Misfire then cut out

Hi, i have a VW Polo PD100 that was sat for quite a while and i never topped up the tank. I changed the oil and filters and had it running on my drive for a total of about 2 hours, no problem. I then drove the car to work, again no problem. But when i started it for the trip home it started misfiring and then cut out and i haven’t been able to get it going since.

I scanned the car for dtc’s with VCDS and none appeared for the engine control module, so i assume the issue must be with the fuel? Especially as it was sat in the tank for around a year. I’m thinking maybe the lift pump sucked up some dirt at the bottom of the tank and pumped it into the fuel system.

I put a pipe onto the lift pump and pumped all the old fuel out and filled the tank with new fuel, i also emptied the fuel filter and filled with new diesel but still no joy. I then brought some redex fuel cleaner and filled the fuel filter with it, i cranked the car for a good while hoping the redex would clear the lines but again still no luck.

I have just removed the tandem pump and injectors and blew compressed air through the feed and return channels, cylinder 1 and 2 were initially blocked but managed to clear them. I have just rebuilt the car but again no joy!!

I am now thinking to remove the tandem pump again and blow compressed air through the channels while turning the engine over by hand to open the injectors.

I am selling the car so i am reluctant to purchase any new parts for it. Can anyone help out?

Check the timing belt before you dig too deep. The last PD that came to me had identical symptoms. Started running rough - then stalled at idle and wouldn't restart. Jumped a tooth or 2. Enough to prevent starting, not enough to cause damage.

No codes either.

gforce1108 said:

Check the timing belt before you dig too deep. The last PD that came to me had identical symptoms. Started running rough - then stalled at idle and wouldn't restart. Jumped a tooth or 2. Enough to prevent starting, not enough to cause damage.

No codes either.

Click to expand...

Just what i was looking for thanks. I thought it would throw a cam or crank sensor fault if the timing was out, will check tomorrow.

So checked the timing and the crack and cam both lock in the same position so it hasn’t jumped any teeth. Thinking maybe i could try adjust the torsion valve, can i see what it is currently at if the engine won’t fire?

I would think the 'torsion valve' (value?) was OK before it should be OK now.

Do the normal dash lights come on including the glow plug light (for a second) ?

I'm wondering if it's a fueling problem.
Is the filter full now?

Do you hear the fuel pump in the tank running when you turn the key on?
If so cycle the key on & off several times to try to fill the filter and prime the Tandem Pump.

Yeah the cluster lights up as normal. I managed to get a cam sensor fault code (G40) but only once and it now only comes back on if i unplug the sensor. I then went on to check the crank sensor but even when its unplugged it doesn’t show a code.

I then checked the wiring to the cam sensor and i am getting ground, 12v and 5v all good. Strangely when i went to check the crank sensor wiring upon checking across 2 pins for voltage i heard an electric pump/motor spinning!!!

I also noticed that fuse 4 on the main distribution panel had blown, it was very dirty so missed it the first time! Also a 5A for the ECM in the interior fuse box had blown. I replaced both fuses and checked the ECM relay 109 (works fine) but still no luck.

I’m leaning towards the idea that the ECM may be dead after blowing 2 of it’s fuses and the wiring for the crank sensor not checking out as it should.

Yeah the filter is full and the tank pump is working as i used it to empty the tank of old fuel.

ECU failure is not real common. If VCDS is reading all the systems, I'd say it's unlikely.
Keep in mind part of fuel is air. Maybe something stupid like one of the big pipes underneath came loose. Do the PDs have an anti-shudder that can stay closed?

Did not see any intake pipes loose when i was checking the timing. I will try removing the pipe to the inlet manifold incase the turbo or intercooler is clogged up? I don’t think so unless it is part of the EGR valve, which i removed a few years ago anyway.

If there is air in the fuel lines how long should the engine crank for before it all bleeds through?

So after doing a wear test on the tandem pump i found that it was not holding pressure and was leaking back through the return line. So i replaced the pump and it started! It ran rough for about 2 minutes then cut out and shown an engine speed sensor fault G28. I checked the wiring again and i am getting 2volts across all 3 pins so theres defiantly a problem on the harness side. Does anyone have a wiring diagram for the crank sensor to ecu?

Might be some useful info in here:
http://forums.tdiclub.com/showthread.php?t=328868

There was also a recent thread on a BEW with wiring damage in the cowl area I believe?

So i got to the ecu and checked the crank sensor for continuity. Pin 1 to ecu is okay, low resistance, no shorts to other pins or ground. Pin 2 is okay, low resistance and has continuity to 1 pin on ecu.

Pin 3 i believe is supposed to be a ground? It is currently shorting to pin 2 and does not have continuity to the chassis. I’m hoping this is the problem.

Still haven’t got to the bottom of this. After a bit of searching i believe the cam and crank sensor faults were due to excessive cranking with the engine not firing.

So i have drained all old fuel, filled the filter with fuel cleaner, changed the tandem pump, lift pump is working, timing is set correctly, no blown fuses or relays, cleared out the fuel lines in the head with compressed air, removed the inlet manifold boost pipe to eliminate any blockages within the intercooler etc.

Anyone have any ideas? I’m trying to avoid just replacing parts as i need to sell the car to fund other projects.

PoloPD said:

So i got to the ecu and checked the crank sensor for continuity. Pin 1 to ecu is okay, low resistance, no shorts to other pins or ground. Pin 2 is okay, low resistance and has continuity to 1 pin on ecu.
Pin 3 i believe is supposed to be a ground? It is currently shorting to pin 2 and does not have continuity to the chassis. I’m hoping this is the problem.

Click to expand...

You will have to find where pin 2 and 3 are shorting.
You do have the ECU and crank sensor disconnected while checking?

Pin 3 shields the wires for the crank sensor and the sensor on injector line 3.
Maybe unplug the injector sensor plug for testing.

Also goes to pin 86 on the ECU.
Should be a brown / yellow wire at the ECU.

"Pin 2 is okay, low resistance and has continuity to 1 pin on ecu."
Pin 1??
I see pin 110. White wire?

wonneber said:

You will have to find where pin 2 and 3 are shorting.
You do have the ECU and crank sensor disconnected while checking?
Pin 3 shields the wires for the crank sensor and the sensor on injector line 3.
Maybe unplug the injector sensor plug for testing.
Also goes to pin 86 on the ECU.
Should be a brown / yellow wire at the ECU.
"Pin 2 is okay, low resistance and has continuity to 1 pin on ecu."
Pin 1??
I see pin 110. White wire?

Click to expand...

It's a PD engine - does your thinking still apply? (lift sensor on #3 us usually VE engine related)

wonneber said:

You will have to find where pin 2 and 3 are shorting.
You do have the ECU and crank sensor disconnected while checking?
Pin 3 shields the wires for the crank sensor and the sensor on injector line 3.
Maybe unplug the injector sensor plug for testing.
Also goes to pin 86 on the ECU.
Should be a brown / yellow wire at the ECU.
"Pin 2 is okay, low resistance and has continuity to 1 pin on ecu."
Pin 1??
I see pin 110. White wire?

Click to expand...

I meant that it has continuity to one pin on the ecu (did not note down which number) so it is not shorting to another which would cause continuity at two pins on the ecu connector.

Yes sensor and ecu disconnected while checking. I tried cutting the wire for pin 3 and wiring a temporary new ground to the crank sensor incase it was causing the sensor to malfunction. Made no difference when checking for dtc’s or attempting to crank, i then tried splicing the new ground onto pin 3 instead again no difference.

If someone knows the crank sensor to ecu pin out on a PD100, 130 or 150 i could overlay the wiring and hopefully eliminate the short.

gforce1108 said:

It's a PD engine - does your thinking still apply? (lift sensor on #3 us usually VE engine related)

Click to expand...

No it does not.
I forgot over seas gets newer stuff then we do.

So overlayed new wiring for the crank sensor and theres no faults when the sensor is connected, when it is disconnected i get a no signal fault so that seems all good now. Got the car running after a long crank and it would run until i left it to idle, at which point it cut out. The same symptoms after i fitted the new tandem pump.

I’m getting a torsion value of around -3.0, not sure if i should try adjusting this as it is set to exactly where it was when it was running fine. Luckily the last owner marked the rocker cover so i know 100% it has not moved.

For anyone reading, i changed the injector seals and its finally running right.

That's interesting.
Mine has been cutting out only when cold. Went away for a week but came back.
Thanks for posting your fix.

blueboy7 said:

That's interesting.
Mine has been cutting out only when cold. Went away for a week but came back.
Thanks for posting your fix.

Click to expand...

I had a similar problem a few years ago, turned out to be the coolant temperature sensor, might be worth a try!

PoloPD said:

I had a similar problem a few years ago, turned out to be the coolant temperature sensor, might be worth a try!

Click to expand...

I still need to check into that. Actually it was suggested by BobnOH in a post I started. But thanks! Leading me think that's most likely the problem. I should probably do it before winter.

BobnOH said:

Just a guess, it could be one of the temperature sensors (or wires), the engine thinks it's warm. VCDS.

Click to expand...