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Thread: 1972 240z 3rd gear+ violent loss of power

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    Default 1972 240z 3rd gear+ violent loss of power

    Hey everyone, over the past few weeks my car has been running progressively worse. I just replaced the spark plugs with new NGK BP6ES plugs and it took away the problems I was having in 1st and 2nd gear (at 5k rpms it would hit almost like a rev limiter, but keep revving sporadically). It was doing this before, but it seems like in 3rd gear or higher it get this violent loss of power and the tach jumps all around. It kind of surges, as if you let off the gas and stomped on it again over and over until you shift or slow down. I think the timing is set around 15 degrees and I am running the pertronix unit and their coil. This isn't something that has been happening for a long time and I don't recall changing anything or making any adjustments prior to this happening. What are your suggestions, Where should I look. Thanks in advance for any help. Any information you can provide would be greatly appreciated.

    Thanks, Elliot

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    Registered User mlc240z's Avatar
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    Might want to check here:
    http://www.classiczcars.com/forums/s...threadid=37452

    What ohm coil?
    Did you bypass the ballast resistor?
    Bart

    5/71 240z, HLS30-31306, mostly stock, ZTherapy SU's, Pertronix, Eibach ProKit, KYB, Poly bushings, 60 amp alternator w/Dave's plug bypass, headlight and parking light harness upgrades.

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    Something's loose. Cars just don't behave that way.

    Check your locking screws on the distributor to start with. Check your centrifugal weights for freedom of movement. Just two places to start.....
    First & Third owner of HLS30-00721
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    Frank in Houston, Texas

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    What locking screws are you talking about? And yes its a 3 ohm coil with no resistor. I'll try the washer thing and see if that helps any. Keep the suggestions coming guys.

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    Registered User olzed's Avatar
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    I have a stock 240z with standard motor and stock ignition. Never had a problem in 15 years. Plugs and points adjustment 10 years ago! On a road car I can't see the point changing to electronic ignition.:

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    Registered User d240zx2's Avatar
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    The screws that keep the dizzy from turning.....
    First & Third owner of HLS30-00721
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    Frank in Houston, Texas

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    Registered User Walter Moore's Avatar
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    That is the way that my car acted when the fuel pump was going bad. It would run fine at nearly any speed until you hit about 60MPH, then it was like the car had a governor.

    (Which basically it did. When the fuel flow reached it's limit the car literally ran out of gas.)

    It sounded like a driveline vibration, but it turned out to be the engine shaking from the fuel failure.
    '71 240Z, Because any fool can drive fast in a straight line.

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    I'm with Walter and wouldn't rule out a fuel delivery problem, such as a plugged filter, or plugged pickup in the tank in addition to a failing pump. It could still be ignition and could be as simple as a loose wire at the coil. My 52 Chrysler did something to this effect with a bad condensor. My bet is that it is fuel though......

    72 240Z HLS30 49052 110 Persimmons/white stick
    72 240Z HLS30 70087 110 Persimmons/white auto 43K
    77 280Z HLS30 400336
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    I changed the plugs and tightened a few screws on the dizzy and the problem went away for maybe 30 minutes of driving and then it came back. The timing is staying consistent and not jumping around when revved. I am starting to think the fuel pump maybe the culprit. The fuel filter only fills up maybe 1/2" at most while the car is running. I blew air in the lines and it didn't clear much up. Also, when I pulled the plugs they were sort of dusty white/tan/redish in color. The car even sputters a little now in the lower RPMs. What are your thoughts?

    Thanks, Elliot

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    Anyone have anymore suggestions? I still haven't figured this out.

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    Crap plugging the fuel lines intermittently at gas tank ?
    Crap fuel flow / pump shot ?
    Crap in carbs ?
    Crap old gas destabilized ?
    Crap in general ?
    Crap / rusted fuel lines ?
    Last edited by Unkle; 05-28-2010 at 04:25 PM. Reason: Forgot some crap.

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    Oh, Crap. Why didn't I think of that??? ;-)
    First & Third owner of HLS30-00721
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    Frank in Houston, Texas

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    The slightly white-ish/light color of your plugs suggests a fuel delivery problem.

    If you were having ignition problems you would probably see black/sooty plugs from incomplete combustion.

    I'm also banking on the fuel pump and/or fuel filter... possibly even the screen at the tank?
    Silver '76 280Z Daily-Driver - "Lindsey" -- HLS30286119
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    With fuel also, had that same issue too in my 77 till I changed out my fuel pump then later fuel pump regulator or what ever that is called also attached to the fuel mounting bracket.
    Last edited by WingZr0; 05-29-2010 at 01:05 PM.
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    I took a couple of videos of whats going on. I just replaced the fuel pump and the problem is still there. I also blew out the fuel lines and that didn't help either. I will add captions to the videos so it's easier to tell whats going on. In video 27 I was in 2nd gear I think and around 5k you can hear the limiter type situation. It does it in second gear now too and I am limited to about 55-60mph now, which is really becoming a problem for driving on the highway.

    Here is the link: http://www.youtube.com/user/Cutlass372

    Clogged fuel tank or electical problem? Float bowls to low? The strange thing is that it came out of the blue. Does it seem like its missing or running out of gas. Let me know what you think.

    Thanks, Elliot
    Last edited by Cutlass372; 06-21-2010 at 04:54 PM.

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    Just solved a similar problem. Found the anti siphon valve stuck in the fuel filter. Would run fine for a while and then quit revving at 3500-4000. Always on the high way. Is the fuel filter full? Check it right after this happens.
    Jim
    Bought my 70Z at 21 with 24,000 miles
    Still own it. Thirty plus years later.


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    I actually just replaced the fuel filter with a different style. The one that I had only filled up a 1/4" of the bottle and I think the filter was in the bottom/middle. The one that I have now fills up the cup 3/4 the way full and the filter is at the top. This had no change in how the car ran, But possibly the valve you speak of is stuck? How did you end up fixing the problem? Do the videos help? I think they show the symptoms pretty well.

    Thanks, Elliot

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    long time owner a7dz's Avatar
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    I replaced the filter the fuel level came up to the top and it runs strong.
    Jim
    Bought my 70Z at 21 with 24,000 miles
    Still own it. Thirty plus years later.


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    Anyone else have any suggestions? I need to get my turbo motor finished so I don't have to worry about this anymore. But, until then I need this car to get me around. Is anyone local that could help me out? Please let me know.

    Thanks, Elliot

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    OK, I'll bite again.
    If you've hopefully ruled out ignition and fuel.
    This is out there but how about an exhaust restriction?

    Anything in the exhaust that could have gone fubar? Maybe don't remember but hit a speed bump and crimped a pipe, muffler rusted internally and collapsed?
    Bart

    5/71 240z, HLS30-31306, mostly stock, ZTherapy SU's, Pertronix, Eibach ProKit, KYB, Poly bushings, 60 amp alternator w/Dave's plug bypass, headlight and parking light harness upgrades.

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    Its possible I suppose, I will go take a look. I have a newish header and twice pipes that are fairly new. I feel like it is more of an ignition problem. Fuel is in the cup and I put on a new fuel pump/filter. Could be possible blockage in the tank. Does the stock 240z tank have a sock on the fuel pickup? Maybe this is clogged? Would anyone be willing to take a look at the problem to see more of what is going on? Maybe it is something simple that I am missing. It sounds to me more like a miss personally, but I am just not sure.

    Thanks, Elliot

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    After watching your tach go wacky I have to believe it has more to do with ignition, like a short somewhere, or maybe you are not getting a minimum of 12 volts at the ignition on wire. Have you checked that wire with a volt meter ? With the engine running there should be about 13.5 to 14.5 volts on that wire, especially if you are running the pertronix. Also make sure those connectors are tight.

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    I will check that when I get home. I checked it when I first installed the pertronix unit, but perhaps something has happened since then. I will check the wires on the pertronix unit and make sure nothing is shorting out or has broken wires. I checked and re-taped a few the other day, but perhaps I missed something.

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