Can you bypass the oil pressure sensor?
 

Friday, I installed a mechanical oil pressure sensor with digital gauge in my 2014 F150, in addition to the stock sensor. I did this, because I was getting a low oil pressure warning on the dash and it would shut the engine down. I’ve done all of the usual suspects to fix the problem, including a new sensor, filter, oil, PCV, clean the throttle body, etc. but it happened again, Thursday.

After doing this, I wondered if I could fool the computer(?) by grounding (or ?) the stock sensor wire and just use my new mechanical gauge*.

The stock sensor/gauge is an on off switch. It tells you if you have pressure or not but not what it is.

What do you think?

* I know it’s there to protect the engine, but millions of cars have driven billions of miles with real oil pressure gauges, like I have now.

http://forums.pelicanparts.com/uploa...1753563212.jpg


http://forums.pelicanparts.com/uploa...1753563212.jpg


http://forums.pelicanparts.com/uploa...1753563212.jpg

http://forums.pelicanparts.com/uploa...1753564234.jpg

Add a resistor to the circuit. Question would be, which way to go…

If he replaced the sending unit then the fault may be elsewhere. I'd Ohm both units first to see if they are normally open or closed. Then I'd reinstall to see what they read both electrically and with the harness off, how they Ohm when the digital is indication sufficient OP. It might be just grounding the hot by pig tailing or isolating the hot while grounding the 2nd wire. I'd be surprised that an OPS would be a resistance type unit. An oscilloscope would be handy to watch it in real time. I'm sure the ECM cares only about the B+.

But what I know about 2014 Fords is on par with my neurosurgery acumen.

Electrical work is not my forte, but I have my old oil pressure sensor and I could Ohm that to see if it’s open or closed. My understanding is, the oil pressure either opens or closes the circuit.

I thought about just grounding the wire to the factory oil pressure sending unit to see what happens….

Pull the ****er out, stick a paperclip in the plug and start it.

See what it does.

It only has one wire.

From a google search:

Here's a more detailed breakdown:
Function:
The sensor's main job is to detect low oil pressure, not to provide a precise reading of the pressure.

Mechanism:
It typically uses a spring-loaded diaphragm and a switch. When oil pressure is sufficient, it pushes the diaphragm against the switch, keeping it open and the warning light off.

Low Pressure Scenario:
If the oil pressure drops below a certain threshold (the "switch point"), the diaphragm relaxes, allowing the switch to close and the warning light to illuminate.

From the last paragraph, it would seem that the wire makes a connection to ground, sends a signal to the ECM for low oil pressure warning, and turns off the engine

So you have good oil pressure with the gauge. Butt I think the big problem pops up when the car has been driven fort several hours, right?
Have you driven far enough to test it yet?
How easy is it to unplug? Could you leave it plugged in and then just unplug it if you have a problem?

If it's a pain to unplug, then sure, just unplug it. I suppose it's possible that the ECU might look for the initial closed circuit but that seems unlikely.

Do you have a warning light with the gauge? If not, I'd fool the ecu at the harness but also wire a light to the sensor.
If its actually activated by ground, I have to wonder if you have a wire rub in the harness somewhere.

Would you kindly share what the pressure gauge reads right before the light comes on?

Mas, it’s super easy to unplug to test it, but I haven’t had a chance to either drive it or unplug it. Hopefully this afternoon. When I go back to work tomorrow, I’ll be driving my two hour commute and we’ll see what happens. And that said, it doesn’t happen every day, it’s random.


Greg, With the stock system, I get a low oil pressure warning on the dash and it immediately shuts off the engine. For me, this only happens at idle, but it’s happened to people driving on the highway. There is no warning. The message comes on and the engine shuts down.

http://forums.pelicanparts.com/uploa...1753639879.jpg


Dixie, the gauge on the dashboard is a dummy gauge. It only tells you whether you have pressure or not, it does not give you accurate readings.

Edit: the stock idle is 600 RPMs. I might buy a tuner that raises the RPMs, to keep pressure up and can correct or calibrate the tire/MPH, as I’ve got bigger tires than stock. I’m not looking for one that will change the engine or transmission parameters

Understood that part. My question more or less is whether if you disable the stock sensor whether you'd have a big warning without having to have eyes on the gauge. Not that you'd need anything that large, but I ran a big red autopower beacon on my dashtop in the hillclimb car to warn of low pressure. My only thought is that a few seconds of zero pressure is possible in a gauge only setup.

That's actually a good thought because it might and if it didn't see the closed position when the key if is turned to on before start, it may trigger a code that if persistent could create a CEL. That would code out as a problem with oil pressure.

Once again, speculating only, However it seems to me that engineers look for ways to keep us from bypassing systems problems so as to keep the service bays busy. Not beyond reason.

that was my thought.

Without the stock gauge/set up, I won’t have the warning light on the dashboard I think. That said, I’m always looking up for traffic and don’t see the small oil pressure gauge at the top left of the instrument cluster

What I would like to do is something you did and that’s a warning light, higher up that grabs my attention

Gotcha, somehow I thought the gauge on the a-pillar was an aftermarket pressure gauge you'd hooked up.

The gauge on the A pillar is an aftermarket, but I haven’t driven the truck yet, where the warning light has come on. Stay tuned!

Update: it’s 100* and I drove just over two hours and 100 miles. At 60 mph and 1500 rpm, oil pressure is 30 psi. At idle, with AC on, in gear with foot on brake, it bounces between 11-15 psi.

At 11-15 psi, you are very low...I think the factory switch is about 7 psi? I am just speculating, but I think you probably had legit failures.

Forget the bypass, drive it and see what the gauge says when you get your next failure. The factory sensor is probably open at zero psi, and then pulls that single wire to ground when pressure is achieved. With the engine off measure the resistance of the switch to ground, it will likely be 'infinite'. If that's the case, ground the wire.

You might need to fool the ECU via a latched relay connected to the starter wire, then powered off when the key is off. But I doubt it...

I see some 0W40 in your future.

0W40? Isn’t that thinner than the 10W30 I have in there now?

I haven’t had a chance to look into it, but what would normal oil pressure at idle and driving be?

If my oil pressure is low, how do I determine whether my engine is just worn out or it’s the oil pump? Unfortunately, on this motor, the oil pump is not accessible from the oil pan. It’s behind the timing chains and cover. Ugh.

40>30. You may need 20W50...but that's all early speculation.

You should have 15psi per 1,000 rpm as a rule of thumb. You had 30 psi at 1,500 rpm, that seems 'fine'. Seeing 11 at idle would worry me, 15 is 'okay'.

What is the highest you see accelerating with cold oil?

And don't forget, there's a 99% chance that your aftermarket gauge is damped, and will hide dips off throttle. It smooths out the data that it displays...

In oils, the 2 numbers are as follows (or reasonably close)
0w, 5w, 10w, etc... are the "cold viscosities" (the "w" stands for "winter" not "weight"). It's a standard that says that when cold, the oil flows at some rate down to xº. So a 10w will flow at temps down to 0º and a 5w will flow at temps down to -15º and etc... (made up numbers, but you get the idea).
The second number is the viscosity when hot. The hot viscosity isn't the flow rate or thickness of the oil, it's due to the polymers in the oil that have expanded and increased the viscosity (increasing it's shear or something like that). So a 40 weight acts thicker than a 30 weight

So I don't know that you'd want/need to change the __w number, but you may want to change the second number to something larger.

What's interesting is that the Driven oil people used to have a chart that said something like "if your bearing clearances are xx, and your expected oil temperatures are yyº, then you are likely going to want to use ##w-## as a starting point for your oil viscosities."

I didn't embed because this image is huge
https://cdn.speednik.com/powerautorax55/wp-content/blogs.dir/1/files/2022/04/what-i-learned-today-bearing-clearances-vs-oil-viscosities-2022-04-04_12-49-04_516744.jpg

Except that his truck idles at 600rpm, so that means that 11psi at idle is over 18psi/1000rpm.

If you connect your sensor/switch to an air regulator, you can adjust the pressure and see where it opens/closes.

Hate to say it but it sounds to me like the bearings are getting thin.

To prepare myself, I’ve been looking at oil pump replacement and engine replacement.

The oil pump is not in the oil pan, but behind the timing chain cover and chains. A lot more involved. But something I could do. The pump is about $300 or $400, but as long as I’m in there, you want to do timing chains, ramps, etc.

An engine swap, would take longer than I would like to do by myself. I would probably have somebody else do it with a crate motor by Ford. The motor would be about ~$6000 plus labor.

This is my last vehicle, so if I could get another 233k miles out of it, it would be worth it

I ordered a tune that gives the ability to increase the idle, correct the speedo for tire size, a little more power, etc among other things. I’ll increase the rpm’s by 100 increments and see if I can get to a steady 15 psi at idle. I know it’s putting a Band-Aid on it, but hopefully buys me some time.

That is true, but the rule of thumb applies more to the high end. He is VERY low on idle oil pressure, and possibly lower than he knows...symptomatic of a serious engine issue.

Personally, I would NOT change the oil pump unless it was easy. That repair sounds like a lot of effort for a 'hope' repair. I'd be looking for a crashed vehicle, or a known good junkyard engine. And a tune that changes the idle rpm is a band-aid that won't help long term. The engine should have sufficient oil pressure to idle. Period.

I lean to the 'thin bearing' comment from JD.

Before I did the oil pump I'd pull the pan and look at a bearing.

Are you thinking worn rod bearings or main bearings or both? Would it be beneficial to replace the rod bearings with std if possible?

For used motors, there were problems with 5.0 engines before 2013 and they are not compatible after 2015, so the best engines to use are 2013 and 2014. That narrows down the candidates considerably. I was doing a search yesterday, and engines were going from low 2000 to 3000. While less than a crate engine, by the time I replaced all the wear parts I wanted to with new, it would probably add 1000 and I would have an engine with unknown history.

And a factory crate motor would likely last a LONG time compared to used or aftermarket rebuild.

The crate motor has a 3 year unlimited mileage warranty. Lakeland Ford sells them for $5800. I’m going to call and see what the cost is to install it.

I would guess worn main bearings, but that's a long way from a 'diagnosis'.

I'm not sure of how much you 'need' the truck, if it were me I would bypass the sensor and drive it, but have a mechanical gauge (anything without a transducer) in the cab.

I would also monitor the idle pressure and switch to a thicker oil as needed. You may get a lot of miles out of it, it's low, but obviously it's not fatal, at least not so far. That annoying shut off feature has helped you.

From those numbers, it does seem that a crate engine is the best value. I'm used to $1,000 engines being available. Not any more I guess.

Hi
I think lifting the idle speed and trying some thicker oils are good options before investing in a new / crate engine.
Other ideas:
Can rod and main bearing shells be replaced with the engine in place ?
Any pressure relief valves in the oil circuit that could be causing the problem ?
Cheers

I’m in construction, so I need a truck every day.
The digital oil pressure gauge is on the A pillar and super easy to see. On my next oil change, I’ll go with a thicker oil.

I called the Ford dealer in FL with the engine for $5800 and they don’t have any. And there are none in the pipeline. He gave me the name of a Ford dealer in Maryland that had three of them in stock. I called them and the price is $6200. I asked the service department there, how much it would cost to install the motor and they said $5000 to $5500. I think I would take a week off and do it myself.

Looking at the official Ford website, it says the engine engines are unavailable. I looked at used engines again and they are about $3000 plus shipping,with a minimum of 100K miles. I think I’ll buy the new crate engine and keep it for the future.

^^^ I’ve just started reading, but it looks like the rod bearings can be replaced, with the engine in place. I did think about replacing the oil pump with a high volume pump and replacing the rod bearings, but that’s a heck of a lot of work and a big gamble, for something that may not work. The crate motor looks like the best idea.

I bumped the idle to 825 RPMs, and that’s got the oil pressure at 18-20 psi.

That sounds good to me. That engine may run like that for another 50k miles.

^^^ I hope so!