Mk2 16v Poor cold starting - think I might have finally found the problem..

Just a thought(yes it hurt like hell), could it be an earthing issue? The g/box earth strap has been known to cause people a lot of tears from what i've heard. Could it be related to that maybe??

 

If it was the earth strap, surely it would be a pain to start when it was warm as well. I tried starting it again tonight after leaving the other plugs in and it started first time. The original plugs were almost brand new and my back-ups were out of my abf. The originals stunk of fuel but were bone dry although a little black. Anyone Know if the 90amp alternator is a direct replacement for the 65?

 

yes, and a 16v passat is the best place to find them, most corrado 16v's have a 65.

 

I've had similar; changed various ignition components which seemed to sort the issue for a few days then it was back to dodgy starting again.

Not sure how comforting it is knowing you've lived with the problem for 10yrs without being able to sort it tbh

Regarding the accumulator, I found that priming the fuel system by turning the ignition to pos. 2 several times before starting will bring the line pressure up to where it should be were the accumulator working; might be worth trying this before you start it. Personally I wouldn't have thought the throttle switch would have any effect on starting ability; that said I can't suggest owt better.

I thought similar; definitely think it's an electrical issue. Even though I'd done it once already, today I checked, cleaned and greased the gearbox and battery tray earths again, just in case.

After starting perfectly with a fly lead from the battery to the coil on Monday, I repeated the exercise yesterday with less than splendid results. So fook knows what's wrong with it.

I also noticed today that (no doubt as a result of my own retardation) the alternator assembly was loose; the bottom bolt having lost it's nut and partially worked its way out of the housing [:^(]

Threads were knackered as a result so I used the bolt off the old engine, made sure the belt was tensioned and nipped everything up. Being electrical I'm secretly hoping that this will sort the problem, although in reality I imagine were the alternator not charging properly I'd have all manner of other problems. Besides, a fresh, fully charged battery failed to sort the starting problem so I don't expect this to either.

The day or reckoning draws ever nearer..

 

Small update for those who might find it helpful.

I've been starting the car recently with a fly lead from the battery positive to the positive terminal on the coil, and it's been starting a lot better. On the old man's advice I checked the voltage to the coil positive today, both with and without fly lead, and got the following:

Potential difference across battery: 11.85v

Without flylead:
PD between coil positive and earth, ignition switch on: 11.74v
PD between coil positive and earth, ignition switch in "cranking" position: 9.5v (ish)

Now the same with the flylead in place:
PD between coil positive and earth, ignition switch on: 11.89v
PD between coil positive and earth, ignition switch in "cranking" position: 10.3v

This indicates that something in the ignition switch circuit is causing a significant voltage drop during the high current draw situation of cranking, which then goes away when the car has been running for a few minutes.

I did try and repeat the tests once the engine had been started, but it started on the button and too quickly to get any voltage readings during cranking.

So I'm definitely thinking along the lines of a knackered ignition switch (a complete sh*t to replace [:^(] ) or a dodgy connection somewhere in the circuit.

I've had the connector off the switch and checked continuity between the live feed and output terminals on the switch, so I know what should go where. Next test is going to be isolating the switch by jumping directly between the terminals on the ignition switch plug; if this works I know the switch is shafted, if not I know to look elseware.

Several other factors I think are worth considering; a) the car has an aftermarket immobiliser fitted, so perhaps this is screwing things up somewhere, and b) there's a sh*tload of water getting into the car through the driver's side door, so I'm wondering if this is shorting something when cold (switch or other contacts somewhere else).

Will probably have another play tomorrow..

 

Cheers John. Today I bypassed the ignition switch completely; got a much better voltage to the coil during cranking (around 10.3 - 10.5v as oppoised to the 9.5v through the ignition) but it was still reluctant to start.

Going to leave it for another day and try it again tomorrow, if I get the feeling that it's starting more consistantly without the ign. switch I'll take it off, fill it with WD40 or contact oil and stuff it in the airing cupboard for a few days, incase it is the damp. The car is like a bloody swimming pool inside at the moment..

If the starting gets no better without the ign. switch I'll get under the dash and start tracing wires as you suggest. The old alarm was bodged onto some wires near the TCI IIRC, although thankfully (!) with scotchlocks, so it was just a case of pulling them off and applying some insulating tape..

Fear not, I'll keep you informed

 

Replacing the ignition switch really isn't all that bad. A morning job, if that. Are you worried about having to deal with the splined metal collar, which needs to be pulled off the column shaft? Even that's dead easy when you know how (mole grips plus bearing puller).

 

Or clamp in vice and tap out with lump hammer and wood block.

As Trev says the job is not that bad, i changed my steering lock housing the other day and it only took a few hours.

 

all your voltage readings seem a bit low to me? might be the immob drawing too much load overnight if the battery is fine? mine are all fairly consistent and much closer to 12, my alarm is factory and wiring unmolested. that said, i have an identical problem
i had a very strange couple of days on saturday/sunday though, it started on the button at least 6 or 7 times on the trot, even from stone cold. i was gutted i was away from the garage at the time so unable to test anything. lo and behold, monday morning, it was back to the ten second foot to the floor cranking [:^(]
i have tested my throttle switch theory this week.. open or shut; no ******* difference! oh well, worth a try.

 

Cheers gents

It's looking more and more like a dodgy ignition switch; jumped it across the terminals on the switch multiplug again today and it started first time. I'll try it for another few days and if it starts consistantly well looks like it's time for a new switch. I've done my best to fill it with WD40, but since I was shooting uphill I don't hold out much hope for it getting well into the switch.

I think I was getting confused about replacing the switch; read the bit in the Haynes manual about replacing the ignition lock (and needing to drill the housing) and must have applied this to the switch as well

I finally separated the splined steering wheel adaptor from the column of the old car last night; in the end I made up a split collar from some convieniently sized thick walled steel tube, clamped it round the adaptor with a jubilee clip and got busy with the bearing puller. Was still a bit of a sh*t to get off, but got there in the end. Also had the steering wheel off the new car, and found that that's got the same (large spline) arrangement.

In the post '90 spec housing, it appears that the ignition switch is retained by a small phillips screw; is this the same in a pre-90 spec housing, and is this the only thing that holds it in? I'm half tempted to try and get it out in situ, but think the easiest way would probably be easier in the long run to pull the whole assy off. Only other thing I could try is a phillips screwdriver bit in a socket I suppose, to get round the problem of it fouling the steering column.

I thought similar, although I put a nearly new, fully charged battery on it some time ago and it still didn't start. Have you tried isolating the ignition switch? If it's a pre-90 car I can show you which terminals to bridge..

 

Cheers

Will give it a few more days of bypassing the ignition switch before replacing the little bugger

 

not tried messing with the switch yet actually! mines a may'90 (build date)

 

Might be worth testing it, just to rule it out if nowt else


Right, I think I might finally have got to the bottom of the problem

Water is p*ssing in through the driver's door as the window seal is shafted, and I've taken out the membrane as it'd been butchered so was useless anyway.

I've long suspected that this water was to blame, but was initially thinking it was affecting the ignition switch. However, while bypassing the switch made starting easier, it still wasn't as consistantly good as it should have been.

I began to suspect the immobiliser, and yesterday after a nice long drive, put the main control module (which is located next to the lower A-post, so right near the leak) into a ziploc bag and sealed it as best as I could.

Tried starting the car on the key a few minutes ago, and it fired up first time. It remains to be seen if it will do this consistantly, but I'm pretty confident I've finally located the source of the problem

 

Just remembered. I used the engine and all the gubbins from my scrapped golf to fit in to my jetta. The golf ran sweet as a nut and started right away on a turn of the key but it was just when it was fitted to the new shell that this problem started.