205 Gti Wiring Loom 1.6

[Have-a-go-al 0]

Hi

 

I have just bought a 205 1.6 Gti rally/track car

 

The engine/loom is the one with the coil mounted on the manifold There is no original fuse box in the car. I have lived the loom up and have a spark but there appears to be no fuel reaching the combustion chamber?

 

Is there anywhere else i need to live the loom up ? or if anyone can point me in the right direction id really apreciate it

 

I was wondering if it could be injectors or throttle position sensor?

 

 

Thanks: Allan

[blessed6383 0]

silly question but i take it your fuel pump is wired in?

[Have-a-go-al 0]

silly question but i take it your fuel pump is wired in?

 

 

Yeah fuel pump running and there is fuel at the rail

 

Thanks Allan

[Have-a-go-al 0]

Had the injectors out and there is nothing

 

Anyone know anywhere local that could wire this corectly for me ?

 

 

Allan

[blessed6383 0]

another silly one fuel lines are correct way round? heres a link to a online manual has the wiring diagrams which has the wire numbers so you can check there getting a signal

 

http://www.buzzboxx.co.uk/Haynes_205.pdf

[Have-a-go-al 0]

Yeah double checked and the fuel lines are the right way round

 

Im getting a shot of fuel from the injectors after i stop cracking the engine, There is preassure at the fuel rail

[Have-a-go-al 0]

Got the car running thanks to Abbey Auto Electrics

 

Dropped the car off 9am had it back to me just after lunch running perfect

 

Highly recomended service

 

Thanks for the help here Allan

[pug_ham 242 3 Cars]

What was the problem?

 

Graham.

[Have-a-go-al 0]

3 Lives not reaching the ECU white and blue wires

 

I would of still been scratching my head now

[DrSarty 90 1 Cars]

3 Lives not reaching the ECU white and blue wires

 

I'm glad you got it fixed, but I'm not sure this is a correct diagnosis of the fault.

 

I don't mean that against you or Abbey, but I mean it might give others a false impression of what's going on in a wiring loom and ECU. Why?

 

Well: an ECU only really needs a switched 12v live. Naturally it also needs an earth. Some ECUs do have a 12v permanent live. That may be the 3 wires that you/Abbey are referring to.

 

The ECU then only really receives signals from sensors (coolant, throttle position, inlet air temp, crank position and perhaps MAP) and triggers things to work by grounding something that already has power, e.g. a relay, ignition amp/coil or the fuel injectors.

 

All of the sensors have a ground (which is an ECU ground and is a wire going back to the ECU itself rather than the chassis or engine), so the other wire from the sensor goes back to the ECU and gives the ECU a value to make a decision on.

 

If a sensor has 3 wires e.g. TPS or AFM, then one will be the ECU ground I mentioned above, one a 5v reference voltage feed out from the ECU, and the third will be the signal wire giving a value back to the ECU, which is a percentage of the 5v ref voltage it was fed in the first place, i.e. the ECU will see 0v, 5v or somewhere (anywhere) in between.

 

***

 

So when installed right, you turn on the ignition and your ECU gets power. It had earth, but needed your 12v by turning the key. No 12v or ground or both = no go.

 

The ECU then usually grounds for a short period a relay on the fuel pump circuit. It literally allows a relay which had power already get the earth it needs. This triggers the relay to pass the power through to the fuel pump for 1-2 seconds, then the earth is removed by the ECU. This is the buzz you get when you switch the ignition on.

 

You turning the ignition on, also sent power to the fuel injectors and coil(s). Now everything's just waiting for more grounds from the ECU.

 

When the ECU (or tachy relay) starts receiving a proper crank angle signal (which is only an alternating voltage as lumps of metal on the timing wheel pass a magnet - again, nothing complicated) it will start grounding the injectors at the correct time to allow them to squirt fuel. Honestly, all it does is ground them, usually 1 and 4 together and then 2 and 3 together, or all 4 at once. It's literally on-off-on-off, but by giving or taking away a ground/earth.

 

Likewise, the ECU will also ground the ignition amp and coil together to trigger the release of the high tension spark to the distributor, or the coil pack to send a spark to (you've guessed it), 1 and 4 together and then 2 and 3 together, in the correct order to ignite the fuel.

 

The other sensors as explained just send a value (mainly resistance or possibly a voltage like the TPS or AFM) all of the time so the ECU knows what's happening, and controls the amount of fuel. Spark advance or retard will either be managed by the ECU getting certain signals from the sensors or a mechanical device.

 

***

 

Now I didn't type that to make myself look clever. I typed it because I would like to encourage less people to be stumped by electronic issues on this forum, as I have battled through them myself and learned that they are never really that difficult.

 

I'm saying it's definitely worth learning a bit of the above and how it works, as it'll help you either fix faults, make your car run better or modify and improve your car, such as fitting aftermarket ECUs and building looms.

 

I appreciate some people will always be a bit wary of piles of wires and electronics, but I am just trying to help remove some of the myth and black magic.

 

Again, the above was only typed to help out anyone with either similar problems or who just wants to gain a bit more confidence with engine wiring. Anyone with similar problems, if they find out the pin numbers on the main ECU plug, they can test with a £6 multimeter what's going on, and potentially avoid garage/auto electrician costs and get motoring quicker.

Edited July 9, 2010 by DrSarty

[Have-a-go-al 0]

Very intresting read

 

I think i worded the diagnosis wrong the wires were not getting live from the ECU

 

 

I really need to understand wiring looms more

 

Allan