318i 1990 - Little collar on HT lead

[eddieg]

Sorry to be so dumb about electrics.

I've just got a replacement set of HT leads for my 1990 318i (M40 engine). I notice on set still on the car - there is a little collar around the HT lead to cylinder 4 (nearest driver) with a lead from it disappearing somewhere near the distributor cap.

Is this a sensor of some sort? Will the car go OK if I leave it off and fit my new HT leads without it. Alternatively, if important, I could leave this lead on and just replace the other 3? Advisable?

On the donor car I took the replacement leads off ( they are nearly new) this collar was there but just dangling and not on the HT lead. The breaker said it drove perfectly OK coming to his yard!

Whats the best to do?

Thanks guys

[town325i]

Its a sensor for the ecu

[eddieg]

Hi, thanks. Can anyone tell me what it does and if the car will run without it?

Basically, it wont fit/slide over the new HT lead. Would a 'proper' new set would come with it attached? I'm left with two options

1) leave this on lead 4 and replace the three other leads
2) replace all leads and leave it off

Whats best?

Thanks

[daimlerman]

The sensor is an early version of a cam position sensor.It tells the injectors to squirt petrol into the correct cylinder,without it,all injectors fire,wasting fuel.

Is it not possible to unscrew one H/T cap and thread the sensor on?

A 'proper' set of leads from GSF will come with the sensor attached.

[Morat]

Just out of interest, what was wrong with the original leads?

[eddieg]

The car still has the originals, I think - they look very old - 20 years. Its only done 40K but probably theres a time dependent element in HT lead deterioration? I came across this almost new set with an almost new distributor of a donor e30 for peanuts and just thought it would be a good idea to change.

[Alex]

Before dumping the original leads, test them with a multimeter. If they read under 6Kohm, they are fine.
BMW leads have a copper core, it does not fail. The caps are the suppressors, they are the bits that fail.
Aftermarket leads are junk IMO, have had them fail after a very short time. OEM are worth the extra money. If yours are reading high, and you dont want to pay for new oem, go to the wreckers armed with a multimeter and find a set that reads within the limits.
The sensor on no4 lead is the cylinder reference sender, it tells the ecu when to fire the injectors. Without it the ecu will fire all 4 at the same time, losing efficiency.

i'am wondering if thats whats happened to mine.

The little circle collar that goes round one of the leads is all taped together. car hesitates and has a lump idle. it did have a bad missfire but that seems to have gone with some heavy pedal pumping (cars been stood for a while and off the road)

Sorry to go slightly off topic

[eddieg]

Thanks for the advice. Will test the existing leads and report back!

[Brianmoooore]

. Its only done 40K but probably theres a time dependent element in HT lead deterioration?

You are confusing BMW with 'other makes'.
I have NEVER come across a duff BMW HT lead, other than the odd one that has been physically damaged.

[eddieg]

Tested original leads for resistace and all fine - so kept them and changed dist cap

The guy I got the leads from said the little collar was just taped onto the HT lead to cylinder 4 without going around it - will this work just as well?

Thanks

[Brianmoooore]

No!

[eddieg]

Thanks Brian, answer clear!