SMC alky- purpose of this pressure switch?


Active Member
A line comes out of the bottle, and runs to a junction, where you have the FP gauge and this pressure switch. This switch was rubbing against my IC neck and broke, so I just pulled it off, filled the hole with a pipe plug and covered the connectors. I was thinking this was just a safety thing...line pressure drops, the switch is triggered and a low fuel light will come on. But I think I'm wrong because while the test button on the controller still shoots alky in the motor, the spray on light doesnt light up when it hits boost.
So what is the purpose of this switch? Can I just jump a couple wires and bypass this switch? I have pressure switches at work, but they're very high end and would be a PITA to wire up. The one with the kit is pretty cheesy. They do make black anodized aluminum ones that are much more robust. I just tagged 22psi and had no alky spraying :eek:...well, it may have been spraying, but I wouldnt know it cause the switch is disconnected and the spray light isnt coming on.
This switch is what that did turn on your spray light. This way you would know for sure that your alchy was really spraying and not just that the pump had voltage to it.
In the older SMC system when the pump had voltage to it, your spray light came on. If your pump went bad, you wouldn't know it till the knocking started due to NO alchy.

Well, I have the kit with the round bottle...the old one I guess. So do you think the kit is spraying, and just not turning on the light? That was the only purpose of that turn the light on when there is pressure in the line? At idle, when I push the prime button, it almost stalls, so I know its squirting. I just dont know if its squirting when Im under boost. Now if I could just get that thing to stop leaking on the outside of the up-pipe. Ive used loctite on all the fittings and tried my best to seal it up, but given its mounted on a bend, and is just held on with a washer and a nut, its inherently flawed. It was like this when I bought it, so I dont know if it should be mounted a different way.
pull the vacuum line off where you plugged it in and apply air via your air nozzle with the motor off. you should hear the pump come off. if you are like the rest of us you plumbed in into the boost gage line so you can probably see at what boost pressure you have it set to come on at the same time.

to get the pipe from leaking we drill and tap the hole we install the nozzle in with a 1/8" pipe thread. we tap it from the outside even though the taper in the nozzle goes the other way. the pipe is thin enough that it does not affect anything. You don't have to really even use any sealer if you do it this way and it looks very clean.

hope this helps.
Thanks for the help. The kit has been set to turn on at about 14-15psi. I was getting on it alot last night at about 20psi, and it was doing really well. The car really moves. The alky is working, but it keeps leaking out of that connection. That prior owner of the kit had drilled a through hole, so I have no meat left to tap. If I had a welder I could fix this right, but no such luck. I'll figure something out. I really want to get a thick walled aluminum elbow and make my own up-pipe.