Joined the hard shoulder club yesterday, first time i've ever broken down on a motorway which was an experience... Safely managed to get out of trouble and after a very cold hour at the side of the road managed to get put on the back of a truck and the polo is back on my drive now.

 

We were cruising at 60 and all of a sudden I noticed our speed dropping - no jolt or judder, nothing to suggest any sudden change apart from the revs and the speed needles dropping. Pumped the gas and the revs didn't change so I popped the hazards on. Warning lights (oil and battery lights) came on. Pumped the brakes and still had vacuum to the servo (thank god), so popped it out of gear and coasted along the hard shoulder to a soft stop. Tried the ignition and the starter and engine turned over but no dice so called for recovery.

 

Yet to venture outside into the cold and have a look this morning but a brief look with a torch when it was on the truck last night didn't find anyting catastrophic visually, no fluid loss or anything obviously out the ordinary. Before we waslked onto the grass verge I briefly checked under the hood and both belts are on - no snapped cambelt or v belt.

 

So my guess is its electrical as its been absolutely fine for ages - if it was a fuel pump failing I would have assumed something would have been going wrong slowly before giving up the ghost but you never know. Its had a new tank for about a year so i doubt a big lump of rust is blocking the filter or the pump screen. Anything else good to check apart from these?

• Spark test on crank over
• Fuel pressure (got no way of doing that passively so I'll just look for a squirt from the SPI when cranking)
• Alternator test (I remember a procedure from a thread on here - something about continuity and resistance across the coil)
• Alternator cables, continuity etc

Of course if it starts now its cold then there'll be something more subtle going on but my money is on the alternator. Any suggestions would be very welcome!

 

 

 

 

 

Just had a quick poke about before it starts to rain...

 

No visibly blown fuses, BUT when i turned to the 1st stop on the ignition there was no sound from the pump priming, just the click from under the bonnet. So perhaps the fuel pump relay? I'll check it later on once the weather clears a bit, might have a spare relay knocking about.

the click maybe the ecu relay ...fuel pump relay is a good start 

 

could use a test light at the pump wiring too

Small gap in the rain so i pulled the pump fuse and gave it a clean (heard they can play up due to their uncovered position), checked the fuel pump relay and it seemed ok. Turned the ignition to point 1 and heard the pumps prime now. Definitely doesn't make all the pre-start noises it used to though, something isn't quite right still.

 

Cranked it and there's fuel on the throttle butterfly so its squirting something out at least.

 

Cranked it and no start, could well be the battery is a bit weak now though. Good excuse to finally buy a battery charger i guess! I'll charge it before testing for spark.

 

 

Both pumps are working and there's fuel getting to the SPI. Charged the battery a bit and had a crank with a plug out - no spark. Checked an HT lead with my timing light while cranking too and it didn't pick up a signal. Think its safe to say there's no ignition.

 

So for a sudden loss of ignition while driving what might be the options? The dizzy cap looks fine, rotor is fine, all the HT leads are good (nice ones too), all the plugs are seated nicely and without corrosion.

 

However the coil looks dead grotty - think its the original. Could the coil have suddenly given up?

Primary coil reading 0.3Ω, Secondary reading 2.3kΩ

Low but not zero. Maybe a winding has fused.

 

What about the Hall sender?

I think there's a test you can do with an LED across 2 terminals to detect when vane passes the magnet.

Hall Sender - testing

 

"Diode test light" guess that's an LED with series resistor such as  470ohms for 12v circuit.

1. Release the lead connector from the Hall sender unit. Check the voltage supply to the sender unit by connecting a multi-meter between pin 1 and 3 of the hall sender plug, then switch on the ignition. A minimum reading of 5 volts.

2. To check the signal from the Hall sender unit, slide the rubber grommet away from the sender plug and with the plug connected to distributor socket, attach the diode test light to its centre and outer (brown/white) terminals. Operate the starter motor and check that the LED is seen to flicker. If it does not, the Hall sender unit is at fault and must be renewed.

Edited 6 December, 20214 yr by dvderlm

Fab, I'll give that a go, thanks 👍

Storm subsided for 10 minutes so ducked outside to have a poke about. Checked for a third time and can 100% confirm no spark. Turns out I don't have any LEDs in my electronics bag so have some on the way but have 11.5v between pins 1 and 3 on the hall sender plug. Never really looked at it that close but it doesn't have a rubber boot and there's no easy way to slip a wire in with the plug on. Sure i'll figure something out though.

Put an led between the centre and negative (right pin) terminals of the hall sender plug. Was a bit of a faff - ended up stripping the wires mostly bare and had them catch on the plug crimps, then slid the plug on with the wires trailing out the side of the socket.

 

Upshot (downshot?) is there was no flashing on cranking so I think the hall sensor is kaput.

 

However...

 

As careful as I was when doing this little bodged test, in my haste I forgot to turn the ignition off when removing the plug. As i said those wires were bare so when I removed it they briefly came in to contact. LED flashed, lots of action from the injector clicking. Have I fried something in the ECU or does this merely reinforce that the hall sensor is dead but the coil is fine? Time will tell...

 

Either way, I've ordered a new Bosch dizzy. Had to order from autodoc as they're getting like hens teeth over here now. Not going to mess around with JP rubbish.

Did you try with LED both ways round between 2 and 3?

A diode only conducts one way.

Only thought of that now.

 

Doubt you've fried anything, that's usually accompanied by smell and silence. 

ECU probably thought engine was turning.

I had the same thought! Tried the wires round both ways, got nada. Tested the LED with 3 and (briefly) 12v off another battery and it lit.

 

Behold my very professional bogan test rig:

 

 

 

Found an OEM coil for 40 quid so I figured it'd not be a bad shout, at the very least it gives me something to do while waiting for the new dizzy.

 

Popped the new one in and figured it was worth a try on the starter just in case....it only bloody fired up didn't it!

 

Not entirely suprised looking at the state of the old (original) coil to be honest, but slightly perplexed at my tests - perhaps the old coil wasn't even providing enough voltage to the hall sensor for it to even work.

 

 

As usual I've ordered another part i don't technically need at present, but a nice new distributor will likely come in handy down the line anyway!

 

Thanks for the pointers, slightly relieved the christmas food shopping doesn't have to be on foot...

 

those coils dont have the best reputation , easy to carry a spare one , dont be tempted to get a non genuine if you do 

I couldn't find anything about those Temic coils aside from they appear to be OEM by their markings. I'd get stuff through VW directly as some folks swear by but I can't get the local parts distributor to talk to me for some reason.

 

Either way I'll definitely carry a spare on next year's S.France drive...

yeah thats factory fit...or bosch /beru just dont bother with the ebay no name £9.99 ones i had 2 dead in the box lol