06 Passat diesel problem fuel starvation with electronic glitches

Bigus

Ok this is a question aswell as an answer

06 Passat diesel runs out of fuel.

As it stops all warning light s come on.

put fuel in car,car starts after much turning over

Engine Runs but all warning lights are on ..... no oil pressure STOP refer to Manual. Parking brake failure , engine light on , emissions , anti skid light on ,glow plug light on etc etc.

I'm told that this is common and told "computer goes mad when they run out of fuel"

i'm told to put key in ignition and scroll through computer via column stalk a few times as this sorts prob.

Low and behold carstarts on the button unlike before and runs fine for 20 mins

Conks out while ticking over & sounds like fuel starvation to me.

I then think maybe still low on fuel so put more in.

Same again.. slow to start but fine if i scroll through trip computer.

So now i change fuel filter in case blocked by dirt.

No water no dirt.

Seems to run better with new filter ....happy days .

Short drive ...... conks out .... restart symthoms of fuel starvation;car drives crap, and when all the warning lights come on after stalling drives a bit better, but telling me no oil pressure STOP.

Go to my indy VW mechanic ..... diagnostics say crank shaft position sensor(sort of ) so fit one with much hassle. car drives fine and subjectively seem much smoother ...until, slight stalling 20 mins later under light throttle.

nursed car back to vw mechanic & stalling gets worse until all warning lights come on ie. oil pressure asd , parking brake etc etc and rev counter stops working.however car drives better after warning lights come on.

Diagnostic computer now says engine rpm sensor faulty (not crank shaft sensor)

Late on friday evening(garage closing) so i say i'll check in tank low pressurre fuel pump and pick up to male sure its not blocked over week end.

Car drives fine on the extended long way home.

Go to take out in tank fuel pump/fuel gauge/ and find it and whole 6 gallons of fuel at about 30 to 40 deg C.

White pump housing all quite blackened but not blocked.
Last word from pub is that there is another filter in -line after tank and this could be blocked causing Pumpto over heat.

DISCUSS !

mathepac

OK long shot.

Unused fuel (not injected into cylinders) in a diesel engine is recycled back to the fuel tank. On its journey through the injector piping and back to the tank it gets heated. On its journey forward again it passes through a fuel-cooler, a type of small rad in-line with the low-pressure fuel feed from the tank. The fuel cooler is usually visible from underneath the car on the driver's side somewhere between the driver's seat and the rear passenger seat.

I would guess that the car is over-fuelling (caused by an air-lock of some kind in the fuel-lines?) The excess fuel cannot get cooled to the optimum ignition temperature with the small quantity of fuel in the tank and the fuel cooler cannot compensate, so the fuel gets hotter and hotter the longer the car runs Contrary to popular belief diesel fuel ignites optimally in a diesel engine when the fuel is cold - 30/40 degress is way too hot.

For a test, how would you feel about filling the tank and testing my theory? Please note that what I am suggesting / describing is a symptom of another fault which will still need to be identified and resolved and I'm not sure what the underlying problem actually is.

The blackened fuel could be attributable to heating, but the fuel filter should be well able to cope. There may be a primary fuel filter between the tank and the fuel cooler, but AFAIK it doesn't require replacement / servicing other than in extremis, which I suppose this is.

I'm guessing this is the 1.9 PD engine rather than the 2.0 CR.

Bigus

Yes 105 bhp 1.9 PD
Thanks mathepac for the reply
There's halftank of fuel in it thats heating at the moment.
I will have a look at that in line filter and coooler this morn and report back.

shamwari

Bigus wrote: »

Diagnostic computer now says engine rpm sensor faulty (not crank shaft sensor)

Engine RPM is usually sensed via crankshaft sensor. What fault code did it generate?

Bigus wrote: »

White pump housing all quite blackened but not blocked.

Might be a red herring especially if the car is old.

Bigus wrote: »

Go to take out in tank fuel pump/fuel gauge/ and find it and whole 6 gallons of fuel at about 30 to 40 deg C.

Last word from pub is that there is another filter in -line after tank and this could be blocked causing Pumpto over heat.

How did you measure the fuel temperature? Fuel at temp should not cause you problems.

I've never heard on an "inline" fuel filter except for the primary filter under the bonnet, UNLESS there is a local gauze or mesh filter within the pickup of the LP pump itself.

ALso this notion of a cooler is something I've never heard of before. I mean, diesel gives problems with viscosity when it gets too cold. In fact, many if not all diesels have a small heater embeded within or close to the fuel filter to prevent waxing in winter. The idea of a cooler doesn't add up to me

mathepac

shamwari wrote: »

...
ALso this notion of a cooler is something I've never heard of before. I mean, diesel gives problems with viscosity when it gets too cold. In fact, many if not all diesels have a small heater embeded within or close to the fuel filter to prevent waxing in winter. The idea of a cooler doesn't add up to me

The engine in OP's car is a VW PD (unit injector) engine and it operates on different principles to common-rail (Fiat) injector systems and a fuel cooler is common to all PD engines IIRC.

Engine codes fitted to that year's Passat are (I think) AVB,AVF,AWX, BGW and all of them incorporate fuel coolers due to the extreme pressure in the unit injectors for the same reasons that turbo systems incorporate inter-coolers - fluids under pressure heat up and expand. In order to optimise engine performance both air and fuel need to be cooled down again. In the case of the PD engines, as I pointed out above, it's the returned fuel that needs to be cooled.

The VW part numbers for the fuel-cooler common to those engine codes is 3B0203492A and I think the temperature sender unit 038906081B is common as well. Don't quote these partnumbers for the 2006 car as they are from partial 2005 documentation and while there were only some changes, the parts may have been superceded.

PD is different to common rail and lots of people are not unhappy that VW is gradually replacing all the PD engines across their range.

If you want to bore yourselves to death with technical detail, register with this site http://www.vagcat.com (it's free) and browse online VW parts catalogues and diagrams.:D

shamwari

Many many thanks for that! Crikey I was totally unaware that fuel cooling was being employed. It totally flys in the face of everything we were thought about diesels!!!

I here what you say about liquids and their expansion and heating when under pressure, but as some common railers are operating at around 2000 bars, why do these have no apparent need for cooling? I'm amazed and confused at the same time!!:)

Esel

shamwari wrote: »

I'm amazed and confused at the same time!!:)

You're confazed!

mathepac

OK, I'll risk a mod finger-wagging for veering wildly offtopic, with apologies to OP.

CR systems must have some means of returning unused fuel to the tank and if they do that they must have a means of reducing the temperature, as if the fuel has been up to the engine in the CR fuel line it must have picked up heat, but as I know feck all about them, I don't know how they manage to cool the redistributed fuel.

All ICEs are designed to operate at an "optimum" temperature; for arguments sake let's call that 90 deg C. The requirement in an ICE is convert the energy from the ignition of the fuel/air mixture into motive power in order to supply the road-wheels with the greatest amount of power for the lowest possible expenditure of fuel. Unfortunately, petroleum mist and air explosions generate a lot of heat which must be conducted away from the engine by cooling fluids, usually a water/anti-freeze solution, lubricating fluids and air. This energy is totally wasted, the heat leaving the vehicle via radiators etc.

One partial solution to this heat /wasted-energy problem is to inject a water-mist or a water-methanol solution (windscreen-washer fluid) into the cylinders with the diesel/air mixture in order to cool the cylinders, improve the ignition efficiency of the fuel and thereby reduce noxious emissions and improve diesel mpg figures. Water or water-methanol used this way actually burns as part of the ignition cycle. These systems are common-place on HGVs in North America where diesel prices at the pumps tend to be higher in most places than petrol and emission control requirements are very stringent in certain states.

Slidey

There are also fuel coolers on the Merc CDI engines (a big plastic spiral of pipe beside the tank) and afaik there is coolers bolted to the floor of some of the Peugeots.

Bigus

Update Problem solved.

Removed ECU and sent to uk checked out fine,

Checked flywheel interface with crank shaft sensor (already replaced) fine
Replaced high pressure pump with borrowed one problem still present.
Removed injectors and got tested .... fine

Ended up re wiring Crank shaft sensor directly to ECU as on other vws before problem solved.

dotz

isnt it amazing how much electronics have f**ked up cars these days. studied auto electrics for a bit and you just dont realise how much every bit of the car is dependant on electrics. if one small thing goes down the car shuts down.

sorry, just a bit of a rant. :-)

Bigus

dotz wrote: »

isnt it amazing how much electronics have f**ked up cars these days. studied auto electrics for a bit and you just dont realise how much every bit of the car is dependant on electrics. if one small thing goes down the car shuts down.

sorry, just a bit of a rant. :-)

Absolutely ... Passat computer was going nuts.

Kenneth Marron

Bigus wrote: »

Ok this is a question aswell as an answer

06 Passat diesel runs out of fuel.

As it stops all warning light s come on.

put fuel in car,car starts after much turning over

Engine Runs but all warning lights are on ..... no oil pressure STOP refer to Manual. Parking brake failure , engine light on , emissions , anti skid light on ,glow plug light on etc etc.

I'm told that this is common and told "computer goes mad when they run out of fuel"

i'm told to put key in ignition and scroll through computer via column stalk a few times as this sorts prob.

Low and behold carstarts on the button unlike before and runs fine for 20 mins

Conks out while ticking over & sounds like fuel starvation to me.

I then think maybe still low on fuel so put more in.

Same again.. slow to start but fine if i scroll through trip computer.

So now i change fuel filter in case blocked by dirt.

No water no dirt.

Seems to run better with new filter ....happy days .

Short drive ...... conks out .... restart symthoms of fuel starvation;car drives crap, and when all the warning lights come on after stalling drives a bit better, but telling me no oil pressure STOP.

Go to my indy VW mechanic ..... diagnostics say crank shaft position sensor(sort of ) so fit one with much hassle. car drives fine and subjectively seem much smoother ...until, slight stalling 20 mins later under light throttle.

nursed car back to vw mechanic & stalling gets worse until all warning lights come on ie. oil pressure asd , parking brake etc etc and rev counter stops working.however car drives better after warning lights come on.

Diagnostic computer now says engine rpm sensor faulty (not crank shaft sensor)

Late on friday evening(garage closing) so i say i'll check in tank low pressurre fuel pump and pick up to male sure its not blocked over week end.

Car drives fine on the extended long way home.

Go to take out in tank fuel pump/fuel gauge/ and find it and whole 6 gallons of fuel at about 30 to 40 deg C.

White pump housing all quite blackened but not blocked.
Last word from pub is that there is another filter in -line after tank and this could be blocked causing Pumpto over heat.

DISCUSS !

It's you wiring going to you tdc sensor it has a break in it just repair it and your done . It's difficult to access ,

colm_mcm

I hope the OP got sorted in the 2 years since they posted




The End.