Cold start issues - LPFP, HPFP, Injectors replacement - Results

[ZoliWorks]

My Mk5 GTI cold starts sounds the same as on your videos every morning...

I still dont think it's fine but it is what it is, I gave up. As long as it starts, it's ok I guess...

Earlier today, 12c outside, it started like a diesel at -20: It started cranking, puffed about twice, died again, then cranked for a bit more and finally started. Take a look at this video on reddit. It was basically that but 2x longer

https://www.reddit.com/r/GolfGTI/comments/1al3gxc/mk5_bwa_rough_cold_starts/

[mjmallia]

That does not sound right for sure.

[ZoliWorks]

Okay I did not think it'd do it again, but surprise! it did... It's 16 degrees celsius outside and you've been sitting in a garage! Why cant you just be normal?!

I gave you brand new injectors, brand new high pressure pump, brand new low pressure pump, new n80 valve, new o2 sensor, the cam chain was done with all new INA parts, including the VVT adjuster and solenoid! and you've been carbon cleaned last year...

[mjmallia]

Are you sure the timing is good still on the chain and belt?

If a tooth out on either one, that would def make a hard to start scenario

[ZoliWorks]

At idle, the chain is sitting quite happily at 1.0 KW when warm but the adjuster is at 26-27 KW even when the requested is 28 KW. The belt hasn't been checked since last year but back then we checked 3 times and both marks were on spot.

I need to take a look at those VVT adjuster ring seals. Those wren't changed and they are rubber/plastic on this engine as far as I know.

[dennis10]

I've been chasing the same cold start issues on my Edition30.  After trying various fixes, late last year I replaced the rubber o'rings in the vacuum pump on the side of the head and that seems to have done the trick.  For a couple of months now it has been starting on the button, no extra cranking, no shaking and rattling into life - just a normal engine start.  Try that if you haven't already?

[ZoliWorks]

I've been chasing the same cold start issues on my Edition30.  After trying various fixes, late last year I replaced the rubber o'rings in the vacuum pump on the side of the head and that seems to have done the trick.  For a couple of months now it has been starting on the button, no extra cranking, no shaking and rattling into life - just a normal engine start.  Try that if you haven't already?

Do you mean the VVT adjuster seals? If yes, then yeah, that's the next thing on my list. I already have the 3 rubber rings and the gasket for the cover, just didnt have time to do it yet.

If you mean the internal seals in the vac pump itself, I'll likely be replacing the whole pump as it's leaking and I haven't had much luck with rebuild kits.

[dennis10]

I mean the vacuum pump seals - seems to have done the trick for me.  I think it is a pretty sensitive engine with regards vacuum etc.

I actually tried to check and replace the 3 plastic o'rings on the VVT housing myself on the weekend because I have an ongoing slight idle misfire.  I also needed to replace the cam cover gasket too - Annoyingly I didn't get the whole job done, I just couldnt get the housing cover off of the VVT/timing chain area.  I started to button it back up and consulted my guide again and realised that I had left 1 black bolt in the housing at the bottom and had removed a silver bolt that was right next to it in an area with no visibility, thinking I'd taken out the right one.  Only realised my mistake after buttoning most of it back up, but the day was getting long and I'd had enough so I gave up - something for another day.  At least it should be a shorter job in the future as I don't need to remove the cam cover again to do this job.  Good luck with yours!

[dennis10]

Any further progress on this issue?

I'm still suffering with cold start problems where it rattles and shakes into life rather than the positive instant startup it should have.  Also some idle misfires show up every now and again, drives faultlessly otherwise.  I've not replaced the LPFP, but it's something I'm thinking about.

Did you replace the pump controller on top of the LPFP in the end?

[ZoliWorks]

I havent touched the vac pump and no ETA when I'll get to it as I was busy fitting S3 brakes front and back and refreshing the turbo with an anti surge core. I've replaced the 3 plastic rings around the VVT adjuster but no difference. I have massive misfires on cyl 3 when idle. It sometimes logs 20, sometimes 80 before it reset. My camshafts look worn out, pitted and rusted so later on this year I'll be replacing the whole head with a CDL head. The cylinders and pistons probably look bad too.

I'll make sure to update this post once I make any progress, but as of right now, due to the hot weather, there are no cold start issues.

As for the pump controller, that's stock. I have a feeling my issues are from the fueling side, but I just cant pinpoint the problem. I feel like the fuel rail or fuel lines fill up with air overnight cause it always makes that bubbling sound when I open the door. But at the same time, if it's cold outside, the cold start issues happen each time I try to start the car, if I dont let it warm up.

I've replaced the lpfp with a continental unit and made absolutely no difference. The aftermarket controller also made no difference.

Current standing:

- New Conti LPFP, stock controller
- New Huco HPFP with VIS internals
- New 200bar rail pressure sensor
- New S3 OE injectors
- New Bosch N80 valve
- New VVT rings
- INA VVT chain, adjuster, controller and tensioner done 30k km ago
- Carbon clean that made no difference whatsoever

- OE stock Vac pump that's leaking oil
- K04 that's quite worn out