Oil Pressure Gauge problems

[Backfoot100]

Have a weird one I need some assistance with. 86 Subrban w/factory 350.

When I picked up my Suburban a couple years ago it had a massive oil leak which turned out to be the oil pressure sender. Replacing it fixed my leak and the gauge worked perfectly for about a year. Then started to work intermittently. It would read normal at about 35-40 PSI and while driving, it would just drop to 10 PSI and back up to normal again. Nothing consistent and completely intermittent. After a few weeks of that it finally quit being intermittent and just stays at 10 PSI.

To test everything out I disconnect the sender lead, turn on the key and the gauge pegs high. Short the sender lead and turn on the key and the gauge pegs low. Weird part about this is at times, when I ground the lead it will be pegged low before I turn the key on. Normal or no?
Pull out the sender and hook up my test mechanical gauge and it idles perfect at 35 PSI. I'm thinking its gotta be a sender.
Get a new sender and it reads 10 PSI constant. How can two senders read exactly the same way? So I go get a third sender and it does exactly the same thing. There's no way a year old sender and two brand new senders all do the exact same thing. Something else has to be wrong but I'm at a loss. Can the gauge be bad? Any way to test the gauge?

Any ideas would be appreciated.

 

[bucket]

Your gauge tests fine. Are your new senders actually senders, or could they be switches? You never know with people at the parts counter these days.

 

[Backfoot100]

Your gauge tests fine. Are your new senders actually senders, or could they be switches? You never know with people at the parts counter these days.

Pretty sure they're senders. I got the first one that lasted a year from a local speed shop. The second one I got from Napa and they first gave me a switch. The sender and switch look nothing alike. It's pretty hard to mistake the two. Took that back and they gave me a sender. Third one was from the speed shop again which I took back after testing it and it didn't work. These things get pricey at $40 a pop.

 

[Arkansas_V8]

Pretty sure they're senders. I got the first one that lasted a year from a local speed shop. The second one I got from Napa and they first gave me a switch. The sender and switch look nothing alike. It's pretty hard to mistake the two. Took that back and they gave me a sender. Third one was from the speed shop again which I took back after testing it and it didn't work. These things get pricey at $40 a pop.

Parts stores aren't known for quality. Sometimes it takes one part to fix a problem and others you have to empty their stock. Don't ever assume a parts store "new" part isn't bad.

 

[Dmack]

After replacing the stock sender in mind twice, I got frustrated and went to a mechanical gauge. Actually swapped all 4 of factory spots ( sunpro temp, water, and volt, then an eBay tach too). No more wondering if accused not.

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[SirRobyn0]

After replacing the stock sender in mind twice, I got frustrated and went to a mechanical gauge. Actually swapped all 4 of factory spots ( sunpro temp, water, and volt, then an eBay tach too). No more wondering if accused not.

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hey, that looks really good, do you have any pictures of it reinstalled back in the truck? And what did you have to do with the housing and circuit board. I might consider doing this as well.

 

[Dmack]

hey, that looks really good, do you have any pictures of it reinstalled back in the truck? And what did you have to do with the housing and circuit board. I might consider doing this as well.

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I used a did grinder to open up the black metal bezel and mounted the gauges to it with the mounting hardware that came with the gauges.

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i then opened up the main plastic gauge holder so they would clear.

From there, it was just running the sensors and wires. I did put did put electrical tape over the portion of the printed circuit that was on that side so it wouldn't short out. Also, I left the bezel rings on the aftermarket gauges, so the clear bezel cover sticks out about a quarter inch, but it still mounts in fine.
The only thing I don't like is the tach has an led back light, while the others have regular bulbs, so the tach is much brighter, but I still prefer mechanical gauges over factory. And this way they aren't hanging under the dash.

 

[Turbo4whl]

After replacing the stock sender in mind twice, I got frustrated and went to a mechanical gauge. Actually swapped all 4 of factory spots ( sunpro temp, water, and volt, then an eBay tach too). No more wondering if accused not.

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X2 looks good!

My 1974 Square was ordered with the factory tach. It came with a factory mechanical oil pressure gauge. And some more useless info, since you probably won't find any of these parts: The medium duty trucks like a C60 (square) with a factory tach had the fuel gauge in the lower part of the tach. This opened up one small gauge opening for the brake air gauge.

I put these parts in my '82 square. This left me a spot to put the vacuum/boost gauge for the turbo I added. Should anyone try to use a fuel gauge from a medium duty truck you need to swap the pulse resister from the back of your original fuel gauge to medium duty.

 

[SirRobyn0]

I used a did grinder to open up the black metal bezel and mounted the gauges to it with the mounting hardware that came with the gauges.

i then opened up the main plastic gauge holder so they would clear.

From there, it was just running the sensors and wires. I did put did put electrical tape over the portion of the printed circuit that was on that side so it wouldn't short out. Also, I left the bezel rings on the aftermarket gauges, so the clear bezel cover sticks out about a quarter inch, but it still mounts in fine.
The only thing I don't like is the tach has an led back light, while the others have regular bulbs, so the tach is much brighter, but I still prefer mechanical gauges over factory. And this way they aren't hanging under the dash.

Thanks for all of that. I like the factory installed look. So often when guys go to aftermarket gauges it looks like they were set in from the front rather than installed like yours do. And I like gauges that look period correct, so no digital or colored back lighting for me. Gauges are not high on my priority list yet, but I have a dead clock and an oil pressure gauge that doesn't always read right. Again thank you and I'll be keeping this in mind.

 

[SirRobyn0]

X2 looks good!

And some more useless info, since you probably won't find any of these parts: The medium duty trucks like a C60 (square) with a factory tach had the fuel gauge in the lower part of the tach. This opened up one small gauge opening for the brake air gauge.

A medium duty gauge cluster would be my first choice, and I'd use the air gauge and tie it into my air shocks. But they are so costly. $300 - $400 on E-bay. While I'm at it, it would be nice to have a speedometer with a tripometer.

 

[73c20jim]

I replaced my gauges with a panel from Inteltronics.

Cheaper than trying to fix all my stock gauges. Plus it had a tachometer.

The speedo can be adjusted to any combination of tires and gears. It has a trip odometer and a 0-60 and a 0-1/4 miles calculator built in.

Works good so far. (Six months).

 

[SirRobyn0]

I replaced my gauges with a panel from Inteltronics.

Cheaper than trying to fix all my stock gauges. Plus it had a tachometer.

The speedo can be adjusted to any combination of tires and gears. It has a trip odometer and a 0-60 and a 0-1/4 miles calculator built in.

Works good so far. (Six months).

If I could have any instrument cluster it would be the one that was in the medium duty trucks with the tach / fuel gauge combination, and the air gauge in place of the clock which I would connect to the air shock system. But those clusters are relatively rare and expensive and cost is a factor. To be honest and please don't take offence to this I don't like the look of most of the aftermarket gauges in the square body. They look out of place to me, but we are all different. I do like the way the sunpro's look and they have aren't too flashy, and they aren't to expensive. I'd probably retain my factory speedo and fuel gauge in that setup though. I'll probably do that down the road sometime.

 

[bucket]

I replaced my gauges with a panel from Inteltronics.

Cheaper than trying to fix all my stock gauges. Plus it had a tachometer.

The speedo can be adjusted to any combination of tires and gears. It has a trip odometer and a 0-60 and a 0-1/4 miles calculator built in.

Works good so far. (Six months).

So what's it got for 1/4 mile times?

 

[shiftpro]

Parts stores aren't known for quality. Sometimes it takes one part to fix a problem and others you have to empty their stock. Don't ever assume a parts store "new" part isn't bad.

Sadly it's all too common these days.
Last year I went through two power steering pumps from NAPA. The first one had a sticky valve, they never honed the bore and it had gall marks in it that held up the pressure valve. The second one had an oversized valve bore... over honed I think and the valve rattled around in there. The 3rd pump was fine and I got it for free for my troubles. All that ****** around I ended up fixing my current pump and now I have a rebuilt (good one... I think) never installed sitting in my parts stash.

 

[Backfoot100]

So I just wanted to bring this to closure. I got the issue fixed.

If you go back and read the opening post, you'll see that everything I did pointed to a sender. The wiring and gauge tested good. The original sender worked for about a year and then quit. I got two other senders and every one of them did the same thing. It only read about 15 PSI and never moved from there.

I found a way to test the sender then. You need a volt/ohm meter measuring resistance and the sender lead disconnected from the sender. With the engine off, if you measure the sender signal lead to ground, it should read a short or 0 ohms. Start up the engine and take the same measurement. It should read somewhere between 30 and 50 Ohms, which is the middle of the standard 90 ohm resistance range of the sender.
Well, my first sender that worked for a year read perfect at 39 ohms.

At this point, all the tests say that the gauge, wiring and sender is good. Everything should work. WTF???????

I wanted to try replacing the gauge but I didn't want to spend the money for a new one from LMC and that not be the problem. I have a **** ton of salvage yards around here but calls to several of them yield nothing for squares.

Fast forward a few months and @Paladin is selling a gauge that I promptly snap up, which ultimately does end up fixing my issue. Life is all good once again.
Thanks Mike for the opportunity.