5 volts to the cold start valve

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PatinaBeforePolish
Posts: 317
Joined: Sun Jan 18, 2015 1:22 pm
Location: Baltimore, Md.

5 volts to the cold start valve

Post by PatinaBeforePolish »

Finally started to dig into an inoperable cold start valve and found it’s only getting about 5 volts while cranking. The valve tests fine, I believe it needs somewhere around battery voltage to work. Checking here if someone has run into this with a known fix or further diagnostic. Thanks!
79 528i
canada karl
Posts: 965
Joined: Tue Jan 06, 2009 3:50 pm

Re: 5 volts to the cold start valve

Post by canada karl »

Don't have a fix but I noticed my 76 530i is harder to start now that the Fall weather is getting cooler where I am. In the summer the car would start right up first try. Now it will crank quite a bit but not fire. Second try it usually fires up. I've cleaned up the cold start valve and everything looks as it should. Everything is set to spec in terms of a tune up. Is there anything more I can do for cold starting? Is there an upgrade for the cold start valve? Maybe I'm experiencing the same voltage issues as PBP?
1976 530i. BMW 59 Triumph TR3A(rolling resto). 67 Triumph TR4A(salvageable). 86 900S Winter car
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Mike W.
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Re: 5 volts to the cold start valve

Post by Mike W. »

The cold start valve is powered by the thermo time switch. There is a new replacement that is electronic that people are having problems with, although the old ones seemed pretty reliable.

Simplistically the path is ignition switch start, to TT switch, thru it to the CSV. After several seconds, the exact time determined by the temp of the switch, it cuts off power to the CSV to prevent flooding.

Something people have trouble with is understanding it's a cold START valve, not a cold condition or warm up device. It only works when the starter is cranking and the TTS feeds power thru.
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter
canada karl
Posts: 965
Joined: Tue Jan 06, 2009 3:50 pm

Re: 5 volts to the cold start valve

Post by canada karl »

Thanks for the info. 8)
1976 530i. BMW 59 Triumph TR3A(rolling resto). 67 Triumph TR4A(salvageable). 86 900S Winter car
PatinaBeforePolish
Posts: 317
Joined: Sun Jan 18, 2015 1:22 pm
Location: Baltimore, Md.

Re: 5 volts to the cold start valve

Post by PatinaBeforePolish »

Mike W. wrote: Tue Aug 31, 2021 11:22 am The cold start valve is powered by the thermo time switch. There is a new replacement that is electronic that people are having problems with, although the old ones seemed pretty reliable.

Simplistically the path is ignition switch start, to TT switch, thru it to the CSV. After several seconds, the exact time determined by the temp of the switch, it cuts off power to the CSV to prevent flooding.

Something people have trouble with is understanding it's a cold START valve, not a cold condition or warm up device. It only works when the starter is cranking and the TTS feeds power thru.
Thank you Mike. I'm looking for diagnostic advice on why it's getting only 5 volts while cranking. I understand it needs somewhere around 12 volts to work. Sounds like the place to start is testing the thermo time switch, then test wiring continuity.
79 528i
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