KJL

I have the plenum removed and thought it would be a good time to check the secondary vacuum actuators. I have a hand vacuum pump I use to check things out on my 72. With plenum removed, where should pump be connected and what lines should be plugged? There are lines to a vacuum pump, sensor (mounted under plenum) and a line that goes to the plenum and connects to the solenoid (not sure what this is for other than solenoid activation?).

Dynomite

You can activate the vacuum pump and check for vacuum leaks as well as Secondary Actuators without using a light since you have the Plenum removed Using Marc Haibeck's technique. Checking Secondary Actuators with Plenum in Place

Marc suggests in regard to Vacuum Pump Operation:
One second of off time is enough to assure normal operation of the secondaries. If the pump stays off longer, it indicates that the system has an extra margin of vacuum tightness. A lot of off time, indicates that the system has a good margin of vacuum tightness. An extra tight vacuum system does not make the engine perform any better than one that allows the pump to stay off for one second.

A 10 second cycle time is of no urgency and quite normal on many vacuum systems including my 90'

scottfab

I would caution you about one item in Marc Haibeck's technique. In it he suggests the a pump cycle time of 1 sec does not effect performance. I suggest this maybe true but can have ill effects on reliability of the pump itself. This only if you are in a habit of turning the ing key on engine off and leaving that way for prolong periods (washing the car or at a cruise in etc) A cycle time of 1sec will quickly cause the pump to fail. Anything less than 10sec or so should be investigated. There is a serious leak !

KJL

Wow, great info. I will need to make a "pin" tool to check this. I figure I may as well check everything while I am in there.

WydGlydJim

Also something to note when talking about secondary actuators, is that some of the actuators were installed wrong from the factory. This condition is clearly visible when the rod going to the secondary valves linkage from the actuator is at an extreme angle. They should be in line with the way they operate, and anyone with any mechanical knowledge would have known this on installation, but oh well.......mine were installed wrong on my old '90. My conventional wisdom, was that since the diaphragms had been run in this way, that I would leave them alone, since turning them around would surely cause the diaphragms to fail. The car has over 70k on the clock now with the new owner, and has shown no problem with the incorrect installation. The other alternative is to replace them, and install them correctly. Here is a picture with the actuators installed incorrectly (but working). The actuator just above the 8-5 coil pack is installed wrong. If it were to be flipped over, the rod would line up, and it would be installed correctly, and the rod would line up straight, instead of at an angle to the secondary valves linkage.

scottfab

Be careful if you choose to change the mounting of the actuators. If they look odd (upside down) to you and you switch them then make sure to bend the L bracket to pull in cleanly. I am fairly sure these were put in at the factory in an apparent assbackward way on purpose (stories from those that worked there) but to any casual observer they look wrong. I switched mine around and bent the L bracket. They work AND look fine. It's nice to still be able to switch the key off and remove it when I leave on vacation etc. But when I put the key in and on all works with the greatest of ease.

Dynomite

I could not agree with you more....excellent description I installed New Canisters on my 90' during top end restoration and put them in so the arm is straight. On my 91' I left them as original....but wait...then I removed them all together

scottfab

Those are some great pics of an in tact LT5 engine. Looks great!