It’s definitely been a while since my last post, sorry! Quite a lot has happened in the last few months so racing my BMW has been put on a temporary pause. I just completed the move to Colorado from Seattle and am just now finally getting settled into a normal routine. I planned to enter a local autocross just to kick some tires and meet some new racers in the area. As you’ll soon read, that didn’t quite go as planned…
The day definitely didn’t go as planned! The event was being held about 42 miles from my new house. Unfortunately, I only made it about 40 miles that morning as the car decided to completely die on the exit ramp from the interstate to the final street where the autocross even was being held!
I parked on the side of the exit ramp pretty much where you see it in the picture above. As this was the main route to get to the event, nearly every single car stopped next to me to ask if I was okay while I had the hood up. I did decide to accept help from a guy driving an amazing Nissan GTR (just so I could ask him all about his car).
My car would crank all day long but it would never try to actually fire. This seemed to mean that there was either no fuel or no spark going to the cylinders. First, I checked all the grounds on the engine and they all seemed fine. Next, I checked the fuse for the fuel pump which was also fine. Finally, I got in the car and cranked the engine while listening very closely to the fuel pump (behind me to the right in the E36) and couldn’t hear it powering up.
So, in a last ditch effort to be able to get the car going for the event, I had the brilliant idea to hit it gently (or so I thought) with a rubber mallet and plastic block that I had (so no sparks). Definitely not a good idea as I knocked a hole in the top of the fuel pump assembly! At that, I called it quits and rang up AAA to bring a flat bed tow truck to take me home. Luckily, I had enough foresight to sign up for Colorado AAA before heading to the track!
Once I got the E36 home, I installed a new fuel pump assembly and began digging deeper to solve the no start condition. I jumpered all sorts of things in the fuse box (DME relay, fuel pump relay, and fuel pump fuses). Turns out that everything was working fine but something was telling the computer not to fire the engine.
The Crank Position Sensor! Covered in 20+ years of grime and grit, the sensor finally failed due to old age and too many high heat cycles that made the plastic very brittle.
Getting to the sensor is a bit of pain as you have to remove the lower radiator tube and contort your arm into position with a small allen key. I basically had to remove the old sensor and install the new one entirely by feel. My BMW started right up after the new CPS was installed. Success!
One big difference that I’ve noticed in Colorado is that my BMW E36 2.5 liter six cylinder is SOOOOOO much slower at high altitude (5000 – 6500 feet) than it was in Seattle at sea level. It’s really crazy how noticeable it is! This got me wondering how healthy my engine really is at over 200,000 miles. The standard way to determine this general health is by completing a compression test on each cylinder individually.
The first step of the process is to get the engine warm and then remove all the coil packs, spark plugs, fuel pump fuse and DME relay.
Then I just threaded in my $20 Amazon compression tester in the spark plug threads, got in the car, pressed down on the accelerator pedal, and cranked the engine over about 5-7 seconds until the needle stopped moving on the gauge. The process worked great and yielded the following results for my engine:
From everything that I’ve read, it’s not so much the absolute value of the compression results that matter (those these look good). What actually matters is the variance from the average value of the results. Most sources say that a cylinder within 7-10% of the mean result means the cylinder is relatively healthy. As you can see in my results, 5 of the 6 cylinders are VERY close to each other and only cylinder number 3 is slightly low in compression. I’ll take it!
Now, how to make my car faster?!?!? There are so many choices out there that I’ll go over in a future post. However, my next post will be about further lightening and handling improvements. Stay tuned!