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ABF'd Mk1 wont start - electrically inhibited?


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What a frustrating new years day. Any help would be hugely appreciated.

ABF'd my mk1 Gti a few years back with a lot of wiring help from rubjonny, and it has been awesome.

A few months ago I had the odd engine cut out after booting it. Started straight away so I din't give it much thought. Then just before xmas it happend twice in relatively quick succession, and got a little lazy to start. So, out came VagCom and boom! Engine coolant temp (G62) Error code 522. Winner! New sensor on order and we're off. Problem didn't re-occur, but I didn't get much time in it before it got wet, so the car stayed in the garage. My passenger foot well fills with water which looks like it comes down via the fuse box (that may well be relevant here).

Anyway, now she doesn't start at all. After new G62 sensor fitted and no start I tried VagCom again and got the same error code. Yes, I did clear after last time. So, cleared again, tried to start, but no error code now….

I've got loads of fuel, and its pumping after fuel filter in engine bay, loads of battery power as keep it on maint charger, and got good spark.
I've probed the earth contact of G62 and it is directly linked to car earth. Positive is directly linked to pin 14 on ECU plug.

I've read it could be crank sensor, but the rpm needle bounces when trying to start - is this where the signal comes from? Am I reading this right?

I've dug out the immobaliser and key 'fudge' to be sure they are still mated as this just seems like the start is electrically inhibited.
I had the inlet pipe off before Xmas and got some blowback from air intake/throttle area during a start attempt - not sure if this is relevant or not, but thought i'd mention it.

I'm now lost and would really appreciate some other things to look at.

Anyway, hope you're all having a better new years day than I am!!!
Many thanks


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Been doing some searching…

I have also tested my coolant water sensors. Both the new and old seem to closely match the thread below at 3500 Ohms around 10 degC, so probably not my issue.

ABF Temp Sensor Testing - Possible Overheating | Club GTI

Also, I have read that if its an immobaliser issue, then the car will fire but quickly cut out. I don't get a fire up, so not likely to be immobalier.

This thread mentions over fueling. mk3 2.0 16v overfueling no start? pls help | Club GTI

I need to check the fueling advance. Is this controlled by the vacuum hose from the inlet manifold to the ECU? It looks OK, but for a couple of quid i'll get a new length.



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Fixed it!

Bad connection on relay 30 stopping ECU from getting power  :$

That bit I said about water coming in. Well, the bad connection looked rusty. Tested it, fine. Cleaned it up, and put it back. Car tried to fire, so kept going and boom. A bit lumpy and smelly coughing out the fuel, but smoothed out lovely!

Well chuffed!


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Been mulling this over in my head, and i'm a little confused.

Firstly, does relay 30 supply power to ECU? shouldn't the coil supply come from ECU aswell? If so, why was I seeing a spark.

What was actually stopping my engine from running as I  had fuel, spark and plenty of cranking power? I would have at least expected it to try and kick in. But there was nothing.

Once the relay was removed cleaned and replaced, it tried to fire immediately, but with all the unburnt fuel it struggled initially, but you could hear it was a different problem.

Just curious as to what was going on.


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Water migration in to the fuse panel is irksome.  Relays can get wet internally and it isn't pretty.  I have pulled some from a breakers that were Trash, so I have started to open them up and checking them prior.  I also have a 9vDC battery in my kit that I make sure that I can at least PICK them.

30 is the ECM Power supply relay.
So if it was Corroded it wasn't supplying proper power to the ECM.  If the Relay contacts got hot, then you may have cold Solder joints on the inside that need tending to or buying a new relay.

Just because you have fire, fuel and air, doesn't mean they are occurring at the proper time… I had a spun crank gear on a 92 that was a real PITA to find, as it wasn't that it was spun but the Crank bolt backed out, and when I checked timing it was fine and started, but giving it gas it would jump time, then as it stopped it jumped back in to time…it was very weird, and I ended up having to replace the crank as the bolt was overtorqued by the previous owners Certified VW TECH when he replace the timing belt,,,,, hint 12pt bolts only are torqued to 60ft/lbs..not the 110ft/lbs that the 6pt are…Certified my AR$E….

I would also suggest that all mk1 owners reseat all fuses and relays on a yearly schedule, as I had a a/c fuse that I had never reseated, and the corrosion on the contacts eventually fried the socket (Thankfully it was an add-on to the main panel and not the fuse panel itself).  Still it was a pain to replace.

If you have water migration on the fuse panel side then I would be looking for the cause, some of the known ones are:
Plugged Rain Drains.
No Water Divertor over the Rain tray.
Missing Grommets in the Rain tray.
Replacement antenna that is missing the Drip stop loop allowing water to run in to the Cabin.
Rust around the windscreen frame or the bottom of the windscreen (look specifically at the corners).

What do Divorces, Great Coffee, and Car Electrics all have in common?

They all start with GOOD Grounds.

Where are my DIY Links?


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Fair point about the timing.
Thanks for the tips on the water ingress, I need to get on that. I don't really like taking it out in the wet, but sometimes I get caught out.

My window seal doesn't look the best either.
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