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TKMotorsport

Ignition System

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TKMotorsport

Hi all,

 

I need some fairly in depth technical assistance. 

I have a 205 GTI 1.6 that will not start. No spark and no fuel. Distributor has been checked, Amplifier has been changed. Tachometric relay has been changed. 

The distributor is outputing an analog rotation signal to the amplifier but the coilpack is not getting a earthing/trigger signal through the Yellow wire thus no engine speed signal to the tachometric relay and engine ecu therefore no fuel. 

The bit im after is what controls the yellow wire trigger? And what just takes the signal. 

My guess is that the amplifier controls the signal. The Engine Ecu, combination meter  and coil all take the signal. 

I have attached the wiring diagram i have been working off. Ths issue is the yellow highlighted wire. 

I have 12vs on the yellow wire with ignition on. Which in a good vehicle intermittently drops to earth to fire the coil. When i turn the car over i get 9vs contant. 

 

 

Wiring (2).png

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PhilNW

When did it last run? 

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TKMotorsport

Recently like initial issue turned up 4weeks ago i looked at it, long story short after fiddiling with the fuse box it started and ran normally. Now its back to not starting again. same symptoms

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TKMotorsport

p.s fusebox was replaced and all connections checked

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PhilNW

In the first instance try using a bulb to check the voltage when turning engine over, it may be your voltmeter does not react quick enough to a fluctuating voltage .

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TKMotorsport

Phil,

 

Cheers for getting back to me. Im actually using an oscilloscope for voltage checks on the coil trigger wire for that exact reason. 

But unlike the correct signal which you should get on that wire (attached) i am getting a 9v flat line. 

Just trying it understand what controls that system and how sensitive it is. I.e would it give me the symptom ive got if it detects an issue on the line

NOrmal.png

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TKMotorsport

@DamirGTI from my various readings on this forum you seem to have a fair amount of knowledge about these cars..... Any ideas

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PhilNW

Does the fuel pump run with a direct feed?

 

What are the voltages on the injector connections if any?

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TKMotorsport

Fuel pump will run yes. No voltage to any injectors as it need a signal similar to the picture i sent to enable the injectors to know when to fire.....

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PhilNW

As I understood the system there should be a supply voltage off the tachy relay with the ecu creating the earth to fire the injectors.

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TKMotorsport

Just by following the attached wiring diagram the highlighted yellow wire is that wire you talk of i suggest. But i belive the signal is created by the amplifier not the tacho relay. Because the 205 doesnt have a crank sensor (so to speak) it uses the coil earthing signal as a crank signal. 

Edited by TKMotorsport

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PhilNW

The injector supply is off a different terminal to the sparks/coil, just trying to see if its a common problem for the ecu, not firing the injectors and/or sparks/coil.

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PhilNW

Have you seen this

 

 

 

 

 

 

 

 

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TKMotorsport

Phil, yea have seen that. The negative pulse switches the relay and then powers the injectors through a different circuit. 

So hence why i haven't got any fuel from the injectors because i have no negative pulse

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PhilNW

What signals/voltages are you getting on all the terminals on the Amplifier?

 

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Telf

Have you changed the Ignition Amp or checked the condition of the plug ?

 

Also the connection between the dizzy and the Amp? They fail on the teflon block at the dizzy, they often have damage on the fly lead from the dizzy or contamination in the fly lead plug that connects to the coil/amp.

 

The amp could be faulty - As far as i remember ( i have an emerald ECU set up now) the Amp receives a signal from the dizzy and opens/closes the ignition ground circuit therefore firing the sparks/injectors.- injectors in conjunction with the Tachy relay.

 

 

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TKMotorsport

Hi Telf,

So i have oscilloscoped the signal output from the dizzy and it is good. Amplifier has been changed for a brand new unit. Although not a blue bosch one i would have thought that it couldn't be completely broken out of the box. Pretty sure we tried multiple amplifiers originally. 

Amplifier plug seems good. Engine bay wiring loom has been checked and recovered professionally so all connections and terminals have been checked recently by a electrician. 

 

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Telf

OK. 

 

In my experience any Amp other than a Blue Bosch unit is a waste of time - they are garbage. Get a blue one.

 

I had a failed blue amp a few years ago before i converted the car. Fitted a new non Bosch amp( i think it was light grey) - nothing - spent ages chasing the fault and finally fitted a blue one out of a mates car- solved the fault immediately.

 

The cable from the dizzy is vital- is it in good condition? The signal output from the dizzy triggers everything.

 

The dizzy supplies a signal at every stroke for the spark plugs but also to the ECU to initiate the injectors as the spark occurs- at least that's my understanding. If this signal is bad you have no spark and no fuel .

 

The ECU  supplies a signal to the Injectors - all on a common wire until it splits at each injector - 1 wire broken or poor contact equals no signal.

 

Also don't forget there is a common return line from the injectors. So even if you are testing at the injector for a signal a multimeter may register a voltage but under normal operation nothing will happen.

 

When you say checked by an electrician- who checked it? how?

 

Where abouts in Norwich are you? I have a complete set of the old 205 ignition in a box - all working. I'm not that far away in suffolk

 

 

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TKMotorsport

Telf,

 

Electrician removed the wiring harness from the engine bay and replaced and connectors, terminals and wires that weren't any good. Then recovered in higher quality sheathing. 

Agree with what you say about the dizzy being the life blood. Although the signal it produces is an analog signal so the amplifier turns it into a more normal 'crank' style signal.

I believe we tried various amplifiers including a blue bosch unit. The weird thing is that it did run and drive well after i spent some time looking at it and now its back to not working at all. 

As it stands the issue with the negative pulse wire is the whole issue with the car. No negative pulse = no fuel. So im not even looking at the injectors yet but i believe they will be ok. 

As soon as i get that signal back the car will run like a dream.. just need to work out why i haven't got that signal. 

 

Thanks for offering the assistance if parts. Where in suffolk are you?

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Telf

has it run since the loom was removed?

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TKMotorsport

Yes has run well for a few months since loom was done. 

Started playing up around the middle of September. It is a race car so that was its last race. I looked at it twice after that and it started to work . 

Now its back to not working again, Cylinder head was changed but that doesn't have much to do with it. 

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TKMotorsport
59 minutes ago, PhilNW said:

What signals/voltages are you getting on all the terminals on the Amplifier?

 

All voltages and earths are good at amplifier. Haven't tested the signal at the amplifier but the continuity between amplifier and dizzy wires are good. 

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Telf

sorry im just trying to get my head round this- hard when you cant see the car- does it crank? 

 

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TKMotorsport

Telf,

 

Yes it cranks. Only reason it wont start is no negative pulse to coil and down the rest of that wire..... tacho, tachymetric, ecu 

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