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(no) cold start valve in 1988 528e

Discussion in 'E28 (1982-1988)' started by Rand524, Jan 14, 2009.

    Rand524 guest

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    Car has problems starting in cold weather - mechanic changed one of the fuel pumps, said the fuel pressure was too low and it cost me $600. It still sometimes takes 10-20 key turns and (occasional) gas pedal flutters to get the thing going, even after taking it back to him several times. He claimed that the car doesn't have a cold start valve, even though my Bently says there should be one, and sure enough, there isn't. Where it's supposed to be, there's just this round 1/2 thick cover thing on a triangular plate attached to the intake manifold with three bolts and connected with a hose and a cable to two other things (I'm clearly not an informed owner). So why don't I have a cold start valve, should I, is that why I have problems starting, and what is the thing that's there? Sorry for the floundering, but this is driving me crazy, not to mention hurting my starter. Thanks for any help.
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    mooseheadm5

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    Nope, no cold start valve on the 88 528e. It runs the later Motronic which just opens the injectors extra long for startup. My 327i conversion sorta did that- I just live with it. I would crank for a little bit (maybe 10 seconds at most) then turn off the key, turn it back on and crank while feathering the pedal. That always worked. There is supposed to be a check valve to keep fuel pressure on the rail in the main fuel pump, and it may be bad if that is not the one he replaced. I may look into an add-on check valve for mine to see if it helps, but the car is currently off the road.

    Rand524 guest

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    More questions of cold starting

    Thanks, Paul. Three questions: 1) How can I tell if the injectors are being kept open long enough for the temperature (it starts great at anything above 35 degrees or so), 2) 1) Does it make sense to install a check valve in the fuel line downstream of the pump to ensure that I'm maintaining pressure (assuming the pressure gets high enough to begin with), and 3) what exactly is that thingy bolted to the side of the intake manifold. Lastly (I guess this would be 4), I read somewhere that by turning the key to just before start, one can power the fuel pump for a few seconds to build pressure and then engage the starter. Does that make sense or was his ignition switch just malfunctioning?

    Thanks for your response so far - I just became a member and am looking forward to a rewarding year!
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    mooseheadm5

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    1. You can't without scoping them and knowing what correct values are.
    2. It might. Iwas looking for some online today. If you find one, let me know and I'll do the same
    3. That triangluar plate is just a blockoff. The cold start injector used to go there on earlier models.
    4. Yes, the ECU is programed to run the fuel pump for a second when you switch it on. If you do this many times and then crank it and the car fires right up, I would suspect that a check valve can help
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    BMWCCA1

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    There may also be a check valve built-in to the main fuel pump. Did your mechanic change the in-tank pump or the outside pump? In olden days, BMW made an external check valve to install at the main pump outlet as a fix for a bid internal check valve. A fuel pressure test with a gauge would tell you if it's losing pressure over time. You say it's hard to start in cold weather but is it harder to start after it's been sitting for a while? Overnight?

    Rand524 guest

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    Much harder to start after it's been sitting overnight, but not if it;s warm. If it sits in the cold for a couple hours or more after that it's somewhat hard to start, but overnight it's the worst.
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    BMWCCA1

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    But overnight, or even a couple days after sitting in warm weather, no problem?

    Rand524 guest

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    correct - when weather is warm, car starts fine even after sitting for several days.
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    BMWCCA1

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    At least that most likely rules out a check valve. Though not, necessarily, system pressure.

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