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Rocky Mountain 356 Porsche Club                                       OVERSTEER                                                                    January 2006   

King:

I have been using an electric fuel pump in my Convertible D for some time. As a safety suggestion, Mike Robbins suggested to wire an oil pressure cutoff switch inline to shut the pump off in the event of an accident.  I asked Mike if he would provide a tutorial, which he did (see below).

Phil

 To: Phil Carney

Subject: Installing oil pressure shut-off switch

I used a Hobbs switch that is available in 3 different pressure settings. As I remember the 3 are 7, 14, and 21 psi. I use the 14psi version. Hobbs is a division of Stewart Warner so your FLAPS might find it in the SW catalog rather than Hobbs . Specify one w/ 1/8" NPT threads. I mounted it at the inlet to the oil filter can as follows:

 Mechanical:

1. Disconnect the connection of the oil line going into the filter.

2. Remove the elbow from the filter can.

3. Screw 1/8" NPT close nipple in the hole where the elbow was.

4. Screw a 1/8" NPT  "T" onto the nipple such that the straight thru section is vertical.

5. Get a fitting same as the one on the bottom of the oil filter can [same as one where that oil line goes into case] and screw it into the bottom leg of the "T".

6. Loosen the clamp on the oil filter can and slide the can up as necessary for the vertical oil line to connect into the new fitting.

7. Screw the Hobbs unit into the upper leg of the "T".  [Some people mount a pressure gauge here.]

 Electrical:

1. You have to run two wires from the switch, through the tunnel and up under the dash.

2. Now you have a choice. You can wire it to only turn off the electric fuel pump or, as I did, kill the ignition also. In either case, you have to wire a switch [simple on-off toggle is appropriate] in parallel w/ the oil pressure switch so you can bypass the oil pressure switch when starting the car. I power the fuel pump from the bottom of fuse no.1. So cut the black wire that goes to the top of fuse no.1 [not the black/white wire....that goes to the coil] and wiring the oil switch and the parallel bypass switch

into that break.

 I've tried to figure out how to have an unobtrusive pilot light to tell me that the bypass switch is ON.....otherwise, if you forget to turn it off after the engine builds up oil pressure, the oil pressure switch is not in the system. I had a T-6 B tach that had the turn signal arrows at the bottom and thought of using the upper left light for that purpose but it was a Normal tach and I didn't want to spend the money for having it

refaced. Have since sold it. Maybe a buzzer in the bypass line would work. The bypass switch makes an excellent anti-theft device if you wire things so the loss of oil pressure kills the ignition.

 Let me know if you have any questions. Mike

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