cybermecium Posted April 27, 2007 Share Posted April 27, 2007 I just got my motor running today after sorting out some ignition problems. I am running an N42/N42 L28 with stock 240 roundtop SU's. Unfortunately I am running the stock 240Z points ignition because at the moment I don't have anything better. When I started it up it first would pop and sputter but not start. If I advance the timing via the distributor very slightly it will run but... revs up to about 4K RPM. I had it "running" at around 1500rpm and opening the throttle had absolutely no effect on engine speed or running conditions. All the linkage is hooked up, ignition and cam timing are correct. What could is be that is causing my engine to either run very very fast or not run at all, with the throttle doing nothing about it? Thanks Jake Quote Link to comment Share on other sites More sharing options...
JSM Posted April 27, 2007 Share Posted April 27, 2007 You check for Vacum Leaks? Quote Link to comment Share on other sites More sharing options...
rchrd989 Posted April 27, 2007 Share Posted April 27, 2007 I recently just got my first engine build running and i noticed that if the brake booster vacume line isnt connected then it will run alot different, and also check the dampening on your slides on you SU's Quote Link to comment Share on other sites More sharing options...
naviathan Posted April 27, 2007 Share Posted April 27, 2007 I recently just got my first engine build running and i noticed that if the brake booster vacume line isnt connected then it will run alot different, and also check the dampening on your slides on you SU's Ummmmm, yeah the brake booster line is a BIG vacuum leak. Quote Link to comment Share on other sites More sharing options...
oinojo Posted April 27, 2007 Share Posted April 27, 2007 I just got my motor running today after sorting out some ignition problems. I am running an N42/N42 L28 with stock 240 roundtop SU's. Unfortunately I am running the stock 240Z points ignition because at the moment I don't have anything better. When I started it up it first would pop and sputter but not start. If I advance the timing via the distributor very slightly it will run but... revs up to about 4K RPM. I had it "running" at around 1500rpm and opening the throttle had absolutely no effect on engine speed or running conditions. All the linkage is hooked up, ignition and cam timing are correct. What could is be that is causing my engine to either run very very fast or not run at all, with the throttle doing nothing about it? Thanks Jake check your linkage jake. The linkage for your old flattops are different since your running the round tops now. Quote Link to comment Share on other sites More sharing options...
cybermecium Posted April 27, 2007 Author Share Posted April 27, 2007 I am using the right linkage that came with the round tops, I am 99% sure that the linkage is not the problem, when I work the action of the throttle by hand it actuates the throttles in both carbs just fine. However, I noticed that the brake booster vac line has a nice crack in it right where it connects to the barb on the intake, and also the PCV hose has a crack in it... probably a major source of the problem. Thanks Jake Quote Link to comment Share on other sites More sharing options...
oinojo Posted April 27, 2007 Share Posted April 27, 2007 I am using the right linkage that came with the round tops, I am 99% sure that the linkage is not the problem, when I work the action of the throttle by hand it actuates the throttles in both carbs just fine. However, I noticed that the brake booster vac line has a nice crack in it right where it connects to the barb on the intake, and also the PCV hose has a crack in it... probably a major source of the problem. Thanks Jake jake, you werent home but your car was open. BAD JAKE!! lol...well anyway i took a look at your linkage and you had it setup upside down. I took the liberty of fixing it for you and all you need to do now is connect the throttle return springs to you heatshield (not installed) Quote Link to comment Share on other sites More sharing options...
Daeron Posted April 28, 2007 Share Posted April 28, 2007 Funny thread... My favorite method of searching for vacuum leaks is to stick a piece of hose about 1/2" or so in diameter, and a couple feet long, into one ear, and fish the other end around the engine compartment. It acts like a stethoscope; cutting out noises other than those happening right there at the tip. OR you could go to harbor freight and buy a mechanics stethoscope, used for pretty much the same thing. Quote Link to comment Share on other sites More sharing options...
JSM Posted April 28, 2007 Share Posted April 28, 2007 jake, you werent home but your car was open. BAD JAKE!! lol...well anyway i took a look at your linkage and you had it setup upside down. I took the liberty of fixing it for you and all you need to do now is connect the throttle return springs to you heatshield (not installed) Ouch, I was assuming at least the return springs were installed! Quote Link to comment Share on other sites More sharing options...
cybermecium Posted April 28, 2007 Author Share Posted April 28, 2007 The throttle return springs are installed, to the air cleaner baseplates, not the heat shield, throttle action and return works fine. (thanks Jon for sorting out the linkage.) Now it starts (after many cranks) and idles at about 1000rpm with no problem. However when trying to crank it sometimes it backfires out the carbs, and while it is idling, if I give it ANY amount of throttle, it spits out the carbs and dies. I am assuming ignition timing? For clarification- firing order is 1-5-3-6-2-4 correct? And cylinder #1 is that closest to the radiator? Thanks for the help, Jake Quote Link to comment Share on other sites More sharing options...
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