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From digest.v7.n440 Tue Oct 14 23:12:01 1997
From: Jim Cash <>
Date: Tue, 14 Oct 1997 22:59:54 -0400
Subject: <E30> Cold Start Function Inoperative

Mike Moore writes:
> I discovered the engine cold start function unfortunately is not
> working. I'm attempting to fix it myself because, well, my wallet is
> anemic after purchasing the car. The Bentley manual is very good but I
> need further information. Can anyone help with this?
> I found that the cold start injector has resistance, about 5 ohms as I
> recall. So I'd guess the injector is good. The thermo time switch
> (engine cold in morning, under 86F) has resistance (like the switch is
> closed as it should be) but isn't less than 1 ohm as I would expect, it
> is more like 3 - 4 ohms. I get voltage when cranking (main relay pulled
> out) from both cold start injector wires but it more like 7 - 8 volts
> each, not 12. I haven't checked fuel pressure and flow to the cold
> start injector, I assume it is OK.


I will bet that it is it he thermo time switch.

I have often posted info that this is a "mercury" filled switch and they get some build up on the contacts after a while.

Try striking the base of the unit ( the big brass nut part) with a small hammer - light sharp taps to dislodge the contamination. Every time my E28 was hard to start when cold I taped this and "fire in the hole".

I could make it last longer by removing the unit (coolant will not escape ) and tapping it and then putting 12 volts across the contacts and quickly alternating the polarity about a dozen times.

It this dosen't solve problem - go get another switch and try it.

I no longer have the schmatics for that switch but the readings will be affected by the fact that it is also a "thermo" time switch - with resistance causing heat to build up and cut it out.

It only operates for about 8-10 seconds to prevent flooding.

Hope this helps


Jim Cash
London Ontario, Canada
E39 450ia

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