Norcal Datsun 620 Posted January 19, 2015 Report Share Posted January 19, 2015 i need help connecting the vacuum hoses back I know they are correct but when I disconnect the egr vacuum hose I don't feel any vacuum at all? im new to datsuns and I really like my 620 everything else is right on except it didn't pass the egr validation I took the egr off and cleaned it, it works fine but im just not getting the vacuum I really don't know what is wrong. I need help with the vacuum diagrams I cant find any that look like the motor I have and I have a 78 dat 620 and it has everything stock Quote Link to comment
datzenmike Posted January 20, 2015 Report Share Posted January 20, 2015 That's because there is no vacuum and no EGR at idle speed. Only when revved up does the throttle plate rise above the EGR port inside and apply intake vacuum. This is also true of the vacuum advance. Does not exist at idle. Of the two ported vacuum hoses on the base of the carb, the rear-most one is the EGR. The front one goes to the distributor. Quote Link to comment
Norcal Datsun 620 Posted January 21, 2015 Author Report Share Posted January 21, 2015 Ok thanks I'll get on that it probably was connected wrong because I made sure I disconnected and connected every thing the same way. I do remember seeing the egr connected to something else not the carb so that's where I'll check Quote Link to comment
datzenmike Posted January 21, 2015 Report Share Posted January 21, 2015 Yes, the EGR is connected to the V V T beside it, and through it, to the carb. The V V T varies the vacuum in relation to exhaust back pressure. Quote Link to comment
Norcal Datsun 620 Posted January 21, 2015 Author Report Share Posted January 21, 2015 Do you have a pic of a l20b that is correct this is the only problem holding me from passing the smog I really want to drive this little truck I wish I can put pictures so u guys can see it. Quote Link to comment
datzenmike Posted January 21, 2015 Report Share Posted January 21, 2015 On a '78 there is a hose from the carb to a temp switch mounted on the side of the thermostat housing. It only opens and allow vacuum through when the engin warms abve a set amount. Thus there is no EGR when the engine is cold. From here the vacuum goes to the V V T which varies the amopunt fv vacuum applied to the EGR by exhaust pressure. Thus the heavier the throttle/load the more EGR is applied. From the V V T there is a hose to the EGR. There is no EGR at idle and full throttle so has zero effect on performance. None, zip, nada, fuck all. At part throttle there is some small loss of power but you won't miss it at all. Your foot will simoply press down on the throttle to compensate for those couple of hp lost. In some coase the EGR can increase the engine efficency because the throttle is open farther than non EGR running and the engine has less work to do sucking in air. If the EGR is crusty with exhaust deposits and does not close properly it will be allowing inert exhaust gasses into the engine when it should not/./ This dilution of the idle mixture will cause severe idle problems or no idle at all. If the exhaust tube from the EGR manifold to the exhaust manifold is rotted or leaking, oxegenated air and not inert exhaust will be added to the air fuel mixture forcing a lean condition and loss of power. Otherwise the EGR has Quote Link to comment
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