How to Test your Oil Pressure Sender

[Zack]

Im writing this because I had to do this today.
A few days ago I noticed my OP Gauge (Autometer Ultra-Lite) reading about 10psi higher than normal. From time to time it would jump around the face of the gauge for a second. I attributed this to a loose connection at the sender. While at the track the other day, it did the same thing in the staging lanes, freaked me out but I ran anyway.
On the way home from the track, all is well until Im just about home. I floor it for a bit, look down and the OP gauge reads ZERO :down:
I pull right over, mess with all the wiring and still zero. Im not convinced I blew up the Oil Pump gears so I drive a few blocks home OK.
Called the tech line at Autometer 1-815-899-0801 and they told me how to test the gauge and the sender; here's how:

Gauge: Hook 12 volts up to the I (Ignition) terminal. Hook a ground up to the 2 remaining terminals (G & S) If the gauge is good, the pointer will move all the way to the right. Mine tested good.

OP Sender: With the sender either in or out of the car, get your Ohm Meter.
Place one lead on the stud, and the other on the shell of the sender.
With the car off, the gauge should read about 240.
If the car is idling, the reading should be about 200.

Swapped a new Sender in and all is well. Pretty amazing though, my OP readings are different now, and more realistic. With the old sender, the car hot and idling in drive, the gauge read 12psi! Now it reads just shy of 25psi, which is probably the more accurate reading. :popcorn:

[merc]

I had a similar problem with my oil pressure gauge and this is my second sending unit. The cost was not so punishing, but I can't explain why it went bad.

[Zack]

Autometer sent one out free, but I could not wait so I bought a new one.
Ill have a spare for 'the next time'!
They offered to send one without proof of purchase

[merc]

Autometer sent one out free, but I could not wait so I bought a new one.
Ill have a spare for 'the next time'!
They offered to send one without proof of purchase

Free, you said free, dang, I am going to look through the trash dumpster.

[Todd TCE]

Free huh? Hmm.
I've replace two of the AM elec senders on the race car over the past year and a half. In my case I attribute it to the race conditions....Seems I may be wrong.

Easy for me to test too; pull sender and start motor! Yup, that's oil. Like this: :awe:

[martyo]

Gauge: Hook 12 volts up to the I (Ignition) terminal. Hook a ground up to the 2 remaining terminals (G & S) If the gauge is good, the pointer will move all the way to the right. Mine tested good.

Be careful not to mix up the I (Ignition) and S (Sender) contacts or you will toast your gauge.


Now it reads just shy of 25psi, which is probably the more accurate reading.

Yes, that is where it ought to be.

[RF Overlord]

Now it reads just shy of 25psi, which is probably the more accurate reading.

That's what mine reads...

[MarauderMark]

With the old sender, the car hot and idling in drive, the gauge read 12psi! :popcorn:



Yep Thats what mine reads. :hankie: Time to give em a call . Thanks for the info Zack ..

[Logan]

Damn... Mine reads 12psi like Zack's did... Sigh... I guess I'll call and get another sender Dammit...

[Todd TCE]

I would not be really surprised to see the 12psi at idle reading. Granted 25psi seems that it must be better, but its not uncommon for the motor at idle to run in the 10-15lb range. Most of the idiot lamps are 6-9psi.

Running, the racers rule of thumb is 10lbs per 1000 rpm is nice to see. Too a reasonable level of course. I doubt a F1 motor runs 140psi.

Dennis might have some service book info on this but I'd not panic on a low psi at idle reading. If it shows 40-50 at speed that's what I'd be looking at.

And if you want more accurate readings you might consider mechanical gauges.

[Logan]

Don't get me wrong, I'm not worried and the gauge does read 40-45psi at speed, so no biggie...

[RF Overlord]

Dennis might have some service book info on this but I'd not panic on a low psi at idle reading. If it shows 40-50 at speed that's what I'd be looking at.

The factory service manual states that the HOT oil pressure @ 1500 RPM should be 138-310 kPA...that's 20-45 PSI for us non-Canadians... :D

[FordNut]

Mine reads about 12 or so at idle. Been that way since I put in the real gauge months ago.

[valleyman]

Mine reads about 12 or so at idle. Been that way since I put in the real gauge months ago.

Likewise, mine drops down to 10 at idle on my digital guage and it makes me a little uncomfortable. Any way to up the idle, even 50-100 rpm would help, without taking out my Reinhart chip and sending it back to Florida?

[Logan]

You can adjust the idle while in park via the throttle body adjustment screw, though to adjust the idle speed while in gear, requires a programming change.

[valleyman]

You can adjust the idle while in park via the throttle body adjustment screw, though to adjust the idle speed while in gear, requires a programming change.


Rats. That's what I thought. Thank you, sir. :cowboy:

[Todd TCE]

Ooooh, I'm going to jump in here on this one and say that's a no-no.

Granted I do not know much of the motor in the MM but from one who has to work on the tuning of the race car motor, I can tell you that if this t-body works a common IAB (idle air bypass) this is NOT a good idea. The IAB controls this the idle and if you open the throttle manually this sends a wrong signal to the IAB which intruns interprets this as a open throttle and maps accordingly.

I conceed that I know what I know from the SHO motor work and my tuner who helps me on it (a former Ford Micro Elec/Visteon engineer) who tells me that the screw is to prevent plate bind only and not to be used to change idle. This is on a 15yr older design, but I'd speak with someone like Dennis before I messed with it.

[valleyman]

I conceed that I know what I know from the SHO motor work and my tuner who helps me on it (a former Ford Micro Elec/Visteon engineer) who tells me that the screw is to prevent plate bind only and not to be used to change idle. This is on a 15yr older design, but I'd speak with someone like Dennis before I messed with it.[/QUOTE]

Good enough for me. I won't be messing with it.

[FordNut]

Seems like my sending unit is about to take a dump too. Just started to be really unstable like Zack's. At idle it's steady, but at cruising speeds it jumps around constantly, depending on RPM maybe between 40-50 psi or 50-60 psi. Maybe this is part of the reason Ford didn't put a "real" gauge on the MM from the factory.

BTW: I didn't get any kind of offers for a "free" replacement sending unit, just the same troubleshooting tips already posted here.

[hbarrett]

My guage typically sits at about ~ 62psi at idle in Park. I don't normally watch the gauge as I drive, so I can't say if it is changing. Is my pressure too high?
I would not be really surprised to see the 12psi at idle reading. Granted 25psi seems that it must be better, but its not uncommon for the motor at idle to run in the 10-15lb range. Most of the idiot lamps are 6-9psi.

Running, the racers rule of thumb is 10lbs per 1000 rpm is nice to see. Too a reasonable level of course. I doubt a F1 motor runs 140psi.

Dennis might have some service book info on this but I'd not panic on a low psi at idle reading. If it shows 40-50 at speed that's what I'd be looking at.

And if you want more accurate readings you might consider mechanical gauges.

[merc]

My guage typically sits at about ~ 62psi at idle in Park. I don't normally watch the gauge as I drive, so I can't say if it is changing. Is my pressure too high?

Are you running at Stock Gauge ?

[Todd TCE]

I wouldn't put a lot of hard faith in any electronic gauge. Manual ones are more accurate from my line of work. 62 at idle sounds a bit high unless you are checking cold or running real heavy oil. Given most of these are new cars and not race built motors, are you really in need of this much hard info? Are we just making something out of nothing? Sometimes gauges can just lead to too much thinking...~! :dogrun: :dogrun: :dogrun: :dogrun:

[RF Overlord]

hbarrett:

The stock oil pressure gauge is a fake that will ALWAYS read ~60 lbs no matter what the actual pressure is. Many of us have replaced the stock gauge with a real working one. This requires replacement of the sender as well as the gauge unit, but it's a simple job. AutoMeter p/n 4327 includes the gauge and sender for about $55 from Summit or Jeg's...the replacement gauge looks almost exactly like the stock unit, except for the green back-lighting; in the daylight, most people can't tell the difference.

[RF Overlord]

Given most of these are new cars and not race built motors, are you really in need of this much hard info? Are we just making something out of nothing?

Todd:

Perhaps you have a point...knowing whether your oil pressure at idle is 15 lbs or 25 lbs may be irrelevant for the most part. The problem I have is that Ford told us we have an AutoMeter oil pressure "gauge" that turns out to not actually be a gauge at all; it's a glorified idiot light. I think this is, if not false advertising, at least bad faith on their part. While knowing the precise pressure at a given RPM may not be terribly useful, I would much rather have the ability to monitor that pressure accurately than to be fooled by a fake gauge into thinking everything is fine when in reality it may not be.