Cold start problem

#1

Spec E30 racer and pal Carlton is prepping his new car for the '13 season and can’t get the car to start when cold. One of the wires that plugs into a sensor on the thermostat housing isn’t connected because the engine builder used that for a temp gauge.

A mechanic told Carlton that the cold start valve may be failing but a friend told me the 325e has a cold start valve, and that the 325i does not.

I’m thinking the brain doesn’t know that the engine is cold and isn’t throwing the needed additional fuel.

Any suggestions?

Carter

#2

Since no one with actual knowledge has replied, I’ll throw out a couple of philosophical thoughts. The common wisdom seems to be that the US M20’s don’t have the cold start valve. I know mine doesn’t although there’s an unmachined boss on my intake manifold where one would go. Fuel injection systems need to know lots of things about the engine and ambient conditions to get the right mixture including ambient and engine temps. To your point the CSV in the L-Jetronics that have them seem to take care of cold start enrichment. In the absence of a CSV I would expect the ECU to use both engine and ambient temps to calculate fuel load. So first and easiest thing to try would be reconnecting the engine temp sensor to the ECU. This actually ought to help performance and economy under all operating regimes except WOT.

#3

Sorry Carter, I didn’t spot the fact that it was you that started this thread yesterday.

The only way Motronic 1.3 knows the temp is the blue sensor on the tstat body. The brown sensor just goes to the dash gauge. The engine will happily start with the blue sensor unplugged so that sensor, or temp in general is probably not the issue. Not impossible tho because a start at 0deg ambient is going to want a richer mixture than 100deg ambient. But chances are the car is not in either extreme.

Jim Levie wrote a dissertation on getting an e30 to start. It’s around here somewhere, I’ll find it.

If there’s nothing really “wrong”, that is to say the engine used to start fine, nothing was changed, and now it doesn’t start fine, the problem is often the driver flooding the engine. That can happen surprisingly easy. The solution is to press the throttle to the floor and keep it there. Motronic 1.3 will interpret that, via the throttle position switch, as the engine’s been flooded and it will dial the injectors back and keep trying to start.

#4

Here’s Jim’s info http://spece30.com/forum/41-electrical-gauges-and-sensors/53136-no-start-no-spark-totally-stumped#53139