1985 BMW 318i Battery Was Hooked Up Backwards Now Won’t Start

Reader Question
I have a 1985 BMW 318i. Refurbished the engine, but someone
put in the battery backwards before getting the car restarted. Now, Fuel, Air and Spark are all ok, it will chug with the gas from the Cold Start Injector, but won’t start. My only guess is the Injectors (new) are not getting correct signal.

I’ve been working through the Bentley Service Manual, with a multi-meter, and have found the injectors’ voltage is ok, as well each is grounded ok, but there doesn’t seem to be any pulse at the injectors. All the electrical checks at each of the main electrical components seem to be ok, which Bentley tells me means I need to replace the component.

I’m wondering if anyone has any advice on which component to start on or other things to check, as opposed to trying/buying all new electronic components. Thanks for any help or advice you can give.
Ben

Howdy Ben,

I really am not much of a BMW mechanic, and there really is a difference between an American/Japanese mechanic and a European mechanic. If someone put the battery in backwards….I think the computer is probably toast, but you really really really need to get someone with the proper know how to take a look. Just about anything you want to take a guess at replacing will cost you MUCH more than a proper diagnosis would, even at the dealer.

Blessings,

Austin Davis