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Missing Oil Switch on 350 5.7 GM?

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pecanflyboy

New member
Hey everyone,
I just bought a 2001 Moomba Mobius. The engine was replaced with a GM 350 crate marine engine last year. While going over everything, I noticed that the hole above the oil pressere sender is empty, and there is an unattached wire dangling nearby. After some research, I've discovered that this is the port for the oil pressure SWITCH. But, it doesn't make sense.

The switch is not there, and the hole is not plugged. I figured that pressurized oil would be pouring out of this hole, but it is not. It's dry.

I traced the wire to the front of the engine, near the Water Temperature Switch, where it is rolled up and secured with a zip tie and attached to nothing.

The engine runs fine, with no warnings or faults. Full of oil, with good pressure.

Questions:
1. Is the Oil Pressure SWITCH required?
2. If it is required, and I purchase a replacement, to where do I plug it?
3. Why is oil not pouring out of the unplugged port?


Thanks,
Jimmy
 
The oil pressure switch is just a switch that normally goes to an Low Oil Pressure Alarm. It's usually an option so you would have to provide the switch and the alarm, also it's normally tied to the Over Temp switch which would go to the same alarm. Can't tell you why it's not leaking unless there is a plug in there? Is the color of the wire Tan/light brown?
 
must be plugged off somehow.... oil will shoot a good 5 or 10 feet out of that hole at speed if open
 
boatin_bob said:
The oil pressure switch is just a switch that normally goes to an Low Oil Pressure Alarm. It's usually an option so you would have to provide the switch and the alarm, also it's normally tied to the Over Temp switch which would go to the same alarm. Can't tell you why it's not leaking unless there is a plug in there? Is the color of the wire Tan/light brown?
Click to expand...

The wires to the oil pressure SENSOR and SWITCH are tied to together. The SENSOR wire is brown with a white stripe, I think.

Since I'm not getting an alarm, I'm just going to plug the hole and ignore the stray wire. I am suprised I'm not shooting oil from the unplugged hole.

Jimmy
 
pecanflyboy said:
The wires to the oil pressure SENSOR and SWITCH are tied to together. The SENSOR wire is brown with a white stripe, I think.

Since I'm not getting an alarm, I'm just going to plug the hole and ignore the stray wire. I am suprised I'm not shooting oil from the unplugged hole.

Jimmy
Click to expand...


They might be tied together physically but they won't be electrically. Daigram below is just for information only to show you what I mean. The 2 switches (oil & O/T) in the red boxes are tied together electrically in the 3rd red box. The oil sender and temp sender in the green boxes have to have separate wires going to the gauges at the dash.

switch.jpg
 
The schematic explains a lot. The wire goes to the front of the engine, and stops. It looks like it should go to the ignition switch, where the oil horn is located.

The hole is threaded but not with a 1/8" or 1/4" NPT. I'm going to look for the switch tomorrow. I still can't explain why oil is not pouring from it when it's running.

J
 
Problem solved. Found an Indmar service representative that told me that the open port is for diagnostics, and not used for the oil pressure switch. Apparently, when the diagnostics tool in used it allows oil pressure to reach the port for testing. The unused wire terminal is normal.
Thanks for the help,
Jimmy
 
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