Intermittent starting issue with k04 APY 20vt (mk1 golf conversion)

Hi all,

Having a starting issue with my ko4 20vt APY conversion I need some help with :S Below is a description of what's going on, and I can't figure out the cause...

29th August:
Drove the car about 40 miles, no problems. Started first time, ran perfectly, no issues. Stopped at my destination and left the car sitting (not running) for probably around 30 minutes. Went to start the car again and nothing. The engine turned, but nothing fired. I usually turn the key to first position to prime the in-line fuel pump, and it usually makes a little whine when I do this and I take that to mean it's primed, then I turn to second position and fire the engine. This time though, turning to first position would only rarely produce the little whine from the in-line pump. So, I checked the pump and the wiring was a little dodgy, bad crimp on the positive terminal. So, got the car towed to a nearby friends and left it there for 5 days while I went back home to get necessary tools etc.

2nd September:
Re-crimped the terminals and reconnected to the fuel pump. Turned the key and started first time, ran perfectly, left to idle for a few minutes and no problems at all. Great, I thought, all solved.

3rd September:
Started the car again in the morning, no issues at all, drove about 50 miles. Halfway through stopped to re-fuel, again, no problems with restarting the car. Got to my destination, again left the car for about 30 minutes, tried to restart. First position, heard the whine, but then the car wouldn't start again... Exactly the same symptoms as last time...

So, I'm confused. The engine turns over, sometimes splutters up to 500rpm and then stalls out, sometimes just cranks and cranks with nothing. I'm going to try leaving the car for a few hours and try starting again.

Thought maybe a hot start issue...but then it fired fine after stopping at the petrol station for a few minutes. Quite confused...Recently my Forge DV has started to "flutter" when dumping boost, don't know if connected at all.

Confused, would appreciate help with fault finding a bit.

Cheers,
Aran

Thanks. Yeah I don't have vagcom to check fault codes right now. Once the car starts it seems to run absolutely fine for an hour now worries...would this be consistent with a crank sensor fault?

Others have told me maybe the 409 relay?

Ok...well, that got technical lol

I still haven't been able to scan the car, but crank sensor looks likely. Anyone got a part number? Cheers!

Ok, so an update on this:

- I found the boost leak causing the flutter, fixed
- I replaced the coolant temp sensor and crank pos sensor
- Scanned the car and no faults
- Took the car for a road trip for about 500 miles this weekend, and when running, the engine feels great. However, again when sitting for about 10 minutes it will fire and then immediately die unless I leave the car to cool off for about 50 minutes
- I noticed a bit of pink around the coolant bottle, and it seems like perhaps the coolant is actually getting way too hot when I leave the car at a standstill after a drive. Seems to me that it's actually boiling and seeping out of the cap at the top of the coolant bottle. Then when I try to start the car it won't because the coolant is so hot, and it needs to cool down. I "think" this sounds consistent with the issue, but happy to get your thoughts.

I'm going to get some more coolant in the system and check for air locks, see if simply there isn't enough coolant running round the system. Then perhaps a timer to keep the coolant running for a time after shutting off? To be honest though, it shouldn't be overheating given it's a modern engine.

Yeah, fans run. Still got that link in it that you put in a few months back - I haven't done anything else to the cooling system after that. Don't know the exact rad or fans, would need to have a shufty later

Re-starting this old thread. Took the car out today and the same issue hapenned once more. I noticed red residue on the coolant bottle top after the car had been standing for a while (and then wouldn't start)…so I think we're definitely getting boiling coolant here!

I've replaced the coolant temp sensor, thermostat, water pump and reflushed whole system and I'm still getting this issue of the coolant boiling, not great.

So I'm thinking (as someone else mentioned) to replace the coolant bottle back to an OEM one from the S3 in case the current bottle pressure cap is loose or faulty, not allowing the system to pressurize properly and thus letting the system boil etc.

But other than doing this and refilling the system, anything else to check / change?

I've changed the crank pos sensor (but not checked that wiring). But the speed sensor? You mean the crank sensor right?

I'll give the wiring a check. Red residue definitely seems to suggest a coolant problem too in any case