1986 Porsche 944 • 50,000 miles

I have a problem starting my 944 porsche (1986) in the colder weather. I live in Wisconsin so the winter temps range from below 0 up to the 50's. This temp. Range makes it almost impossible to start the engine when cold. The only way I can get it to start is by bringing the car into my garage and using a portable heater overnight to get the ambient temp up to around 70, then the engine will start. It turns over fine but I'm wondering if its the ratio of air and fuel intake or something just isn't firing right in the engine?
October 29, 2012.

BRRR! I'm in Wisconsin too, ... And I really hate cold weather.

Try some starting fluid when it gets cold. If that helps, look at the intake air temperature sensor and / or coolant temperature sensor. You should be getting a priming squirt from the injectors when you turn on the ignition switch, and the length of that pulse is determined by air or engine temperature. One potential clue is the engine may run poorly once started until it warms up.

Also check the fuel pressure. If it bleeds down overnight due to a leaking injector, that raw fuel sitting in the intake manifold will get the engine started in warmer weather but in cold weather it won't vaporize well and the engine won't get fuel until the pump builds pressure again. That occurs more slowly during cranking due to the battery voltage being drawn down.

Oct 29, 2012.
Will a simple engine block heater or oil pan heater help with start-up or potentially fix the problem?

Oct 30, 2012.
If that was the proper fix, the car would have come from the manufacturer like that. You have to determine what is missing when it doesn't start. That is going to be spark, fuel, compression, or valve timing. Compression and valve timing aren't going to change with temperature. That leaves spark and fuel. Spark is not varied according to temperature but fuel metering is. That's why I suggested the starting fluid to verify that.

A block heater might trick the Engine Computer into thinking it's warmer than it really is but that isn't solving the problem. It will be programmed to give less of a priming squirt when you turn on the ignition switch when it's cold so it might start even harder. On the other hand, if the intake manifold has time to get warm, what little fuel comes in will vaporize better so it might start easier, but that won't help after the car has been sitting outside at work all day.

Be aware too that in that time period a lot of cars had "cold start" injectors that were separate from the regular injectors. I never worked on any of those but if there's a problem with that system, it results in hard starting but it runs fine once started.

Oct 30, 2012.