How soon could a DB-engined FW190 entered combat?

According to the motor bible "Flugmotoren und Strahltriebwerke,Gersdorff/Grasmann" the BMW139 (1500PS) was a 14 cyl two row radial. A 18 cyl engine, the BMW140 (projected 2000PS) started development in spring 1937 but was already stopped end of 1937. After acquiring Bramo, BMW cancelled on sept 1938 all running engine developments like BMW 139 and BRAMO 329 and introduced the new number block of the 800 series.

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I have been trying to find reasons for BMW 139 cancellation and replacement with 801. The latter was more powerful but heavier. Some books state that BMW 139 was unreliable and could not be debugged. Is this correct? in any case the reliability of BMW 801 was far from satisfactory. Could this be a case of "not designed here" syndrome?

There is an often repeated statement here that the BMW 801 is unreliable but never said how this shows. The Fw190A is my fav aircraft and I've a lot of books concerning the evolution of this plane. In all books there is a chapter of the heavy difficulties that occurred during begin of development mostly due overheating in the tight Fw fuselage. This was a rather critical situation and the RLM was near to cancel the whole project. Fortunately a team of engineers with members from Fw, BMW and Rechlin officers was built to solve the problem. Finally at fall 1942 the job was done and the engine airframe combination worked well. This teething problems are well known but in none of the books reliability problems were noted after that. Same in the motor bible "Flugmotoren und Strahltriebwerke,Gersdorff/Grasmann" which contains a large chapter of the BMW801i nothing is noted.
cimmex

I recall seeing a statement somewhere that the BMW 801 was basically a developed version of the BMW 139, one change being the inclusion of a two speed supercharger. This makes sense - for a host of practical reasons, it was very common for engines to be developed in an iterative fashion (Merlin, DB 600/601/605, Jupiter/Pegasus, M-34/AM-35/AM-37/AM-38 ...,). Also, the Germans would have been aware of the R-2600 and this would have given them some confidence that a high power 14 cylinder radial engine was a viable technical proposition. Note that, on top of the issues involved in cooling two rows of cylinders, 18 cylinder engines present special problems because of complex vibrational modes - considerable work was needed to bring the R-2800, the first really successful 18 cylinder engine, to a developed state. Most early 18 cylinder engines, such as the Fiat A.80, were hardly more powerful than established 9 cylinder engines and had various problems. Aside from this, if the BMW 139 was a double BMW 132, it would have had a diameter about 3 inches larger than that of the BMW 801; such a difference does not seem to be noticeable in photographs/drawings of aircraft fitted with these engines.