Maybe an easy question about guages

[71cruiser71]

So my recently rebuilt 2f (from an 87` 60) has this low oil pressure reading. It never goes higher than the middle even under higher rpms. It usually stays right above the second tick. and also I think my guage cluster is reading temperature incorrectly because when I shut off it falls to H and the guage doesn't move past this marker. It's like it's backwards.
The picture is at 2500 rpm on the freeway <speedo temporarily disconnected>

Any ideas? Thank you

 

[Jonathan Hanson]

I can't speak to the temperature gauge, but the oil pressure gauge on my 73 FJ40 has always read low, even when I bought it with 25,000 miles on it and even after I had it completely rebuilt a few years ago, including a new oil pump. So I wouldn't worry about it as long as it moves up when you accelerate, and drops back down while idling. Our HZJ75 does the same thing; I've contemplated just disassembling the cluster and bending the damn needle a bit to make me feel better.

 

[71cruiser71]

I can't speak to the temperature gauge, but the oil pressure gauge on my 73 FJ40 has always read low, even when I bought it with 25,000 miles on it and even after I had it completely rebuilt a few years ago, including a new oil pump. So I wouldn't worry about it as long as it moves up when you accelerate, and drops back down while idling. Our HZJ75 does the same thing; I've contemplated just disassembling the cluster and bending the damn needle a bit to make me feel better.

It doesn't really change or increase with rpms. I will check specifically tmrw. It's usually higher during warmup, then falls right where the picture is.

 

[vfrer]

Seems to be in a normal spot on the gauge. First thought is are the gauge and the sensor matched? Running a late 80's engine in an early 70's truck may be part of the problem but not sure. If I were concerned I would get an aftermarket gauge and get some readings. Think it should be in the 45-50 psi range. Then you know it is good.

 

[GA Architect]

So my recently rebuilt 2f (from an 87` 60) has this low oil pressure reading. It never goes higher than the middle even under higher rpms. It usually stays right above the second tick. and also I think my guage cluster is reading temperature incorrectly because when I shut off it falls to H and the guage doesn't move past this marker. It's like it's backwards.
The picture is at 2500 rpm on the freeway <speedo temporarily disconnected>

Any ideas? Thank you

View attachment 3217003

Check out post #10 & #17 in this thread -> click here <- = "peace of mind, maybe"

 

[Malleus]

Why not connect an oil pressure gauge to the block? Then you'll know exactly what the pressure is. This is the only way to check a dash gauge that is little better than an idiot light.

While not exactly lab quality, you can get your answer for $30:

 

[Grayscale]

On a 2F, the oil filter is a major obstacle to oil pressure. What is your oil's viscosity, when was the last oil filter change? What brand/make of oil filter? Clean electrical connections as far as what is easily visible?

Right now, I have much less observed oil pressure than during the summer. 5W-30 full synth, AC Delco filter.

 

[3_puppies]

IIRCC the temp senders changed how they worked in the early 70's.
do you still have the old temp sender? swap it out

 

[pjohnson]

The factory gauges are really just indicators of change, a little better than an idiot light.
The only way to know what is actually happening is to connect an actual gauge that reads values. Once you know the true values, assuming the values are normal, you can compare that to where the gauge needle sits and know what 'normal' is for your vehicle's gauges.

 

[71cruiser71]

Seems to be in a normal spot on the gauge. First thought is are the gauge and the sensor matched? Running a late 80's engine in an early 70's truck may be part of the problem but not sure. If I were concerned I would get an aftermarket gauge and get some readings. Think it should be in the 45-50 psi range. Then you know it is good

I'm pretty sure the oil sensors look the same, but could use different insides? Same with water temp but slightly different. Could use different electronics though or readings, I was wondering this. I will also check connectors.

 

[71cruiser71]

On a 2F, the oil filter is a major obstacle to oil pressure. What is your oil's viscosity, when was the last oil filter change? What brand/make of oil filter? Clean electrical connections as far as what is easily visible?

Right now, I have much less observed oil pressure than during the summer. 5W-30 full synth, AC Delco filter.

I just changed the oil a month ago, I've always used 10w-40 conventional with a wix filter. I live in California I don't see very many cold days but it does get hot out here. But I do use Lucas oil additive that supposedly "helps reduce dry starts" but I don't know how much it actually changes or works.

 

[Grayscale]

Well, the synth is better for cold, but, on a hot engine, it shouldn't matter, the pressure should be up, synth or conventional. I liked conventional, until I found out that full synth is basically the same price, plus a few dollars. My pressure reads just over mid mark, 5W-30 O'Reilley synth oil, delco filter, kick-vent open, heater on, sweater-weather.

New OEM oil sender units are available.

Sludge could inhibit oil pressure. But, you reported installing fresh oil and filter, so you have already addressed that. When I ran a conservative addition of Marvel Mystery Oil, it really seemed to get around, including thru the exhaust, so that wasn't too desirable, but neither is failed lubrication. Has the PCV valve been inspected/cleaned lately?

 

[71cruiser71]

IIRCC the temp senders changed how they worked in the early 70's.
do you still have the old temp sender? swap it out

It's been awhile but I'm pretty sure I used the original sensor? I don't want to misspeak but I remember the temp guage having this issue since I've switched to the 2f and I think I had to use the original temp sensor because the one for the 60 is different? Not positive but I will check

 

[Grayscale]

The factory gauges are really just indicators of change, a little better than an idiot light.
The only way to know what is actually happening is to connect an actual gauge that reads values. Once you know the true values, assuming the values are normal, you can compare that to where the gauge needle sits and know what 'normal' is for your vehicle's gauges.

I've entertained the same idea, however, on my Cruiser everything seems quite repeatable. Is it the sending unit, the gauge on dash, or the owner's manual that can't be depended on?

 

[pb4ugo]

I've entertained the same idea, however, on my Cruiser everything seems quite repeatable. Is it the sending unit, the gauge on dash, or the owner's manual that can't be depended on?

Its all three. Factory gauges regardless of manufacturer all seem to be less than accurate. I use the 40's gauge cluster with my sbc. I figure if they're showing signs of movement then I'm OK. If the temp gauge goes to the extreme or the oil press gauge shows no sign of life, then there's a problem. My amp is by passed and use an idiot light.

 

[Grayscale]

Its all three. Factory gauges regardless of manufacturer all seem to be less than accurate. I use the 40's gauge cluster with my sbc. I figure if they're showing signs of movement then I'm OK. If the temp gauge goes to the extreme or the oil press gauge shows no sign of life, then there's a problem. My amp is by passed and use an idiot light.

Do you trust the fuel sender, or is it better to look in the tank?

 

[Malleus]

I'm pretty sure the oil sensors look the same, but could use different insides? Same with water temp but slightly different. Could use different electronics though or readings, I was wondering this. I will also check connectors.

The gauges aren't electronic, they're electrical. There aren't any logic boards, just resistors; even the 80 series works this way.

 

[Grayscale]

Can you do a voltage reading between the sender unit and vehicle ground so we can compare sending unit readings?

 

[pb4ugo]

Do you trust the fuel sender, or is it better to look in the tank?

What's the alternative? In my experience, the 40's fuel gauge is the one that's weird. It seems it doesn't stay on F for very long and it rides close to E for a longer time. It seems a 1/2 a tank means it has slightly more than a 1/2 a tank, then falls quickly, then sits close to or on E for a while. I guess I need to carry a gas can and see what happens. I'm still trying to figure it out on my red 40 because I've been trying to tune for mpg's, which I've never done b4. Like I said, I'm using the stk factory gauges and senders with my sbc. I trust all of them. They run in between the hashes and show movement.

 

[FJ40Savvy]

Gauges on the 40 are indicators only, I look for changes from the normal positions that I have seen on my truck. As reference, here is the information from the 73 owner's manual on the gauge ranges. An 76 owners manual may give you the same reference information.