Vacuum Advance Delay Valve - Updated
Number: J82/39Date: September, 1982
Subject: Specification Changes to Distributor Vacuum System
Models: 1983 XJ-S
A vacuum regulator, part number EAC 5157, has been incorporated into the distributor vacuum advance system.
As in the 1982 model year vehicles, a timer relay inhibits the distributor vacuum advance for 45 seconds after each engine start up. After 45 seconds the system provides vacuum advance to the distributor. In order to obtain a more efficient idle, the vacuum regulator (see C1 in illustration) is introduced into the system between the solenoid vacuum valve (see Q in illustration) and the distributor advance capsule (see J in illustration). The lower part of the vacuum regulator is sourced to the air cleaner side of the throttle butterfly. Under idle conditions, atmospheric pressure operates on the vacuum regulator thereby limiting the vacuum to the distributor advance capsule.