325i Auto: Cranks but Not Starting

[BristolE30]

Unless I’ve misread it sounds like the issue is still lack of spark? You’ve got fuel, air but no spark(or one weak one?).

I think you’ll have to work your way backwards from the spark plug to the lead to the coil etc and test it all again. Something is missing and if you say you’ve tested it all but it’s still not starting, unfortunately you’ve missed something.

[MunsterScot]

The car doesn't have a Cat fitted (at least it doesn't any more) .

I have tried a 2nd coil but that didn't work.

I was reading back down the posts in case I missed anything. I spotted that Brian wrote "A duff CPS call still produce enough 'noise', under certain failure conditions, to provide enough signal to be integrated and activate the fuel pump, without producing the pulses to be amplified into sparks." a while back.

This got me thinking (might be a longshot).

I know the original CPS is faulty as there was no power to the fuel pump and it measures open circuit when tested with a multi-meter.

Both replacement CPS's have been "Meat & Doria". I'd initially though the original replacement was the wrong one which is why I got the second one but it turns out they are both the same. Could it be the Meat & Doria CPS's don't work with the E30 ECU's (the same CPS is used across a variety of car models & manufacturers)? The thing with the M&D CPS's is that the body of them is all plastic with just a small metal pin sensor on the end. The original CPS had an all metal body. I realise about different manufacturers having slightly different designs but for the E30 does the body on the CPS need to be metal?

Could it be the M&D CPS's create enough 'noise' for the E30 ECU to activate the fuel pump but not provide enough signal pulses to be amplified into sparks?

Should I try another CPS from a different manufacturer? If so, is there a recommended make or just go to the dealer?

[BenHar]

Another reason for a third relay might be the cold start bodge on the 1988 cars.

That relay was mounted on the side of the fusebox, and, IIRC only applies to the 2.0 litre.

My 1988 325i had it and it was mounted with the two relays under that cover.

But they were dealer fit, I think, so could vary.

Ben

[Brianmoooore]

They were dealer fitted, but if they mounted that relay there, they would have had to evict the lambda relay base first.
To the OP: If the cat. and lambda sensor are gone, then the relay can be/should be removed as well

[Brianmoooore]

I know the original CPS is faulty as there was no power to the fuel pump and it measures open circuit when tested with a multi-meter.

Both replacement CPS's have been "Meat & Doria". I'd initially though the original replacement was the wrong one which is why I got the second one but it turns out they are both the same. Could it be the Meat & Doria CPS's don't work with the E30 ECU's (the same CPS is used across a variety of car models & manufacturers)? The thing with the M&D CPS's is that the body of them is all plastic with just a small metal pin sensor on the end. The original CPS had an all metal body. I realise about different manufacturers having slightly different designs but for the E30 does the body on the CPS need to be metal?

Could it be the M&D CPS's create enough 'noise' for the E30 ECU to activate the fuel pump but not provide enough signal pulses to be amplified into sparks?

Should I try another CPS from a different manufacturer? If so, is there a recommended make or just go to the dealer?

If the engine was OK before the original CPS failed, and it has been proven that it did fail, by measuring O/C, then it would be logical and a reasonable assumption that fitting a replacement CPS would solve the problem.
But it hasn't, and, after extensive investigation, nothing else can be found to be wrong.
A logical deduction would be that the replacement TPS is the problem, but it is a VERY simple device - just thin enameled copper wire wound around a bar magnet.
What is the clearance between the tip of the TPS and the toothed steel wheel?
There are three pins in the TPS plug. Two should have a resistance between them, which you've measured and posted, and the third should be insulated from the first two. Which two pins have the resistance between them?
Are you satisfied that the plug on the new TPS and the socket on the loom fit together properly and have you measured that resistance at the engine ECU plug?

[MunsterScot]

Car was running ok before CPS failed. It had failed to start a couple of times previous to failure of CPS but when running it was fine.

Checked the original CPS again this morning. It is reading O/C between all pins.

I measured the distance between the tip of the CPS fitted to the car and the toothed steel wheel and it is approx. 1.2mm.

Measuring the resistance on the new CPS at the plug. Looking at the pins in the plug if pin 3 is the pin beside where the cable comes out the plug then I measure 496 Ohms between pins 1 & 2. O/C between pins 1 & 3 and between 2 & 3. CPS re-connected and measuring resistance across pins 47 & 48 of the ECU plug I also measure 496 Ohms so signal getting to ECU.

My other M&D CPS measures 489 Ohms between pins 1 & 2 and O/C between pins 1 & 3 and between 2 & 3.

496 Ohms does seem on the low side when measuring. When looking at the CPS web-page it says 540 ohms +/- 10%.

So my thoughts are:
1. I know the original CPS has failed.
2. The chances of two things failing (CPS & something else) at the same time I'd expect to be low (but not impossible).
3. As Brianmoooore has said, after extensive investigation, nothing else can be found to be wrong.
4. Both new CPS I've tried are Meat & Doria and the same model.
5. Potentially, M&D CPS creates a large enough signal for the E30 ECU to energise the fuel pump but not create spark.

Next step: Try another CPS from a different manufacturer?

[Brianmoooore]

CPS to toothed wheel clearance should be 1.0mm +/- 0.3mm, so within spec. there.
The DC resistance of the CPS is a function of the gauge and length of wire used to make it. OE sensor is 540m ohms, but an aftermarket one with slightly thicker wire would read less.
My next step would be to try a good used OE sensor, to prove the point one way or another. You can always sell it on.
Wire can go over the top of the engine for temporary installations.

[MunsterScot]

Thanks again Brianmoooore.

I'll try and tracked down a good used OE CPS. Failing that I'll get a new one from the dealer. Once I fit it I'll report back with an update.

I was looking through some of the old documents for the car. There is an invoice for a new 5 Button G5 Clifford Alarm remote (would this be the original alarm?) and for a Laserline security 931 / 921 immobiliser system. I can't see how it could be either of these that is stopping the car from starting given the testing that has been done.

[Brianmoooore]

The Clifford wasn't an OE or BMW approved alarm, but the original purchaser could have specified anything he liked.
It is just possible that a very cleverly fitted alarm/immobiliser is the problem, but I've yet to come across one. It would have to be connected to the engine loom, so check carefully along its length for non standard wires sprouting from it.
A capacitor connected between the coil negative and earth is a very effective immobiliser. Get the capacitance just right and the engine will splutter and cough, but won't catch. Enough to keep a potential thief there trying for longer than they would like, risking discovery. That's why I asked for resistance readings along and to earth for the black coil wire.

[MunsterScot]

Still trying to track down a good used OE CPS. In the mean time I've been doing some more reading. On 'e30owners.com' in relation to the CPS it mentions the following in one thread: "turn it over on starter and see if rev gauge lifts, handiest way of diagnosing rather than part swapping etc". When I try to start the car there is no movement from the rev counter. Fuel gauge reads and the temperature gauge give a flick but nothing from the rev counter.

Would this also point to the CPS signal is not being interpreted by the ECU (as the ECU is not sending a signal to the rev counter)?

[Brianmoooore]

I've suggested watching the rev. counter in cases like this a few times on this forum, and considered mentioning it in this thread, but the tacho. drive is close to the coil drive in the ECU, so I'd already decided you wouldn't see any movement.

[Blanca]

I was going to suggest you might check the distributor isn't 180 degrees out (TDC rock) but I guess you have a cam mounted dizzy so it's not possible, is it?

[Brianmoooore]

Spark has been checked direct from the king post of the coil, so distributor not relevant.

[Blanca]

distributor timing, could be on TDC rock ?

[MunsterScot]

Well I gave up trying to find a good used OEM CPS so ordered one from the dealer. Took them 2 weeks to get it in due to Brexit (I'm in Ireland) and €167 later I picked it up from the dealer yesterday afternoon.

Fitted it this morning. 1st turn of the key and she lives. It was the CPS all along.

So I now have a spare coil & ECU as well as 2 Meat & Doris CPS's that don't work with the car.

So my suggestion to anybody else that needs to replace there CPS go OEM from the dealer. Might cost more but could save you a lot of time and money in the long run.

Next: Change the coolant and replace the rubber fuel lines under the bonnet. The joy of owning an E30 never ends.

[HenryM3]

Surely the M & D cps are still within their warranty period, you should return them. Recoup some of your money.
I just picked up an ICV pipe I ordered early December and they charged £4 lass than when originally quoted

[Brianmoooore]

Halleluiah!!
I'd love to know exactly why the M&D version doesn't work though. To get a 'scope on its output and see what's different about its waveform.
As I've said earlier, it's not a sophisticated sensor - just a coil of thin copper wire wound around a magnet, which generates a half wave AC sinusoidal voltage. The frequency is determined by the toothed wheel, and the voltage is largely irrelevant. It will change greatly with engine speed, but will be heavily clipped as soon as it enters the ECU, to form something close to a constant amplitude square wave.
I wonder if it could be a polarity issue? Be interesting to swap the signal and earth wires over.

[martauto]

Halleluiah!!
I'd love to know exactly why the M&D version doesn't work though. To get a 'scope on its output and see what's different about its waveform.
As I've said earlier, it's not a sophisticated sensor - just a coil of thin copper wire wound around a magnet, which generates a half wave AC sinusoidal voltage. The frequency is determined by the toothed wheel, and the voltage is largely irrelevant. It will change greatly with engine speed, but will be heavily clipped as soon as it enters the ECU, to form something close to a constant amplitude square wave.
I wonder if it could be a polarity issue? Be interesting to swap the signal and earth wires over.

I`ve been watching this and I`m sooooo glad it`s sorted for you

Mart.

[MunsterScot]

Have to say thanks for all the help over the past while with suggestions of what it could be and what to check.

[Tineca]

Brilliant news 8

[Brianmoooore]

Meat & Doria are a long established reputable company based in Turin. One sensor could be faulty, but for a second one to be is unlikely. It seems more likely that there's a design fault.
Could be worth contacting their technical department to ask if there have been other complaints about this particular sensor.
There's a 2 year warranty on those sensors, so you at least be able to get a refund on them.










you

[Blanca]

Great news, finally sorted. never ending story owning an E30 for sure.

[BristolE30]

Well I gave up trying to find a good used OEM CPS so ordered one from the dealer. Took them 2 weeks to get it in due to Brexit (I'm in Ireland) and €167 later I picked it up from the dealer yesterday afternoon.

Fitted it this morning. 1st turn of the key and she lives. It was the CPS all along.

So I now have a spare coil & ECU as well as 2 Meat & Doris CPS's that don't work with the car.

So my suggestion to anybody else that needs to replace there CPS go OEM from the dealer. Might cost more but could save you a lot of time and money in the long run.

Next: Change the coolant and replace the rubber fuel lines under the bonnet. The joy of owning an E30 never ends.

Hah called it!! It sounded so so very similar to the symptoms we had on a 318i. Cranking, fuel but only one weak spark. New CPS also fixed it. Weird you had so many issues with replacement parts. She lives on glad you sorted it

[paultv]

I have a "pattern" CPS which when attached, the car will not start - it's new and is part plastic - I'll post the make on this thread so others reading this can avoid it.

Paul

[BristolE30]

Well I gave up trying to find a good used OEM CPS so ordered one from the dealer. Took them 2 weeks to get it in due to Brexit (I'm in Ireland) and €167 later I picked it up from the dealer yesterday afternoon.

Fitted it this morning. 1st turn of the key and she lives. It was the CPS all along.

So I now have a spare coil & ECU as well as 2 Meat & Doris CPS's that don't work with the car.

So my suggestion to anybody else that needs to replace there CPS go OEM from the dealer. Might cost more but could save you a lot of time and money in the long run.

Next: Change the coolant and replace the rubber fuel lines under the bonnet. The joy of owning an E30 never ends.

Hey man, were you able to work out what brand the OEM is when it arrived? I'm guessing Bosch? Sometimes hard to work out thought with all the bm branding

[MunsterScot]

Hi BristolE30,

Short answer = No.

There was no other branding on it apart from BMW. It is an all metal sensor like the original one that I took off. The Meat & Doris sensors had a plastic body and just a small metal pin in the middle of the end of the sensor that points to the crank .

[BristolE30]

Hi BristolE30,

Short answer = No.

There was no other branding on it apart from BMW. It is an all metal sensor like the original one that I took off. The Meat & Doris sensors had a plastic body and just a small metal pin in the middle of the end of the sensor that points to the crank .

Yea I thought so... part number 12141720856 right? Think I’m going to bite the bullet and buy one to see if it’ll fix my dodgy idle

[MunsterScot]

Yes, 12141720856 looks right. Are you going to the dealer to get one?

[BristolE30]

Yes, 12141720856 looks right. Are you going to the dealer to get one?

Yea have done. £130 eek

[boxclever1753]

Yes, 12141720856 looks right. Are you going to the dealer to get one?

Yea have done. £130 eek

Me too, to hopefully fix my non starter. Same part, same cost from Cotswold. Will report back

[BristolE30]

Yes, 12141720856 looks right. Are you going to the dealer to get one?

Yea have done. £130 eek

Me too, to hopefully fix my non starter. Same part, same cost from Cotswold. Will report back

Ah nice one! That means there is only 1 CPS left in the UK now haha

[boxclever1753]

Yea have done. £130 eek

Me too, to hopefully fix my non starter. Same part, same cost from Cotswold. Will report back

Ah nice one! That means there is only 1 CPS left in the UK now haha

Ha! Well mine arrived today and it still won't start. But that is one more thing off my check list!!

[MunsterScot]

boxclever have you worked through the zones no start checklist:

https://www.e30zone.net/e30wiki/index.p ... oubleshoot

It's a good place to start.

[boxclever1753]

boxclever have you worked through the zones no start checklist:

https://www.e30zone.net/e30wiki/index.p ... oubleshoot

It's a good place to start.

Thanks dude - yes, working through that checklist currently. If you read the last few posts on my thread here, you can see where i'm at.

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