[JRP3]

The saga continues. Replaced the check valve in the tank, no change. Moved the switch inline between the tank and the booster, still won't hold pressure, but now the pump keeps running unless I tap or squeeze the switch, then it shuts off, system leaks, comes on again, etc. So the switch is bad. Don't know if trying to adjust the pressure messed it up or what. System will still hold pressure if I hold my finger over the pump exhaust, so I have no confidence that replacing the switch will solve the pressure issue. Anyone recommend a pressure switch? This one is setup through a relay so it doesn't need to handle much amperage.

[david85]

rctous sold me a vacuum switch for my car. I haven't used it yet, but he has been using them for a while and I do trust brian.

[JRP3]

Do you have a brand and part number? Brian's been MIA for a while.

[david85]

http://www.anver.com/document/vacuum...-adj-ncno!.htm

[JRP3]

Turned down the adjusting screw on the pressure switch and it's shutting off properly now. My feeling is that the internal valve on the pump must be leaking slowly enough that the valve on the tank isn't closing off because there isn't enough of a pressure differential. I'm trying to find a diagram of the pump, I think it's a Thomas, don't have it in front of me right at the moment.

[dtbaker]

I think ALL the pumps have some leak-back... always need a check-valve 'upstream' to prevent leaking.

[JRP3]

That's the thing, I do have a check valve upstream, and it won't close off when the pump is in the system. I even replaced the check valve with another, same thing. Draw a vacuum, pinch off the hose, unhook the pump, release the hose, it holds vacuum. Put the pump back in the system, draw vacuum again, check valve won't close.

[JRP3]

It's acting as if there isn't enough leak back to force the valve closed.

[few2many]

Really hate to ask this question, try not to take offense, is the check valve facing the right way? The arrow should face the pump, not the tank. could be some trash in check valve, vaccuum pump coul have bad reed valves.
Have you individually isolated and tested the components, or tested as a whole system?

[tomofreno]

It's acting as if there isn't enough leak back to force the valve closed.

Seems it could be...if the check valve is just a bit sticky, or has too much inertia, and the leak back through the pump is very small. How 'bout if you mount the check valve so gravity assists in closing it?