I know the oil pressure gauges on these trucks are idiot gauges. But is there any accuracy to them?

What I mean is, I am going to post a picture, and would anyone be able to tell me about how many psi it corresponds to? Or are they all so inaccurate that on one truck it could be 20psi, and another it could be 40 psi?

Here's my trucks gauges after about 45 minutes of mixed driving.... 55mph/2300RPM highway and some other riding up and down the hilly roads I live on in east Tennessee with a bed full of oak wood. No idea on the weight, but surely around 1500 pounds.

This is at about 650-700RPM at a stop, and I waited until it would drop as low as it would go. Any guesstimates? Or is it just too inaccurate to be the same from one truck to the next?

Pretty much between the R and M in NORMAL. While driving, even lugging around 900-1000RPM, it goes on up to A or L. And yes, my temperature gauge hardly ever goes above that. And I have excellent heat.

 

Quote:

Originally Posted by Freaksh0w

I know the oil pressure gauges on these trucks are idiot gauges. But is there any accuracy to them?

I would say yes, BUT, they're slow to react to changes + they're susceptible to
failure of the instrument voltage regulator behind the cluster. Although, when
that thing has problems, it affects ALL gauges except the ammeter so it should
be pretty obvious that something is wrong.

Quote:

Here's my trucks gauges after about 45 minutes of mixed driving....Pretty much between the R and M in NORMAL. While driving, even lugging around 900-1000RPM, it goes on up to A or L.

I have a recently-installed set of AutoMeter gauges installed in my dash
alongside the factory variants; for oil pressure, a centered needle is around 50
PSI; the A in NORMAL is around 75.

Quote:

And yes, my temperature gauge hardly ever goes above that. And I have excellent heat.

Mine looks pretty much the same (goes perhaps a bit further to the right), and
just about all Fords of this era I've encountered behave the same way.

I have a 195 degF thermostat and a brand-new water pump, thermostat &
radiator on a freshly-rebuilt 400 engine.

EDIT: Want to add that I was also running a mechanical gauge for a while along with the
two electrical variants, giving a total of 3 oil pressure gauges.

Know what? It turned out the mechanical one was slow to indicate pressure on initial
morning start-up in the dead of winter, it didn't become responsive until after the engine
had been running for a few minutes.

 

I seem to remember reading somewhere that the larger engines (400, 460) have a bit higher oil pressure than the smaller ones. Is that true?

Or will the numbers be about the same for all the engines?

 

I honestly have no idea; my M-block 400 is a variation of the Cleveland block (which is
known for having high oil pressure). But, my daily-driver 1986 Tempo 2.3L carries 60 at
speed, 40 at idle, so....

 

Oh ok. I just wanted to ask.

I do seem to remember a Haynes manual I have (somewhere, hidden away where I've yet to find it) that listed the oil pressures for the various engines, and the 460 had oil pressure a fair amount higher than the 302 or 351. I'm not sure if it listed the 400 or not.

 

I do not hold too much faith in the stock gauge. Some days it will read hi, some days it will read low, and some days it will read both. My temp gauge used to be just like yours. It drove me crazy because I knew it was heating up fine. I replaced the sender the other day since it was 4 or 5 dollars and now it reads between the M and the A, although it has slowly started creeping back a little the longer it has been in there.

 

i'm sittib here lookin at all of y'alls temp gauges and mine never reads that low. usually somewhere bear the "m" im normal. but the trucks not running hot.

 

Everyone is just guessing. If you want to know what your oil pressure is, you have to install a real gauge.

 

Quote:

Originally Posted by andym

Everyone is just guessing.

No; as I said - and have posted pics of in another thread - I have run three gauges
in tandem... two aftermarket and one OEM, and my OEM equates to about
50PSI (as indicated by the aftermarket gauges) when the OEM needle is straight
vertical.

But, I agree, the best thing to do if you really want to know how your engine is
behaving is to install aftermarket gauges as the OEM variants merely give you
general approximations + are susceptible to component (cluster voltage
regulator in particular) & electrical failures.

 

I have an autometer in mine, in the little opening under the gages (hee hee) and it reads between 40 and 55 depending on RPMs. Really easy to set up and worth every penny.

 

... good info... thx for the post!

 

Old post, but since I don't see anyone has mentioned it the oil pressure gauge in 80-86 trucks is not an "idiot gauge" in the sense of an on/off switch with a certain PSI to trigger it. These are real gauges that read relative pressure, the gauge reading increases with psi though is slow to respond and is not calibrated so while needle pointing at N may be 15 psi in one truck it may be 6 psi in another. No idea what Fords tolerances were but if you are familiar with a particular truck's gauge readings it gives an indication if something is going south. Either way, it's best to get a real gauge.

The '87 and up trucks I believe were just an on/off pressure switch set at about 7psi, 7+ psi and gauge read wherever it fell with voltage through a resistor and under that it read zero.

 

Hey, cadunkle...I commented on this old post because I'm researching this exact issue/question on my 86 350... and I'm getting a lot of head scratching info. Several great posts re the topic of the gauges and how they work etc. One that I found particularly interesting was a link posted by tecgod13 in this thread https://www.ford-trucks.com/forums/1...t-is-this.html where the discussion is all about the "idiot gauge" issue.

Some simple testing found that, you're right... the gauge IS an actual gauge... however, in my truck, I confirmed that the sending unit to my gauge is in fact a switch:



It's either on or off... no variable resistance. It makes continuity a @ 4-5 lbs and when my truck was running the gauge would simply sit smack dab in the middle and never move. Not very helpful.

Reading the article (from the link above) confirmed that Ford did indeed treat the gauge as an "idiot gauge" but it CAN be converted back to official gauge status by using a real oil pressure sending unit... and eliminating an often found 20 Ohm resistor found in the line. (supporting what you mentioned about the 87 and up models) (oddly, mine doesn't have the resistor )

To confuse things further... THIS little item is used as the Fuel cut-off switch:




which I have not been able to bench test successfully, yet (although it must have been working because my truck would run) but I ordered a new one anyway. A little hard to find, oddly as I was never able to find one that was "compatible" with my year and engine size (460). And the guy at my local parts shop was surprised too as he said that this part was used on practically every other model BUT mine... so... I'm confused.

Anyway... that's my story and I'm sticking' to it... unless someone has more info and can set the record straight about it