2.9 Runs With No Oil Pressure?! Is This Possible?

[1986ranger]

2.9 Runs With No Oil Pressure?! Is This Possible? - Resolved

In the process of troubleshooting a truck(history unknown) I just got I decided to run some cleaner through the oil. I drained the oil and changed the filter. I filled truck with new oil and cleaner. I ran it for 15 minutes and went to change the oil and filter and here is where it got interesting. When I pulled the 15 minute old filter off, it was completely empty and bone dry inside! I then hooked up a mechanical oil pressure gauge and got no oil pressure. Then I started the truck, and disconnected the line to the gauge at the block. No oil came out! The filter I removed before this process had oil in it like normal but I have no idea when it was last changed. Does this mean I really have no oil pressure? Would the truck even run with no oil pressure? The truck runs and drives, but poorly. It's an '87 with a 2.9.

Update: See below.

 

[almostclueless]

It MIGHT run temporarily, while it self destructs internally.....and the hydraulic lifters would pump down, making it run even worse.


Every second an engine runs with no oil pressure after the layer on the parts is pushed out, horrible damage occurs.


If nothing is being pumped, and the engine has been run, it's time to take the engine apart and see if anything is salvageable.

 

[90rangersuper]

i had a 80 f-150 with the 300 i-6 in it, ran it for about 2000 miles with about 1 quart in there, now before i get shit for not checking the oil i was only 16, you know what they say young, dumb and full off ... It ran great for about a year after I put oil in there, it probably did f the motor though i lost compression on 2 cylenders, who knew the truck had abour 350,000 on it

 

[bagdranger]

If your getting no oil pressure at all I dont think driving it or running the motor too long would be a good idea. yes it is possible for the truck to run with no oil pressure. On the other side running it with out pressure could wind up tearing up the motor. IE spinning rod or main bearings or cam bearing, which would be alot of work. But the no oil pressure issue could be a bad oil pump or clogged pick up tube. If you've driven it and it runs poorly you might have a problem listed above. My opinion if you wanna check the obvious first pull the oil pan and check the pick up tube for the oil pump and see if its plugged. Maybe when you put the cleaner in it something pluggged the tube up so the pump isnt able to get oil from the pan. While you have the pan off id make sure you didnt spin a rod bearing by just grabbing the rod cap and seeing if it moves any, if it does i'd almost wanna bet you spun a bearing from no oil pressure. Need anything else just ask.

 

[1986ranger]

Well assuming I lost oil pressure when I changed the filter and put the cleaner in, it has idled for about 20 minutes with no pressure. I suppose I could have clogged the oil pickup in my cleaning the process, but it seems very unlikely it would have have plugged instantly before ANY oil got in the filter. Seems to me whatever is going on has been going on for a while. The pressure gauge has been hooked up since I got the truck, and it has read zero the whole time. I just assumed it didn't work. Today I tested it and it seems it is working fine. Assuming the gauge has worked the whole time I have had the truck, I have run it for a a couple hours with no oil pressure and it has behaved the same the entire time, no deterioration.

Assuming the engine did not self destruct right away, how would it run with no pressure to the lifters, etc? If this engine is shot, I have another good 2.9 to put in. I have no interest in rebuilding this one.

 

[MAKG]

It's possible the engine is running in 100% bypass. It's not supposed to do that, but it's the only way you're going to keep a filter bone dry without making a nasty racket with the lifters, at least.

 

[1986ranger]

It's possible the engine is running in 100% bypass. It's not supposed to do that, but it's the only way you're going to keep a filter bone dry without making a nasty racket with the lifters, at least.

But that would not explain why there is no pressure reading at the gauge, would it? I am going to try another filter just in case I got a faulty one, but it seems to me that the gauge has read zero since I got the truck.

 

[cocoasranger]

I'd put a new filter with the same filter number as the one you took off (with oil in it) had. Also, if you took off the oil sending unit and ran the engine without oil shooting out the hole, then you have no pressure, at least to the top end. Could also that be the oil pump pickup fell off, has a plugged screen, or the oil pump drive sheared off, or the main oil passages to the top end are plugged. Just some thoughts for your consideration.

 

[AllanD]

My thought is that there really isn't any oil pressure.

Your "engine flush" washed "crud" down into the oil sump where it clogged the oil pump pickup.

So while the oil pump is spinning it is sucking on a plugged straw.

I've seen this happen twice on 2.9 engines and three times on 4.0's

that "crud" in the oil pan CAN be removed without dropping the pan.

Drain the oil and replace the drain plug.

Pour two or three cans of NON-aerosol "carb cleaner" into the oil pan and let it sit overnight.

THEN pour three quarts of oil in and start the engine
Run it GENTLY only if it shows oil pressure, but definatly
drive it until it's completely warm befotre draining the oil
and changing the filter again.

I know of one 4.0 engine that this happened to that is still running
three years after the original event.

AD

 

[1986ranger]

My thought is that there really isn't any oil pressure.

Your "engine flush" washed "crud" down into the oil sump where it clogged the oil pump pickup.

So while the oil pump is spinning it is sucking on a plugged straw.

I've seen this happen twice on 2.9 engines and three times on 4.0's

that "crud" in the oil pan CAN be removed without dropping the pan.

Drain the oil and replace the drain plug.

Pour two or three cans of NON-aerosol "carb cleaner" into the oil pan and let it sit overnight.

THEN pour three quarts of oil in and start the engine
Run it GENTLY only if it shows oil pressure, but definatly
drive it until it's completely warm befotre draining the oil
and changing the filter again.

I know of one 4.0 engine that this happened to that is still running
three years after the original event.

AD

While this sounds very plausible, I don't think it has had oil pressure since I got it. I find it hard to believe my flushing clogged it up so fast that it did not get one drop of oil in the filter. Not to mention the gauge (that I thought was not hooked up) was hooked up and reading zero the whole time. Also, it runs the same after I did my flush as it did did before. This all makes me think it has had no oil pressure all along. Now, how it has run this long still boggles me though.

 

[AllanD]

On the one that survived the clog was so bad that the engine could be run with the oil pressure switch sitting on the radiator support and no oil came out the threaded port.

AD

 

[1986ranger]

Dropped the pan and took a look. This looks to have been a problem long before I got my hands on it. Still ran surprising well considering.

 

[Psychopete]

Man, that sucks. 2.9L is a tough little bastard though! Plannng an engine swap, or are you considering buying a new truck?

Pete

 

[1986ranger]

Man, that sucks. 2.9L is a tough little bastard though! Plannng an engine swap, or are you considering buying a new truck?

Pete

This truck is getting the good running 2.9 from my 86 and will be sold. Then the 86 is getting a 5.0. Any idea what could cause a failure like that?

 

[MAKG]

Any idea what could cause a failure like that?

Your engine flush.

It does NOT look like the usual sludge deposits (except for the stuff around the oil pump body). It looks loose.

And it's BAD if it expelled a crank or rod bearing. A piece of dirt got in there and spun it. And if this happened a long time ago, you forgot to tell us about the engine knock. So, I think it JUST happened.

FYI, you probably have a "real" (variable) oil pressure gauge on a 1986. Not like later RBVs. The real sender looks kinda like a bell. However, it's not unheard of for the push-on connector to fill with copper salts and read open (cold). Until it's taken off and put back on again; that scrapes the corrosion off.