No ignition on hot days
Moderators: GRNSHRK, ron, bfons
No ignition on hot days
Hello all
I have a 1981 e12 based car and it has an intermittant/ semi predicable issue. On a hot day +30C and it stands in the sun for a bit I often have a no start. As in engine does nothing, no turn whats so ever. I get clicks from relays but beyond that nothing. If I bump start it takes straight away. In winter I no issues.
I am thinking the temperature of the day will not impact engine compartment temperatures... so it must be something in the cabin. But given I do get some response from the key turning on I don't think it is the ignition switch.
I have a 1981 e12 based car and it has an intermittant/ semi predicable issue. On a hot day +30C and it stands in the sun for a bit I often have a no start. As in engine does nothing, no turn whats so ever. I get clicks from relays but beyond that nothing. If I bump start it takes straight away. In winter I no issues.
I am thinking the temperature of the day will not impact engine compartment temperatures... so it must be something in the cabin. But given I do get some response from the key turning on I don't think it is the ignition switch.
81 BMW 635csi RHD Euro manual.
02 M5
02 MCoupe
02 M5
02 MCoupe
Re: No ignition on hot days
I think I would try to mark off the obvious culprits first. Battery/starter. When it happens, get someone to turn the key and start jiggling wires at the battery and starter to see if you can locate the problem. Tap relays, and starter. Then check power at starter to see if you are getting power to the start terminal wire. If not work backwards.
Re: No ignition on hot days
Have a look at the "No Spark" troubleshooting guide.
viewtopic.php?p=236244#p236244
I know you mentioned the engine doesn't even turn over, but many of the tests will be universal.
For a complete "no start" troubleshooting guide, refer to HPSI Motorsport’s excellent Bosch Motronic Fuel Injection Tech Article.
https://hpsimotorsports.com/blogs/tech- ... ch-article
viewtopic.php?p=236244#p236244
I know you mentioned the engine doesn't even turn over, but many of the tests will be universal.
For a complete "no start" troubleshooting guide, refer to HPSI Motorsport’s excellent Bosch Motronic Fuel Injection Tech Article.
https://hpsimotorsports.com/blogs/tech- ... ch-article
04/1986 635csi Euro spec
Australian Delivered, RHD
Australian Delivered, RHD
Re: No ignition on hot days
Thanks guys. Will start working through the tests.
81 BMW 635csi RHD Euro manual.
02 M5
02 MCoupe
02 M5
02 MCoupe
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Re: No ignition on hot days
Try changing the coil.
- 86_6series
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Re: No ignition on hot days
Are you saying that on hot days you get clicking in the start mode? Then, if you jump
the battery the car starts? But not hot days the engine turns over and starts ok?
What temps are hot & not hot?
the battery the car starts? But not hot days the engine turns over and starts ok?
What temps are hot & not hot?
86-635CSi
96-MB C220 SOLD
98-740i
71-Continental MK3
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Re: No ignition on hot days
biggles, you mention that you have an '81 that is E12 based, but that was the changeover period for Euro 6ers and you may have Motronic injection and not L-jet
You should check this as it would help with diagnosing your hot no start problem
You should check this as it would help with diagnosing your hot no start problem
Bobbo
1980 633 CSi Cypress Green/Pearl Beige
2017 X5 M Sport Xdrive 35i Carbon Black/Ivory White
2005 330 Ci ZHP Cabrio Imola Red/Bone/Black
Re: No ignition on hot days
I am back with the car an trouble shooting... ofcourse problem never manifests when I am troubleshooting.86_6series wrote: ↑Thu Feb 02, 2023 11:31 am Are you saying that on hot days you get clicking in the start mode? Then, if you jump
the battery the car starts? But not hot days the engine turns over and starts ok?
What temps are hot & not hot?
On a hot day, the engine will not overheat but just hot cabin or unerbonnet. Summers push 30C thats usually when it happens. I have not tried jump starting when it is not starting, I always bump start (rolling down a hill and dropping the clutch) will get it going everytime. In one instance it happened at the shops around the corner so I walked home an went back an hour later (it was staning in the sun) and it still wouldn't start. So seems to be ambient temperature related. In winter I rarely have the issue.
I sometimes feel that it is the ignition key unit that is the issue. Maybe hot cabin temprature makes a worn switch not make contact?
Battery fuses, relays all seem good, I have swapped out most the crucial relays.
The car is Motronic
81 BMW 635csi RHD Euro manual.
02 M5
02 MCoupe
02 M5
02 MCoupe
- Ralph in Socal
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Re: No ignition on hot days
Try connecting a jumper cable (just the negative cable of a jumper cable set) from the battery negative to the starter body or ground strap at the starter. Do this when you're in the no start condition. If the car cranks and starts then your problem is in the.negative side of the circuit
I had the same issue a few years back and found that the end of the negative battery cable was corroded against the engine block mount. Cleaned up that connection and car has been fine since
It also doesn't hurt to spray contact cleaner into the ignition switch. Put a multimeter at the Blk/Ylw wire at the starter solenoid and make sure you're getting +12V there when the ignition switch is turned to start position. No +12V means the issue is in the positive side of the start circuit.
Ralph
I had the same issue a few years back and found that the end of the negative battery cable was corroded against the engine block mount. Cleaned up that connection and car has been fine since
It also doesn't hurt to spray contact cleaner into the ignition switch. Put a multimeter at the Blk/Ylw wire at the starter solenoid and make sure you're getting +12V there when the ignition switch is turned to start position. No +12V means the issue is in the positive side of the start circuit.
Ralph
There is a very fine line between "Hobby" and Mental Illness.
85 635csi Zinno Auto
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83 635 Euro Arktik
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- 86_6series
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Re: No ignition on hot days
I think Ralph is on the right track. My thought was the battery terminals, make sure they're
cleaned and making good contact and it has 12+ volts.I had a no starter engagement when engine was @ operating temp.
turned out to be the starter solenoid. The starting circuit did not have enough to overcome the solenoid
magnet. I replaced the battery and starter and never looked back. I think there are about 11 connections in the starter circuit that the battery has to fight through.
cleaned and making good contact and it has 12+ volts.I had a no starter engagement when engine was @ operating temp.
turned out to be the starter solenoid. The starting circuit did not have enough to overcome the solenoid
magnet. I replaced the battery and starter and never looked back. I think there are about 11 connections in the starter circuit that the battery has to fight through.
86-635CSi
96-MB C220 SOLD
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71-Continental MK3
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Re: No ignition on hot days
Are you trying with a/c turned off?
Re: No ignition on hot days
So managed to get it in a no start condition.
The starter solenoid IS getting 12V. I jumpered the negative back to the battery and no change. I was interrupted before I could get any further.
So looks like a faulty solenoid?
The starter solenoid IS getting 12V. I jumpered the negative back to the battery and no change. I was interrupted before I could get any further.
So looks like a faulty solenoid?
81 BMW 635csi RHD Euro manual.
02 M5
02 MCoupe
02 M5
02 MCoupe
- Ralph in Socal
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Re: No ignition on hot days
Consider applying +12v directly from the battery to the solenoid. Just as a final confirmation step as the starter is actually a lot of work to remove.
Secondly, consider the B35 starter replacement instead of the regular and larger B34 starter. Much easier to install as hardware location is accessible with sockets instead of just a box wrench
Ralph
Secondly, consider the B35 starter replacement instead of the regular and larger B34 starter. Much easier to install as hardware location is accessible with sockets instead of just a box wrench
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)
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)
Re: No ignition on hot days
Will try that.
Away for another month and will tackle it when back.
Away for another month and will tackle it when back.
81 BMW 635csi RHD Euro manual.
02 M5
02 MCoupe
02 M5
02 MCoupe
Re: No ignition on hot days
So manage to get some more diagnostics done.
The solenoid is getting an ignition signal, the motor turns when the solenoid is bridged (bendix stays off though).
So, it's pretty much a faulty solenoid. I will start looking into the solenoids but how servicable are they? Can they come off without removing the starter?
The solenoid is getting an ignition signal, the motor turns when the solenoid is bridged (bendix stays off though).
So, it's pretty much a faulty solenoid. I will start looking into the solenoids but how servicable are they? Can they come off without removing the starter?
81 BMW 635csi RHD Euro manual.
02 M5
02 MCoupe
02 M5
02 MCoupe
- hornhospital
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Re: No ignition on hot days
They are serviceable, but the starter will have to come off. I replaced the solenoid and bendix on my 633 several years ago. I got the replacement from WrongAuto (RockAuto), and it was wrong. There are two types of forked levers that go from the solenoid to the bendix. One has the fork ends that fit in a slot on the bendix. The other type has slotted fork ends that fit over a raised ring on the bendix. RockAuto sent what was supposed to be a matched set. NOPE. The solenoid had the same fork type (ends fit in a slot) as the old one, but the bendix had the raised ring. I couldn't get the fork off, so I disassembled the old bendix and the new one and swapped the fork engagement part. It's been working for 6 years.
By the way, when removing the starter, the flat 17mm box end wrench in the trunk tool kit is your friend.
By the way, when removing the starter, the flat 17mm box end wrench in the trunk tool kit is your friend.
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"