Timing question
Thread Starter
Instructor
Joined: Oct 2004
Posts: 173
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From: Hattiesburg MS
Timing question
While working on my car's timing I noticed that the RPM increases when the vacuum advance is unplugged. Shouldn't it be the other way around? If this shouldn't be happening, can someone give suggestions on how to correct it?
Thread Starter
Instructor
Joined: Oct 2004
Posts: 173
Likes: 0
From: Hattiesburg MS
Vacuum hose was plugged. Set idle to 700 RPM and timing was adjusted to 8 as under hood sticker says. When vac line was reconnected the RPM dropped and engine died. Adjusted idle speed to keep engine running and disconnected vacuum line (and plugged it) again. Engine speed rose by about 200 RPM.
After this, I took the cap and rotor off to check the advance weights. They move fine but the part they actuate does not move. Should this part be able to move by hand? Could this be the cause of the problem described above?
After this, I took the cap and rotor off to check the advance weights. They move fine but the part they actuate does not move. Should this part be able to move by hand? Could this be the cause of the problem described above?
Racer
Joined: Nov 2001
Posts: 478
Likes: 3
From: Huntsville AL
Sounds like either the advance plate in the dist. is stuck and/or the vacuum advance diaphram is leaking. Try hooking up a vacuum pump to the hose going to the vaccum advance with the cap off and see if it moves with vacuum. If you don't have a vacuum pump just suck on the hose and watch for movement. If no movement the plate is stuck. If it doesn't hold vacuum the vacuum advance needs to be replaced. Hope this helps.
YBnormal...drive a vette
YBnormal...drive a vette
Thread Starter
Instructor
Joined: Oct 2004
Posts: 173
Likes: 0
From: Hattiesburg MS
Okay, stayed up all night trying to figure this one out. I had replaced the vacuum advance module 2 days ago and it is still working fine. Last night I took the dist. out, removed gear, removed shaft form housing, and got the centrifugal advance working freely. Put everything back together and retimed engine for 8 deg BTDC @ 700 RPM with vaccum advance line disconnected and plugged. Once done I reconnected the vacuum advance line and the RPM dropped aggain. I don't understand how this can be happening. Has anyone ever heard of this before?
Melting Slicks
Joined: Nov 2001
Posts: 2,668
Likes: 43
From: Eastern US XX
Originally Posted by Mr Fanuc
While working on my car's timing I noticed that the RPM increases when the vacuum advance is unplugged. Shouldn't it be the other way around? If this shouldn't be happening, can someone give suggestions on how to correct it?
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Team Owner
Joined: Apr 2001
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From: S.W. Ohio. . . . . . NRA Life Member
Sounds like either the advance plate in the dist. is stuck and/or the vacuum advance diaphram is leaking.
You should have the exact same amount of vacuum present whether the line is plugged, or attached to the vacuum advance actuator (at the same RPM ... obviously).
