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Thread: Hard starting after sitting for short while

  1. #1
    Join Date
    Jul 2009
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    '88 735i, '06 RSX

    Hard starting after sitting for short while

    On to the next problem it seems, as is common with E32s...

    I left my E32 735 undriven this week, came to use it tonight to go to Friday night dinner....was very hard to start. Cranked for about 10 seconds before it started, then quit. Cranked again for 10 seconds, started up very weak with my foot on the throttle all the way down, then eventually came up to speed and idled rough. eventually it smoothed out a little bit, but acceleration was still sluggish and the car acted like it was missing sometimes under heavy load. Within the past 10K miles, it has had new plugs, new battery, new alternator, and new fuel filter, had top tier gas this whole year while under my ownership. You guys think its fuel pump, fuel injector, or maybe even AFM related?

  2. #2
    Join Date
    Jan 2005
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    11/88 E32 750iL+98 E36M3
    2 possibilities: a sign for a defective fuel pump check valve, all the fuel under pressure in the lines from fuel pump to fuel pressure regulators drains back to the tank. But I thought you installed a new check valve some months ago? https://www.bimmerforums.com/forum/s...k-valve-repair
    Another possibility is that the fuel injectors are leaking and flooding the cylinder, then ignition is also not that easy.
    Air leaks? When you have started the engine, spray some break cleaner around the intakes, but careful, that stuff burns quickly.
    Smoke test is of course the best.
    Last edited by shogun; 10-13-2017 at 10:24 PM.
    Shogun tricks and tips for the E32 series are HERE!

  3. #3
    Join Date
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    Quote Originally Posted by shogun View Post
    2 possibilities: a sign for a defective fuel pump check valve, all the fuel under pressure in the lines from fuel pump to fuel pressure regulators drains back to the tank. But I thought you installed a new check valve some months ago? https://www.bimmerforums.com/forum/s...k-valve-repair
    Another possibility is that the fuel injectors are leaking and flooding the cylinder, then ignition is also not that easy.
    Air leaks? When you have started the engine, spray some break cleaner around the intakes, but careful, that stuff burns quickly.
    Smoke test is of course the best.
    Yes, I forgot to mention I did the fuel check valve not so long ago.

    Perhaps it is the injectors, I have not changed them. Would running some cleaner maybe help fix the leaky injectors? I would have figured the detergents in top tier gas would have prevented something like this..
    i forgot to also mention, slight smell of fuel after driving for a short bit and turning off the car.

    personally I don't like to play with flammable fluids near a running engine, but I also don't have a smoke machine...hmm. Does anybody have a vacuum hose diagram for all locations on the m30b35?

  4. #4
    Join Date
    Jan 2005
    Location
    Japan
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    11/88 E32 750iL+98 E36M3
    2nd from bottom, vacuum hose diagram http://www.nmia.com/~dgnrg/page_2.htm
    CroughtonE32 has a good pic of the connection on the underside of the intake.

    Fuel line pressure/leak you could test, see workshop manual, also here some info https://www.injectorrx.com/leaking-fuel-injectors/

    also make a stomp test https://www.bimmerforums.com/forum/s...e-pedal-faults
    Last edited by shogun; 10-14-2017 at 12:11 AM.
    Shogun tricks and tips for the E32 series are HERE!

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