Ignition Control Module

[mikinoz]

Good thing I had a cup of tea handy before opening this thread this morning. Fingers crossed it starts again today Liam.

How are the wipers going, are they stronger/faster than before as well? I wonder if that is all related.

Glad you got to take it out for another drive!

[Golf Loon]

Aaaah the curse of the early Mk1 wiring.

Sounds like you are a patient man Liam.

That car has the last year of the early fusebox, after that, VW went to the Cabriolet style fusebox with proper blade fuses. Dunno if that helps.

When I had it, it would either fire straight away, or you would swing it for a while, BUT if you went away and came back in 15mins, it would then start straight up. Once started, it was good all day.

Doesnt sound as if you have the same symptoms.

I also changed it to the later electronic dissy, with the TCI module that you are taking about, as the car originally had points!

Good luck.

[abreut]

2 things I would try would be get a new ignition switch. You can try that without the difficulty of removing the old one, just unplug the harness from the old one and plug it into the new one and just turn it over with a screwdriver. If you want to go for a drive just use your keys to overcome the steering lock. The ignition switches do go faulty and if they have had a heavy set of keys hanging off them for many years they can die.

The other thing is engine earths. That old braided earth strap from the gearbox, to chassis, to battery earth may look fine, but check the resistance on it. I had electrical problems for ages because of that damn lead. I now have 2 engine earths.

I have had a hall sensor die on me once but I don't think they generally go intermittently. Good luck.

[roccodingo]

Aaaah the curse of the early Mk1 wiring.

Loon has hit the nail on the head, check for inconsistent current flow in the harness' whilst moving the harness about. These older cars pretty well all the engine bay wiring is heat baked by now, leading to brittle wiring that can cause these types of issues.
Ignition switch and earthing also come well into the play here also.

Possibly try a new fuse / relay plate if you can source one cheap enough, any water in these things renders them pretty useless.. look for water entry behind the relay plate location ( light rust stains on the inside of the car ) which will give evidence that the relay plate has indeed been swimming !!

good luck lads, your going to need it .

[Lima]

Thanks for the replies.

This morning I tried the car and it started okay, but idled very roughly and stalled. I was able to start it up again next go and with a bit of gas pedal keep things running.

Just now I tried the car again, and like this morning the car started okay, idling roughly, but a bit of throttle was all that was needed.

With the car running I went for a quick zip around the block. A few hundred m from home the tacho needle started bouncing, otherwise the car was still running okay. However it cut out just before I pulled into my driveway and after parking the car I can't get any joy out of the old dear.

[Lima]

When I had it, it would either fire straight away, or you would swing it for a while, BUT if you went away and came back in 15mins, it would then start straight up. Once started, it was good all day.

Once I got the fuel pump relay sorted the car usually worked like this for me too. Although, if I drove it to work, for example, it would take a few goes to get it started in the afternoon, but was a repeat of the morning process and, generally, if you cold hear the fuel pump going you knew that it was going to start.

Somehow, somewhere, something has become worse and prevents the car from behaving consistently.

[Golf Loon]

You said the tacho needle was bouncing, that sounds like an earth problem to me.

I reckon get a new fat earth wire for the engine as an extra, you cant have too many.

Also one from the fusebox and maybe one for the dash loom.

Try that and see if it makes any difference.

[Lima]

Thanks for the suggestion. I checked the main earth strap today and cleaned it up a bit. Didn't make any difference.

The tacho needle wasn't bouncing all the time, just a few seconds prior to the car cutting out.

[gldgti]

Thanks for the suggestion. I checked the main earth strap today and cleaned it up a bit. Didn't make any difference.

The tacho needle wasn't bouncing all the time, just a few seconds prior to the car cutting out.

tacho bouncing is usually becuase of low voltage - like a really big load on the battery (cranking on a low charge, or flat battery, or a massive short.)

i would do as loon suggests, check for both bad earthing (also check between engine and gearbox). someone with more experience of the petrol fuel pumps may chime in here - is it possible for them to pole out and short???? (thus causing a massive short, voltage drop and tacho bounce)

[Lima]

Today's update (got it started)...

Yesterday I tested the spark to all four plugs. I tried 2-3 start attempts each time. Plugs 1 and 2 gave nothing. Plugs 3 and 4 gave a little spark on one occasion each. No surprise then the car wouldn't start.

I didn't think to do a simple test to the main lead into the dissy from the coil. So I did that today by following the instructions from the Poor Richard's How to keep your Rabbit alive book (thanks Steve. I tried it 3-4 times and there was a spark each time. Mind, the spark only last half a second or so, but it fired immediately on turning over the key.

I then decided to try another test from Poor Richard's book on the HT leads, where you stick a screwdriver where the spark plug would go and hold the shaft of the screwdriver a few mm away from a bare metal point on the engine block. When turning over the ignition a spark should bridge that gap. Your supposed to hold the HT lead with some pliers to prevent shock, haha.

First plug, from cylinder #1 ... no spark.
Cylinder #2 ... massive spark, bit of a shock for me and the car almost fired into life.

So I plugged the lead back onto the plug and it started perfectly. It was idling a bit rough but I was able to get a couple of laps around the block and another 10 minutes of idling before it...

...cut out again!

However, it did fire up again immediately after for a couple more starts. Then it cut out again and I haven't been able to get it to start.

I retested the main lead into the dissy and, yep, there was still spark. Although, the colour of the spark was orange, which, according to Poor Richard means the ignition coil is on its way out.

But, IF, the spark into the dissy is relaible, as it appears to be, then either the HT leads or dissy cap/rotor must be shagged ... right?

Matt, if I was to get new HT leads, do I need to get anything tricky/different to the OEM spec given the distributor is not original?

[Golf Loon]

Check the rotor mate.
I changed it not long ago, if its shagged again, mabe there is movement in the dissy shaft and you need a new dissy.
The leads should be the same as Mk3 and pretty common

[Peter Jones]

is it possible for them to pole out and short???? (thus causing a massive short, voltage drop and tacho bounce)

Absolutley, this is exactly the sypmtoms they display when they wear out.

The rotor siezes and draws 20 Amps + usually blowing it's fuse.

Pete

[Lima]

Check the rotor mate.
I changed it not long ago, if its shagged again, mabe there is movement in the dissy shaft and you need a new dissy.
The leads should be the same as Mk3 and pretty common

Thanks Matt. So, if I need a new distributor do I need a later Mk1 version or Mk3?

[Golf Loon]

Thanks Matt. So, if I need a new distributor do I need a later Mk1 version or Mk3?

You need a GTI Mk1 or 2 one with vacuum andvance and electronic ignition.

I have a few if needs be.

[Lima]

So it turns out the hall sender is stuffed. Should have a brand new dissy ready in a week or so. Fingers crossed this resolves the starting issues. Will be nice to have the old dear running reliably.