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Buick Forum: 1985 Buick Century Limited 3.8 warm hard start issues...
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  1. #1
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    1985 Buick Century Limited 3.8 warm hard start issues...

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    Hi everyone, this is my first post, and I really hope I can find some answers. I have an '85 Buick Century with a 3.8, and it only has about 60k miles.

    The problem:
    For as long as I can remember, and my mother, when it was her car. This car takes many many cranks to start if it has been warmed up and then left sitting for 10min or so. At that point you pretty much have to wait for it to get dead cold again if you want an easy quick start. However if it has been warmed up and say you're just shutting it off to fill the tank at a gas station, it also fires up quickly with no problem. I haven't exactly timed it but my best guess is it takes about 10 min or so for the problem to appear. When it does finally start in that situation the engine runs a little rough for about 5 seconds. This problem has not changed one bit over a LONG period of time as well, it has not improved and it has not got worse.

    Other then that I have noticed 0 performance issues on this car, I see lots of people complaining about random stalling and stuff but no, this is a problem free car except for this one problem, and I would love to get it fixed before I need a new starter motor. My only guess is possibly leaking fuel injectors, or perhaps a bad coolant temp sensor? Is there one for the gauge and then one for the computer? Because the one for the gauge seems to operate just fine.

    I'm posting here hoping that this is a common or known about problem with these motors, but I haven't had much luck.

    Thanks ya'll!

  2. #2
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    Re: 1985 Buick Century Limited 3.8 warm hard start issues...

    I would borrow a fuel pressure gauge (autozone?) and check fuel pressure and also see if the injectors are leaking after shutdown. You should hold pressure for some time after shutdown if the injectors are good. Usually there are two coolant temp sensors, gauge and cpu. I would diagnose first and not throw parts at it. Any codes?

  3. #3
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    Re: 1985 Buick Century Limited 3.8 warm hard start issues...

    Could be a heat soak issue (ICM) ((Ignition Control Module)) ?
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  4. #4
    ryenie is offline Full Member My Buick(s): 95 Monte Carlo L36
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    Re: 1985 Buick Century Limited 3.8 warm hard start issues...

    Is it carbureted? The only fuel pressure spec i can find is 5 1\2 - 6 1\2 psi while idling, much to low for fuel injection. fuel injected is typically closer to 40 psi give or take a little. Might have more to do with electronic choke, or something of that nature. Might also want to check the plugs.

  5. #5
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    Re: 1985 Buick Century Limited 3.8 warm hard start issues...

    Hey everyone, I found this because I googled a similar problem and realized I never got any email notifications from any of your replies! So Sorry about that, I will correct it.

    Anyways, car has about 70k on it now and the problem has changed... I replaced the fuel pump and filter that actually totally solved the hard start issue! Before even when it was dead cold it could take a few cranks to start, but now it starts on the first crank. But now it is back, it is again only hard to start after it has warmed up and it sits for a few minutes, but now it is actually even harder to start then before, I really have to give it gas and keep the rpms up for a while before I put it into gear, otherwise it will stall. My gut tells me this is related to other issues.that have never.gone away such as a shaky idle, and random moments of jumpy/hesitation to accelerate. It also sometimes idles high now.

    Let me tell you what else I've done. New plugs, and new injectors.

    So now I am thinking EGR, FPR, MAF, coolant temp sensor? Is there more than one on these pos motors? How can I narrow this down more without throwing parts at it?

  6. #6
    zcoop is offline Buick Newbie My Buick(s): 1990 Century V6
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    Re: 1985 Buick Century Limited 3.8 warm hard start issues...

    I am not a car expert and fairly new to cars, but I had to replace several pieces in my cooling system. (I have a 1990 Century) It would surprise me if your coolant temperature sensor had a problem. In the beginning of my problems with the system I thought that there could be a problem with the temperature sensor, but after looking into it, it is really hard to cause your temperature sensor to "wear" out.

  7. #7
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    Re: 1985 Buick Century Limited 3.8 warm hard start issues...

    Quote Originally Posted by zcoop View Post
    I am not a car expert and fairly new to cars, but I had to replace several pieces in my cooling system. (I have a 1990 Century) It would surprise me if your coolant temperature sensor had a problem. In the beginning of my problems with the system I thought that there could be a problem with the temperature sensor, but after looking into it, it is really hard to cause your temperature sensor to "wear" out.
    Thanks. Ya I'm not sure about that either, I have a coolant temp sensor for the gauge and I know that is working fine, so I would be surprised too if a separate sensor is faulty. Whatever sensor controls the electric fan also works properly, even though I have no idea where that sensor is. I replaced the FPR, no change, I replaced the MAF, no change. What component tied to spark could behave this way is my question now.

  8. #8
    BK3 is online now Junior Member My Buick(s): 2002 Century
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    Re: 1985 Buick Century Limited 3.8 warm hard start issues...

    I would also clean the throttle body, if you haven't done so in a while.

  9. #9
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    Re: 1985 Buick Century Limited 3.8 warm hard start issues...

    Quote Originally Posted by BK3 View Post
    I would also clean the throttle body, if you haven't done so in a while.
    Can you be more specific? I've taken off the throttle body recently to gain more room when I replaced the thermostat. It is just an aluminum housing with a round flap in it, wasn't dirty at all, and if it was dirty I'm not sure why anything would be affected unless it was so dirty that the flap was getting stuck, which in my mind would be pretty difficult because of how strong the spring is.

  10. #10
    BK3 is online now Junior Member My Buick(s): 2002 Century
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    Re: 1985 Buick Century Limited 3.8 warm hard start issues...

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    The throttle body is more complex than you think. It contains several air passages for idle air flow, contains the IAC, and throttle position sensor.
    If any of the passages are clogged or nearly so, idle can be effected, along with performance. Google "Cleaning throttle body" for more information.

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