Triumph Repair: 79 TR7 deceleration by-pass, vacuum gauge, vacuum leak

Question
I forgot to mention in my previous question that my Lucas distributor vacuum retard unit doesn't seem to work. With the hose unplugged from the unit and the vacuum leak plugged there is no change in idle speed. I assume that the diaphragm is damaged and I tuned the carbs around this to keep the idle down. Could this be what's causing the slow deceleration? I plan on replacing the Lucas distributor with a supposedly more reliable Pertronix distributor.

Answer
Hi Michael,

Did you test the vacuum hose for vacuum? And did you check it with a timing light? You should have tested it with a vacuum pump to see if the base plate moves or better still find a Mighty Vac to hand pump vacuum and watch the plate move or note the vacuum gauge either hold vacuum (good diaphragm) or see it loose vacuum (bad diaphragm) I have seen many with a good diaphragm not move the plate due to a mechanical problem which replacing the diaphragm will not correct.

Find out what is wrong before buying parts.

Howard