Wiring for jectonic injection system on GTi. How is it connected?

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Wiring for jectonic injection system on GTi. How is it connected?

Post by David » Sun May 15, 2016 10:53 am

Hi all, I have a little job on, which has really got me lost. I don't know much about petrol engines, and can't work this one out.

I have been asked to reconnect a Jetronic injection system on a GTi 8 valve engine after it has been off & messed with. I have read my Haynes book from front to back and can't find a simple answer anywhere. Even the wiring diagram appears to be incorrect.

It says the system is triggered off the coil negative, I have got the coil working, as there are only 3 wires, live, permanent negative, screwed to the body & the 3rd wire, which must be the "pulse" wire.

The Jetronic ECU, I have got working to an extent. It controls the fuel pump, all the plugs are on the engine for the sensors & injectors, & the constant live is connected to the battery, & about 3 negative wires, with rings on, earthed out near the battery. I have read all the injectors are triggered together, so the order is insignificant. & that is about it.

There is a brown plug which is near the bulkhead, one wire needs to be connected to ignition live & the other I don't know what it does. Also there is a single green wire, with a red plug on, which again I don't know what this does.
If I connect the red plugged wire to the coil, it just opens the injectors & keeps them open, & if I connect the other wire in the brown plug to the coil, it shorts everything out.

The red plugged wire connects to pin 3 (I think) of the ECU & one side of all 4 injectors, & the green wire in the brown plug goes to pin 1 (I think) of the ECU. The green wire in the brown plug appears to have 12V through it when the ignition is on.

Could someone please inform me what I am missing here.

Thanks in advance.
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Re: Wiring for jectonic injection system on GTi. How is it connected?

Post by rutter123 » Sun May 15, 2016 12:06 pm

Hi David i have a gti here with jetronic if it helps i can take some pics and email them to you as the wiring has not been altered or tampered with in any way it's all original. I cant help with colour coding as colour blindness stands in my way, from what i recall there are only 3 wires feeding the airflow meter ECU and about 8 or 9 wires going to the earth on the inner wing, if i can help you out i will gladly send some pics if you can pm me your email with details of which wiring pics you need.
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Re: Wiring for jectonic injection system on GTi. How is it connected?

Post by David » Sun May 15, 2016 12:34 pm

Thanks for the reply.

It is all the wires under & around the battery tray that I really need pictures of. I don't know how original these wires are, or if they are even originally bx wires. They just look like someone has had a hobby of messing with them. None of them seem to fit together.

I will send my Email address in a PM.

Thanks again.
1992 Citroën BX 1.9 Diesel Meteor 4x4 - The Project.

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Re: Wiring for jectonic injection system on GTi. How is it connected?

Post by David » Sat May 21, 2016 2:15 pm

I'm back again with this issue. I have still got nowhere with it & the engine keeps shooting flames down both manifolds when cranking using easy start. Will this be the ht leads the wrong way?

Also how many relays with how many wires should be next to the engine? I have only 2 that control the engine ecu, pump & injection circuits & there are 4 wires in both. Does this sound right or are some missing?
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Re: Wiring for jectonic injection system on GTi. How is it connected?

Post by Kaapelimies » Sat May 21, 2016 10:32 pm

David wrote:I'm back again with this issue. I have still got nowhere with it & the engine keeps shooting flames down both manifolds when cranking using easy start. Will this be the ht leads the wrong way?
Sounds like somebody connected the HT leads thinking the cylinder 1 is in the distribution end. It is in the flywheel end. 1-3-4-2 in the distributor cap (if it has one).
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Re: Wiring for jectonic injection system on GTi. How is it connected?

Post by rutter123 » Sun May 22, 2016 12:25 am

Are you sure the mechanical timing is set properly i.e your cambelt has not slipped a tooth or 2 ? from memory my gti had 3 relays next to the battery 2 for the injectors and 1 for the fuel pump IIRC. You should be able to set your HT leads correctly working from TDC on the firing stroke no1 cylinder flywheel end in relation to the position of the rotor arm.
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Re: Wiring for jectonic injection system on GTi. How is it connected?

Post by David » Sun May 22, 2016 2:47 pm

Thanks again for the replies.

I have had the cam cover off the engine & reconnected the leads as they should be. I think 2 were backwards, but can't be 100% sure as I pulled them all off & started from scratch.

The timing belt appears to be in the correct place; I have removed the timing covers & read the haynes book, and it says the 2 timing marks are in the cam at around 7 o clock, & the crank is a 9 o clock. I have put pins in both & they slotted in, So I assume the timing is correct.

Are you sure all the relays are for engine control? There are 4 in total, but 1 is for the ABS, & 1 is for the fog lights, just leaving 2 for the engine.

I connected the "pulse" pin of the coil directly to a rev counter & it was jumping while cranking the engine, so I just need to establish where this wire goes on the ECU. Does it go directly to it or does it go elsewhere?

Thanks again for the help.
1992 Citroën BX 1.9 Diesel Meteor 4x4 - The Project.

1992 Citroën BX 1.9 TXD (with GTI engine; Mulleys old car) - Parts car.

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Re: Wiring for jectonic injection system on GTi. How is it connected?

Post by David » Sat May 28, 2016 3:11 pm

I have not had much time to look in to this further, however I believe part of the wiring is actually missing (thanks Rutter for pointing this out), which is why I can't get it to work.

The 4th relay that I thought was for the ABS is not. It must be the missing piece of this puzzle. Does anyone know how it is connected up? It somehow connects the coil, injectors, rev counter & ECU all together.

I have looked on many Peugeot 205 GTi sites, but nothing mentions what I simply need to know, and the wiring seems to be different on them anyway.

Thanks in advance.
1992 Citroën BX 1.9 Diesel Meteor 4x4 - The Project.

1992 Citroën BX 1.9 TXD (with GTI engine; Mulleys old car) - Parts car.

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Re: Wiring for jectonic injection system on GTi. How is it connected?

Post by Jaba » Sun May 29, 2016 12:18 am

If you look in Haynes wiring diagram for all models 1987 > circuit V shows the L Jetronic circuit. There are only two relays used one for 12v ignition via pin 2 of the ECU t'other for the injectors and pump.Both look to be live all the time with ignition.
The circuit shows an onboard computer which does not exist. The 4 way plug is shown as connecting to a fuel calculator unit so this will not correspond to what you have. As far as I can see it can be left disconnected as long as the pump is getting 12v and pin 3 is connected to the injectors and I suppose the extra air for cold starting device has 12v too.
Time perhaps for the usual ignition checks : sparks, distributor, rev counter moving when cranking then taking it from there.
The ignition amp, h t coil, dizzy and ECU are the likely culprits if any of these checks fail (as long as its wired up ok)

Its difficult to suss these things out from a distance so if my ramblings are not helpful - well at least I tried.
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Re: Wiring for jectonic injection system on GTi. How is it connected?

Post by David » Sun May 29, 2016 10:07 am

Thanks for the reply, any information is very helpful.
The coil and distributor appear to be connected correctly & working as there is a spark & the rev counter the jumps when cranking, therefore I simply need to know what to wire from the coil goes to the ecu, and what pin in the Ecu it goes to. I have seen the wiring diagram and it completely threw me, it just shows pin 1 being connected to the coil, but when I tried this it appeared to short ECU out, and the only other wire is pin three on the ecu which opens injectors constantly. I don't have any more wires on it, not even a 4 pin plug for a fuel calculator or computer, which it shows in the book.

If someone could look how their gti is actually wired up that would be very helpful.

Thanks again in advance.
1992 Citroën BX 1.9 Diesel Meteor 4x4 - The Project.

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Re: Wiring for jectonic injection system on GTi. How is it connected?

Post by David » Sat Jun 04, 2016 1:30 pm

After messing with this for weeks I finally have some answers on how it is connected up. I can't believe that no one knew on here!

Pin 1 of the coil (the thicker grey wire) is connected to ignition live, Pin 2 (the thin green wire) is the pulse wire, which goes to the ECU & rev counter, [see below], (both in the red plug), & the wire on its own, with the ring connector is the neutral.

There are 8 wires that come off the ECU wiring harness that go underneath the battery tray. The thickest blue wire with a bare connector goes to the battery,
The thick blue wire with the white plug goes to the fuel pump,
Pin 1 of the brown plug (with 2 thin green wires) goes to ignition live, Pin 2 goes to the coil 'pulse' wire & rev counter (which in turn goes to pin 1 of the ECU),
The thin green wire with the red plug is left disconnected (it connects to the negative side of the injectors), Then there are 3 neutral wires, 1 brown wire on its own & 1 brown and yellow joined together.
1992 Citroën BX 1.9 Diesel Meteor 4x4 - The Project.

1992 Citroën BX 1.9 TXD (with GTI engine; Mulleys old car) - Parts car.

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2011 Ford Focus Zetec - Daily Driver. (Absolute bone shaker).

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Re: Wiring for jectonic injection system on GTi. How is it connected?

Post by rutter123 » Sat Jun 04, 2016 6:07 pm

Well done but is the car now running?
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Re: Wiring for jectonic injection system on GTi. How is it connected?

Post by David » Sat Jun 04, 2016 7:30 pm

That is a point. It starts and runs... like a bag of spanners. :lol: :roll:

All the injectors are firing & all the spark plugs are working in sequence, but it doesn't seem right to me, its like its running down a cylinder & it throws blue smoke everywhere.
1992 Citroën BX 1.9 Diesel Meteor 4x4 - The Project.

1992 Citroën BX 1.9 TXD (with GTI engine; Mulleys old car) - Parts car.

2004 Citroën Xsara Desire. (Now gone).

2011 Ford Focus Zetec - Daily Driver. (Absolute bone shaker).