The Red battery light of Joy - Page 4

Nognar · #31 9th November 2020, 04:30 PM

Its an interesting post but for me I ran out at half a tank before I changed the pump but after the battery/ alternator died. Though it could be pump died in the first instance, then when replaced it did not seat/ seal perfectly and its sucking up air.

Currently plan is to circle locally burning off fuel to see what happens, good news is an S8 on short journeys can be quite thirsty so it should not take long

Luckily the car is a "Hybrid" as its got LPG so I can swap over to get me home when it happens, also with a Jerry Can in the boot I also consider it a Range Extender.

Nognar · #32 13th November 2020, 02:48 PM

Currently still circling in Sport mode locally like a Jumbo Jet burning off fuel to see what happens.

Previously the car stopped and would not start again with a little over half a tank of petrol.

As of now its running on petrol no problems with a little under half a tank so we will see!

Nognar · #33 15th November 2020, 09:05 AM

Long drive yesterday and still going strong at now under 1/3 tank

Though of course it was all going too well...

Drove through a puddle and and the speedo died which is far from helpful, P0501 code on VAGCOM now with a failed Vehicle Speed Sensor. Never mind another job to do, I am assuming this is the one around the gearbox?

VAGCOM also confirmed no speed signal either is coming through.

ABS sensors all working and OK from each of the four wheels so I don’t think it’s that. Also without a working speedo, whilst everything else on the dash is OK it really upsets the fuel gauge without that speed signal.

MikkiJayne · #34 15th November 2020, 09:13 AM

Rather odd that the speed signal affects the fuel gauge

Its just a resistance driving a gauge.

The VSS might just be a wet connector. Its on the left hand side just above the output flange.

Nognar · #35 15th November 2020, 09:24 AM

Thank you I will take a look.

Fuel gauge is fine at standstill then when driving it bounces up and down like a slow old fashioned VU meter on a hifi. My thoughts were it maybe needed a signal from the speedo to work out range and it was getting upset.

I may order a new speed sensor anyway, does anyone have the right part number?

MikkiJayne · #36 15th November 2020, 10:05 AM

The VSS is 01F409191.

The fuel gauge has a conditioning circuit to reduce its response time so it doesn't jump up and down as the fuel sloshes about so that behaviour is also slightly odd.

What are the interior lights doing while the car is running? Do they pulse at all or are they stable?

Nognar · #37 15th November 2020, 10:22 AM

Everything else is ok and interior lights all ok.

I will leave it for a day or two to dry out and have a look, I will also order a new VSS also just to cover that.

Nognar · #38 15th November 2020, 01:01 PM

Yep still bouncing when driving and putting on the brakes etc.

As mentioned it only started to do this after the Speedo died, though its driving Ok and not running out of fuel which is a bonus.

I will replace the VSS and then perform an Exorcism.

MikkiJayne · #39 15th November 2020, 01:14 PM

I wonder if part of the conditioning circuit does have a link with the VSS so that it slows the response time of the gauge when the car is moving? Perhaps if it is stationary the circuit is disabled so that you get a quick response when filling with fuel, and so with the VSS broken its just showing the fuel sloshing around.

It'll be very interesting to see how it behaves with a new one

Nognar · #40 18th November 2020, 04:27 PM

Evening all and an update.

The VSS/ connector has clearly dried out and now the speedo is working again. With a working speedo I can confirm the Fuel Gauge works and remains steady. It does not move around as the petrol was sloshing about as I had before with no speedo.

Secondly the car has run into the petrol reserve with no problems which is good news.

I will keep an eye on it and make sure I always have LPG also just in case.

But to confirm this is what I think happened.

Regulator in the Alternator wore out and gave a red battery light, in turn this drained the battery and during this low voltage period it killed off or at least upset/damaged to some extent the old fuel pump. When starting the car again it drove for a short time then died on half a tank of fuel and would not start again. New fuel pump put in but still would not start though all connected, power was going to it and had half a tank of fuel. Refitted everything, checked it all and its seating etc to make sure and still no luck. I then topped the petrol tank up 100% and it started fine and has been driven and used a full tank of fuel with no problems at all.

So my thoughts are as suggested putting more fuel in allowed the pump to be primed/ filled the bowl/ pickup/ remove airlocks and at that point it worked fine.

So time to drive it more