No Crank Issue

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Sbeaud
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Re: No Crank Issue

Post by Sbeaud »

Perfect! Just by the sound it seems to crank at a higher RPM. On the road for a few more weeks before winter sets in... :cry:
1988 M6
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Soperman
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Re: No Crank Issue

Post by Soperman »

I have studied this, and other similar threads, in order to fathom out a frustrating non-starting problem I have with my car '85 M635 RHD.

Turn ignition key, all dash lights illuminate, but otherwise nothing else happens. Aargh!

I should point out that...

- New(ish) high quality battery kept on constant trickle charge when car parked up for any lengthy period.
- All electrical items working fine.
- With key inserted and turned to "run" , the car fires up perfectly when I jump pins 11(start signal) and 14 (battery) of the diagnostic port.
- Trying with an alternative spare key is unsuccessful.
- No changes, no previous related work carried out, no accessories fitted etc.
- This was an intermittent problem, but it's now a permanent one.

As a result of reading this, other similar threads, and a gut feeling that the problem was within the steering column, I installed a brand new ignition switch (part number 1 371 094.1) figuring it be the necessary cure, however the car still won't fire with the key.

Any help, any at all, would be very gratefully received. After all, spring is here and I want to get on the road in my car when lockdown is lifted!!
Last edited by Soperman on Sat Mar 13, 2021 2:55 pm, edited 2 times in total.
E24 M635CSi
emac
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Re: No Crank Issue

Post by emac »

Not sure if this helps, but page 26 (PDF page) or page 115 of the actual document is the start circuit diagram. Maybe a loose connector or bad relay?

https://bimmertips.com/wp-content/uploa ... -Chart.pdf
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Soperman
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Re: No Crank Issue

Post by Soperman »

Thanks emac. If I'm being honest, electrical diagrams are as bewildering as they are daunting. Interpreting these things is not my strength. Nuts and bolts I'm comfortable with, electrics I am not.

I'll give learning how to troubleshoot electrics another go.....
E24 M635CSi
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Soperman
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Re: No Crank Issue

Post by Soperman »

K5 & K7 unloader relays tested, and they're OK. Need to look elsewhere.....
E24 M635CSi
emac
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Re: No Crank Issue

Post by emac »

I think you are going to have to study that diagram and start checking wires/connectors for power. Maybe start at the ignition switch to see if you have power in the start position.
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Ralph in Socal
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Re: No Crank Issue

Post by Ralph in Socal »

The Red wire is power supply to the ignition switch. Your dash lights come on when you turn the key so you have +12V at the Red wire

The Black wire is +12V start signal to the starter when the ignition switch is in the start position. Probe that Black wire for +12V starting at the connector block. You will find the end of that Black wire (Start signal circuit) at the starter solenoid. It is Black with a yellow stripe after it goes through a couple of connectors and relays

If you don’t have +12V at the starter solenoid then there is a fault in the circuit. I think the circuit also passes through the OBC relay on later cars. Good luck

Ralph
There is a very fine line between "Hobby" and Mental Illness.

85 635csi Zinno Auto
84 528i Euro
83 635 Euro Arktik
81 528i Kastanien 5-speed
88 528e Bronzit (Granpa Car)
86 535i Auto (For Sale)
81 633 csi (retired)
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Soperman
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Re: No Crank Issue

Post by Soperman »

I made up my mind to really try and fix this today, so I printed off the relevant pages from the Electrical Troubleshooting guide, made some tea, and told the wife and kids that they could find me in the garage if they really needed to speak to me.

I decided to test at the starter motor, but couldn't really access it from above, so jacked the car up, reached for the Black/Yellow wire and confirmed 0 Volts on ignition start.

So back to the other end and I dropped the lower steering column cover to examine the connector block of the the recently installed ignition switch. As Ralph surmised I had voltage at the incoming Red wire, and so went to test the Black/Yellow that heads off on its winding path to the starter motor.

Well bugger me sideways if it didn't feel a bit loose. So I re-crimped the spade connector, firmly re-attached the damn thing and hey presto, the car starts perfectly on the key. \:D/ :D

In the end, just the very simplest of fixes. Thank you chaps!
E24 M635CSi
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Ralph in Socal
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Re: No Crank Issue

Post by Ralph in Socal »

I’ve done it several times on multiple cars. Best way to troubleshoot No Crank.

Well done Soperman!!!

Ralph
There is a very fine line between "Hobby" and Mental Illness.

85 635csi Zinno Auto
84 528i Euro
83 635 Euro Arktik
81 528i Kastanien 5-speed
88 528e Bronzit (Granpa Car)
86 535i Auto (For Sale)
81 633 csi (retired)
emac
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Re: No Crank Issue

Post by emac »

Great job!!! I was hoping it was something simple.
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86_6series
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Re: No Crank Issue

Post by 86_6series »

I love HAPPY ENDINGS.
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96-MB C220 SOLD
98-740i
71-Continental MK3
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