Oil pressure warning light on

CALLUM STANLEY

MEMBER
1987 VOLVO 740
185,000 MILES

I bought this vehicle several months ago. The oil pressure light started flickering within days of first driving it. I didn't stop driving it because the flickering was slow at first, so I knew nothing really bad was happening. I did my first oil and filter change, I hoped that would help, but the light just got brighter. My next guess was faulty Oil Sensor. I replaced that, still nothing changed. Because the light is always on, I keep a very close eye on the oil level, so that's not the problem. I don't think the problem is to do with the oil pump or clogged filter, cause the engine sounds great. No knocking or large vibrations.
I'm thinking the problem has to do with the wiring, cause the little connector does fall of the sensor every now and again (the light still flickers when this happens). And it looks really old. Would it have something to do with that? And how does one replace that kind of wire?

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

If you need to replace the connector, chances are you will need to find a good used one from a salvage yard. I question if they are still available.

If you do that, simply remove the old one and wire in the new one.

As far as the oil pressure, what I suggest is this. Since there doesn't seem to be a difference with the pressure sensor attached or disconnected, chances are you are correct and there is a wiring issue. However, if you want confirmation, it's really easy to do.

Most parts stores will lend you a mechanical oil pressure gauge. Basically, you remove the oil pressure sensor on the engine and screw in the mechanical gauge. That will tell you if there is low pressure.

I attached a pic below showing the manufacturer's pressure specifications.

Let me know if this helps or if you have other questions.

Take care,
Joe

See pic below.

Image (Click to make bigger)

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Sunday, August 29th, 2021 AT 9:06 PM

CALLUM STANLEY

MEMBER
2 POSTS

Thanks for the reply.
I decided to start by removing the wire. Pretty soon I realized the wire was just copper, no insulation. I replaced as much as I could and attached the old connector to the new wire. Because the connector falls off, I just squeezed it with a pair of pliers so that it fits on much tighter. Put the key in the ignition, and the light comes on, so the connection is being made. Turned the vehicle on and the light goes off. So everything is working, and the engine is fine! Thanks again!

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Tuesday, August 31st, 2021 AT 12:02 PM

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

I'm glad to hear you found the problem. Please make sure there is no bare wire still present. Additionally, make sure you are using replacement wiring that is equal to or a heavier gauge. We don't want any problems.

Let me know if you have questions. Also, please feel free to come back anytime in the future if you have questions. You are always welcome here.

Take care,

Joe

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Tuesday, August 31st, 2021 AT 6:22 PM