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Thread: cold start difficulty, help!

  1. #1

    cold start difficulty, help!

    I know there has been some previous discussion of mfi cold start problems but I think I may have a different problem.
    My 72S, out of the blue, just became difficult to start. ie: much cranking and then firing and slow to come up to rpm on the hand throttle. It has been intermittent as sometimes it would start right up with the hand throttle up and immediately turning the ignition and starter.
    Once warmed up, the car runs great and starts fine when warm.
    Now it won't fire at all with the hand throttle up and only barely fires with the hand throttle closed. I smell fuel as if the engine is flooded.
    The spark plugs are normal color but have carbon fouling. After cleaning the plugs I still have the same problem starting.
    It seems like the car is getting too much fuel and not enough air or spark.
    I tried starting it with the cold start enrichment devise on top of the fuel pump disconnected and there was no change. This should only work in very cold temps anyway but I thought it might be malfunctioning.
    I seem to remember Cornpanzer having a similar problem he discussed here or on Pelican. He was having a cold start problem that had to do with too much fuel instead of not enough fuel on start up.
    Any help would be great.
    Thanks
    Scott
    Scott Marshall
    911 S Registry member#724
    1981 Porsche 911SC
    1993 Porsche 968 Clubsport
    1961 Abarth Record Monza, 1964 Abarth Simca 2000
    1962 Abarth 1000GT, 1964 Abarth 850TC Nurburgring

  2. #2
    If this has started happening out of the blue, I would suggest looking at the thermostat hot air hose for the injection pump, make sure it is not blocked, or disconnected, also make sure the thermostat is also clean and can move freely. The other area to check is your ignition system, sounds like it may not have its full spark

  3. #3
    The thermostat hot air hose has nothing to do with it starting. You need to have the parts to diagnose and fix. Go throught the factory manual and do the system check, it is quite easy. You need to check this system before you start fixing what isnt broken. Does the cold start soleniod work? Is the system powered? Is the power relay working? Is the thermal time switch properly functioning? These must be checked and verified, then move on.

  4. #4
    The cold start solenoid works whenever the ENGINE is cold, not when it is cold outside. The other function is the timing function of the thermal time switch. You say you smell fuel, sounds like something else is wrong.

  5. #5
    We have found many times in the past exactly what I described above, to have been the full, or major cause of just this starting problem. I suggested the igniton as the car obviously has no fuel supply issues. You could also check the thermostat shim pack for shim quantity. Just my 0.20 cents worth. Might also be, that down under we see things upside down to you guys up there.

  6. #6
    Thanks for the help so far. I will look at the mfi components and check the ignition components. I'll post if I can figure it out.
    Scott
    Scott Marshall
    911 S Registry member#724
    1981 Porsche 911SC
    1993 Porsche 968 Clubsport
    1961 Abarth Record Monza, 1964 Abarth Simca 2000
    1962 Abarth 1000GT, 1964 Abarth 850TC Nurburgring

  7. #7
    Jeff:

    MFI issues are always a mystery. My car runs great when it is warm (the engine) even though it uses a bit more fuel than I would have hoped - I get 9 - 11 mpg in the city.

    But when the engine is cold, it's really rough. I start OK, using the hand throttle to start it, but driving it is a challenge. It bucks like a bronco, and I need to really give it lots of gas out of a dead stop. As it warms up, I reduce the throttle feed, and then it's fine.

    I know that I need to look into the cold start system, but I am not sure where to start. I don't want to screw things up more than they already are, and being a NOVICE (big letters to show how big a novice I am) the likelihood of a negative impact is possible.

    Any help on how to proceed - what steps to check first, then second - would be helpful. BTW, I have a full set of service manuals.

    TIA

    larry
    Early 911S Registry Member #537

    73 - Viper Green 911E Targa - Kermit - Gone but not forgotten

    Kermit's Short Story and Pix on the 911E Website

    06 - Lexus IS250 MT6
    98 - Volvo 70V XC

  8. #8
    Quote Originally Posted by teescott
    I know there has been some previous discussion of mfi cold start problems but I think I may have a different problem.
    My 72S, out of the blue, just became difficult to start. ie: much cranking and then firing and slow to come up to rpm on the hand throttle. It has been intermittent as sometimes it would start right up with the hand throttle up and immediately turning the ignition and starter.
    Once warmed up, the car runs great and starts fine when warm.
    Now it won't fire at all with the hand throttle up and only barely fires with the hand throttle closed. I smell fuel as if the engine is flooded.
    The spark plugs are normal color but have carbon fouling. After cleaning the plugs I still have the same problem starting.
    It seems like the car is getting too much fuel and not enough air or spark.
    I tried starting it with the cold start enrichment devise on top of the fuel pump disconnected and there was no change. This should only work in very cold temps anyway but I thought it might be malfunctioning.
    I seem to remember Cornpanzer having a similar problem he discussed here or on Pelican. He was having a cold start problem that had to do with too much fuel instead of not enough fuel on start up.
    Any help would be great.
    Thanks
    Scott
    Scott, it may be going way too rich when cold. Rather than disconnecting the solenoid, try pinching off the cold start fuel supply hose as it leaves the cold start solenoid. This is probably the most simple and effective way to get that circuit out of the picture - if it's easier to start, then you know where to look for problems.
    Leaf green 72T, SOLD!
    Gone back to my MoPar roots!

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