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What is this plug for?

cucvrus

Well-known member
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Not 100% sure but that is the way it is supposed to be. I never really knew but it has one just like that up under the dash. It it is not broken just re-tape it and put it back in place. It has a diode in place. But I do not know its technical propose. Someone will come along and tell you specifics.
 

Gradient

New member
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Location
San Diego/CA
Not 100% sure but that is the way it is supposed to be. I never really knew but it has one just like that up under the dash. It it is not broken just re-tape it and put it back in place. It has a diode in place. But I do not know its technical propose. Someone will come along and tell you specifics.
Yeah, it appears to be purposeful. This was a radio truck and I know diodes are used to remove noise (interference), but just wanted to make sure.
 

NovacaineFix

Member
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Location
San Diego, California
the one on the left is definitely oil pressure, the other is a coolant sensor but for cylinder water temp, probably for the ICE diagnostic system, since the gage/idiot light sensor is on the driver's side head by #1 cylinder with a single green wire.
Typically GM uses yellow/black for coolant temp switches for computer equipped vehicles, so since this does not have a computer, I can only assume it is for the ICE system.

What part of SD neighbor?
 

cucvrus

Well-known member
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I did not see the lower red writing. The one on the right is the glow plug engine temperature sending unit. That is the old type. They make a new style now. But if that one works that's fine. Check the wires going to that sending unit. I know I have seen them worn thru. Good to know that is a noise reduction diode/resister. I just seen them there and never had any trouble with them so I freshened up the tape and tied it to the harness. Injection pump time. I am about to change mine also. Good Luck.
 

Warthog

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That is the diode of the water-in-fuel sensor. It is shown in the wiring diagrams and also the Diodes & Relays Helpful Threads sticky. There is another one just like it for the GEN2 exciter circuit. It is behind the dash.

The single wire sensor on the left is the oil pressure sensor. The one on the right is the glow plug tempature sensor.

In the parts tech manual you can find picture of all of these along with the GM part numbers.

When I first started with MVs I would brouse thru the parts manuals to become familiar with what the individual parts where and what belonged where. I do not try to remember each part but have learn where to look for it.

Also by looking at the diagrams I can tell what is missing. Many of the trucks I have bought over the years have had things removed for one reason or another.
 
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Gradient

New member
28
0
1
Location
San Diego/CA
the one on the left is definitely oil pressure, the other is a coolant sensor but for cylinder water temp, probably for the ICE diagnostic system, since the gage/idiot light sensor is on the driver's side head by #1 cylinder with a single green wire.
Typically GM uses yellow/black for coolant temp switches for computer equipped vehicles, so since this does not have a computer, I can only assume it is for the ICE system.

What part of SD neighbor?
Hey neighbor, I'm in Clairemont. Where are you? It'd be nice to have a CUCV buddy, I'm kinda on an island here.
 

Gradient

New member
28
0
1
Location
San Diego/CA
That is the diode of the water-in-fuel sensor. It is shown in the wiring diagrams and also the Diodes & Relays Helpful Threads sticky. There is another one just like it for the GEN2 exciter circuit. It is behind the dash.

The single wire sensor on the left is the oil pressure sensor. The one on the right is the glow plug tempature sensor.

In the parts tech manual you can find picture of all of these along with the GM part numbers.

When I first started with MVs I would brouse thru the parts manuals to become familiar with what the individual parts where and what belonged where. I do not try to remember each part but have learn where to look for it.

Also by looking at the diagrams I can tell what is missing. Many of the trucks I have bought over the years have had things removed for one reason or another.
Thanks Warthog. I did look through the manuals, but I must have missed it, although I only looked carefully through the civilian manual I have.
 

Gradient

New member
28
0
1
Location
San Diego/CA
I did not see the lower red writing. The one on the right is the glow plug engine temperature sending unit. That is the old type. They make a new style now. But if that one works that's fine. Check the wires going to that sending unit. I know I have seen them worn thru. Good to know that is a noise reduction diode/resister. I just seen them there and never had any trouble with them so I freshened up the tape and tied it to the harness. Injection pump time. I am about to change mine also. Good Luck.
Yeah, I really don't want to put the money into this engine as I plan on doing a 4bt swap. I just did the electric fuel pump upgrade and it made a huge difference, unfortunately it ran great for about 10 seconds but it exposed a weakness in the IP seals. The throttle shaft seals started dumping fuel on the plenum.
 

NovacaineFix

Member
662
1
18
Location
San Diego, California
Met Gradient of all places at the Home Depot, Nice Guy.

We talked a bit and I think it started drawing attention, most everyday folks aren't used to seeing CUCV's gathering in masses, lol
 
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