View Full Version : cold start injector

03-23-2010, 04:07 PM
I am interested in buying a euro 1982 635csi. the car is 400 miles away, but I have travelled to buy cars before.
The owner states that the cold start injector needs replaced and therefore the car doesn't run. I was under the impression that a fawlty cold start injector would just make it run at low rpm until warmed up and then it would run just fine. I was hoping I could drive the car home if I purchased it, but I am led to believe that there is more wrong with the car than the owner admits to if it doesn't run at all.
Any advice appreciated.

03-23-2010, 04:58 PM
Without a working cold start valve, the car will never start! Also, check for a faulty thermo-time switch. They both need to be in working order, otherwise, you will have a no start each and every time.

03-23-2010, 05:14 PM
That's just completely untrue, sorry. The CSV doesn't do anything at all above about 50 deg F (which is generally is now in most of the USA), and it will always start without it given enough cranking. Besides that, CSVs almost never go bad. You're right to be skeptical OP, there is definitely something else wrong with the car.

03-23-2010, 05:24 PM
Layne is right, I've tried to start my car (in minus 12 celsius temps) without the CSV and it just took a little more time and you have to use the throttle to keep it running for a short time. After that everything works as normal.

03-23-2010, 05:26 PM

The CSV has nothing to do with the car actually running, so if that's his story he is either misinformed or hiding something else.

03-23-2010, 05:55 PM
Well, maybe I'm wrong by overstating or maybe I'm right, but if the car does not start within the few tries and you were to continously crank the engine, it will flood for sure, thereby, creating another issue why the engine will not fire.

03-23-2010, 05:58 PM
It won't flood. The reason it's harder to start is that it needs the extra fuel from the CSV. So once the injectors get the proper amount in there it starts. You'd have to have no ignition to flood it.

03-23-2010, 06:16 PM
It won't flood. The reason it's harder to start is that it needs the extra fuel from the CSV. So once the injectors get the proper amount in there it starts. You'd have to have no ignition to flood it.

Actually the motronic may know if the firing signal is sent and prevents the injectors from opening if the plugs/coil don't get their spark signal sent to them, thus preventing a flooded condition. Kinda like what Kai's oven shoulda done.
Not sure how the ECU would know if each plug is firing. I know some newer ECUs in modern cars know when there is a misfire(plug not firing by secondary current measured or by a change in combustion temp of that cylinder bank).

Agreed though, something else is wrong with the car if you can't ever get it started and have it run at all.

03-23-2010, 06:38 PM
Here is an excerpt from the Bosch fuel Injection & engine Management book on the cold start process:

"Cold-start enrichment quickly becomes a problem if the engine does not start right away; due to a marginal batter, ignition components in poor condition or whatever. Enrichment during cranking must be cut back in a matter of seconds; if it goes on too long, the air-fuel mixture will to too rich to ignite. The spark plugs may become fuel-fouled, particularly when they are cold, and the engine will not start."

03-23-2010, 06:45 PM
Yes, but that would only be the case if actual enrichment (in this case the CSV) would be going on. The CSV sprays a véry strong mist of fuel in the intake manifold, if that would continue too long the spark plugs could become fuel-fouled I guess. The CSV is only there because with a cold intake manifold a part of the fuel from the injectors would condensate to the intake runners (and thus result with a mixture to lean to ignite).

If the CSV doesn't work it will only take some extra time for the injectors to get enough fuel sprayed around until the mixture becomes rich enough to ignite. With only the injectors working (CSV not) it will therefore never flood.
The normal injectors will also be used to enrich the mixture, but this is nowhere near the amount of fuel that the CSV sprays.