strange starter issue help guys im going nuts

[Boostesi]

To start I have a 1990 bmw 325is with a1995 m50tu, 5 speed. The m50 came from an auto 325i and I had dave at markert motor works do my harness and remove all the auto plugs ( depined) and all new c101connector and pins. I have a brand new beck arnley starter. It has an unused post on the solenoid. The unused post is a male spade terminal. My starter sometimes will only crank one revolution and then cut out. It will do this several times in a row. Sonetimes she cranks fine and starts right up. It seems to get worse on hot days. All connections are new and clean at the starter. I have 12 v at the black/yellow wire under the dash while cranking. Battery is new interstate. Ive tried by passing the ignition switch with a push button start and it still does the same thing. I have one 8 guage ground strap on the e30 motor mount arm to the frame rail.I dont know if im missing one or something.

[Boostesi]

Here is a video to better describe the problem, the whole time im holding the key forward even when its not crankinghttps://www.youtube.com/watch?v=RXQEWRRWzss&feature=youtube_gdata_player

[Boostesi]

https://www.youtube.com/watch?v=RXQE...e_gdata_player

[jlevie]

Use a test light to monitor the black/yellow wire's connection to the starter. If that light is on when the starter fails to operate, there is a problem in the start circuit. If the light is on, there's a problem in the power or ground to the starter or you simply have a bad starter. The factory rebuilds are pricey, but they work. Anything else is iffy.

[Boostesi]

Use a test light to monitor the black/yellow wire's connection to the starter. If that light is on when the starter fails to operate, there is a problem in the start circuit. If the light is on, there's a problem in the power or ground to the starter or you simply have a bad starter. The factory rebuilds are pricey, but they work. Anything else is iffy.

did you mean if the light does not come on then there is a problem in the start circuit

[jlevie]

The black/yellow wire is the starter solenoid control. It is only hot when cranking. So if the light fails to come on when you turn the key to start no power is reaching the solenoid.