Hi everyone,

I haven't had this truck for very long. I got it from my brother who put a new CAI on it and new oil pan (oil change and the drain plug tore the pan) and cleaned the pickup tube because it was kind of dirty. Also did some work on the exhaust. He said after he put the new oil pan on it and cleaned the pickup tube, it showed zero oil pressure. Well he decided not to mess with it and just let me have it. Brought it to me on a flatbed and pushed it into my driveway. He had driven it quite a bit before this with no problems.

Now that I have had a chance to work on it, I replaced the following items:
-Gates Water Pump, just because
-Hayden Fan Clutch, could not get it old one off the water pump. Cut the shaft and took the fan blade off to reuse.
-Mellings Oil Pump (what I thought was wrong with it) filled with oil and rotated manually to lube it up.
-Mellings Timing Chain, Cam & Crank Sprocket, and Tensioner. Right chain guide broke on the tensioner and the timing chain was riding on the bare metal. Noticed after I got the timing cover off. Realized you had to pull the chain to get to the tensioner. So I replaced it as a set.
-New Mopar oil filter
-New 7 quarts of Havoline High Mileage Syn-Blend 5W-30. Bought 2 of the 6 quart boxes and just measured out 1 quart from the second box.

Put it all back together and zero oil pressure on the infamous dash gauge, noticeable lifter tick. Removed oil sending unit and Installed a mechanical pressure gauge. Still zero pressure. Fine, didn't want to drop the pan to do the oil pickup tube, but might as well at this point. Drained the oil to reuse. Loosened the nut off the driver side motor mount, cut a two foot piece of 2X4 and jacked up under the timing cover and power steering pump enough for the pan to come out by pushing back and then tipping the rear of the pan towards the ground sliding out at an angle. Inspected oil pan and its clean a whistle. Nothing alarming noted after dropping the pickup tube and windage tray. Pickup tube has seen better days but has clearly been cleaned. Possibly OEM? Has the cover piece over the pickup screen. Put a rag over the oil pump end and sucked and blew threw it. No noticeable obstructions. Installed new windage tray and new pickup tube with new o-ring that came with the oil pump. Put oil pan back on, lowered engine, and tightened the motor mount bolt. Refilled with oil and let it sit for a while to all settle down to the pan.

Using mechanical gauge:
1st start - zero pressure
2nd start - 10 PSI, dropped to zero after idling a couple of minutes
3rd start - 20 PSI, dropped to zero after a couple of minutes of idling
Every subsequent start idles at between 4-6 PSI. Gauge needle moves up and down every few seconds. Lifter tick almost completely gone after truck has warmed up.Tried to put it in drive once to drive to the end of the street. As soon as I left the driveway, it hit zero. Shut the truck off and pushed back into the yard.

So any tips or suggestions on what to check from this point would be appreciated. What is the idea pressure ranges I should be seeing when idling vs driving. I tried to be as detailed as I could, so hopefully that helps.

 

Wow. You must be frustrated
So everything was fine until.... Bro did an oil change and stripped the drain plug thread? or was he changing the oil due to an issue?

I think you should be seeing at least 35 to 45 psi at idle with an increaae as rpm rises.
Im baffled.
At zero or low oil pressure I would expect alot of lifter clatter...possibly some crank bearing noise etc. ...your saying the lifter noise is gone but still low oil pressure?
My first thought is to recheck pressure with a different mechanical gauge.
Are there two sensors near oil filter on that model year?

 

It was just a regular scheduled oil change at 3K mile interval. He drained the oil and something happened when he put the drain plug back in. He said it tore the pan, but it could have just been stripped threads. He took the pan off and it sat like that for a week until the new one came in. He thought maybe it had lost prime for the oil pump. The truck has 258K miles on it. I checked his oil when I got the truck and there isn't any metal in it. There is only the one sensor above the filter.

I'll take the gauge out of the oil sender hole later this afternoon and see if I can get oil to squirt out of the hole when i bump it over. Might take me a bit to get another gauge. I had to buy a new battery and terminal yesterday for it and I hadn't budgeted for that. I'll try sticking it on my Firebird and see if the gauge reads around what the dash shows on it.

 

I pull the gauge off the plastic line for it and oil was coming out like it should. I hooked the gauge back up to the line and its showing 35+ lbs. I revved it once slightly and the pressure went up with the rev. However, there is a new sound that it was not making last night. It sort of sounds like something loose is vibrating against metal. Here's a 13 second clip of the noise. Didn't want to keep it running in case its something serious. Windy noise in the first 7 seconds is the air off the fan blade which is why I moved the camera. I took the serpentine belt off to rule out a pulley related noise. Noise is still there. I can't really pinpoint where its coming from.

 

Not making that sound anymore. I apparently left that transmission cover piece off that goes over the back of the oil pan and the thin little dust shield thingy was rattling. also the two transmission cooler lines that run down the side of the oil pan, forgot to put the line clip back on the oil pan stud so it was rattling also against the oil pan. I wish that was the end of it, but I'm not that lucky I guess. I took it for a small drive about 200 feet down the road and back. Idling pressure is great. As soon as I hit the gas under load, the pressure drops and stays down until I turn the truck off and let it sit for about a minute. Then I start it up and have pressure again...until I hit the gas.

 

Do you still have mechanical gauge hooked up or are you using the dash gauge as reference?
It almost sounds like you have oil pressure but for some reason you are not getting proper pressure readings ????

 

I was using the mechanical gauge for that test since I still had it hooked up. So I put the electrical gauge back in it. Started truck and it showed pressure to the line in the middle. I tapped the gas and no change. If I hold the throttle at anything above an idle for more than a few seconds, the pressure drops to zero and the check gauges light pops on. It doesn't show oil pressure until I shut the truck off and turn it back on. I don't even have to wait. Off and right back on and it shows pressure until I hit the accelerator. I let it back out under its own power and coast forward a bit and it didn't lose pressure. Then I gave it some gas for about 100 feet and the pressure hit zero again. Im at a loss. I took the sender off and the oil squirts a little out the hole, pause, squirt. It keeps going like that. I'm done for tonight. When I get off tomorrow, Ill have my wife hold the accelerator at about 1500 rpm which is where I had it when the gauge hits zero. Maybe I got a faulty oil pump or something else is restricting the flow?

 

Just throwing these out there for ya as possibilities

I believe there will be an oil pressure relief valve in the oil pump (maybe you can check old one). Maybe this is not cooperating. Anything above idle pressures and its sticking open dropping oil pressure until it senses no pressure at all when you shut down engine....then on restart it works properly until once again pressures go up ??
However Im having difficulty thinking this happened to old pump AND new pump.

Only other thing which I havent physically observed for years...but there was a pic here a while ago of a hemi with bad and I mean terrible sludge on top of heads in rocker arm area. ...
All oil being pumped into valve covers and not able to return to oil pan and thus a low oil pressure...??
This is prob unlikely cuz it sounds like your engine was properly maintained.

 

I pulled the valve covers and it looks great. Nothing loose or broken. I was thinking it could be something clogged internally where I can't see it. So I ran some Motor Medic through it and let it idle five minutes as the bottle says. I then drained it and the oil came out only slightly darker than it went in. Still looked great and and when I strained it, there wasn't anything of note in the filter. Put a new Mobil 1 extended filter on and filled back up with Mobil 1 Full Syn high Mileage. Started it up and ran great to the store, no pressure drops. Came back out and started it up and did not want to keep pressure. It would go to the middle of the gauge and then drop and just keep repeating this. When I took the filter off, there was a lot of pressure still even after having already drained the oil. As soon as I loosened the filter a bit, hot oil came gushing over the sides of it. Not quite hot enough to burn, but still uncomfortable since I wasn't expecting that.

My brother mentioned last night when he changed the oil, the old filter had sort of collapsed on itself like it had a ton of vacuum on the inside. Said he practically destroyed the filter before he was able to get it off.

I did read a article somewhere that mentioned using a pesticide sprayer hooked up to the oil galley ports at the sending unit to pump pressurized oil backwards from that point to lube the top of the engine and bottom while clearing any blockages. Then checking the pan to make sure the oil pickup tube is still clear. Another article mentioned a screen right behind the sending unit port that gets clogged sometimes causing a faulty sensor reading.

Also, that vibrating noise is back on every cold start, but goes away after its warm. Sounds like something loose but I still cant find it. Sounds like its coming from the front of the engine. I took the belt off again and its still there. So either something timing chain related is loose or something else is loose. It goes away also if you rev the engine a little.

I looked at the old oil pump and pictures of the new and the pressure caps are held in with snap rings. The new one, Mellings M342, has push pin type thing in front of one the one on it.

I did see that pictures of the sludge buildup that you mentioned. I agree that was pretty horrible to look at.

When I first got my Firebird and finished putting the engine back together, it had oil pressure problems also which in the end was because of a faulty PCV valve. Blueish White smoke so thick I don't think I had to worry about mosquitoes for awhile. Changed the PCV and it all went away. Anyways, got one of those coming in today to change out also.

Here is a video of the gauge antics. I verified this with the mechanical gauge afterwards, but didnt get a video of that.

 

I put the PCV valve in and it seems to have fixed it. Still have that vibration noise until it warms up. It takes a moment, like 4 or 5 seconds to build the pressure when I first start it, but it seems to be fine after that. I drove it about 10 miles round trip over two tries without the pressure dropping. I'll hold off on blowing the oil through those oil galley ports until it tries to mess up again. PCV valve was caked in sludge and was stuck open. I broke the stem part off when I pulled it out. Had to fish the rest of it out with needle nose pliers. I will let you know what happens over the next week to see if it fixed it long term or not. Im wary about driving to far away from the house at the moment.