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Join Date: Dec 2008
Posts: 164
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How to test the boost pressure switch?
I suspect that the boost pressure switch of my 930 doesn't work. When I had troubles with my wastegate (shot membrane), the pressure went up all the way to 1.4 bars and nothing happened. Normally, the switch should have cut the injection at 1.2 bars. Before buying a new switch, I would like to be sure it's the switch itself that is at fault and not something else. Is there a way to test it?
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Guards red 1989 930 convertible, Rarlyl8 Dual Outlet Street Muffler, K27S turbo. |
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03-09-2015, 07:08 AM
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It is supposed to cut out at 1.1 bar. It has a small internal spring which lifts and breaks contact to the earth circuit for your fuel pumps. Crude considering the precision it is supposed to work at. But the only way to really test it is to mount it in something you can dummy 1.1bar+ into it and measure the continuity of the circuit in the switch - between the terminal and body. There should be continuity til you get to 1.1 bar then the circuit should break. If you can pressurize the manifold you can do it that way, or remove and find a fitting you can screw it into with a pressure gauge teed in. Bit of fiddling around with improvised plumbing. Plastic fittings will work if more available.
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-) |
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03-09-2015, 05:40 PM
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Join Date: Jul 2008
Location: Central Washington State
Posts: 4,403
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I think I tested mine once, just by hooking up a suitable diameter rubber hose to the threaded end, with a small hose clamp to hold it in place. Then dialed my air compressor regulator way down and checked it with an accurate gauge. Otherwise as Alan described.
Do make sure your issue isn't simply with a poor connection at the wire end.
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Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, B&B intercooler, stock 3LDZ. |
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03-09-2015, 05:53 PM
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Hi Mark. Yes rubber tube, anything that can hold it, and allows you to tee into a gauge and pressurise.
If it has a bad connection, it will shut down pumps - no earth circuit. Regards Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-) |
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03-09-2015, 07:32 PM
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Join Date: Dec 2002
Location: Long Beach, CA
Posts: 1,263
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A radiator pressure tester works well for this.
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03-10-2015, 02:52 AM
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Registered
Join Date: Jul 2008
Location: Central Washington State
Posts: 4,403
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Quote:
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Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, B&B intercooler, stock 3LDZ. |
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03-10-2015, 04:41 AM
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Join Date: Dec 2008
Posts: 164
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I will try it with a wheel air valve stem inside a piece of tube. Thanks.
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Guards red 1989 930 convertible, Rarlyl8 Dual Outlet Street Muffler, K27S turbo. |
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03-11-2015, 07:22 AM
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Quote:
Alan
__________________
83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-) |
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03-11-2015, 07:45 PM
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