RE: [Chrysler300] No vacuum to distributor on 300H

Mike ---it is probably ported vacuum, (qv) no vacuum until certain carb throttle plate opening..this is to avoid full advance at idle, when vacuum is highest.; hard to test this end of what it does at carb, I think---- except if car is driven and loaded, carb slightly open,.(when advance is / should be active); it is not active again at WOT, even way before that , to avoid high load knocking ; also engine load (=vacuum at RPM ) dependent .You can assume it works, it is just a shaped hole into carb, precisely placed just above throttle plates-- or blow out with shop air. If straight in, a small wire ; I seriously doubt that end is ever wrong . Unless connected wrong, It is not to go to manifold vacuum. The other end in distributor can get a bad (torn or rotted) diaphragm that moves the advance in distributor. You can check with Mity Vac tester . Put vacuum from hand tester into hose to distributor, pump up, then do not pump, it should hold. If you cannot get vacuum or it drops in 30 sec or so you have a bad diaphragm. You could probably watch it move inside if so inclined as you pump.

Diaphragm failures not uncommon, then you get no vacuum advance at all, = poor mpg on cruise and sluggish at lower RPM . Advance vacuum unit has a number stamped on underside of arm, I forget if half or double the vacuum advance degrees, more to it than just that, but need to get right one. May look the same and be wrong. There are real pros on here , like Don Verity, on setting up distributors! More likely advance weights or initial timing (set with vacuum off) is to blame..might have it setup, checked on a machine. Also ethanol gas gets wrong air fuel mix, too lean, on non FI cars . It needs different AF ratio than carb gives it. No cure except real gas.

John

From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of Michael Moore mmoore8425@xxxxxxx [Chrysler300]
Sent: Tuesday, October 20, 2015 2:52 PM
Cc: Intl 300
Subject: [Chrysler300] No vacuum to distributor on 300H

I have been intermittently working on my 300H the last few years in my spare time to make it roadworthy. I keep coming back to the crummy engine performance. Past test drives have diverted me to doing a 100% brake job, front torsion bar rebuild and steering box rebuild.

The car just doesn;t have as much power as I would expect, even considering the awful gasoline. I finally recalled the car sometimes ran prety poorly when the vacuum line to the distributor was left disconnected. I checked that this morning, even disconnected it while it was running. The vacuum hose is clear, but when I connect my vacuum guage to the line I find no vacuum, Zero at any engine speed.

Do any of our experts have any suggestions before I start digging in?

Thanks, MIke Moore

300H