Hi all!

I have a 94 polo classic, 8valve, petrol, monometronic, 6n. Manual transmission. AEE I believe.

Problem: polo would crank but only starts if given gas, but cuts out after a few seconds even if gas pedal is given movement. It worked fine a few weeks ago but does not start anymore. I also searched for an immobilizer but dealer says the models issued here do not have immobilizers. Or is there one that I could not find - (I've searched for a module over, under, beside, behind the fuse box/steering wheel/ac compartment)?

Car condition: already checked/done/replaced
Engine
- recently overhauled head (was working fine after service)
- new ignition coil
- spark going to plugs
- this model does not have an immobilizer equiped on it
- no alarm
- hall sender working as it fires when given gas but everything just stops after a few seconds
- old fuel pump relay is new (ignition may be wired to that relay too) but new electronic pump has its separate relay
- oil level within limit
- heater core bypassed, but sensor untouched
- all plugs ok. Also swapped out plugs with new ones
- aux fan relay high busted and not connected but it has been that way before when it was still starting
- engine timing follows timing marks and dizzy at tdc #1 (please correct me if i have set this wrong)
- new battery
- starter newly serviced and is cranking strong

- Multiplug cleaned
- engine harness and harness to ECM wire resistance checked and 0-.09 ohms
- pulse and 5-6v voltage getting to injector. Injector fires only at start and drips afterwards - fuel lines clean, new
- inspected inside of ECM for burns and all OK

- CTS replaced as the old one had erratic measurements when submerged in hot water. Cold shows 1400-1500 ohms.
- cleaned engine, hood, starter ground
- hall sensor is working as there is spark during crank
- air filter is new
- all doors and trunk open, locked, relocked then opened with key

Additional info: Radio is a Blaupunkt 105 - code light flashing when key is out. Also, If I could remember correctly the parking lights no longer flash when the key is in the ON position. When the #21 fuse is taken out and reinstalled, the power to the old pump resumes to prime but does not have power when the driver's door is open or before start or even during crank - even if the dome light opens when driver's door is open.

Timing is currently set:
- flywheel hole shows 2nd mark centered
- cam mark on O.T. arrow
- dizzy cap on 1st HT wire (moved it back and forth and still no start)

ECM part number is 6K0 907 311 (no letters follow)

I disconnected ECM and started vehicle to see if the result would be the same. Car wont fire at all after crank - normal. If ECM is plugged in, car starts for a few seconds and it dies no matter what.

Carb
- monometronic carb cleaned, injector responds to 12v pulse during bench testing, injector cleaned and orings intact
- injector has pulse during crank
- fuel pump is an after market electric pump which works when key is ON position
- cleaned / cleared out fuel line going to pump and carb
- new fuel filter
- fuel stops spraying from the single injector after the initial 12v pulse feed to the injector

Ecu
- power and ground at ECU plug
- tried swapping ecu with a working one but still wont start???
- OBD / VAG cannot connect to ecu
- i only see battery and oil red lights come on when ignition key is ON, no check engine light visible
- Vag / OBD Port does not have power at ground and +12v wires
- already cleaned ecu, ignition, dizzy contacts

Fuses and relays
- all fuses ok
- existing relays all individually checked and are ok
- there are no relays beside the ECU in the bulk head and there is no #30 relay found on the fuse box under steering wheel
- all connections behind fuse box connected
- in00 registered on dash after performing the reset
- no ecu relay? Since there is 12v power on each end of ECM pins
- blaupunk amo105 code light flashes when key is OFF
- I hear the original fuel pump relay 167 go on when key is ON and then it clicks off after a second when key falls back to the ON position from crank. This relay is new but new electronic fuel pump is not using this as it was converted after the original did not work.

Ignition
- all wires connected after aftermarket alarm was removed
- there is no accessory position and goes straight to ON from OFF
- red wire is live, black/red wire has ground when OFF, and black to black/yellow wires have 12v when key is moved to ON position

I cannot find:
- ECU relay
- crank or speed sensor (if any aside from hall sensor). Or is it by the rear main seal / tranny?
- Does the large relay like box for fan control module stop the engine from running or idling? One of the large pins is burned but shouldn't this cause no-start conditions?

Your thoughts on what else I have left out to make it run again...

TIA!

First Welcome to the forum.

As far as I know all the 6N's left the factory with an immobiliser fitted as standard and your symptoms are classic immobiliser doing it's job! the box is about the size of a cigarette pack mounted between the fusebox and the steering column, if you remove the shroud around the ignition switch you will see the sensing coil around the body of the ignition switch

Fuse # 21 15 amp supplies the power to pin 16 of the diagnostic plug and pins 3 & 4 are the grounds, the K line on pin 7 goes to a junction strip on the fusebox and this goes off too the control units, this can suffer with the corrosion on the junction strip that will stop you communicating with the modules.

There is no "ECU" relay

The only speed sensor is the one in the distributor

The only way the fan control module would stop the engine is if there was a direct short and it was taking all the power

Thank you Nige for your reply.

Regarding the immo, I have checked the black surround "aerial" and it does not have any wire coming out of it. Also, the key is only a rubber cover at the back with the logo on it. Tracing the ignition switch wires lead to the rear of the fuse box directly. But it does have a Blaupunkt radio that has the code led blinking when the key is not ON - no SAFE written on the display, only the time.

When I checked the VAG plug, no +DC is supplied to pin 16. I will check the VAG wires and clean out the leads going to the fuse box. Checking the +DC was done via the VAG ground pins and the body ground using a multimeter. There is no CEL light when I turn ON the key, just the oil and battery leds.

I have tried running the vehicle without the fan control module too. But it didn't start.

When I got the polo, The 02 was unplugged, but ran fine. Also fuse 21 was blown but ran fine. Replacing fuse 21 allows old pump priming (still connected. I just fitted a new one since it was intermittent). But pump does not sound at all on ignition, crank or when the doors are opened.

Edited 3 September, 201412 yr by HardcoreShad

The coil around the ignition switch should have 3 wires coming from it, and goes direct to the immob box, but looking at the pictures it looks like someone has been chopping into the main wiring with all the black insulation tape !! So it might have been removed ??

The fuel pump relay is fed +12v from the ignition switch and the ECU provides the earth, So when you turn the key to ignition ON the pump relay momentary energises to pressurise the fuel lines then if it gets a GO signal from the immob the relay is re-energised to sustain the fuel pressure for the engine to run, ( only on the 6N2 onwards does the pump relay energise with the drivers door opening), unless it was a modification for the Asian market ?? but it's not shown in the dealer wiring diagrams??

The diagnostic for the engine ECU goes through the immob box

There are actually 4 wires coming from the ignition switch plastic harness.

- black is 12vdc (comes on when ON)

- solid red is 12vdc main supply from batt

- red/black is ground

- yellow/black is also 12vdc (comes on when ON). I do not understand why there are 2x 12vdc wires that get voltage when key is ON... There is no accessory slot when turning the key either. Goes straight to ON. I will trace where this solid black wire leads to. The gauge of it also looks like it is not a cluster carrier and simply powers an individual item (immo perhaps hidden somewhere else).

Please pardon me for wrapping the wires in electric tape. Yes, it has been hacked by the alarm installer of the previous owner! Had to find the matching wires from that particular alarm to take all of the components out. But all this happened while the alarm was still there a few weeks ago. Thinking that the alarm had an engine cut feature, I took it out and hooked up all the standard connections.

Currently, the pump is being supplied 5-6volts only, when I ground the multimeter to body and the other terminal to +DC wire to the pump. It only gets 12vDC if I replug the fuse 21. Could this be a short? Relay for the pump disengages after crank. It is on when cranking. - Meaning the 12VDC is supplied while cranking, but ECM does not send ground signal that is why it is not engaging pump.

"The diagnostic for the engine ECU goes through the immob box" - Is there anyway for me to verify or start the trace of wires for the diagnostics? Are these the same with the VAG wires from the plug? Because the VAG plug goes direct to the rear of the fuse box.

I wish there was an immo visible by the column as I could have solved this with the help of all the CP threads on it. Fingers XD as I agree these are symptoms of a safety feature. The radio installed is a factory Blaupunkt AMO 105 issue and has the code led blinking when key is off. Could this have the immo function? Detaching the radio harness could bypass its safety feature?

ECM harness goes direct to rear of fuse box as well. Didn't VW release ECMs with built in immo's? But key is just a standard key, which worked before. Key is surrounded by a solid rubber boot and not the one which can be split in half. No chip signs on external of key by the boot too.

Edited 3 September, 201412 yr by HardcoreShad

I may also have set the timing incorrectly...

1st try:

- I used the 1st arrow on flywheel (crank moving clockwise so tranny end is CCW) - crank pulley marker before the plastic marker on front cover

- marker dead on OT mark at cam

- Dizzy on 1st HT

2nd try:

- I used the 2nd arrow on flywheel (crank moving clockwise so tranny end is CCW) - crank pulley marker after the plastic marker on front cover

- marker dead on OT mark at cam

- Dizzy on 1st HT

Also, does the heater core have a sensor that needs to be disengaged if it was bypassed? (heater core leaks water into cabin that is why I bypassed it. Bypass was done after no start situation but it leaked before the no start situation.)

There should be 6 wires from the ignition switch (European market)

4mm RED (30 terminal) Battery supply fusebox connector H1/2

4mm RED/BLACK (50 terminal) to starter motor solenoid fusebox connector H1/1

2.5mm BLACK/YELLOW (X terminal) to X contact relief relay fusebox connector H1/3

1.5mm BLACK ( 15 terminal ) to Fusebox connector H1/4

1.0mm GREY ( P terminal) to fusebox connector H1/10 then out on H2/5 to parking light switch

0.5mm BROWN/RED ( S terminal ) to fusebox connector H1/7 to Radio and lights on buzzer

The radio "safe" has nothing to do with the immob

Pin 7 of the diagnostic goes to the terminal strip on the fusebox then to pin 3 of the immob box then out from the immob box pin 2 to fusebox U1/1 out on pin G2/2 to the ECU pin 29 GREY/White 0.5mm wire

The fuel pump relay gets it's supply from the BLACK wire from the ignition switch, the earth is from fusebox connector G1/3 RED/YELLOW 0.5mm wire to pin 25 of the ECU, the supply is from the 30 connection (Battery supply) in the fusebox then out via fuse # 18 20 amp via fusebox connector M/2 to the fuel pump 1.5mm RED/YELLOW wire

The correct method of setting the timing is in this link http://www.clubpolo.co.uk/forum/index.php?showtopic=334766#entry2630671

No sensors in the heater matrix and nothing that would affect the engine running

Alright, I will check the ECM wires you have indicated above so that I could also determine if it leads to an immo somewhere. The info you provided will help me further the wiring tests. Really appreciate it... Will clean contacts for VAG plugs as well. So the K line should also lead me to the immo. Will post an update once I have completed the checks.

Thank you for providing me the link to checking ignition timing. But what I am unsure of is the timing marks on the engine. Which flywheel / crank pulley marker should I follow to correct the crank-to-cam timing? I have seen instruction in the forum but I don't have the usual marks shown there. I only have 2 arrow pegs on the flywheel, seen through the peep hole, the mark on the crank pulley cover and the OT mark on the cam rear cover.

Here's a pic of the timing belt alignment marks it's for the 1.4 8v engine but it's the same for all the 8v petrol engines in the 6N

Going through the pic Nige, I don't see any visible markers for the cam opposite of the OT mark. So i just alingd the cam mark with the OT mark on cover.

Then for the crank shaft, I used the "0" mark on the flywheel.

The dizzy is set after tdc - will fine tune when started.

Mk2 is also set this way from haynes i recall. So just cross checking between marker references, was i able to set timing properly?

Still cleaning connections and will try cranking after.

"Pin 7 of the diagnostic goes to the terminal strip on the fusebox then to pin 3 of the immob box then out from the immob box pin 2 to fusebox U1/1 out on pin G2/2 to the ECU pin 29 GREY/White 0.5mm wire"

- I checked pin 7 of the VAG plug and it goes to a brown link socket, which in turn goes directly through the firewall hole and into pin 29 of the ECM (white/grey wire). No immob in between.

- yellow wire pin 15 of VAG plug - leading straight to ECM pin 11 of ECM

- brown wire pin 4 of VAG plug - leading to a big brown ground strip on the very side of the foot well

- red wire pin16 of VAG plug - leading to a 4-wired plug by the driver's door. audi part vw 6k0959741. On this plug is a white wire, and 2 red/green wires. Switching on the ignition with the plug removed transfers the +VDC from white to all three red red/green wires. But power does not come from the audi part. It simply receives the voltage supplied by the wires. Pin 16 of VAG is an always +VDC on pin.

*Also confirmed connectivity with the multimeter (battery unplugged).

I then checked U1/1 and there is another white/grey wire but now leading to the back of the radio.

I would also like to double check the valve shims. Do the shims have the same clearances for both intake and exhaust?

Please pardon me for asking this as Iam working off a 90-94 haynes mk2 manual and do not have the actual 95-2000 manual.

Edited 4 September, 201412 yr by HardcoreShad

U1/1 was a typo error it should of been U1/2, I can't find anything connected with U1/1 ??

Pin 15 to pin 11 on ECU pin 11 is not listed as a used pin ?

There are no valve shims the tappet blocks are hydraulic and are self adjusting

There should be casting "PIP" that is the alignment mark for the cam pulley

Goodmrng Nige! :-)

Updated my post before yours regarding the +VDC wire of pin 16 from VAG plug.

Here is the pic where pin 7 of VAG goes direct to the ECM and a pic of the head internals.

Here are the pics where the pin 16 of VAG plug leads to.

Yes, U1/2.

Yellow VAG pin 15 wire goes to pin 11 on ECM.

Polo still wont start upon trying now and OBD still wont connect. But there is spark and fuel.

Not sure on that picture for the pin 16 RED wire, it should go to a commoning strip in the fusebox for the battery supply??

Here's the info on the tappet blocks

Test sequence – Start engine and run until radiator fan has switched on once. – Increase engine speed to about 2500 rpm for approx. 2 minutes. If the hydraulic tappets are still noisy, locate defective tappet as follows: – Remove cylinder head cover. – Rotate crankshaft clockwise until cam of tappet to be checked is pointing upwards. – Determine play between cam and bucket tappet. – Push bucket tappet down lightly with a wooden or plastic wedge. If when bucket tappet is pushed down, a 0.2 mm feeler gauge can be pushed between camshaft and bucket tappet, bucket tappet must be renewed.

Note

When new bucket tappets have been installed the engine must not be started for about 30 minutes. Hydraulic compensation elements must settle (otherwise valves will strike pistons).

My Autodata info shows no connection used for pin 11 ??

I will perform a high impedance hall sender test tonight... It could also be a fault as some senders, specially if well made like VW's senders are more resilient than others. The current sender may fire for a while and lose effectivity when heated a bit by current. Because I remember testing each spark plug wires (5900-6100ohms each) having fast sparks and then they slow down before the engine starts to stall. All in 2 seconds of crank-start.

If this is a no go, I will send in the ECM for a test. Too much time lost on diagnosis :(

I would still count on your autodata Nige, but it is very much a posibility that units issued here were modified to cut down on vehicle selling costs.

There really isn't anything left to check I reckon. Timing is correct, head rebuilt, there is gas and spark. The ECM just stops output of running signal. So the hall would be my next check after this, even though if there is initial sparking. Probably it should be doing multisparks rather than one big spark as it is electronic. My test from crank and holding the HT wire to ground just shows one large spark vs the usual 1 beginning and 1 end spark per cycle.

But if you guys have anything in mind, please feel free to dive in. No right and wrong replies...just good ideas from great people. :)

Update...

- ECM returned negative for problems

Would anyone be kind enough to correct me if my hall sender values are correct or still up to specifications?

- I get on and off pulses of .22 and .08 volts (setting at 20v on the multimeter)

You should have a minimum of 9v between pin 1 & 3 of the distributor connector and a pulsed 5v between pin 2 & 1

Aha! Think this is it Nige... Tnx for the hall sender values.

I had 12v on pins 1&3 for testing purposes. Then I got pulses of .22v and .08v only between pin2 and common ground. Fingers XD. Will check if there is a separate hall sender available so that I can replace it.

I also disassembled and cleaned the internals of the fuse box and checked/cleaned all plugs, connectors, fuses, relays, etc. That is out of the way then. Failure to connect to my Innova OBD reader is still there though. Checked the site for ross tech. It instructed to check for voltage and that wasn't the prob on the K-line. Tried connecting without the K-line and the other one too, but no go. ECM is working though.

The part number for the sensor is 030905065

Update...

- Hall sender replaced with a new one

- Put in a gallon of gas to add to the existing

Will try out tomorrow AM as it is kinda late to try cranking...

Just to confirm. The firing sequence is 1-3-4-2. Number one is where the 1st HT should be pointing to the small mark on the dizzy and not the dot mark inside the dizzy cap?

Edited 17 September, 201411 yr by HardcoreShad

Yes the order is 1,3,4,2 I don't have a distributor to hand but I think?? #1 lead is at the bottom (6oclock position) and the rotor arm rotates anti clockwise as you look at it

When I put the piston 1 and flywheel on TDC, the dizzy rotor points to the 2 o'clock position but the mark on the dizzy housing wants a 12 o'clock position. This is with the timing mark on the dizzy gear set correctly.

The plugs are in the order of 1-3-4-2. But I am getting blowbacks. Rotor moves in a clockwise position on this one. I double checked it by cranking the starter with the dizzy cap off to make sure.

Should I then proceed with the 6 o'clock position for number one?

Or I could just go back to setting the dizzy housing mark dead on the 2 o'clock position and put the HT 1 right on that?

Edited 17 September, 201411 yr by HardcoreShad