Rough start up and light flicker of ignition light on dash

[Brenjacques]

I don't know if these two things are related but recently I've had trouble with start up on the rocco, it's taking more turning over and when it does fire it's not firing on all cyls but builds up over 10 seconds or so and runs fine after. Normally the car fires first time and runs perfectly so this is a new problem.

I've also noticed tonight (as it was dark) a bit of a flicker from the ignition/battery light when the car was still and ticking over.

I don't know if these two are related but they probably are and I've not actually looked into it yet so before I do I thought I'd ask if anyone has had a similar problem and if it's likely to be anything in particular.

The plugs are new and it's just had a replacement dizzy cap and rotor on. HT leads are just over a year old but the ignition coil and module are both quite old, if not original. The battery is a Yuasa and probably a couple of years old, but I don't suspect this as it cranks over fine.

[kidcrewbob]

Possibly the alternator on the way out causing the battery to be sub-optimal or belt slack / slipping maybe ? - is it still cranking as fast but longer or does it seem slow to turn over? Ditto coil I guess but the flickering light may be the one to persue initially......

[Brenjacques]

I've checked the voltages this afternoon and have a steady 14.6v on the battery terminals, similar voltages at both of the alternator cables. It turns over fine, isn't sluggish or anything, it's just the actual firing that seems to be the problem until it's ran for a few seconds.

I've checked the voltages at the coil, the two black cables were showing a steady voltage, the other socket which has a red and green cable on was showing 13v but it was jumping up and down which could indicate a fault? I'd expect all of these voltages to be quite steady and not erratic. A photo of the coil for reference: https://flic.kr/p/2k2HQfQ

All earths look okay from what I can see and I measured continuity with a multimeter, they were all virtually 0 Ohms.

There is also a green/black cable disconnected near to the distributor. I'm not sure what this is for but it doesn't have any earth connection or voltage?

Photo of the loose cable:
https://flic.kr/p/2k2JtKL

[GT_II]

Are you confident the slow starting is an electrical rather than fueling issue?

[kidcrewbob]

Yeh good call - I’ve had such a fuelling issue which I put down to vapour lock - I removed the restriction I’d put in the return side of the swirl pot and all seems ok ..........for now!

[Brenjacques]

Fuelling has crossed my mind but when I get it started while it's running lumpy, if I put my foot on the accelerator it does rev up fine albeit rough until all cylinders are firing. Surely if it's a fuelling problem the engine would bog or splutter if I press on the accelerator? Once started and it smooths out there's not any flat spots or other issues.

I did remove and refit some ignition loom plugs earlier to clean the contacts and it looks like that has cured the feint ignition glow. Startup feels very slightly better but still not right. I'm wondering if the ignition module is slightly faulty as the jumping voltage on the coil terminal looks a bit suspect, I'd expect a nice steady voltage with maybe some occasional variation but not constantly jumping up and down.

[GT_II]

I was thinking maybe too lean rather than too rich, eg not enough choke. Or maybe the 3-point unit isn't giving enough throttle for start-up (assuming you have the Pierburg carb).

[mark1gls]

Clean the earth cable from the battery to the chassis to the gearbox mount, it’s a poor design and the gearbox mount is not a great place to earth the engine and dirt/crust can cause problems.
VW did change the design on the Mk3 golf and the earth cable is similar but from the gearbox mount the cable then runs onto the gearbox bell housing bolt.
You can try to extend what you have with another bit of earth cable the gearbox mount to the gearbox bell housing or find a Scrap yard and get a Mk3 earth cable.

[Brenjacques]

Thanks for all of the tips, I replaced the coil today, also fitted a new cambiare ignition module but this failed to work straight out of the box? I reconnected the old one and the car started first time but this may be due to the cranking/non firing helping a bit when the new module was fitted, I'll try again in a few hours and see if it starts straight up or lumpy again.

The removed coil is ancient so there's the chance of a slight short or damp ingress causing problems there. Thinking of other possibilities could the distributor be faulty? Would a problem with the vacuum advance cause difficulty starting or would this cause misfire at different revs? Also maybe the ignition timing has drifted a bit (if this is possible), it's probably been a while since it was last set up.

[Brenjacques]

Further update today, whilst out for a drive I noticed the battery light flickering again, this time more brightly than before. I've done a few checks and the battery voltage with the car idling is still a steady 14.55v so I don't think it is the alternator, if I rev up it does dim and go out but returns at idle.

I've also noticed if the rad fan comes on or if I switch on headlights the light goes out again so I presume it is an earthing issue somewhere. I've cleaned up the main earth cable from battery to chassis and gearbox, I've also cleaned up the earth strap from the head cover to coil and both have good continuity throughout. The alternator has good continuity to earth as does the engine, battery etc but it is still flickering.

Does anyone have any ideas as to which earth it could be? I'm going to look at the wiring diagram but I think the fact that it stops with ancillaries switched on will eliminate a few. I wonder whether it could be an earth problem with the battery light circuit itself and just throwing up a non-fault due to its own bad connection.

[mark1gls]

Remove the alternator regulator and check you have 2 bushes left, I’ve had a set that worn out and I started to get electrical issues?

It’s 2 screws to remove it and check/clean the metal prongs which connects to the regulator.

https://www.ebay.co.uk/itm/Voltage-Regu ... SwOy1an~tn

[Brenjacques]

I've had a few people suggest the regulator to me so as they're cheap enough I just bought another one and fitted it today, made sure all of the connections were nice and clean but still the same problem.

I've noticed that it's actually only doing it when the battery is fully charged, from starting cold in the morning it takes about 10 minutes just idling before it starts to glow and if I turn the engine off and start it again it's out for 10-15 seconds, obviously enough time to top the charge up after the drain from cranking the engine.

To be honest the high current alternator lead to starter motor doesn't look to be in the best condition, I wonder if this is a possible cause, although I'd expect it to have more trouble when charging the battery rather than when the battery is at full charge

[PeteGLi]

Also check that the blue 'exciter' wire from the alternator is not frayed/corroded anywhere. It has a single connector near the battery, which connects the engine bay side of the wire to the fusebox loom.

[Brenjacques]

I checked the blue wire, it's in good condition with no damage and virtually no resistance either, I also cleaned the plug up and checked the resistance across each end of the plug and that is also fine. Beginning to run out of ideas now

[james butler]

if your alternator light flickering goes out when you turn anything on i would say this is an odity of the car but normal.
mine has been doing that for years, i even swapped alternators and it was still the same.
if i turn the lights on or the blower fan it goes out.
i was once told the voltage regulator can cause this especially when the battery is fully charged as it then resorts to pulsing fully on and fully off causing the flickering.
turning anything on give the alternator something to do and the flickering goes away.

regarding your starting issue can you remove your sparkplugs and get a good clean photo of it to show us please
i have a feeling i might know what your problem is but need to see your plugs