1972 240z 3rd gear+ violent loss of power

[KDMatt]

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?

[WingZr0]

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.

Edited May 29, 2010 by WingZr0

[Cutlass372]

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

Edited June 21, 2010 by Cutlass372

[a7dz]

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.

[Cutlass372]

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

[a7dz]

I replaced the filter the fuel level came up to the top and it runs strong.

[Cutlass372]

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

[mlc240z]

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?

[Cutlass372]

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

[Zforce]

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.

[Cutlass372]

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.