Hi guys. I just got my second e28 535i a month ago (i still have the other, exact clones). Yet another great car. Anyways, just like the last one, it is already bending me over and making me beg for mercy. This is the deal. Initially when I bought the car, it was approx. 50 degrees and the car would take aprox 3 seconds of cranking to fire up. The temperature has since dropped more and more. The car began to require several attempts to start it if it was cold. If warm, it would start right away. Eventually, nothing less than pushing it down hill and popping it into gear would start the car (thank god I live in a parking garage with ramps). Then this would not even work and I had it towed for a diagnostic. The guy who did the diagnostic claimed that the fuel pressure was good and judged that the computer must be at fault. I doubted this because I imagined it was probably a relay. I put the new computer in today (i replaced one in my old car with success) and it still would not start. Plenty of battery power, no fuel. Any answers? Crank position sensor? Power to the ECU? AFM? I'm going in tommorow morning to get more info. Give me as many ideas as possible.

Fuel pump, fuel pump relay, fuel pump fuse. That's all I can think of right now.

How exactly did the mechanic determine that the fuel pressure was good? Did he bypass the relay?

The above post by theseeker411 covers the most common areas. After you test the above issues you may want to consider testing the OBC (note: I am speaking from my experience with my M5).

Test OBC:
Turn the car to the run position. In the engine bay, grab the ICV or listen for it to turn on. If it does not turn on, check your OBC. You should hear a hummm from the ICV. If the ICV does not turn on check your OBC connections in the ETK and bypass the OBC. Here is a link to the ETK online
http://www.shadetreebmw.com/Default.aspx?userAction=TechArticleSearch&mdlfYear=E28&art_typ=_Gen%20-%20Electrical&author=All&srch_txt=

Second, check your fuse box for all relays and fuses. As it turns out my 88M5 has a fuse the ETK fails to mention. It is located on the engine fuse box, left hand side, outside the fuse box where the AUX fuse goes. Here is a link to my post on mye28
http://www.mye28.com/viewtopic.php?t=28232&highlight=
or you can check out my garage:
http://www.shadetreebmw.com/wjosh.aspx

Also another person had a starting issue on mye28
http://www.mye28.com/viewtopic.php?t=28300&highlight=

Try that and read those post. Let me know if you still can't figure it out.

The guys at the garage havent called me back yet, but that extra fuse box that youre talking about always had me puzzled on my other e28...i thought it was for an alarm system or something (why the fuck isnt it labeled). I will check on the the things you mentioned, but looking back on all this, I thing the cold start valve might be my real problem. Let me exlain and tell me if this logic sounds right. The car became harder and harder over time to start when cold. The valve could be faulty, which would explain why even though fuel pressure is evident and so is spark, the car isnt getting the gas it needs to fire up. Ill let you know if I find anything else out.

Could also be your cold start valve going bad. Pop the hood and look at the drivers side of the engine block, under the intake manifold. Is there gas present? If so, the cold start valve is dead. Have fun replacing that sucker. Most have found that the easiest way to get to it is to take off the intake manifold.

Agreed - for some reason I thought you were not getting fuel.

Regarding the extra fuse box - I am not sure that is the same on your car, but like you I did not know what it was for. I thought it was the mobile phone installation. Turns out I was wrong.

Good luck with the cold start valve -

Well, the shop still cant figure out what the problem is, Im sending it to a bimmer dealer today. They still asert that its the computer because of no ignition spark...they also told me it has to be reporgrammed with install but I dont think thats true; I swapped out an ecu in my old 535i and it fired right up, bmw laughed at me and told me thats impossible (like id lie about it). OK, against my previous csv assertion, this makes more sense to me....crank position or timing sensor unit...because this would explain why the computer is sending no spark intially, and why id be able to push start the car to turn it over because of a surge in engine speed? Any more ideas or am I crazy?

I've never had to reprogram one when installed, maybe I was just lucky but I do not think so. However I cannot make a dif. statement on that.

I don't look forward to your bill from the dealer - If you get it back let me know and we can go through next steps. Also do you have a bentley manual? If not get one as they are pretty good for these cars.

check the fuel pump in the back, always the prob with e28s, check the o2 sensor too

Long cranking times in cold temps are usually caused by a blocked cold start valve or bad thermo/time switch. Fuel pump check valve problems will cause long cranking time at any temperature.

I seem to remember reading in the Bentley manual about low battery voltage, and it sounded like it doesn't take much, having negative affects on the DME. Cold temps would only exacerbate that situation, especially during starting. It's a shot in the dark, but check the batt voltage. I think either 12.2 volts or 13.2 volts is a battery with only 25% charge.

My '86 had a bad crank postion sensor that would fail when hot and work when cold. It is located in the bell housing on the driver side. $92 from the dealer.