Re-Built my E90, now can't get engine to turn over and start. No spark on plugs.

[dferrari888]

2008 BMW 328XI (N51 Engine)

2 Years ago took my car into the shop for a knocking sound in my engine (102,000 miles) :/... dealer told me I spun a rod bearing in my engine and that it was no good. BMW quotes me $20,000 to replace the engine.... I opted for the more adventurous route and decided to replace the engine myself. I purchased a used N51 engine at a junk yard earlier this year (39k miles on the engine). I pulled all the working parts from the old engine and installed onto the new one, mounted it into my existing transmission and into the car.

Flash forward to today's problem...I put a brand new starter in the engine and the starter cranks the engine, but the engine refuses to turn over. Fuel pressure is good; I disconnected fuel line on top of engine and fuel sprays out of the line. Also, with my car sitting for nearly 2 years in my garage I DID drain the old fuel and added 6 gallons of premium gasoline directing into the fuel tank via the fuel pump access underneath the rear seats. Brand new oil in the engine, I also replaced all 6 spark plugs, and sprayed fogging oil into each spark plug well as a mechanic friend advised me to do so on an engine that hasn't been started in a while. Finally, I pulled one of the spark plugs, grounded it and observed the spark plug when I attempted to start the car and there is no spark on the plug.

Anyone have any ideas what I could have missed in rebuilding this car that could cause no spark on the spark plugs? I am a self taught mechanic and everything I did to rebuild my E90 was done based on repair manuals, help from mechanic friends, and youtube/internet research. I am no expert, but do believe I reassembled the car properly and I think I have everything hooked up correctly.

Any ideas on what could cause no spark on my plugs and thus prevent the engine from turning over? This is my first post on Bimmerforums! Many thanks in advance to anyone that took the time to read this and offer a hand. Thanks guys!



I can provide pictures and dm videos of the non-start if it would help anyone give me some ideas. I just posted some random pics below of the car/engine.

PAQK0997.jpgIMG_0343.jpgIMG_0352.jpgPAQK0997.jpg

[sgtfury40]

Are the ignition parts from the new engine or your old one? Remember everything on this car needs to be programmed into the cars computer to function properly, or function at all.

[dferrari888]

So by ignition parts you mean the coils and starter? The starter is brand new and the coils and the entire wiring harness are from the old engine. In terms of reprogramming everything, can I reset the ECU to allow for the new/different parts?

[MarcoZandrini]

Hue many cylinders did you check for spark? I’m betting that it’s more general then just one cylinder.
Are the ground straps for the coils in place? Yes, the DME supplies the ground to fire each coil individually, but there’s at least one ground strap that has to be inscribed. Is the crankshaft position sensor properly aligned and connected?

[dferrari888]

Thanks so much for the replies. I appreciate you guys trying to help out. Some additional information today....I checked the ground straps and Marco you were correct, one of the straps was garbage. I replaced it with an after-market strap I got at autozone but it isn't a perfect fit. (I will order BMW ground strap today). Even with replacing the ground strap the car will still not start...just cranks and cranks with the starter moving but the spark plugs will not fire at all. Also, I hooked up my OBD reader to the car and I got the dreaded error code "U0100 - Lost communication with ECM/PCM" I also tested the two small ground cables going to the spark plugs and I am getting a continuous circuit. Finally, I noticed one of the relays in my fuse box was extremely hot so I replaced it. The U0100 code really frustrates me because that could be any one of a hundred different things...The car computer turns on and runs fine, the starter runs and tries to crank, the battery is fully charged and brand new, anyone have any other ideas I could try?

[MarcoZandrini]

Let everything cool down. Now, start checking and rechecking all electrical connections. Remove each one and spray some electrical contact cleaner in both sides of each connector. That code means that the engine computer (DME in BMWspeak) isn’t properly communicating. Open the DME box and check it for anything obviously wrong such as a burned component, etc.

[dferrari888]

I GOT IT!!!! Thank you for the help!!! I disconnected literally everything inside the ECU box, cleaned it, and reconnected everything. One of the large connectors going directly into the PCM wasn't flush and I connected and voila! I still have a bit of work to do in terms of reassembling the front end, exhaust, etc etc., but knowing the engine works is big. Thanks so much for your continued help! Here is a quick video of the start (sounds rough because I have the cat disconnected and the O2 sensors out.

[MauiM3Mania]

Moved from BMW General Discussion sub-forum.

[shadowpuck]

awesome!! congrats on getting it running!

[MarcoZandrini]

Glad we could help!

[ECSTuning]

Congrats on getting here running! Glad it was something simple.

James