Mysterious non start problem
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Mysterious non start problem
1988 BMW 635 Csi automatic
The problem has baffled my mechanic, the battery shop, friends and myself. With a new battery the car started every time for a while. Then it gradually starts less frequently until is requires a jumper box and then not even then. They only thing that will get the car to start every time is if I hook up jumper cables to the battery from running vehicle.
Two days ago I put a brand new 750 CCA Interstate battery in it. Wouldn't start. The Interstate battery people hooked up a huge 900 CCA battery. Wouldn't start. Though they were dubious I asked them to bring over their shop truck and hook it up with jumper cables. Car started immediately.
All the battery connections and grounds have been cleaned. Still only a jump from a running vehicle will start it.
Any thoughts would be greatly appreciated. We are baffled in Chico.
The problem has baffled my mechanic, the battery shop, friends and myself. With a new battery the car started every time for a while. Then it gradually starts less frequently until is requires a jumper box and then not even then. They only thing that will get the car to start every time is if I hook up jumper cables to the battery from running vehicle.
Two days ago I put a brand new 750 CCA Interstate battery in it. Wouldn't start. The Interstate battery people hooked up a huge 900 CCA battery. Wouldn't start. Though they were dubious I asked them to bring over their shop truck and hook it up with jumper cables. Car started immediately.
All the battery connections and grounds have been cleaned. Still only a jump from a running vehicle will start it.
Any thoughts would be greatly appreciated. We are baffled in Chico.
Re: Mysterious non start problem
What happens when it doesn't start? Does it still crank? Does the solenoid click?
'82 528e - M50B25 + GS6-37BZ
'83 633CSi - Megasquirt and a 3.46LSD
'83 633CSi - Megasquirt and a 3.46LSD
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Re: Mysterious non start problem
Nothing happens. No click no rotation of starter when there is an attempted start now with a brand new battery, a 900 CCA battery jumped into the system. The ONLY thing that works every time is a jump from a running vehicle.
Re: Mysterious non start problem
Hopefully someone who knows well the electricals on later cars can answer, but I think autos have a relay under the dash which delivers power to the starter solenoid. I would look there.
'82 528e - M50B25 + GS6-37BZ
'83 633CSi - Megasquirt and a 3.46LSD
'83 633CSi - Megasquirt and a 3.46LSD
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Re: Mysterious non start problem
Bakemono: Interesting. Can anyone post a photo of the relay in place and/or a section in an electrical diagram? My '88 is an automatic.
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Re: Mysterious non start problem
All automatic cars of all manufacturers have what I call a neutral safety switch that prevent a car from starting in gear and your foot on the brake. I know the 6s have it as well and believe it is mounted on the shift mechanism. Put a dvm on that and check for continuity. Start simple first and then work your way backwards
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
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flickr.com/photos/bertsphotos.
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Re: Mysterious non start problem
What I just can't fathom is why a jump from a running vehicle works and a jump from a jumper box designed to start cars or a monster of a 900 CCA truck battery do not even cause the starter to move or the solenoid to click. Baffling. What could be the difference? Electricity is electricity. In all three cases I am sitting in the car with it in Park and turning the key. The dash lights come on but no response whatsoever unless I am jumping it with a running vehicle. Sometimes my 1993 Chevy truck. Sometimes my 2010 Ford Edge.
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Re: Mysterious non start problem
I had a no start about 2 weeks ago. A wire had all but broken, but was still able to send voltage ,until amps were required. I'd start with how much voltage is getting to the starter, then work back.
good luck!
good luck!
Re: Mysterious non start problem
The only thing I can think of here is that the slightly higher alternator voltage is breaking through a bad connection, but that's a reach. More than likely just co-incidence though. You need a methodical approach with a multimeter to solve this.Radical Racing wrote: ↑Mon Jul 13, 2020 11:43 pm What I just can't fathom is why a jump from a running vehicle works and a jump from a jumper box designed to start cars or a monster of a 900 CCA truck battery do not even cause the starter to move or the solenoid to click. Baffling. What could be the difference? Electricity is electricity. In all three cases I am sitting in the car with it in Park and turning the key. The dash lights come on but no response whatsoever unless I am jumping it with a running vehicle. Sometimes my 1993 Chevy truck. Sometimes my 2010 Ford Edge.
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
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement
Re: Mysterious non start problem
I had this problem for 14 years . I have replaced the ignition switch , starter relay , neutral safety switch , starter solenoid and even had the starter serviced . To no avail . I just had my tech install a push button switch ,that’s how I’ve been using it for 14 years , a couple of weeks ago a forum member advised me just to run an extra wire from terminal 87 of the start relay located under the dashboard . He instructed my tech to run the wire directly to the starter solenoid together w/ the original yellow black wire that is connected to the solenoid . And it worked , no more push button starter needed . Car starts via the ignition switch even if it’s hot or cold .
Hope this helps .
Hope this helps .
84 BMW 635CSI/a
89 Porsche 911 Turbo
88 Ferrari Mondial 3.2 Cabriolet
89 Porsche 911 Turbo
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Re: Mysterious non start problem
pgh880: Thanks so much for this solution. However how do I identify the start relay? There is a lot of stuff under the dash board. Can I trace a particular colored wire(s) from the ignition switch? What gauge was the new wire you ran?
Re: Mysterious non start problem
You can install the Bosch WR1 Starter Relay. Get it from Amazon.
It provides direct voltage from battery to the solenoid via the WR1 Starter Relay. Its an additional starter relay.
It provides direct voltage from battery to the solenoid via the WR1 Starter Relay. Its an additional starter relay.
Re: Mysterious non start problem
Here is a picture of the starter relay located under the dashboard driver side . You remove the kick board (cover)
There are several cube relays underneath . The one of the starter relay had a yellow/black wire , same color as that of the yellow/black wire that is connected to the solenoid of the starter . I think my only used a gauge 14 or 16!am not sure . From terminal 87 of the starter relay he ran a direct wire towards the yellow / black wire of the starter solenoid .
We did not trace the wire from the ignition switch , since I knew were the starter relay was located .
There are several cube relays underneath . The one of the starter relay had a yellow/black wire , same color as that of the yellow/black wire that is connected to the solenoid of the starter . I think my only used a gauge 14 or 16!am not sure . From terminal 87 of the starter relay he ran a direct wire towards the yellow / black wire of the starter solenoid .
We did not trace the wire from the ignition switch , since I knew were the starter relay was located .
84 BMW 635CSI/a
89 Porsche 911 Turbo
88 Ferrari Mondial 3.2 Cabriolet
89 Porsche 911 Turbo
88 Ferrari Mondial 3.2 Cabriolet
Re: Mysterious non start problem
Here is the picture .
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- Purple Hella relay
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84 BMW 635CSI/a
89 Porsche 911 Turbo
88 Ferrari Mondial 3.2 Cabriolet
89 Porsche 911 Turbo
88 Ferrari Mondial 3.2 Cabriolet
- hornhospital
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Re: Mysterious non start problem
Please direct-upload the picture. Photobucket not only blurs the photo but they plaster their logo across the face of it, further interfering with viewing.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann"; '95 M3 "Ashlyn"
'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann"; '95 M3 "Ashlyn"
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Re: Mysterious non start problem
86-635CSi
96-MB C220 SOLD
98-740i
71-Continental MK3
96-MB C220 SOLD
98-740i
71-Continental MK3
Re: Mysterious non start problem
I hope its as easy as that but Im no techie and Idont know how . I found this picture in this forum . I'm too lazy to go to my parents home were my 635 is garage to take a picture of my starter relay .hornhospital wrote: ↑Tue Jul 21, 2020 10:20 am Please direct-upload the picture. Photobucket not only blurs the photo but they plaster their logo across the face of it, further interfering with viewing.
84 BMW 635CSI/a
89 Porsche 911 Turbo
88 Ferrari Mondial 3.2 Cabriolet
89 Porsche 911 Turbo
88 Ferrari Mondial 3.2 Cabriolet
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Re: Mysterious non start problem
pgh880: Thanks for the photo and info. Going to my warehouse tomorrow to see if I can find the relay and them the the BMW dealer. First replace the relay and them the secondary wire through the firewall to the stater.
Re: Mysterious non start problem
Good luck . Tell us how it turns out .
84 BMW 635CSI/a
89 Porsche 911 Turbo
88 Ferrari Mondial 3.2 Cabriolet
89 Porsche 911 Turbo
88 Ferrari Mondial 3.2 Cabriolet
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Re: Mysterious non start problem
OK back on this problem after dealing with family issues. Removed the drivers side kick panel and could see ONLY two black large size relays. Could not see any black/yellow wires. So to the person that said the starter relay is there I wonder if the configuration is different for the 88 - 89 cars compared to the earlier cars. I have printed out the entire BMW 635 Csi electrical troubling shooting manual. There is single start relay ashown but no part number or location to be found or 87 pin. I went to my local BMW dealership and even they said they could not help me. They also said they called BMW national office and they said they could not help. Unbelievable!!!!!!!!!!!! I am so frustrated. Please help! Car will only start if jumped from a running vehicle.
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Re: Mysterious non start problem
Can someone please post a photo of some sort of diagram showing where the start relay is located on a 1988 635 Csi. Another poster put up photos of relays from and 1985 and mentioned running a second black/yellow wire to the starter solenoid but search as I might nothing in my car looked the same as his. Over a year now fighting this non start problem.
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Re: Mysterious non start problem
Did you open the link I sent you? The location is on PDF page 153 and printed page #7000-4.
The upper left photo shows the location on a 1988.
https://www.millerperformancecars.com/f ... Manual.pdf
The upper left photo shows the location on a 1988.
https://www.millerperformancecars.com/f ... Manual.pdf
86-635CSi
96-MB C220 SOLD
98-740i
71-Continental MK3
96-MB C220 SOLD
98-740i
71-Continental MK3
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Re: Mysterious non start problem
I have had a complete printed version of the 1988 Electrical Troubleshooting Manual for five years. All I can find is a wiring diagram showing how the relay is hooked up to the system but no actual info as to where its physical location is within the car. Maybe I am missing something but currently at a loss as to what to do. As per your suggestion I removed the drivers side kick panel. There was no single purple relay and no black/yellow wire at the kick panel OR at the solenoid.
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Re: Mysterious non start problem
There is a picture of the starter relay on page #7000-4 of the link I gave you.
Are you saying that you looked in that location
and the relay isn't there?
Are you saying that you looked in that location
and the relay isn't there?
86-635CSi
96-MB C220 SOLD
98-740i
71-Continental MK3
96-MB C220 SOLD
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- Ralph in Socal
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Re: Mysterious non start problem
Hopefully these pics can help
First is the Ignition Switch. Maybe not the same as yours but wiring is similar. Large Red Wire is +12V coming from Battery and C101 connector. It provides constant voltage to Ignition Switch at all times. You can see solid black wire also. That wire only gets +12V when switch is in start position. You should be able to see that black wire enter the white connector. Black wire from Start Relay plugs in and connects to that black wire. The connector can be found along the outer side of the steering column under/behind the kick panel Next pic is start relay. Solid black wire connects to Ignition Switch connector. Black/Yellow comes out of relay and goes to starter. Location varies with year but it’s also under the kick panel. Ralph
First is the Ignition Switch. Maybe not the same as yours but wiring is similar. Large Red Wire is +12V coming from Battery and C101 connector. It provides constant voltage to Ignition Switch at all times. You can see solid black wire also. That wire only gets +12V when switch is in start position. You should be able to see that black wire enter the white connector. Black wire from Start Relay plugs in and connects to that black wire. The connector can be found along the outer side of the steering column under/behind the kick panel Next pic is start relay. Solid black wire connects to Ignition Switch connector. Black/Yellow comes out of relay and goes to starter. Location varies with year but it’s also under the kick panel. Ralph
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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)
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)