Oil Pressure Switch

[BigMacDave]

Ok, silly question but i want to be sure.

I searched the forum but could not find the answer.

I have a 1978 124 spider

I also have three manuals, and they all three show/point at what i think its the wrong thing.

I am trying to replace the Oil Pressure switch. The manuals say it is on top of the block, and the color wires indigo them and indeed there are two sensors/switches up there. However when i take them out, they are obviously not oil, more likely water temp. They are solid on the bottom (no pin hole) and much larger in diameter than i would think.

I did find another switch very low close to the filter, i did not take it out, but my guess that is it? Seems an odd place to measure oil pressure, but then, there are a lot of things that seem crazy on this car

Also, can anyone point me to the preferred brand or type of switch.

Thank you.

David.

[Nanonevol]

Curious what manuals gave you that information. Can't help you on suggesting a brand but your assessment on its placement is correct.

[BigMacDave]

Ok, so after looking again, (at the Haynes because it has the wire diagram) i realized my error. It is indeed pointing at the Oil Pressure Gauge Transmitter in the right spot. From first glance and being frustrated, it looks like it is on top, but it is actually slightly to the side. That area on the map has a lot of stuff going on and i must have looked at the wrong line.

[BigMacDave]

hello all.

ok, so what i was going to do (and i have seen many examples of) was to install a T connection on the block where the oil pressure gauge transmitter is, so i can also install the oil pressure safety switch to control the relay that controls the electric pump.

first trouble comes in the form of the screw on block and gauge are WAY bigger than a 1/8 NPT. the set up calls for everything to be 1/8 NPT (which the oil safety switch is)

does anyone know if i can just the lead off the oil pressure gauge and split it? i assume it is a ground signal when the engine has pressure? one lead would go to the light and the other lead would go to negative side of the relay.

I'm thinking this will give the same result. oil pressure is present, switch is triggered, sends ground to relay, and relay sends power to fuel pump.

Thank you,

David

[So Cal Mark]

a pressure switch that operates a light is closed without pressure, open with pressure. Otherwise your warning light would be on with pressure

[BigMacDave]

ok. i haven't had a chance to put a meter on it, but that doesn't sound too bad.

I think that tells me the wire is an open ground, but doesn't ground until engine is off, completing the circuit and turning the light on. then the engine is on, the circuit opens and no ground so the light turns off.

if thats the case, i could run a lead off the gauge to the relay that will ground and open the relay cutting the power to the pump when the engine is off and the light is on.

Im trying to do what the safety switch does which is cut power to the pump when the engine is off.

don't care about a switch, want it all automatic, and safe so if the car is (god forbid) in a wreck, the pump doesn't keep pumping gas on maybe a fire, because the switch wasn't turned off.

i don't think I'm re-inventing the wheel, but i can't find any solid info in the forum or on the web what others have done besides a switch. The safety switch comes from the bug guys, and it works very well, but like i said, its the wrong thread size.

[aj81spider]

I don't know if anyone has done an oil pressure cutoff, but there are lots of threads on using inertial switches. Here's one:

http://www.fiatspider.com/f15/viewtopic ... t=inertial