What determines a 1 or 3 pin oil pressure sensor?

[454cid]

I think my sensor is going out, and the gauge is starting to wander more.... and there's a good chance that's one of my oil leaks. When I check rockauto, there are both 1 pin, and 3 pin sensors, and some of each specify they're for a gauge, rather than a light.

I haven't tried to reach it yet recently, but when I've looked for it before I couldn't see it. The sensor is pretty buried. I'd like to place an order before taking things apart....so what determines which sensor I need?

I'm working on a 454, of course.... I've seen a few oil pressure sensor sockets online. What's worked for you? Reviews and forum posts talk about them being too long/short/fat for various applications.

https://www.rockauto.com/en/moreinfo.php?pk=945025&cc=1353451&jsn=29002

 

[alpinecrick]

Even on my 5.7's the sender is a Royal Pain to access--even when I had the trans out and accessing it from the rear it was STILL a pain.
My special socket doesn't work--not enough clearance as the firewall "curves over" right there. It was back to am open end wrench. Be nice to have a stubby wrench that's big enough (can't remember the size of wrench needed).

Every time I or my buddies thought the oil sender was leaking, it was not......
I do recall years ago on a friends 7.4, after he cleaned around the sender, then checked it after driving it, that wasn't where the oil was coming from.

So before beginning the agony of removal and installation, I would take the time to confirm and best you can if it's the sender that's leaking.

And I don't don't know how to tell if it's 1 or 3 pin without pulling the connector off--and even that's a pain in the butt with my 5.7 K1500's. Not very helpful, am I?

 

[RawbDidIt]

I think my sensor is going out, and the gauge is starting to wander more.... and there's a good chance that's one of my oil leaks. When I check rockauto, there are both 1 pin, and 3 pin sensors, and some of each specify they're for a gauge, rather than a light.

I haven't tried to reach it yet recently, but when I've looked for it before I couldn't see it. The sensor is pretty buried. I'd like to place an order before taking things apart....so what determines which sensor I need?

I'm working on a 454, of course.... I've seen a few oil pressure sensor sockets online. What's worked for you? Reviews and forum posts talk about them being too long/short/fat for various applications.

https://www.rockauto.com/en/moreinfo.php?pk=945025&cc=1353451&jsn=29002

The sensor is a PITA to get to, but you shouldn't need to take anything apart *IF* it's the same as a 5.7l. I would imagine the 3 prong is for those with the oil pressure gage in the dash as opposed to just the dummy light. Best way to tell which you have is to just unplug it and look at the inside of the harness rather than pulling the sensor first. The harness wasn't bad to pull once I found the sensor, but again, this is on a 5.7l, not the 454. JIC it happens to be the same for yours, here's a video of how to find it without removing the distributor cap, as far as removal, the cheap oil pressure tool from autozone worked for me, if not, a short 1 1/16" wrench should to it.

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[Schurkey]

I have an L29 454, but I've never needed to dick with the oil sender. Like the Vortec small-blocks, and the oil switch for the fuel pump on TBI small-blocks, it's cleverly hidden to the driver-side of the distributor.

My service manual says "J-35749 Oil pressure sending unit socket". It looks somewhat like the Lisle tool I bought, but haven't used on a Big Block yet.
https://www.amazon.com/gp/product/B0002SR2RY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I bought this tool because my other oil-pressure sending unit socket (same wrenching size) is not deep enough to fit the "long" body of the modern sensors. It's 1 1/16", but the wrenching surface is "special" so an ordinary 6-point socket isn't a good fit.

1 terminal vs. 3 terminal? Almost certainly because a 1 terminal is for the gauge (or light) only, while a 3-terminal is used for the gauge (or light) plus two terminals for a normally-open switch that powers the fuel pump in parallel with the fuel pump relay. That way, if the fuel pump relay, harness, or ECM fails, the fuel pump will still run if the engine has oil pressure.

 

[someotherguy]

Those 1 pin senders are for the much older trucks that have separate oil pressure gauge sender and oil pressure switch for the fuel pump circuit.

You're somewhat lucky in that your 7.4 has the sender sitting straight up at the top of the block just ahead of the bellhousing; yes it's deep down there and buried, but it's straight into the block instead of sideways in a super fragile brass 90 degree fitting like a small block.

I had a pic where I circled it for easier spotting but can't find it at the moment, however this is the source pic I used. You can see it below the distributor just ahead of the bellhousing, driver side:

You must be registered for see images attach

You *might* be able to get to it from underneath the truck...

Richard

 

[88monteSS]

Mine wasn't bad at all to do. I think I pulled the coil bracket out of the way & then just laid on the intake to do it

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[brian c lindsey]

call dealer parts with vin , they can give you part number, and that will tell you

 

[454cid]

Those 1 pin senders are for the much older trucks that have separate oil pressure gauge sender and oil pressure switch for the fuel pump circuit.

Older trucks were my initial thought, but Rockauto has several single pin sensors listed for my truck. I suppose it could just be wrong. I do find weirdness in parts listing every so often.

You're somewhat lucky in that your 7.4 has the sender sitting straight up at the top of the block just ahead of the bellhousing; yes it's deep down there and buried, but it's straight into the block instead of sideways in a super fragile brass 90 degree fitting like a small block.

Yes, I've read of that brass fitting problem. I'm thinking maybe one of my new wobble extensions might work here.

You must be registered for see images attach

You *might* be able to get to it from underneath the truck...

Thanks for the picture. I may try from the bottom, but I suspect my front driveshaft will be in the way.

 

[454cid]

I climbed on top of the engine today and while I could not actually see the oil pressure sensor, but I could feel it. I unplugged it, and the pigtail only had one wire.... I thought for sure it would be a 3-wire. I'm glad I didn't order it before looking. I did not feel any oil down there, so it must not be leaking, but the gauge is squirrelly.

 

[Busted Knuckle]

3-Pin oil pressure: One pin drives the gauge. The other two are switch contacts that run your fuel pump, supplying +12. This went bad on mine - oil into the connector. It can be another gremlin that's hard to find. Gauge was low n wobbly.

ECM will Deliver power thru the FP relay for some time period and then remove its drive, depending on the power to be supplied through the oil pressure sender. This will protect against fuel pump-out in case of a rollover or other blown engine event.

There's a sweet socket that will make life easy dealing with this. 1-1/8 super deep.

https://www.ebay.com/sch/i.html?_from=R40&_nkw=gm+oil+pressure+socket&_sacat=34998&_sop=15