I have a 1979 Corona and am wondering if anyone has a good handle on the problem with the Auxilary Accelerator Pump (AAP) problem, and can provide details about it. Thanks.
New and old Toyota car and truck content at Toyoland!
20R engine (carbureted)
May 31, 2007
May 31, 2007#1
A pretty common problem on early Toyota with the 20R engine - like the Celica, Corona, Truck.
Failure mode is usually when the diaphragm, in the auxiliary accelerator pump, in the carburetor. The AAP is designed to allow a longer accelerator pump stroke when cold.
A failed diaphragm will result in very high CO emission due to sucking gasoline straight through the accelerator pump circuit. First thing I would check would be the manifold and gasket at #4 runner (location of EGR valve) for leaks.
Failure mode is usually when the diaphragm, in the auxiliary accelerator pump, in the carburetor. The AAP is designed to allow a longer accelerator pump stroke when cold.
A failed diaphragm will result in very high CO emission due to sucking gasoline straight through the accelerator pump circuit. First thing I would check would be the manifold and gasket at #4 runner (location of EGR valve) for leaks.
June 14, 2010#2
i have a 1978 corona 20r engine. just recently got it running. vacuum hoses were mismatched. i need a detailed diagram if anyone knows where i could find one. the one in chiltons manual is small and i couldnt make sense of it. is there a simple way to do get rid of all these vacuum hoses . maybe change the carb and rotor. also, i have put about a thousand miles on it since i got it running and now when i hit the accelerator pedal, its like it takes gas from the carb. however when it is idling it purrs like a kitten.
June 19, 2010#4
figured out the problem was a clogged fuel filter. I'll have to check on the weber carb
