Stranger starting issue once warmed up, please help?

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Sticky4
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Stranger starting issue once warmed up, please help?

Post by Sticky4 »

89 635csi

The car starts no problem when cold. But once hot it takes 2 or 3 times to start. It will always start and does no problem but only on the 2nd or 3rd time when hot.

Any ideas?
plip1953
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Re: Stranger starting issue once warmed up, please help?

Post by plip1953 »

Mine's started to exhibit similar hot start characteristics, so I'll be following this thread with interest O:)
Phil
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wogden700
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Re: Stranger starting issue once warmed up, please help?

Post by wogden700 »

When it wont start, does it fire a few cylinders and then die, or does it not start at all? Does giving a little throttle help? How does it run otherwise? and how is the idle? It could be the idle control valve staying open, or possibly another vacuum leak.
Another phenomenon is a heat soak where the gas in the fuel lines vaporizes. This is common in aircraft engines that have constant flow injectors, but in theory this shouldnt happen in the FI system in our cars. But a bad check valve or injector could cause this.
Other issues with the various sensors could cause the car to think it is cold starting when in fact it is hot.
this is a great resource that explains the FI system very well.
http://www.hiperformancestore.com/Motronic.htm
1985 635CSi Diamondblack/Llama
1991 750iL (sold)
baders
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Re: Stranger starting issue once warmed up, please help?

Post by baders »

wogden700 wrote: Sun Apr 12, 2020 1:03 pm When it wont start, does it fire a few cylinders and then die, or does it not start at all? Does giving a little throttle help? How does it run otherwise? and how is the idle? It could be the idle control valve staying open, or possibly another vacuum leak.
Another phenomenon is a heat soak where the gas in the fuel lines vaporizes. This is common in aircraft engines that have constant flow injectors, but in theory this shouldnt happen in the FI system in our cars. But a bad check valve or injector could cause this.
Other issues with the various sensors could cause the car to think it is cold starting when in fact it is hot.
this is a great resource that explains the FI system very well.
http://www.hiperformancestore.com/Motronic.htm
That link has been dead for a while.
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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86_6series
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Re: Stranger starting issue once warmed up, please help?

Post by 86_6series »

It worked for me Baders
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beemerguru
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Re: Stranger starting issue once warmed up, please help?

Post by beemerguru »

So did anyone have a list of possbile things to check?

My '84 is in the same boat..starts perfectly and instantly runs to redline if asked...until it has about 20 miles and engine warms up. As long as you're cruising, runs great. But when you pull up to a stop sign the engine starts bucking and trying to stall...and finally stalls and won't start.

Let it get cold and same all over again. Dangerous in traffic so need to know what to test
Greg Hutchinson

'84 633CSi with 478K miles
'81 Euro 635CSi needing assembly

www.airheadadventure.com
Ronnie Wilson
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Re: Stranger starting issue once warmed up, please help?

Post by Ronnie Wilson »

Hi

Get your Injectors serviced. Then using the Bentley Manual check the Fuel Pump Delivery and the Fuel Pressure Gauge.

Good look
Ronnie
Liverpool uk.
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wogden700
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Re: Stranger starting issue once warmed up, please help?

Post by wogden700 »

Follow the link in my previous post. It will help you to diagnose the issue. It helped me when I had a vacuum leak last fall.
1985 635CSi Diamondblack/Llama
1991 750iL (sold)
Sticky4
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Re: Stranger starting issue once warmed up, please help?

Post by Sticky4 »

wogden700 wrote: Sun Apr 12, 2020 5:33 pm Follow the link in my previous post. It will help you to diagnose the issue. It helped me when I had a vacuum leak last fall.
I will, but man the article will take me a week to read! Lol
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Re: Stranger starting issue once warmed up, please help?

Post by baders »

86_6series wrote: Sun Apr 12, 2020 1:56 pm It worked for me Baders
Weird !! Definitely doesn't work for me.
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
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Re: Stranger starting issue once warmed up, please help?

Post by rmmrmm »

Don't want to go off topic here but I cant get that link to work either...weird as it comes up on google search but cant get a link to the hiperformancestore to work - maybe a timing thing..... will try later...
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plip1953
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Re: Stranger starting issue once warmed up, please help?

Post by plip1953 »

baders wrote: Mon Apr 13, 2020 2:33 am
86_6series wrote: Sun Apr 12, 2020 1:56 pm It worked for me Baders
Weird !! Definitely doesn't work for me.
Same for me - tried it all kinds of ways and no joy!
Phil
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86_6series
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Re: Stranger starting issue once warmed up, please help?

Post by 86_6series »

Here it is in a word doc.
Maybe this will work.

[The extension doc has been deactivated and can no longer be displayed.]

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Re: Stranger starting issue once warmed up, please help?

Post by rhanley 635csi89 »

89 635CSiA (11/88 build)
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Re: Stranger starting issue once warmed up, please help?

Post by wogden700 »

It works for me on my Android, My Chromebook and even on the Mac at work (shh dont tell).
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Re: Stranger starting issue once warmed up, please help?

Post by hornhospital »

Same here. Worked on three laptops, two tablets and my smart phone. Not sure why you can't open it.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann"; '95 M3 "Ashlyn"
plip1953
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Re: Stranger starting issue once warmed up, please help?

Post by plip1953 »

wogden700 wrote: Mon Apr 13, 2020 3:53 pm It works for me on my Android, My Chromebook and even on the Mac at work (shh dont tell).
I guess it's probably down to the browser that I'm using - Microsoft Edge.
Phil
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plip1953
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Re: Stranger starting issue once warmed up, please help?

Post by plip1953 »

86_6series wrote: Mon Apr 13, 2020 12:12 pm Here it is in a word doc.
Maybe this will work.

Bosch Motronic Basic Motronic 1.1 1.2 1.3 Fuel Injection Technical Article.doc
Perfect, thanks :-)
Phil
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rmmrmm
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Re: Stranger starting issue once warmed up, please help?

Post by rmmrmm »

86_6series wrote: Mon Apr 13, 2020 12:12 pm Here it is in a word doc.
Maybe this will work.

Bosch Motronic Basic Motronic 1.1 1.2 1.3 Fuel Injection Technical Article.doc
Yep this worked - brilliant and thanks!
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plip1953
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Re: Stranger starting issue once warmed up, please help?

Post by plip1953 »

Given that all the vacuum lines on my car are the originals from 1988, I guess now would be a good time to replace them!!

I'm being a bit lazy here, but do BMW sell vacuum pipe by the metre or in specific part no lengths?
Phil
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Rondel Fan
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Re: Stranger starting issue once warmed up, please help?

Post by Rondel Fan »

My first guess would have been fuel pump pressure check valve. When warm/bad they can allow pressure to bleed down rapidly and make starting hard. An open throttle will help when warm. When cold the engine is aided by the cold start injectors etc so starting is easier.
Sticky4
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Re: Stranger starting issue once warmed up, please help?

Post by Sticky4 »

Rondel Fan wrote: Tue Apr 14, 2020 5:23 pm My first guess would have been fuel pump pressure check valve. When warm/bad they can allow pressure to bleed down rapidly and make starting hard. An open throttle will help when warm. When cold the engine is aided by the cold start injectors etc so starting is easier.
I’ll try this seems easy, any idea how to install? ;)
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Re: Stranger starting issue once warmed up, please help?

Post by Rondel Fan »

I may have gotten ahead of myself. If I searched correctly some years may have one, and some may not, as least on the pump. Here is what it might look like.
https://images.app.goo.gl/U8TUhiYxLJkoZQd29
Basically mounted on top of the outlet side of the pump, between the pump body and the banjo fitting.
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