oil pressure relief valve?

[Gadfly]

I have a 3.0L V6 in a '99 Ranger 4x4. Sudden loss of oil pressure. This was REAL loss of oil pressure and not the sending switch, as after I noticed the light and gage showing zero pressure, I killed the engine and coasted. The oil was a little low, so I put oil in to the proper level -- and the engine would not turn over.

I towed it home and manually oiled every friction surface (long story, but trust me). Finally managed to get the engine to turn using a heavy chain wrench, bc could not get enough torque on harmonic balancer bolt.

Engine started and ran fine after it blew the extra oil out of the cylinders.

Zero oil pressure, so after running perfectly for some 30 seconds, I shut it off.

Pulled pan and oil pump. Tested oil pump, and it works fine.

Reinserted shaft up into the camshaft drive for the pump and attempted to turn it with a wrench. I figure if the shaft drive gear were bad, I should be able to turn the engaged shaft, but I cannot.

Since I found hardly any trace of metal in the pan, I think this engine is worth saving, but I am at a loss.

QUESTION: Where is the over-pressure bypass switch for the oiling system?

I figure it is stuck open.

But it's just a guess. I'm open to suggestion :black_eye:

[Wicked_Sludge]

ive never heard of such a switch...i dont think it exists.

how do you know you have no oil pressure? have you verified with a mechanical gauge? have you checked to make sure said gauge doesnt have any kinks in the line between gauge and engine?

running the engine for 30 seconds with no oil pressure would be pretty obvious. engines dont sound right with no oil pressure.

one possibility is a spun bearing...but i still think you have a gauge problem of some kind.

[martin]

That's a good question. I assume that the motor is edis in which case I would suggest pulling the oil pump drive gear, because you cannot turn it with the oil pump drive shaft is not a viable test for a damaged gear. If the motor has a distributor you could disregard the above comment as the motor would not run with a damaged gear.

[Gadfly]

No. It's, of course, the same design of engine block, but they removed the distributor when they went to electronic ignition. There appears to be a cap structure in its place with wires coming out -- for timing I assume. However, even though the oil pump shaft gear is fused and the shaft cannot be turned manually -- the gear is damaged.

I can't locate a replacement procedure for that. Hope the gear is not broken off the camshaft.

This has turned really expensive, extended, and annoying

[Gadfly]

So nobody knows how to replace the gear mechanism that turns the oil pump shaft from the gear cut into the camshaft?

[Ranger5.0]

oil pressure bypass switch? No such thing....the oil pressure control valve is in the pump, it keeps the oil presure from getting to high. So you say it wouldnt turn over when you got it home? Interesting, thats usualy the sign that its to late, and shes scrawed, check the oil pressure with a mechanical gauge, thats what we do at the shop when we get low or no oil pressure complaints

[Ranger44]

Just a wild idea, please do correct me if I am wrong....but a bad or going bad CPS (Crank Position Sensor)?

[Ranger5.0]

how would that cause the oil pressure to drop? or keep the enging from even turning over?

[mrmrrck]

Your truck doesn't have a distributor, but it has instead a Camshaft syncronizer. It replaces the distributor and it controls the signal for the fuel injectors. The gear at the bottom of the Sync is just like the old distributor gear but weaker. It breaks or strips. When it does it stops the oil pump. Trust me I know! I'm rebuilding my motor right now because my Sync went bad and my oil pump shut down. Spun the #5 rod bearing and chewed up the thrust bearing on the crank. All the parts are back from the shop and I'll be putting the engine back together today and the rest of this week. The Sync is held in the motor just like the distributor was. One bolt size 13 if I remember right. Pull the sync out and check the gear. also check the shaft to make sure it's not bad either. It will strip and then not turn the oil pump.

[Gadfly]

Thanks guys

Yeah. It's the camshaft synchronizer. Strange that it is fused and can't be turned with a wrench with the oil-pump shaft, and yet, still supplies drive to the Hall-effect sensor to keep the engine running. Freaky. I'm anxious to have a look at the business end of the thing when I get it out today.

Thanks for everyone's help.

Looks like it's time to crank the No. 1 piston to TDC and get to work :o)

Oh, and yes. The oil system over-pressure is handled within the oil pump mechanism itself.

[Bob Ayers]

Thanks guys

Yeah. It's the camshaft synchronizer. Strange that it is fused and can't be turned with a wrench with the oil-pump shaft, and yet, still supplies drive to the Hall-effect sensor to keep the engine running. Freaky. I'm anxious to have a look at the business end of the thing when I get it out today.

Thanks for everyone's help.

Looks like it's time to crank the No. 1 piston to TDC and get to work :o)

Oh, and yes. The oil system over-pressure is handled within the oil pump mechanism itself.

The engine will run without the camshaft position sensor. It uses the crankshaft position sensor.