Non Mopar oil pressure oddity

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mad accountant

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A while back I bought a 99 Ranger with the 4L V6, with about 135,000 miles on it. Nothing much to look at, but drove well and everything else looked OK. Met the guy selling it so it was already warmed up.

It sat for about a month until I put it into service as my daily driver, and lo and behold, when the engine is cold the oil pressure gauge shows zero pressure for the 1st 4-5 minutes of driving, then pops right up to normal. Scared the crap out of me first time I saw it, but reasoned what the hell, it was fine when I bought it, I'll get a junkyard motor or rebuild this one if it blows.

7,000 miles and 2 oil changes later I'm not seeing any problems. No lifter tick, no prematurely blackening oil, no overheating, no shiny stuff in the oil, still gets about 19 MPG. So my question is this: Anyone know of any known oil pressure problems with this motor anyone knows about? If it's a simple sending unit or shorted wire I'll probably take care of it just because it bugs me. If it's something else I'll probably just leave it.
 
If you really had 0 oil pressure, the engine would not likely have survived the 1st session like this without serious damage. (A full synthetic might allow it to survive for a few minutes, but the key word there is MIGHT.) So, it is very likely the sender or the gauge itself sticking.

The big lesson to learn from this is if you see 0 oil pressure STOP the engine NOW. It is very unwise to not fix the pressure indicator right now; buy an after market gauge and sender right now and slap it in.
 
Has it ever had the camshaft synchronizer replaced? This is a very problematic issue for both the 3.0 and 4.0 engines. They are at the rear of the engine where the distributor "would be". The cam sensor is mounted in the top and the bottom is driven off the camshaft gear and it also drives the oil pump. They barely get any splash lube and often burn the bushings up. When they do, you are lucky if you hear it. It emits a very high pitch sound like a bird chirp or a belt squeak. Eventually if not replaced, they will seize and break and a catastrophic engine failure will result.

I doubt that has anything to do with your problem, but it's good information to be armed with if you did not know about it.

Sounds like maybe some sludge around the oil pickup or an electrical issue with the sending unit.
 
I would hook up a mechanical gauge and check it cold. When you start it up if that gauge reads zero, then you have a problem.
 
RustyRatRod said:
Has it ever had the camshaft synchronizer replaced? This is a very problematic issue for both the 3.0 and 4.0 engines. They are at the rear of the engine where the distributor "would be". The cam sensor is mounted in the top and the bottom is driven off the camshaft gear and it also drives the oil pump. They barely get any splash lube and often burn the bushings up. When they do, you are lucky if you hear it. It emits a very high pitch sound like a bird chirp or a belt squeak. Eventually if not replaced, they will seize and break and a catastrophic engine failure will result.

I doubt that has anything to do with your problem, but it's good information to be armed with if you did not know about it.

Sounds like maybe some sludge around the oil pickup or an electrical issue with the sending unit.
Click to expand...

Thanks for the info RRR. :prayer: I'm leaning toward the gunk around the oil pickup or something with the sender itself just because I seriously doubt this was a problem that occurred the day I took delivery of it; it had probably been going on a while. If the problem was in fact no oil pressure on start up it would have gone boom long before I got my hands on it. Just curious if this was a common problem or not; if I'm going to pull the motor to replace the oil pump I'd just rebuild/refresh the whole thing at the time.
 
Try smacking the dash top. You know, the technical tap. Might just be a sticky gauge.

If I want an alternator gauge in my Dakota, that's how you do it.
 
If it runs without a check engine warning lamp on, or intermittent warning "Ding" sound it cant be a actual oil pressure problem. The computer is looking for oil pressure signal first. A gauge for the driver to look at is kinda secondary.
My best guess is the gauge has attitude problem.
 
Most Ford oil pressure gauges are not actual gauges. They are more or less go-no go indicators. If the engine has oil pressure it the gauge will stay more or less in the center of the range. It is not a linear gauge.

If it does not rattle on start-up it has oil pressure. You might try removing the oil pressure sending unit and see if it is gunked-up (technical term) on the end or in the end of the passage to it.
 
Like said above, my ranger has just a dummy light type deal mocked up to look like a oil pressure gauge. You can tell becuase it *never fluctuates*. I'd say if it had zero oil pressure that engine would be telling you about it.
 
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