1.8 8v EX rough start

For all Carb and Injection engines, standard or modified plus non-standard engine transplants. Heads; Blocks; Cooling (including heater issues related to the cooling system); Mounts etc

Moderator: Scirocco Register

Forum rules
Hints, tips and guides for repair and modification - the FAQ section on the main website is worth checking first for information relating to common faults and technical help. Useful posts and guides will be added to the FAQ http://www.sciroccoregister.co.uk/scirocco-faq
Brenjacques
Posts: 93
Joined: Sat Jan 19, 2019 3:07 pm
fill in the right answer: 15

1.8 8v EX rough start

Post by Brenjacques » Tue Jun 01, 2021 1:57 pm

Hi all,

I started covering this topic in another thread quite some time ago but I'm still having problems so thought I'd make a new one.

Basically the starting idle on my scirocco is quite rough, seems as though its misfiring for the first few seconds, runs a bit lumpy but with revving smooths out and is fine afterwards. It's been like it for a while but I've racked up a lot of mileage on it so I think it's to do with the ignition system rather than engine itself. Timing is all good and spot on and really doesn't make a difference if adjusted slightly either direction. Carb is a replacement weber, had the problem before this was fitted too but again this has been set up correctly and performs just as it should.

The engine holds fluids fine, doesn't use/lose anything nor is it burning anything off either, spark plugs are in good condition. Over the last couple of years it's had a new coil, HT leads, dizzy cap, rotor, plugs. Tried another ignition module but had no effect.

Beginning to question the Hall sensor/distributor as I have some oil ingress there. Second is the carb flange as it was replaced about 2 years ago and read stories of the new ones splitting easily - although I'd expect running issues to be continuous if this was the case.


Does anyone have any other ideas/input? I have some time off next week and hope that I can get it cured.



RussGLAuto
Posts: 116
Joined: Sat Jul 14, 2018 11:51 pm
fill in the right answer: 15
Location: Spalding

Re: 1.8 8v EX rough start

Post by RussGLAuto » Wed Jun 02, 2021 2:02 pm

Hi Bren,

Feel your pain. Check the fuel system for rust, it will manifest itself as tiny black particles visible in the engine bay fuel filter. Can be from the fuel filler neck, tank and hard fuel lines routed under the chassis.

And no, the filter won't keep them all from your carb inlet and playing merry hell with the running.

Speaking from experience.

Russ


Daily Driver - 2017 Volvo XC90 T8 Twin Engine - Polestar - Arctic White
Weekend Wagon - 50k 1982 Mk2 Scirocco 1.6 GL Auto - Diamond Silver
Other Half's Wagon - 2008 Mazda 2 1.5 Sport - Cosmos Blue
Daughters Curb Scraper - 2016 Fiat 500 1.2 - White

Brenjacques
Posts: 93
Joined: Sat Jan 19, 2019 3:07 pm
fill in the right answer: 15

Re: 1.8 8v EX rough start

Post by Brenjacques » Wed Jun 02, 2021 9:10 pm

Hi Russ,

Good point, I'll definitely give it a check. I looked at the filter some months back and it was okay then, but you never know what can happen in a short space of time.

It's an annoying fault, the car otherwise performs fine which makes it hard to diagnose, after 10-15 seconds it's gone.



mark1gls
Posts: 3597
Joined: Thu Apr 02, 2009 9:28 pm
fill in the right answer: 10
Location: Somerset

Re: 1.8 8v EX rough start

Post by mark1gls » Wed Jun 02, 2021 10:29 pm

How do you start the car?

It could be your technique starting the car which could be the problem as you have replaced most things and it’s no different.
An old car running a carb with a manual chock where you have to adjust the right mixture of fuel and air for it to start first time from cold is tricky.
I do find my Mk1 Scirocco GLS with a Webber carb needs to idle for a few seconds for it to smooth out while the Mk1 Golf GTi when running right will fire up straight away and idle smoothly at 1000 rpm.

Carb cars you are meant to use the accelerator pedal to help starting, try pressing the pedal to the floor once and 1/2 choke before starting then just a little press on the pedal when turning the engine over...
Try different ways to start the car and see if that makes any difference, it’s not going to cost anything so worth a try....


Mk1 78 Scirocco GLS 1.6 FR, weekend toy.
Mk1 88 Golf GTi cabriolet 1.8 DX. Daily drive.
Membership No. 323

GT_II
Posts: 253
Joined: Fri Feb 24, 2017 12:18 am
fill in the right answer: 15
Location: Warwickshire

Re: 1.8 8v EX rough start

Post by GT_II » Thu Jun 03, 2021 12:25 am

It certainly sounds more like a fuel issue than ignition, if it performs well after 15 seconds - mixture too rich or too lean on start up.
mark1gls wrote:
Wed Jun 02, 2021 10:29 pm
Carb cars you are meant to use the accelerator pedal to help starting
... except when the carb is equipped with a throttle position actuator (aka 3-point unit) as on the Pierburg 2E2, unless the engine is hot in which case extra throttle is required...


1992 VW Scirocco GT II 1.8 90PS Brilliant Black 30k
2011 VW Caddy Van C20 Startline 1.6 TDI 102PS Beluga Blue 60k
2015 Skoda Yeti SE Outdoor 1.2 TSI DSG 105PS Brunello Red 30k
2013 Fiat 500 Pop 1.2 69PS White 35k
2009 VW Fox 1.2 54PS Uranium Grey 55k

Eagle1
Posts: 106
Joined: Sat Oct 14, 2017 1:15 pm
fill in the right answer: 15
Location: Devon

Re: 1.8 8v EX rough start

Post by Eagle1 » Thu Jun 03, 2021 11:16 am

Has the fuel separator been changed and or the fuel pump. If you have the weber fitted you should be able to use the taller Mk2 Golf version. I also routed my fuel pipe from the tank round behind the offside headlight to the fuel pump with a clear barbed fuel filter. It takes it away from the engine heat. You may need to secure the pipe so it doesn't catch the alternator fan pulley. Is it only lumpy at idle or are there more problems at speed or acceleration.



Brenjacques
Posts: 93
Joined: Sat Jan 19, 2019 3:07 pm
fill in the right answer: 15

Re: 1.8 8v EX rough start

Post by Brenjacques » Thu Jun 03, 2021 11:28 am

Hi all

I don't think it's really to do with the way the car is started. For about the first year of ownership it was fine, first turn of the key and it shot straight into life, this had a peirburg on it at the time it developed the fault and the fault remained after I switched over to a weber. I normally give it a couple of presses of the accelerator and gradually press down on the pedal as I'm turning over but no matter how you try it will run lumpy for 10-15 seconds. You get the occasional time it will lstart fine but it's not often.

I was thinking about the fuel pump and seperator this morning, they're both original as far as I can tell so they've been on the car since 1985. I have considered changing the fuel pump for this reason but if it was at fault I'd surely have more problems than just starting.

The car is otherwise fine, I drive it daily and once running I have no problems at all, it's just starting that seems to be a problem.



Eagle1
Posts: 106
Joined: Sat Oct 14, 2017 1:15 pm
fill in the right answer: 15
Location: Devon

Re: 1.8 8v EX rough start

Post by Eagle1 » Thu Jun 03, 2021 1:24 pm

I have a Mk1 Golf with a Weber that had similar problems. Changing the separator and fuel pump have made a difference.



Brenjacques
Posts: 93
Joined: Sat Jan 19, 2019 3:07 pm
fill in the right answer: 15

Re: 1.8 8v EX rough start

Post by Brenjacques » Thu Jun 03, 2021 2:14 pm

I going to replace the pump and see if it makes any difference. Really relying on a 36 year old pump on a daily is asking for trouble anyhow and it'll be interesting to see what improvement (if any) it makes.

As a side thought what about vapour lock in the fuel tank? I don't know how well these tanks breathe but I had another car a few years back that would pull fuel back when switching off due to it creating a vacuum whilst driving. Presumably the vent in the fuel cap had blocked - could a similar thing happen to these tanks or are they vented on the tank itself.



GT_II
Posts: 253
Joined: Fri Feb 24, 2017 12:18 am
fill in the right answer: 15
Location: Warwickshire

Re: 1.8 8v EX rough start

Post by GT_II » Thu Jun 03, 2021 11:19 pm

The original fuel cap has a one-way valve - allowing air in to the tank to replace fuel pumped out, but preventing fumes escaping from the cap as the fuel warms up which pressurises the tank.


1992 VW Scirocco GT II 1.8 90PS Brilliant Black 30k
2011 VW Caddy Van C20 Startline 1.6 TDI 102PS Beluga Blue 60k
2015 Skoda Yeti SE Outdoor 1.2 TSI DSG 105PS Brunello Red 30k
2013 Fiat 500 Pop 1.2 69PS White 35k
2009 VW Fox 1.2 54PS Uranium Grey 55k

Brenjacques
Posts: 93
Joined: Sat Jan 19, 2019 3:07 pm
fill in the right answer: 15

Re: 1.8 8v EX rough start

Post by Brenjacques » Tue Jun 08, 2021 9:41 am

I think the tank should be okay then, the cap is in good condition with no corrosion so its probably working fine. I have all of the parts now so I'm going to make a start tomorrow. I'll start with the seperator and fuel pump initially and see if they make any difference. Will be intersting to see if the originals are full of dirt dragged up from the lines.



Brenjacques
Posts: 93
Joined: Sat Jan 19, 2019 3:07 pm
fill in the right answer: 15

Re: 1.8 8v EX rough start

Post by Brenjacques » Sat Jun 12, 2021 12:48 pm

Just to update the thread, I replaced the fuel pump a couple of days ago. I haven't done the seperator yet as the hose from pump to seperator isn't in great condition and I don't want to disturb it too much, I have some new hose ordered and I'll get the seperator done when that arrives.

Upon removing the old pump and operating it with my hands it was very squeaky and noisy and so far after fitting the new pump I've had no issues *touch wood* with rough starting. Fingers crossed this has cured it and the problem was a weak pump.

As a side note the brake pads have also been changed, been sick of them clacking for the last year or so. Funnily enough all anti rattle shims were there but not really doing their job.