Part Of The Ignition System Failing On 1.9 Gti

[Weser 30]

Hi again all I'm after a little bit more help from you lovely people!

 

Still having a little ignition problem with my 1.9. I can be driving along and then the car will start juddering and rev like it is only firing on two. I will do this for a minute and stop and then do it again. It could have breaks of up to 15mins before it does it again.

 

Now the thing is when I drive to work 20mins in the morning the car is fine. it never does it. It only seems to occur when the car is hot.

When I turn the car off sometimes (when its hot) it wont start. It just turns over and over. There is no spark.

I did have a problem with the fuel pump it wasn't coming on but I have hardwired it in so is always on. There is definately not a fuel problem. You can smell the petrol when its turning over!

 

I think the problem lies with either the ignition Amp or the dizzy. or maybe the tachymetric relay for the fuel pump. The thing is I am not sure how the ignition system works. Is there a crank shaft sensor?

 

If someone could explain how it all works (in laymans terms), I am quite technical honest! I just dont want to start changing parts willy nilly.

 

If anyone could help with the problem that would be great.

 

If anyone is in North essex and can help that would also be handy

[matthewm 1]

You camshaft turns the distributor, which sends a firing signal to you ignition amp via the lead coming out of the side of dizzy. Your coil has a permanent 12v, but is earthed via the ignition amp, so when the dizzy tells the amp to fire, it brings in the coil, which puts the big bang on to your HT lead to the dizzy cap, which will be lined up to give you your spark.

 

Later models/MI16's have a crank sensors which tell the ECU to bring in the amp, which then earths the coil, same principle with dizzy cap then.

 

Sounds like you problem is the ignition amp, very common.

 

Cant remember exactly how the tachy relay works and whether its integrated in to the ignition system or if it just controls the fuel pump, someone will probably be along shortly and be able to elaborate on that....

Edited September 24, 2010 by matthewm

[Weser 30]

You camshaft turns the distributor, which sends a firing signal to you ignition amp via the lead coming out of the side of dizzy. Your coil has a permanent 12v, but is earthed via the ignition amp, so when the dizzy tells the amp to fire, it brings in the coil, which puts the big bang on to your HT lead to the dizzy cap, which will be lined up to give you your spark.

 

Later models/MI16's have a crank sensors which tell the ECU to bring in the amp, which then earths the coil, same principle with dizzy cap then.

 

Sounds like you problem is the ignition amp, very common.

 

Cant remember exactly how the tachy relay works and whether its integrated in to the ignition system or if it just controls the fuel pump, someone will probably be along shortly and be able to elaborate on that....

 

 

Thanks for the info Matthew. I understand that bit. I really need to know the bit inside the dizzy which tells from the crank when to give the spark

 

Mine is a later model (1992) so probably does have a crank shaft sensor.

 

Does anyone know where this is? And other little parts. I know where the dizzy ignition amp and coil are! (just about )

[blessed6383 0]

the crank sensor will come of the top of the gearbox iirc mine does on the mi16 it should connect to he distributor black 3 pin plug

[matthewm 1]

Thanks for the info Matthew. I understand that bit. I really need to know the bit inside the dizzy which tells from the crank when to give the spark

 

Mine is a later model (1992) so probably does have a crank shaft sensor.

 

Does anyone know where this is? And other little parts. I know where the dizzy ignition amp and coil are! (just about )

 

If you have a crank shaft sensor it will be on top of the gearbox, up against the engine, below the thermostat housing. The later Motronic ignition with the crank sensor doesn't have a distributor, just a dizzy cap.

 

As for the distributor, it fits in to a recess in the end of the cam shaft which spins the internals of it, not taken one apart to see exactly how it does it, but it detects when its in a certain position, perhaps TDC, then gives out the signal to the amp. Same as a crank angle sensor if you like.

[large 33]

THIS may help.

With the problem you have no one can tell you exactly what it is. We can however narrow it down. If you can get access to a working car to borrow bits this will help.

 

The first thing I would look at would be ignition amp then leads then the coil.

[Weser 30]

Ok so here is where I stand now.

 

I have no crankshaft sensor.... Thats one thing eliminated. Because mine is the jetronic system

I have had a god read or the Haynes manual and understand how it all works.

 

I dont think it is HT leads because when the car is running all the leads deliver sparks and if they were not working then the problem would happen much more often. Also I dont think it is the coil as it looks fairly new and the same applies it would be happening much more.

 

The problem has started occuring when cold now as well.

 

As far as im concerned it leaves we with two possible causes. Ignition Amp or Dizzy. Now personally I think it is the dizzy because the ignition amp is just transitiors. At first I thought it was the Amp because it was only doing it when it got hot which made sense.

 

Anyway I haven't got a car that I can swap parts from. So I going to start with an igniton amp (as its cheaper) then if thats not a solution I will do the dizzy.

 

Sound good?

 

Thanks for the help guys