thedarkie Posted September 30, 2012 Share Posted September 30, 2012 (edited) I haven't done a compression test on these cars (or anything carbureted), is there anything particular about the procedure beyond removing all the plugs and testing on a warm engine with throttle wide open? Do you disconnect the ignition source as well? How about fuel? I did a search and lots of threads come up, but (seemingly) none regarding the testing procedure. Thanks in advance Edited September 30, 2012 by thedarkie Quote Link to comment Share on other sites More sharing options...
ihiryu Posted October 1, 2012 Share Posted October 1, 2012 On an EFI car I disconnect the fuel pump relay, so I'd suppose you should do the same. Quote Link to comment Share on other sites More sharing options...
thedarkie Posted October 1, 2012 Author Share Posted October 1, 2012 Doesnt the vacuum from the engine pull fuel through the carbs? I wouldnt have thought disconnecting the pump would be necessary... someone confirm? Thanks Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 1, 2012 Share Posted October 1, 2012 (edited) The procedure for EFI & Carbs is identical: throttle is blocked at WOT. There is no vacuum in the manifold when cranking in either system. It's the premise of "flood clearing" a carbureted engine holding it at WOT: no vacuum to suck any more fuel out of the carb while cranking to dry out the cylinders and hopefully fire once the mix is correct. On an EFI engine, disabling the pump keeps fuel from being injected, while the carb being held wide open stops fuel from being introduced to the engine, on an EFI ENgine it will still be injected. It doesn't need vacuum to atomism fuel, high pressure from the fuel system and injector spray pattern take care of that. Edited October 1, 2012 by Tony D Quote Link to comment Share on other sites More sharing options...
tamo3 Posted October 1, 2012 Share Posted October 1, 2012 http://www.atlanticz.ca/zclub/techtips/compressiontest/index.html Quote Link to comment Share on other sites More sharing options...
Leon Posted October 1, 2012 Share Posted October 1, 2012 I'm not sure about the 280Z, but most modern EFI systems have a "flood clear" mode, i.e. if the TPS detects WOT at cranking the ECU will turn off the injectors. Quote Link to comment Share on other sites More sharing options...
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