Buggered BX

BX Tech talk
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Ian_Fearn
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Post by Ian_Fearn » Fri Aug 05, 2005 7:47 pm

Theres 3 wires that go into the coil from the connector.

2 are thin, 1 is thick.

Is the 12v wire the thick one?
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Jaba
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Post by Jaba » Fri Aug 05, 2005 9:36 pm

Weird. This model uses the wasted spark principle....which ,means I believe, that all the cylinders get a spark from the coil at EVERY revolution.
So you should see a spark even when the piston is at BDC.
If you have no spark at all on cylinders 2 & 3 then you have a straightforward ignition problem. No spark at every other revolution is not an often seen type of failure. Further electronic diagnosis would be ideal to narrow it down to the > TDC sensor > coil pack > leads > plugs. or alien intervention to save our planet by the likes of Klattoo (The day the Earth stood still).
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Post by Ian_Fearn » Sat Aug 06, 2005 10:27 am

Where is this TDC sensor?

The leads are proven to be fine, i've swapped the coil pack and replaced the plugs.

All thats left is the sensor? Surely if this is a redundant spark system then the TDC sensor is working because i am getting a spark on 2 cylinders.
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Post by AlanS » Sat Aug 06, 2005 12:43 pm

Have you actually physically seen that there's no spark or are you coming to that conclusion because if you take the leads off it makes no difference?
If so, go back to the injectors because they have fine filters in the end of them which can easily block up.
There are also plugs on the top that have a habit of not making good connections but this usually only happens after they have been unplugged.
A compression test on teh offending cylinders may also show some clues.
I've had reservations right from the word go about this being ignition based and I've yet to see anything to make me change my mind.
The CAS would have an effect on all cylinders not just 2.


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Jaba
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Post by Jaba » Sat Aug 06, 2005 12:49 pm

TDC sensor is in the flywheel housing section of the gearbox right at the top, close to the engine block. Its sort of underneath where the AAD and thermostat is.

BUT its not going to be that. Have you changed the 5 wire ignition module located on the inlet manifold ? This has separate circuits for 1/4 and 2/3. This is where your problem is. Either the module itself or the connections to pins 6 and 7 or maybe the circuit via the circular plug back to the ECU pin 2 is where you will find the cause.

Be sure to check the condition of the connectors in the 5 wire plug. These get loose or become damaged from time to time.

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Post by Ian_Fearn » Sun Aug 07, 2005 10:09 pm

I've checked for sparks and number 2 and 3 are DEFINATLY NOT sparking at all.

Yesterday i thought it had fixed itself when i wanted to move the car to work on it and it ran perfectly.

Within a few miles after hitting a bump in the road it went back to running on 2 cylinders.

I've located the ignition module, the wiring appears to be ok. Do i need to swap it?
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Post by Jaba » Mon Aug 08, 2005 12:12 am

Have you verified the condition of the connectors inside the plug for the HT coil ?? Also have you got a circuit from HT coil pins 2 to ignition module pin 6.

If this circuit looks ok then its probably the ignition module but first check out the circuit back to the ECU from module pin 7 to ECU pin 2. If this is o/c have a look at the circular engine multi connector.

If you find no problems here you could then prove if it is the ignition module by checking for a pulse at pin 6 for cyls 2&3 and comparing this with pin 1 for the other 2 cylinders. Any difference points to a problem here. Then do the same check on pins 2&7, if these are different then its the ECU that is playing up, if they are the same then its the ignition amplifier module.

OR just have a look at the circuit for MP 3.1 ignition and check the circuit for continuity from the HT coil to the ECU.

My money is on a wire broken internally somewhere then on the ignition module.

The Wolf Blass is kicking in now - hope my post makes sense.

Ciao.
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Post by Ian_Fearn » Sun Aug 21, 2005 7:34 pm

I'd just like to say that my Hurricane is now fixed and running brilliantly. :D


Once i'd managed to track down the correct ignition module from CX Automotive in Ripley Derbyshire who had it on the shelf the car has been back to its brilliant self again!


Thanks very much to everyone whos offered the advice. :wink:
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Post by Jaba » Sun Aug 21, 2005 7:46 pm

Good news Ian. Glad I got something right for a change!
The Joy of BX with just one Citroën to my name now. Will I sing Bye Bye to my GTI or will it be Till death us do part.