cannot get previa ignition timing to 5 degrees- stays at 20 or best at 12

[ahats]

rotated dist. all the way clockwise to stops and best degree marking is 12. The E1 and TE1 contacts are connected. I am using a typical 80's error timing light. RPM runs rough at 12 degrees but best at 20 degrees- about middle the dist. travel range. A second question is the fuel vacuum regulator robbs the vacuum of 2 in. when connected to regulator. If not connected, the engine runs higher rpm and the gage moves down from 18 to 15 in. vacuum. Any thoughts? Andy

[timsrv]

The 1st thing to do is verify the electronic advance is working correctly. Check the timing with the jumper across E1 & TE1, then pull it out and check timing again to confirm the advance is turning on/off. If that checks out then maybe the distributor or the exhaust cam is a tooth off. There is also a possibility the rubber insulator shifted on the crankshaft pulley. You can check this by pulling the #1 spark plug and positioning the engine to TDC of compression stroke by using the position of the #1 piston (stop when the piston gets closest to the plug hole). After you find the spot, check the timing mark on the pulley to verify it's close to 0 deg. If that checks out pull the valve cover and verify the marked timing chain link lines up with the mark on the sprocket. If that checks out then verify the marks on both cam gears are aligned. If that checks out then your distributor is a tooth off.

Based on what you said your fuel regulator may have a blown diaphragm. Take a piece of vacuum line and use it to apply suction to the regulator. You can use a Mity Vac but I usually just use my mouth. If vacuum can be applied and held, then the diaphragm is good. If you just keep sucking air then you'll need a new regulator. Tim