Page 1 of 1
5 volts to the cold start valve
Posted: Sat Aug 28, 2021 11:45 am
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!
Re: 5 volts to the cold start valve
Posted: Sat Aug 28, 2021 7:26 pm
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?
Re: 5 volts to the cold start valve
Posted: Tue Aug 31, 2021 11:22 am
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.
Re: 5 volts to the cold start valve
Posted: Tue Aug 31, 2021 1:52 pm
by canada karl
Thanks for the info.
Re: 5 volts to the cold start valve
Posted: Thu Sep 02, 2021 6:43 am
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.