Roly - 9/22/2011 6:33 AM

The 30 s power comes from a relay on the pre 2000 Gs. You can here it click off after the key is turned off.
There appears to be a slight difference between the setup on the pre and post 2000 Gs or at least with mine there is. On the vacuum pump there is a pressure switch. On the diagram that Dutch posted it indicates two pipes connected to it. One connected to the white and the other to the black. On my G there is only the one pipe going to the black connector. This means that when the pressure in my system reaches the preset presure the pump switches off. Once the diff locks are actuated there is no flow through the system (ignoring leaks). So the small electric pump and the reservoir is fine to keep the vacuum correct and hold the locks on. The non return valve stops the vacuum disappearing when the manifold vacuum changes.

Here's any easy test- disconnect the second pipe on the white connector on the pressure switch. Seal the hole in the pipe. Turn on the key (don't startengine) press the centre difflock and the little pump will start. Wait until the preset vacuum is reached and it will switch off about 30-40 secs. No more burning out the pump

AlanMcR - 9/22/2011 7:48 AM

It does seem that the electric vacuum pump is a frequent gasser problem.  The diesel versions make use of the engine driven vacuum pump alone. 

Perhaps a better gasser solution would be to buffer the dips in intake manifold vaccum with a couple of one-way valves and a large vacuum reservoir?  One could cap off a frame cross-tube to make a 2 gallon vacuum reservoir.  Unlike using the frame tube for pressurized air there is no need to worry about moisture accumulation.

W5YK - 9/22/2011 5:00 PM

There is a good thread covering some of this in detail...

http://www.pointedthree.com/disc/forums/showthread.php?tid=10358

Some random points:

There is a vacuum reservoir in the G500 - it is in the front wing, driver side.

If you have the center locker on when you turn off the engine, the switch pack keeps it on for 30 seconds (and the pump is therefore on too, since it is wired to the center locker solenoid).

If the engine is on, the pump runs continuously.

When the engine is off and a locker is selected, the pump will run until it gets to 0.6 Bar, then it turns itself off internally. Turns back on if vacuum gets below 0.4 Bar.

If you want to check your pump and vacuum system, just turn off the engine, select center locker, listen for pump to come on, listen for it to go off after about 1 min. If it goes off, you are good. If it stays on - problem. This tests pump, lines, check valves, center lock diaphragm i.e. everything.

fernweh - 9/22/2011 5:18 PM
but I do believe the other lockers need to be switch on as well, to test their vacuum line systems too...

...If the pump will run until it gets to 0.6 Bar, when the center locker is selected, the engine is off and the ignition is on - it should also turn off at 0.6 Bar when the engine is running. Right?

W5YK - 9/22/2011 12:11 PM


Another random information point - my front and rear lockers will engage and hold even without the pump.

shochu - 9/23/2011 3:35 AM

i think TC locker is dependant on vacuum (as it is diapraghm based)
whereas front and rear are not vacuum dependant, but can only turn on after TC locked

W5YK - 9/22/2011 10:11 PM



Good points Karl. If you turn them all on, it includes the intensifiers in the test.

You are right, the pump will turn off IF it gets to 0.6 Bar of vacuum with the engine running. But it never will pull that much vacuum with the engine running (not on my G500 anyway).

Another random information point - my front and rear lockers will engage and hold even without the pump.

fernweh - 9/23/2011 9:45 AM

I'm not sure how the intensifier for the front and rear axle is responding when only a reduced vacuum is present. Will the intensifier only deliver a reduced hydraulic pressure to the diff lock actuator or regardless of the vacuum level when activated always produces the same hydraulic output pressure?

Karl

Razon - 9/23/2011 12:46 AM

This is not important, but as a small note:
0.4 bar is more vacuum than 0.6 bar.
When you measure absolute pressure (including vacuum), you start at zero psi, then the pressure goes up to 0.4bar (in this case) then even more pressure gets you to 0.6 bar ( but less vacuum)...and if you keep increasing the pressure you get to 1bar: the normal pressure that's all arround us, or 1atm.

So, The pump will run till 0.4 bar then turn off....it will turn back on if vacuum drops below 0.6 bar.

Fernando BR - 9/24/2011 11:15 PM

Only to remember that lockers vaccum line are also connected to engine vacuum on gassers 463 , not sure on diesel ones.

Front and rear lockers normaly will work in the case that vacuum pump is out of combat cause engines produces enough vacuum. Diff locker that is only pneumatic wont work without vacuum pump.

BTW early 463 small pump is enough to the job , why use that monster they introduced on G500? My 300GE never had lockers troubles after 20 years ( my 500 also but has only 6 years) . G 500 2001 + system is much more complicated

300 GE is electrical , 3 switches , 3 relays, etc.... At the end 463 lockers are reliable, 460 are bullet proof.