85' 635csi | Cranks but no Spark

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NRVOUS6
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85' 635csi | Cranks but no Spark

Post by NRVOUS6 »

Greetings Gang,

I've recently purchased an e24 and have just given it a bath for the first time since 1996, and cleaned the interior. I really love the color & styling of these cars. I've wanted one for awhile and this one fell in my lap.

Anywho - under the hood it's clear someone has done some upkeep. New wires, plugs, cap & presumably button. I pulled the fuel lines and cranked to be sure I had good fuel flow, and I do. I pulled each fuse and they all look pristine as well. So, next up Im trying to get it to fire up!

I tried a new coil to no avail so next up I'm going to get the meter out and start checking things. Firstly, I want to be sure the wires going to the coil are sending power then move ahead.

Before I get lost in a sea of possibilities, is there a short list I should punch through, or just bounce through the top of mind possibilities?

Thank you all for your help & input.
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85' BMW 635csi, 60k miles, Zinnoberot
01' DINAN 7 S62 Swap Six Speed - Stratus Grau
02' 4.6is DINAN X5 S2 Supercharged
833/3258 produced | 1/27 Dinan X5's
Greenville, NC
85MSteinway
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Re: 85' 635csi | Cranks but no Spark

Post by 85MSteinway »

verify you have no spark? Or just assume since it wont turn over? if car sat since 1996, I'd check injectors... dump the fuel and change filter. But, if you really don't have spark at the plug and you have changed coil then I'd double check the rotor cap then start working backwards from there. clean connections , make sure you got the right wires going to the right plugs/coil. keep working backwards till you get to the ecu checking for corrosion and cleaning etc. there are threads on here that will explain how to check your ecu. I'm no expert in that department.
L6
85 M635
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NRVOUS6
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Re: 85' 635csi | Cranks but no Spark

Post by NRVOUS6 »

Thanks!

It turns over / cranks like a champ to eliminate that question. Just nothing after that.
85' BMW 635csi, 60k miles, Zinnoberot
01' DINAN 7 S62 Swap Six Speed - Stratus Grau
02' 4.6is DINAN X5 S2 Supercharged
833/3258 produced | 1/27 Dinan X5's
Greenville, NC
daz635
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Re: 85' 635csi | Cranks but no Spark

Post by daz635 »

This document on fault finding Motronic 1.1 will help you out a lot https://drive.google.com/file/d/1X2hPji ... Vsk9N/view

Have a good read thru it

As the poster above has said ensure that you have spark at all the plugs and work backwards.

Check that you have voltage at terminal 15 on the coil with the ignition on

Check you speed and reference sensors as the car will not start without a signal from them to the ECU.

Check your main and fuel pump relays as well
'86 Euro 635 #1887204 Schwartz (086) Buffalo Schwartz Interior
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NRVOUS6
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Re: 85' 635csi | Cranks but no Spark

Post by NRVOUS6 »

Awesome! Thank you!
85' BMW 635csi, 60k miles, Zinnoberot
01' DINAN 7 S62 Swap Six Speed - Stratus Grau
02' 4.6is DINAN X5 S2 Supercharged
833/3258 produced | 1/27 Dinan X5's
Greenville, NC
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NRVOUS6
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Joined: Thu Nov 21, 2019 6:09 pm
Location: North Carolina

Re: 85' 635csi | Cranks but no Spark

Post by NRVOUS6 »

Was able to test several things in between over eating at Thanksgiving.

1- Checked #86 & #30 on main relay, good
2- Relay clicks when ignition turned,good
3- Power to coil #15 & #1 good, ohms check out too
4. Checked power to injectors, good
5. Bought spare OBD brain, made no difference

Tomorrow-

6 - Check you speed and reference sensors as the car will not start without a signal from them to the ECU.

7-Check your main and fuel pump relays as well

8- Buy 32mm remove fan/replace rotor button
Can anyone confirm which i need, i see 2 part numbers on realoem searching by vin.

“11 Rotor 1 01/1984 06/1987 12111734110 $30.76 ENDED
11 Rotor 1 01/1984 06/1987 12111715906”

Thanks to all! 🦃🚗
85' BMW 635csi, 60k miles, Zinnoberot
01' DINAN 7 S62 Swap Six Speed - Stratus Grau
02' 4.6is DINAN X5 S2 Supercharged
833/3258 produced | 1/27 Dinan X5's
Greenville, NC
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Re: 85' 635csi | Cranks but no Spark

Post by hornhospital »

Having 12 volts at the injectors doesn't mean they are working. The ECU _grounds_ the injectors to fire them. If you aren't getting grounding pulses from the ECU, the injectors won't fire.

Test them by spinning the engine with a noid light connected to the injector wiring harness plug. You can make a noid light from a #194 light bulb. Bend the wires so they fit in the plug, pop it in there and spin the engine. If you get a pulsing light, the signal is there to fire the injector.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann"; '95 M3 "Ashlyn"
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Re: 85' 635csi | Cranks but no Spark

Post by Brucey »

NB when you say 'checked' you mean with a meter? If so this is 'necessary but not sufficient' . Feeds need to be checked under load if you want to be sure of their integrity.

The typical failure mode of the main relay is that it still clicks, still tests OK with DVM, but has an iffy contact inside it that won't allow the injector firing current (which is momentarily very high) to flow correctly.


So when you say 'check' and 'test' if you have done this properly it is much more than just prodding around with a DVM.

So for example a good test for the main relay might be

a) substitution with a know good (new) relay
b) temporarily replacing the main relay with jumper wires in the socket
c) using a substantial load (eg a headlight bulb) and checking for voltage drop under load.

cheers
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NRVOUS6
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Re: 85' 635csi | Cranks but no Spark

Post by NRVOUS6 »

Checked the reference & speed sensors which have both seen better days. Neither offered up any readings on the ohm meter as pointed out in the above pdf/manual. I checked the harness side of the car on the sensors and they are getting power. I did replace the rotor, which was also ready for the bin.

As it reads, the car won’t start without the reference sensor. It appears the speed & reference sensor are the same PN.

12141708619

Sound right?
85' BMW 635csi, 60k miles, Zinnoberot
01' DINAN 7 S62 Swap Six Speed - Stratus Grau
02' 4.6is DINAN X5 S2 Supercharged
833/3258 produced | 1/27 Dinan X5's
Greenville, NC
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Re: 85' 635csi | Cranks but no Spark

Post by hornhospital »

Correct. They are the same part.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann"; '95 M3 "Ashlyn"
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NRVOUS6
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Re: 85' 635csi | Cranks but no Spark

Post by NRVOUS6 »

hornhospital wrote: Sat Nov 30, 2019 12:03 am Correct. They are the same part.
Thanks! After 35 years, i’ll buy 2. 😎
85' BMW 635csi, 60k miles, Zinnoberot
01' DINAN 7 S62 Swap Six Speed - Stratus Grau
02' 4.6is DINAN X5 S2 Supercharged
833/3258 produced | 1/27 Dinan X5's
Greenville, NC
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NRVOUS6
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Location: North Carolina

Re: 85' 635csi | Cranks but no Spark

Post by NRVOUS6 »

hornhospital wrote: Sat Nov 30, 2019 12:03 am Correct. They are the same part.
Another question:

Do I have 2 pulse generators / CPS? If so that means I'd need (3) of the above part number.

1 as reference sensor (bell housing)
1 as speed sensor (idk yet)
1 as pulse generator on the front of the engine

I just ordered 2 as I'm not getting any resistance from the two on the top of the engine in the "tray".
85' BMW 635csi, 60k miles, Zinnoberot
01' DINAN 7 S62 Swap Six Speed - Stratus Grau
02' 4.6is DINAN X5 S2 Supercharged
833/3258 produced | 1/27 Dinan X5's
Greenville, NC
baders
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Re: 85' 635csi | Cranks but no Spark

Post by baders »

NRVOUS6 wrote: Sat Nov 30, 2019 6:01 pm
hornhospital wrote: Sat Nov 30, 2019 12:03 am Correct. They are the same part.
Another question:

Do I have 2 pulse generators / CPS? If so that means I'd need (3) of the above part number.

1 as reference sensor (bell housing)
1 as speed sensor (idk yet)
1 as pulse generator on the front of the engine

I just ordered 2 as I'm not getting any resistance from the two on the top of the engine in the "tray".
I think it is a different sensor;
https://www.realoem.com/bmw/enUS/showpa ... Id=11_3034

This sensor serves the diagnostic plug only, and is not needed for the engine to run.
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement
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NRVOUS6
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Re: 85' 635csi | Cranks but no Spark

Post by NRVOUS6 »

That’s good to know.

The one on the front is $216. 🥃

BMW Position Transmitter - Genuine BMW 12521287784

635CSi, M3
Available
Ships in 1 business day
On Sale
Original: $227.49
Price each: $216.12
85' BMW 635csi, 60k miles, Zinnoberot
01' DINAN 7 S62 Swap Six Speed - Stratus Grau
02' 4.6is DINAN X5 S2 Supercharged
833/3258 produced | 1/27 Dinan X5's
Greenville, NC
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Re: 85' 635csi | Cranks but no Spark

Post by Brucey »

NRVOUS6 wrote: Fri Nov 29, 2019 10:40 pm Checked the reference & speed sensors which have both seen better days. Neither offered up any readings on the ohm meter as pointed out in the above pdf/manual. I checked the harness side of the car on the sensors and they are getting power. I did replace the rotor, which was also ready for the bin.

As it reads, the car won’t start without the reference sensor. It appears the speed & reference sensor are the same PN.

12141708619

Sound right?
speed and ref sensors do occasionally fail but the chances of both failing at the same time are incredibly remote. I'd therefore suggest that you get someone competent to give you a second opinion on the tests you did; it is very easy to use the wrong settings on a DVM and end up getting misleading readings.


The speed and ref sensors are indeed the same pn but they are usually marked so that you don't plug the wrong one in the wrong socket in the harness, eg with a zip tie around the wires or something.

The front crank sensor is not involved in running the engine. I would go as far as to say if this one 'tests bad' too, then you have almost certainly done the tests wrongly.

cheers
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NRVOUS6
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Re: 85' 635csi | Cranks but no Spark

Post by NRVOUS6 »

Brucey wrote: Sun Dec 01, 2019 1:52 pm
NRVOUS6 wrote: Fri Nov 29, 2019 10:40 pm Checked the reference & speed sensors which have both seen better days. Neither offered up any readings on the ohm meter as pointed out in the above pdf/manual. I checked the harness side of the car on the sensors and they are getting power. I did replace the rotor, which was also ready for the bin.

As it reads, the car won’t start without the reference sensor. It appears the speed & reference sensor are the same PN.

12141708619

Sound right?
speed and ref sensors do occasionally fail but the chances of both failing at the same time are incredibly remote. I'd therefore suggest that you get someone competent to give you a second opinion on the tests you did; it is very easy to use the wrong settings on a DVM and end up getting misleading readings.


The speed and ref sensors are indeed the same pn but they are usually marked so that you don't plug the wrong one in the wrong socket in the harness, eg with a zip tie around the wires or something.

The front crank sensor is not involved in running the engine. I would go as far as to say if this one 'tests bad' too, then you have almost certainly done the tests wrongly.

cheers
The tests were carried out correctly, verified the settings.
85' BMW 635csi, 60k miles, Zinnoberot
01' DINAN 7 S62 Swap Six Speed - Stratus Grau
02' 4.6is DINAN X5 S2 Supercharged
833/3258 produced | 1/27 Dinan X5's
Greenville, NC
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NRVOUS6
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Location: North Carolina

Re: 85' 635csi | Cranks but no Spark

Post by NRVOUS6 »

She’s back among the living!

I replaced the rotor button, cap, crank sensor on the front, and the 2 in the bell housing. Tapped the key and she fired right up!

Next up, start changing fluids.

🚗🦈
85' BMW 635csi, 60k miles, Zinnoberot
01' DINAN 7 S62 Swap Six Speed - Stratus Grau
02' 4.6is DINAN X5 S2 Supercharged
833/3258 produced | 1/27 Dinan X5's
Greenville, NC
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