BMW N55 Engine Rebuild Project Part 10 – BMW Crank, No Start Troubleshooting

Has this been the longest project ever or is this just how YouTube driven projects go? Welcome back to the last video in the BMW N55 engine rebuild series. This BMW 335i N55 project has been one of the most fun for me, but also one of the more frustrating projects I have ever done. In this video, I will show you what else I did after installing the engine, there are plenty of things to do while doing a swap on a car this age. I will also go through the steps I took and all of the things I tried to get it started when it would crank forever, but not start. This crank, but no start condition took a lot of my time and you will never guess what it was.. I felt a little dumb after figuring it out. At the very least, there will be some kind of conclusion by the end of the video, but before we get there, let me remind you what happened in the last video.

After rebuilding the engine, I installed the high-pressure fuel pump, oil filter housing and of course the VANOS solenoids. Then I ran the fuel lines to the fuel pump as well as to the injectors and on the other side I installed the new exhaust manifold with the turbocharger. At the front side of the engine, I installed all of the pulleys, the vibration damper and then I ran the wiring looms. After doing the rest of the small parts, the engine was ready to be put into the car and connected to the transmissions. Of course, there is a lot more to it, but I was able to try starting it at that point. If you’d like to see details, check out the previous video in this playlist.

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Right after installing the engine and the rest of the necessities, I scanned the car for codes and deleted anything that was in the history. Then I turned on the ignition to see what would happen. I heard the fuel pump come on and the water pump started pumping and building up pressure as well. These were good signs! Prior to this, there were no signs of life coming from the engine and the fix for that was a ground wire that wasn’t making good contact. Now I was able to scan the DME and the rest of the modules and I was sure the engine would start. I’ve connected my other car for some power annnnnd this is all I got in return. (Play starting click 7077). The engine would crank for as long as you had battery power, but would not start.

This is where I started to think really, really hard as to what could be causing this engine not to start. Sure, I still didn’t have the exhaust or axles or some of the sensors installed, but the engine SHOULD HAVE STARTED now!

From my basic understanding the engine needs 4 things to start: air, fuel, spark and compression. So, I started checking one at a time from the easiest to the hardest. I knew the engine was getting air since there was no obstructions or even air filter installed at this stage. This wasn’t the problem. I then checked the spark. I pulled one of the sparkplugs out and cranked the engine. It was nice and bright, so now I was certain that the spark was not the issue, but what about the fuel? Is the engine getting proper fuel? I was expecting the low pressure fuel pump to turn on each time I was about to start the car as it seems to be that way on my Z4 and it’s the same platform. However, it did not. I was worried the fuel wasn’t getting to the fuel rail. So. I grabbed my ThinkTool Scanner and looked at the data stream for the rail pressure. I had a perfect 12 mPa or about 1750psi of pressure. That’s definitely plenty to make the engine go. To triple check that it wasn’t a fuel issue, I connected a cheap-o oscilloscope to the injector to see that it was getting a signal to fire.. which it was. Now the only thing that was left was compression. Unfortunately, I don’t have compression readings on video but all 6 cylinders were at about 180 PSI, which is just fine for this engine and would not be a cause for the engine not to start.

But of course, with modern engines, even if you have all that you need, your engine still may not start if the computer tells it not to. Or at least that was my thought at the time. I connected any and all sensors that I could find, cleared the codes and tried again. At this time the only code that was present on the car was A738: JBE Power Supply Interrupted. My next mission was to figure out what this code was about and how to fix it. Since I had no other codes, I was certain this would be the solution to my no start issue. As the first step, I bought a used JBE module off eBay and swapped it out. The job is fairly easy, but you do have to remove half of the interior on the passenger side to get to the module. After 30 minutes, I was ready to give it another go.. but unfortunately, it made no difference in my case. The code remained active.

At the same time, I noticed that the car would no longer lock using the button on the inside or even from the key fob. This had to be the issue as the key communication is vital to the engine starting.

Electronics are definitely not my strongest skill set when it comes to cars, but with a help of a few friends online, I tracked many wires, checked resistance on certain wires, replaced fuses and relays, but the JBE code remained active. In the last-ditch effort, I bought the entire fuse box online to see if it would make any difference. Replacing the fuse box didn’t take too much time as I’ve already had good access, but the main power wire that came in did give me some trouble. I knew these are a common failure point on these cars, so it was important not to damage anything. Fifteen minutes later, the new fuse box was in! I erased the codes one more time and guess what?? The JBE Code was gone! I was ecstatic and 100% expecting the engine to fire up.. but guess what? Now I had ZERO codes and the same no start condition I’ve been dealing with for weeks now.

My engine had everything it would need, so what else could it be? I know the computer needs to know position of the engine when it’s cranking in order to have it timed properly, so I decided to check the crankshaft sensor. I removed the starter and tested to make 5 volts were getting to the sensor. All was good there. Since I was running out of options and wanted to rule out as many things as possible, I ordered a used one online for a few bucks and replaced it and as you guessed it, nothing changed.

I then replaced the camshaft sensors, using the old ones I had from the original engine and even swapped out the VANOS solenoids in case they went bad somehow and even updated the DME, JBE, CAS and other modules to the latest firmware. All to no avail.

Since the engine wouldn’t start at this point, I figured I’d get busy with finishing the rest of the items on my list and hoping that at some point the solution will come to me or someone will give me a suggestion I can try. The first item for me was re-attaching the rest of the exhaust. When I initially removed it while removing the engine, I had to cut off the bolts as they were rusted on and wouldn’t come off any other way. That meant removing them from the catalytic converter, getting new downpipe exhaust gaskets and a set of new bolts. It all came together rather nicely after that. After re-hanging the rest of the exhaust and tightening the enforcement plates, it was ready to roar.. well once it starts.

Of course, in order for the car to move or even be lowered from the jack stands, I needed to put the front axles back in. I have a video on how to remove these and as they say, the installation is just the opposite of removal. Only catch here is to use new seals and of course a new axle nut. Once both of the axles were in, I could fill the front differential with gear oil.

Many of you suggested installing an aftermarket charge pipe, so I got a VRSF kit. I swapped the sensor and got it in place. It’s an easy upgrade and seemed to be made of quality material, definitely a better quality over the OEM charge pipe that cracks after a couple of installs or removals not to mention it looks much better.

While working on all of these items and thinking back to all of the suggestions and help I got from wonderful BMW enthusiasts online, I went over the possibilities in my head over and over again. What could possibly make the engine not start when it clearly has everything it needs. 

The only logical explanation at this point was that the engine wasn’t timed properly. BUT HOW? I have reviewed the video I have made on replacing the timing chain and it was done correctly, everything lined up and the engine was in Top Dead Center.. or was it? Let’s investigate.

I couldn’t think of any way to actually test this so I went to work taking off the valve cover and everything that was in the way. The entire process took me about an hour and a half total and that was mostly because I could get the gasket to stay in place when reassembly. I’m moving ahead of myself here, but after taking off the valve cover here is what I found. VIDEO I got to work making sure the timing was perfect this time and still wondering how could I mess up this bad. I have re-watched my video on the timing chain replacement and you can clearly see that the timing was done correctly. Then I remembered that last minute I decided to replace the chain components for new ones and that’s when I must have rotated  has cost me hours and hours of troubleshooting, but I don’t blame myself too much as I learned a ton as to what makes the engine go and what it needs to start. Would I have been happier if it started a couple months ago when I first installed it? Absolutely, but, at the end, the engine is now running and I can’t be happier! There are many other things I want to do on this car once the budget allows, so stay tuned!

Well guys, this might be the longest video I have ever done and if you stuck to the very end, thank you! Let me know in the comments what mistakes you’ve done doing big projects like this and how did you figure it out. I’m curious to know and maybe it’ll make me feel just a little better about this one. Thanks for watching and I’ll see you in the next one!