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Thread: Can't figure this "Cold Start" problem out.

  1. #1
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    Can't figure this "Cold Start" problem out.

    I need some help with this one. I have a bmw 528i 1999 with 173,000 miles.
    I have this problem now for two months and it takes me 2 minutes of cranking to get the car started upon a cold start. After the car starts it runs perfect. When its warm the car starts every time and runs perfect and smooth.
    New items in the car or recently replaced are:
    -ECT
    - lower coolant hose temperature sensor
    - New MAF
    - Vanos seals replaced 20 k miles ago
    - fixed the EGR system
    - replaced lower and upper intake boots ( I have no vacuum leaks)
    - new adjuster unit
    - CCV replaced 20 k miles ago
    - new battery
    - all fuses are checked and good
    - fuel pressure solid on 52 psi
    - changed out fuel pumps between my 1997 and 1999 528i ( still same problem)
    - cleaned throttle and ICV
    - new air filter and oil filter

    I have had a conversation with an respectable injector cleaning company. If i have leaking injectors then it should also have problems starting when car is warm, which i dont have. It was also mentioned that i would see black smoke for a short period, which i dont have.

    I am thinking of having a software problem or still leaking injectors.
    Like to ask for y'all input to solve the problem as described above
    Thanks

  2. #2
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    Perhaps temperature sensors. See these links

    http://wds.spaghetticoder.org/en/e39...r_temperature/
    http://wds.spaghetticoder.org/en/zin...1214_M0TAN.htm

    The MAF is ignored during starting and the DME uses coolant and air inlet temperature to calculate injection timing (duration) If one or other sensor is off spec far the mixture may be out of spec enough that the engine won't start.

    EDIT: you can check values being return by each sensor with a BMW compatible diagnostic reader. With luck one of them won't be sensible and you'll have the culprit.
    EDIT2: not to insult anyone's intelligence, but be sure the test is done when the engine is stone cold. Not when you drive it in & you know it will start again. Don't laugh, I seen worse.

    Regards
    RDL
    Last edited by rdl; 12-07-2012 at 10:47 PM.

  3. #3
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    I really appreciate your input RDL. Thats the only sensor i havent replaced yet. It was interesting to read that the MAF is not involved in a cold start and the reading is coming from the air intake sensor. Its always great to learn something i didnt know. Hoping that the sensors are the same between my 1997 and 1999. That will give an option to swap. I did measure the resistance following the Bentley manual, and it was within spec. I will swap it out tomorrow and report back.

  4. #4
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    Quote Originally Posted by Dutchman71 View Post
    ...
    It was interesting to read that the MAF is not involved in a cold start and the reading is coming from the air intake sensor.
    ...
    Keep in mind that the MAF is ignored on both cold and hot start. My hypothesis is that one or both sensors might be giving false readings a low temps but are accurate at higher temps.

    Also, the coolant sensor mentioned is the one in the head, not the lower rad hose. I didn't see that you replaced that one. FYI, it is sometimes called the dual temp sensor. It is consists of 2 thermistors in one body. The instrument cluster coolant temp gauge uses one, the DME uses the other.

    Regards
    RDL

  5. #5
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    The coolant sensor your mentioned is the ECT and has been replaced. I agree with you about the MAF and the IAT sensor. The MAF was replaced so the only thing left is the IAT. Its a negative temperature coefficient sensor. When temp rises it decreases the resistance. So the lower ends works good, but the higher end doesnt. Will replace tomorrow. I think its only 25 dollars.
    I also took the pressure off the fuel rail to see if it start in one time. This is the third time doing it. The first time the car started and i thought i found the culprit with the injectors, but i did it again to make sure i was right, but same problem occured again. Tomorrow will try it again and see what happens.

  6. #6
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    I would try to replace the crank sensor if you continue to have long cold start.

  7. #7
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    I am sorry. I forgot to add the crankshaft sensor to my list of items that have been replaced.

  8. #8
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    Quote Originally Posted by Dutchman71 View Post
    I am sorry. I forgot to add the crankshaft sensor to my list of items that have been replaced.
    Did you use BMW crank sensor? Aftermarket crank sensor is not to be trusted.
    Serious.

  9. #9
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    Yes. Original and bought at bmw dealership 120.00. I live close to the dealership. I am getting ready to pick up the IAT sensor. Doesnt a crankshaft sensor give problems at every start up?

  10. #10
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    Quote Originally Posted by Dutchman71 View Post
    Yes. Original and bought at bmw dealership 120.00. I live close to the dealership. I am getting ready to pick up the IAT sensor. Doesnt a crankshaft sensor give problems at every start up?
    Not always, because temperature does effect the resistance and therefore it effects how its behavior, this is why aftermarket sensors are sub-par due to how they were fabricated (cheaper material are more susceptible to temperature)

    So with all that said an OEM BMW sensor is the best but doesn't mean it will last forever, it could still be bad at one end of the spectrum of temperature and good at the other. So keep in mind, if all else doesn't resolve your cold start.

    However, your car with 175K miles there are a few things that could cause your cold start. One of them is low compression, low compression cylinders could also be the cause of hard cold start.

    The other cause could be low battery voltages. How is your battery and alternator?

  11. #11
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    Battery is brand new and altenator was replaced 10 k ago. I will take some compression reading and let you know. I installed the IAT and still same problem so far. Maybe the sensor has to adjust for a couple miles. Will try again tomorrow to see if it starts better. I was thinking of a cracked cylinderhead, but i dont have any symptoms that would support that. I will check the plugs to see if one of them is white, but i dont believe thats my problem thou.
    I just rebuild this 325i 2003. I would like to take a break.

  12. #12
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    Do the proper diagnosis instead of throwing parts at it. Simple diagnosis would cost you a lot less than all the parts you've thrown at it. Install a fuel pressure gauge and start the car, shut it off, and let it sit overnight and check the pressure again. This should tell you if it's a fuel related problem.

  13. #13
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    Has a scanner been utilized?


    /.randy

  14. #14
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    Everything with the fuel pressure is tested, also letting it sit overnight pressure has been tested. I have 3 bmw's and solved many issues. I am not a newbie to bmw.
    The only codes i get are random misfire codes, due to the long cranking period. I dont get any other codes that would be helpful to solve this issue.

    16valex my compression is 120 to 125 psi. Except the number 3 cylinder is 115. I checked the number 3 cylinder 3 times, but cant get it any higher. The car was warm when i took the readings. It is an older car so i dont believe its too bad to be around 120. I checked all sparkplugs and they look good. They are dry and light brown.
    I havent timed this car, so decided to re-time it and clean all the parts involved while i am at it.
    It will all be back together tomorrow and will update.
    I only have a bmw scanner, but i do not have the live feed software for computers.

  15. #15
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    I wasn't talking codes, I was talking a scanner. What values is the DME seeing for each sensor and how is it reacting while cranking. It would sure take a lot of guess work out of this. You would be able to see what the DME thinks the ECT (to pick one example) is. this would cover not only your new sensor, but all the wires and connectors between.

    Your misfire codes aren't set during cranking, the conditions aren't there. Among other things, misfire detection requires engine speed of over 512 rpm for at least 1000 revs.


    /.randy

  16. #16
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    I see. Your right, but i dont have a scanner. I am a dyi guy, but computers is not my strongest part. How much do they cost and where do you recommend i should buy it. Is this INPA etc your talking about?

  17. #17
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    Inpa is the cheapest and most accessible, if not the most turn-key. There are others. Even an OBDii scanner with a generic datastream will get a lot of the stuff needed for a successful start.


    /.randy

  18. #18
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    I will look into the scanner Randy. I am just curious why would the ECT only act up on cold start and not at every start?
    I have had a software reflash on my other two beemers, which solved some issues i had in the past.

  19. #19
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    I'm not saying it's the ECT at all, that was just an example pulled from earlier in the thread. If the DME says it sees 50F from the sensor, and it's a cold motor and 50F ambient, you can pretty much assume the sensor and all it's wiring is good. 10 seconds, no parts, and you're on to looking at the RPM (or TPS or IAT or...) signal.


    You may not find anything amiss with a scanner. But to work with computer controlled systems, you really ought to be able to talk with the computer in realtime.


    /.randy

  20. #20
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    Quote Originally Posted by Dutchman71 View Post
    ...
    I also took the pressure off the fuel rail to see if it start in one time. This is the third time doing it. The first time the car started and i thought i found the culprit with the injectors, but i did it again to make sure i was right, but same problem occured again. Tomorrow will try it again and see what happens.
    I saw in one of your later posts that the IAT sensor did not solve the problem. So much for that theory.

    Are cold starts prolonged battery endurance tests every time? Or only most times? If every time, there must be some significance that releasing the pressure in the fuel rail worked that one time.

    Was there any difference at all between the 1st the 2nd trial? E.g. release pressure immediately after stopping engine first time, waited an hour before releasing pressure on 2nd trial. Was the wait time between stop and next start attempt different between 1st and 2nd trial? Ambient temperatures similar? etc.

    If you start a cold engine, what would happen if you immediately stopped the engine before any temperature rise and tried to restart? Would it start quickly?

    You mentioned in first post that you'd checked fuel pressure. Was test done while starting? Or while running?
    Any chance that you could put a fuel pressure gauge on while running, stop the car, leave gauge in place, monitor pressure while starting cold engine.

    Regards
    RDL

  21. #21
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    Thank you Randy. It would be nice to have the scanner right now. 10 seconds beats the two months trouble shooting this issue. I will definetely look into it. Thanks for your input.

    RDL i had a good feeling changing the sensor. It all would have made sense, but .
    The cold starts are every time. It doesnt matter if its cold that morning or not. That one time that it started after releasing the pressure on the fuel rail must have been a fluke. I tried it twice after and it still didnt wanted to start. It started after cranking two minutes.
    The fuel pressure when turning key to ACC is right away 52 psi. It stays at 52 psi thru out the cranking process at cold start.
    If the car finally starts and i shut it down right away, then it will restart with no problem and will drive and idle perfect until i get back to the cold start.
    The fuel pressure after shutdown will reduce slowly thru out the day.
    I talked to a respectable injector cleaning company and with my symptoms it was not likely to be caused by leaking injectors, because leaky injectors would also cause problems at a hot/ warm engine. It would also cause a short puff of black smoke, which i dont have.
    I took compression readings and decided to retime the engine. I havent timed this beemer since i bought it. I will have it back together tomorrow. You never know, it might start.
    I think its a software issue. The scanner would be nice, have to look into it.

    When i crank that long, you can smell the gas out of the exhaust. No surprise to me when you have to crank that long
    Last edited by Dutchman71; 12-08-2012 at 11:18 PM. Reason: Automerged Doublepost

  22. #22
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    Dutchman71, I still think you have a fuel pressure is issue. I would replace the fuel pressure regulator. Item #3 from attached link.

    http://www.realoem.com/bmw/showparts...30&hg=13&fg=10

  23. #23
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    Quote Originally Posted by Dutchman71 View Post
    ... stuff deleted ...

    When i crank that long, you can smell the gas out of the exhaust. No surprise to me when you have to crank that long
    Raw gas smell on prolonged cranking suggests either lack of spark or immediate severe flooding. Given that you have already checked fuel pressure and injectors, I'd try to confirm spark.

    See the attached images of the ignition circuit. The relay and fuse F5 in image "ignition1" are both located in the engine electronics box under the passenger side cabin air filter. Beware that the e-box F5 is not in the F5 glovebox panel - a blunder in BMW's drawing configuation control. See image "Ignition2" for spark plug coil schematic.

    As first step I would check a cold engine for
    A) good ground on pin 2 at spark plug coil connectors before trying to start
    B) B+ voltage on pin 3 with key at run and also during start

    I have assumed that the no start cranking is pure "no kick" no start, not a sputtering "almost" start until the engine finally catches. If the sputtering variety, verifying spark becomes much more difficult and you will probably need a diagnostic system &/or oscilloscope to confirm the spark good or bad.

    I'll cross my fingers for you that it turns out to be something as easy to correct as a sticky relay.

    Spagetticoder wiring diagrams is partially inop for me this morning. Try this alternate site if you need addtional info
    http://www.bmw-planet.com/diagrams/r...9new/index.htm

    EDIT: I've assumed your model year has the MS42 DME. If I'm wrong be aware that the MS43 ignition wiring is different.

    Regards
    RDL
    Attached Images Attached Images
    Last edited by rdl; 12-09-2012 at 09:48 AM.

  24. #24
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    It does want to start while cranking, but dies right the way if it does. It will go up to 300-500 rpm and dies. I only get it started when pushing the accellerator. If i dont then it will just crank. When i crank and it start then the rest of the day everything is great until the cold start comes around. I will check out your suggestion, when i get the timing finished.

  25. #25
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    See the PDF in this thread for description of the MS42 operation on the chance that it may help. File is too large for Bimmerforums upload limits.

    http://www.bimmerfest.com/forums/sho...10#post7239010

    Regards
    RDL

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