Oil Pressure Sending Unit

MIDEVIL214 · Feb 1, 2016

I'm trying to solve a high pressure reading on the stock oil pressure gauge. Been through two BWD units from Oreilys and one Duralast (usa) from Autozone. I think something else is going on. The oil pump was changed not that long ago. I used a standard pressure/flow Melling pump. Probably have 50K or so on rebuilt mostly stock 302. Seemed to read 40 at idle and 70 at cruise for a long time.

Current unit(s) read about 70 at idle and 80-90 at cruise speed (2K). I have a new solid state IVR. Can those increase the psi gauge reading? I didn't adjust it from the way it came.

The wire attached to sender shows 5.6 volts steady. I grounded the wire in "run" and the gauge will peg all the way to the top past 90 psi. Disconnected it slowly drops just below 0. Would this point to a bad sender for the third time?

TAC71 · Feb 1, 2016

Factory gauges are at best an fancy indicator. Get a accurate mechanical gauge to install temporarily to get a proper reading. Then you will know where your pressure is at and then use that info to see what the stock gauge is indicating.

Crush · Feb 1, 2016

If you are using the sender with the little plastic cap on top then it is for a light not a guage. U need the big dome shaped one for a Guage. Some time in the 90's for started using fake oil pressure guages. They used the same sender for both lights and guages but for guages they put a resister between the sender and guage to simulate a normal reading in the guage. End result was no matter how much pressure you had, too little or too much it always had a normal reading

tirewater · Feb 1, 2016

(doh, repost of the above info, left my window open too long)

Did you test your oil pressure using a tester or separate gauge?

I'd double check my oil pressure with a separate gauge, just to eliminate the possibility that something could be wrong with the oil pump, relief valve, or any blockage after the sender extension. Mechanical oil pressure gauges are ~$10, although a tester may be a more prudent buy (~$25 at harbor freight).

MIDEVIL214 · Feb 1, 2016

I understand all about the accuracy of these sending unit/gauges but 90 psi out of no where seemed odd.

Haven't tested with mechanical gauge yet, only stock cluster. Picking up an adapter fitting to do so in the next day or two. I am using the original bell-style sender with a single post.

bmc69 · Feb 2, 2016

MIDEVIL214 said:
I am using the original bell-style sender with a single post.

Out of all oil pressure sending units I've used, those are typically quite accurate.

But nothing beats at least testing with a good quality mechanical gauge, even if the setup is temporary.

bmc69 · Feb 2, 2016

MIDEVIL214 said:
Current unit(s) read about 70 at idle and 80-90 at cruise speed (2K). I have a new solid state IVR. Can those increase the psi gauge reading? I didn't adjust it from the way it came.

The wire attached to sender shows 5.6 volts steady.

Does that solid state IVR still pulse-width (on/off) the voltage output like the OEM ones do? Plus, a problem due to IVR output would affect the other two thermal-element gauges as well..fuel and temp.

66broncoCT · Feb 2, 2016

There was a thread on here where the person had used one of those solid state regulators and all his gauges started reading high so he turned it down somehow. I can't find it but Paul (dirtdonk) was involved so maybe he'll see this and chime in. If I remember correctly there was a tiny crew you could turn to change the voltage. Is it just your oil pressure gauge or all of them? And is it only since you replaced the ivr?

MIDEVIL214 · Feb 2, 2016

The IVR does not pulse like stock. Come to think of it the temp gauge did go up 10 or so degrees after installing the IVR. I attributed that to a more accurate reading though. The fuel gauge isn't that reliable as the Sherman tank reads empty with 6 gallons of fuel even at their suggested ohms.

I know those solid state IVRs are adjustable but there was no mention of a need to turn it down out of the box. Maybe Ill bump it down to 4 volts and see.

EDIT: The Precision Electronic Instrument Voltage Regulator I got from WH is not adjustable. The stocker looked to have an adjustment knob though.

DirtDonk · Feb 2, 2016

Interesting. The ones I looked at a few months ago were adjustable. Maybe the manufacturer changed the design.
Your 5.6 actually looks lower than I remember, so it in itself was not a red flag to me when you first posted up.

But as everyone is suggesting, get a comparison with another gauge to make sure. Whether mechanical (preferred still) or electric of a different brand, at least you'll have a point of reference. The fact that your temp gauge went up slightly is a clue that your system is seeing more voltage than it used to, but not necessarily more than it expects.

If you find an adjuster after all, don't go all the way down to 4v. That's too low and, if things read correctly after that, would indicate to me something else wrong with your system. I would just try 5v to 5.2v maybe.

Good luck.

Paul

MIDEVIL214 · Feb 3, 2016

Thanks Paul. The IVR I received is not adjustable and the website says its preset now.

I put a mechanical gauge on the bronco and got 62 psi cold on startup. It settled to about 52 psi warm at idle. With the solid sate IVR installed the stock gauge shows a little over 70 at idle.

I grabbed the original IVR and was able to adjust it. I turned it down to were the gauge would read 55-60 psi at idle but my temp and fuel gauge were reading low at that point and the oil pressure gauge was dancing a little.

Good news is my pressure isn't off the charts. Is the next step the gauge itself? It would peg quickly to the top when the sender wire was grounded. Toying around with ordering a Motorcraft Bronco spec. sender.

DirtDonk · Feb 3, 2016

Pesky little buggers.
If when you've got the gauge thing figured out and you end up not using the new IVR, let us know. Sorry about the hassle. But maybe it's a good thing that it highlighted some other issues.
You know... Rose colored glasses, and all that.%)

Glad your old one still worked decent. Kind of strange though, about the three reading a little inconsistently between themselves.

With your description of the needle moving fairly quickly, I would suspect that the gauge is not dampened properly anymore. However, that should not normally effect the final readings when it settles to where it's supposed to be.
But maybe the lack of dampening is having some effect, or is at least a symptom of another underlying problem with just that one gauge.

Maybe turn the stock one back up slightly to get the others reading more correctly and see where it falls. You may find that you can use either one at that point, and through further investigation you might find that even the other two gauges are slightly off. If so, whenever you get one reading correctly, the other two are off.

Always a fun time in the Bronco electrical world!

Paul

MIDEVIL214 · Feb 3, 2016

Took a closer look and found a microscopic philips head on the constant voltage IVR. It wasn't where the old IVR adjuster was so I missed it. Looks like it only adjusts down to 5.2 volts though. The gauge still reads a little above 70 psi at idle at this setting.

Installed the stock IVR and turned it up to a fluctuating 2.5-3.5V. Coolant temp and fuel were pretty close but oil psi was reading above 70 still.

Looks like I may need to order a gauge Paul.

Oil Pressure Sending Unit

MIDEVIL214

Jr. Member

TAC71

Sr. Member

Crush

Bronco Guru

tirewater

Sr. Member

MIDEVIL214

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bmc69

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bmc69

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66broncoCT

Full Member

MIDEVIL214

Jr. Member

DirtDonk

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MIDEVIL214

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DirtDonk

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MIDEVIL214

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