no damage was done in the previous bodgery
I think that's the problem anyway, need to find a decent picture of a good one
Further progress
I realised I didn't need a picture as I had a pump on the shelf :-[
That was revealing, someone had definitely been here before. Either the suction or return pipe was placed over the breather, blocking the correct route for the metal connecting spring ::)
Fixed that, bonded the metal to the top plate with araldite type resin and reinstalled. Well, I did after figuring out that the infamous baffle was lose, so I manipulated it into place and hope it holds
The gauge still showed 10 litres, even though the resistance was 50 ohms. I cleared SID and did a power cycle and at last Tech 2 could see an empty tank.
Put 5 litres in, still empty
Put another 5 litres in, still empty
Long story short.... after checking the rest postion of the float on a flat surface, replacement is not the reverse of removal, you have to have the alignment mark at the 90 degree position as WIS says, otherwise the float jams somewhere
So, after resetting to factory value and subject to tweaking tomorrow, I think we're sorted
Well done! :)
If you get all this sorted, what will you do for the next three weeks? :)
Oooh I have plenty to do, not just Saabs, and some work too, hopefully
Aero engine rebuild ("noisy tappets")
Sirens
SIDs
Two Aero service kits for green and grey
2.3t estate rescue (not mentioned this yet, needs sump drop, oil filter, noisy, thought chain at first, but maybe just a pulley
Now that the shed and fence are substantially complete, I have to sort out the passenger seat movement switches in the 9-5. The front up/down is not working.
The Carlsson needs the drivers seat belt looking at. It's become slow to retract. I thought that that problem, which was common on the early cars, had been sorted. I also have to take the bumper off again to fit a new headlamp bulb. We were driving around last month and I noticed that one headlamp looked yellower that the other, when it lit up the car in front of us in the traffic jam. A further check showed that it was indeed dying. I've also got to source a different mount for the iPhone in the Carlsson. SWMBO uses Waze now, rather than the OE satnav which does not really have any effective traffic info on it.
Fingers crossed on the seat it is just the connector that is coming loose. Had that on the green car, but it affected all controls. The best bit is this is just simple electrics, no bus messages to be fiddling with..... unless that changed for the DE
Headlamp off to change a light bulb ? Seems faintly ridiculous to me, a bit like removing the bonnet to change spark plugs, what were the designers thinking?
The headlamp bulbs can be done in situ with small hands, but it's very awkward. If you have large hands (and a bit of arthritis) the job is really a choice between removing the bumper and headlights, or removing the air box and pipework on the RHS, and the wash bottle tube and battery on the LHS.
If you fiddle about and try and do it with fingertips, things can get bent. I did that years ago on my old Rover 600 and the bulb wasn't seated properly. Things got very hot with the poor earth and the headlamp casing melted out of shape!!
I don't have small hands (well, that's what my girlfriends said) but never had a problem with bulbs. I don't have the added complication of arthritis though.
I was going to do things on the cars today but both involved working with the doors open. The wind was so strong that it wasn't safe. The doos kept blowing shut .
So I had a look to see if I really could do the headlamp bulbs without removing the bumper. And I can't.
Even with the washer tube removed on the LHS there's a loom to the extra fuse box in the way, and on the RHS there's an aircon pipe very close. I think the V6 is a bit more tightly packed than the other cars.
Finally since the caps have been on for 10 years untouched, I can't turn them the required quarter turn to get them off. They're seized, so when the wind drops, the bumper and lights wiil come off and the filter removal strap used to undo them.
It does look a bit tight. A splash of WD40 into the contact area can help the plastic rotate, just like with the red connectors that get stiff with dirt
I guess there's no fix for the height adjustment yet either then.
The fuel tank seems to be behaving itself. The gauge is nearly at the bottom, and Tech 2 thinks there is 2 litres left. Mind you, it said 2 litres when I left for home and she consumed 1364 ml fuel on the trip.
DTE says 16 miles
The resistance reading tells me there is a little bit more in the tank, but I'm not too bothered about that, an extra 3 or 4 litres may come in handy at an important time.