Strange 535i starting Problem???

[islandphile]

There was no previous indication of any problem....went to start the car yesterday morning and it would just turn over but not fire...checked fuses, all ok....fuel pump inside gas tank is brand new and lots of pressure in the fuel lines. Cranked it over a few more times, nothing... waited five minutes. Tried again and it started, and ran great all day with no indication of any problems, so warm/hot starting is not a problem.

I put in a new ignition coil this morning and turned her over...wouldn't fire...kept trying and nothing. Eventually took the airbox out and cleaned the crank position sensor...tried a few more times, finally on the third try she fires up, and runs great all day starting up fine even after sitting for 4-5 hrs as long as the engine is even a little warm, and I should say it starts without hesitation on both days as long as the engine is even slightly warm.

Any ideas? My parts guy thinks crank or cam position sensor...I'm baffled.

Everything is new, spark plugs, wires, cap, rotor, and now coil.

[islandphile]

Well, I thought maybe cleaning the crank position sensor would have helped but...this morning I'm back to square one.

I've cranked it over for 10 minutes and not even a prayer.

Any ideas would be appreciated :)

[Bill R.]

Well, I thought maybe cleaning the crank position sensor would have helped but...this morning I'm back to square one.

I've cranked it over for 10 minutes and not even a prayer.

Any ideas would be appreciated :)

[islandphile]

Thanks Bill...Where are those located and how are they checked??

[Bill R.]

Thanks Bill...Where are those located and how are they checked??

[islandphile]

It's a 1991 e34 auto.

I just took a pic of the fuse box & relays...Is this where I should be looking?

http://www.sounddomain.com/memberpage/392547/4

[Bill R.]

passenger side. The closest one to the fender is the fuel pump relay...the orange one in the pic here... the white one is the dme or main relay..
http://www.bimmernut.com/%7Ebillr/images/fuel%20pumprelay.jpg

To troubleshoot it remove the relay and jumper across it. Frequently just removing and replacing the relay will clean the contacts enough that it will start working again...but if not jumper across the relay and see if the car will start.






It's a 1991 e34 auto.

Here is a link to a pic of the relays to make pointing it out easier.

http://www.bmwe34.net/e34main/maintenance/electrical/LKM.htm

[islandphile]

Cool man...I'll try that right now!!!

[islandphile]

Well...the relays work fine...This is one of those times I just want to take a sledge hammer to it...

I looked on a Bocsh K-Jetronic trouble shooting page for some help.

http://www.forparts.com/techbosKjectronic.htm

Do I have an Aux air valve on the m30 motor? Or a sensor plate? If so where are they and should I check those too?

[Bill R.]

by the fuel tank... if its running then put the relay back in and have someone crank the engine with the coil wire removed from the coil and held about 1/2 inch away... do you see spark when its cranking... If you do then check for spark from the dist cap to the plugwire by pulling a plugwire on one cylinder where it goes into the cap and holding it about a 1/2 inch away and cranking.. if spark visible there...If the fuel pump is running and you have visible spark then you need to get a noid lite and check the injector harness to see if the injectors are triggering...














Well...the relays work fine...This is one of those times I just want to take a sledge hammer to it...

I looked on a Bocsh K-Jetronic trouble shooting page for some help.

http://www.forparts.com/techbosKjectronic.htm

Do I have an Aux air valve on the m30 motor? Or a sensor plate? If so where are they and should I check those too?

[islandphile]

by the fuel tank... if its running then put the relay back in and have someone crank the engine with the coil wire removed from the coil and held about 1/2 inch away... do you see spark when its cranking... If you do then check for spark from the dist cap to the plugwire by pulling a plugwire on one cylinder where it goes into the cap and holding it about a 1/2 inch away and cranking.. if spark visible there...If the fuel pump is running and you have visible spark then you need to get a noid lite and check the injector harness to see if the injectors are triggering...

Thanks Bill.

Now, lets remember that this problem ONLY appears when the engine is cold.

Once it runs even for a couple of minutes, it will start for the rest of the day, and once up to temperature it will start after sitting for up to 5-6 hours...it just WON'T start in the morning **scratches head**.

My guess is it is something to do with a sensor in the Fuel Injection System that needs to warm up, I just don't know which one.

Bill, BTW, the fuel pump is just 3 weeks old and like I said once the car starts it's smooth sailing for the rest of the day...if I only knew why it won't start.

[islandphile]

I didn't want to do this but looks like I'll just have to start replacing sensors one by one to see which one it is.

So no one has had this Cold Start Problem???

[Bill R.]

always start with the basics. First make sure that you're getting fuel, regardless of the fact that the pump was changed 3 weeks ago. Check the pump and make sure that fuel is getting to the fuel rail and that it has adequate pressure, Then you make sure that you're getting spark, first at the coil, then at the plug, this process narrows it down , you can get spark at the coil but not at the plug if the cap,rotor,wires, or plugs are bad. If you can verify that you have fuel and spark, then you're next step is to determine if the injectors are opening. These steps will get rid of most possibilities for the cause, check fuel , fuel pressure, check spark and check fuel injector function. In the space of about 10 minutes you can narrow your choices way down. Otherwise just start changing sensors randomly.









I didn't want to do this but looks like I'll just have to start replacing sensors one by one to see which one it is.

So no one has had this Cold Start Problem???

[ryan roopnarine]

...i'd suggest to you, if no one has anything else to add, that you leave the car for a morning (which you have off), hook up a fuel pressure gauge the night before, and observe what the pressure is at the rail (as you've just replace the pump) in one of these cold start situations.... this might help some

http://minimopar.knizefamily.net/fuelsystem.html

if you have proper pressure at the rail, then you could begin looking at sensors without wasting any money unnecessarily.


I didn't want to do this but looks like I'll just have to start replacing sensors one by one to see which one it is.

So no one has had this Cold Start Problem???

[islandphile]

Thanks guys...I've checked spark at coil (brand new 2 days ago) and at the plug...all is well (New wires, plugs, rotor & cap 2 months ago). There is good pressure at the fuel rail, the regulator is 2 months old also.

I'm not sure about the injectors (the milege is excellent since I had the head ported & polished and installed EAT chip and K&N filter), but once I get her started it runs perfect & starts perfect until dead cold.

[islandphile]

I'll let you guys know what the problem is and what it took to fix it once I've got it figured out.