Sudden Loss of Oil Pressure

-
JGC403

JGC403

Well-Known Member
Joined
Nov 22, 2010
Messages
1,046
Reaction score
48
Location
Baileyton, TN
I had a voltage problem that I wanted to check if I fixed, so I started the truck it was cold out let it idle to warm up to around 100 degrees, idled it around the block pulled it back into the drive by now engine was around 140 ish. I was sitting in the drive way revving the engine a little trying to adjust the accelerator pump on the FI tech fuel injection system. I just happened to look up and saw the oil pressure go from around 40 at idle and creep down to 0 in a couple of seconds. I shut it down as soon as it hit 0. Started it back up the next day and oil pressure still read 0, I think I gave it enough time for the pressure to come up before I shut it down.

There is less than 250 miles on the 383. The oil pressure gauge is a new Auto Meter mechanical gauge. I have Milodon external oil pickup 21001, I have the correct length oil pump drive shaft. Oil Pump is a high pressure, high volume Pump, I think its Mopar Performance. Camshaft is the smallest Mopar Performance solid lifter cam. Deep sump 8 qt oil pan, and windage tray.

I was thinking something happened with the oil pump driveshaft, so I pulled the oil pump since its easy enough to get to; everything looks ok. I can move the oil pressure relief if I stick something in there to move the piston. How far does the oil pressure relief move? If it was stuck open I should see the top of the piston in the cavity closest to the cap that the oil pressure spring is under?

Since its a solid lifter cam I couldn't tell if I actually lost pressure, its not like the tappets got louder, they can't since they are solid. So it could be the gauge. I know I have a working mechanical gauge on the duster. Its a cheap-o one but I know it works. So I'll pull that off the Duster and put that on the 383 quick to check. I hope that is all it is is just a gauge.
 
Last edited:
My 440 did that. I never knew it lost oil pressure. Spun a bearing. Culprit was the oil pump was banging off the Schumacher mount. Didn't clearance it enough.
 
Did you check the intermediate shaft? They have been known to shear.
 
Last edited:
I had a push rod go through a rocker arm once popped the lifter out of the bore lost all oil pressure.
 
roccodart440 said:
My 440 did that. I never knew it lost oil pressure. Spun a bearing. Culprit was the oil pump was banging off the Schumacher mount. Didn't clearance it enough.
Click to expand...

The 383 is in a truck, the engine mounts that are near the pump bolt right to the block. I had to notch the mount when I assembled it the first time because it hit the pump because of the taller oil pump with the Milodon adapter. The pump came right off so I think there is enough clearance around the pump.

If a bearing spun wouldn't there still be oil pressure at the oil pressure port on the back of the motor?

furyus2 said:
Did you check the intermediate shaft? They have been known to shear.
Click to expand...

That is what I was thinking and why I pulled the oil pump. The Intermediate shaft is still in the engine, nothing fell out when I removed the pump. I was able to push up on the shaft a little and felt it bottom out on the distributor. I tried pulling it out of the block and it won't move. I can turn it a little and I can feel it climbing the gear on the camshaft.
 
Last edited:
JGC403 said:
The 383 is in a truck, the engine mounts that are near the pump bolt right to the block. I had to notch the mount when I assembled it the first time because it hit the pump because of the taller oil pump with the Milodon adapter. The pump came right off so I think there is enough clearance around the pump.

If a bearing spun wouldn't there still be oil pressure at the oil pressure port on the back of the motor?



That is what I was thinking and why I pulled the oil pump. The Intermediate shaft is still in the engine, nothing fell out when I removed the pump. I was able to push up on the shaft a little and felt it bottom out on the distributor. I tried pulling it out of the block and it won't move. I can turn it a little and I can feel it climbing the gear on the camshaft.
Click to expand...
Have you tried a large flat blade screwdriver in the slot to rotate it out? Long needle nose pliars work too.
 
I had that happen when I was really low on oil. I had a leak I knew about but didn’t realize how low it was. Might take a peak at the dipstick.

Jake
 
furyus2 said:
Have you tried a large flat blade screwdriver in the slot to rotate it out? Long needle nose pliars work too.
Click to expand...

I haven't removed the distributor. I was trying to pull the intermediate shaft out the bottom. If It sheared off it should of came out.
 
xLURKxDOGx said:
I had that happen when I was really low on oil. I had a leak I knew about but didn’t realize how low it was. Might take a peak at the dipstick.

Jake
Click to expand...

Oil level is good.

I think I'm just going to put it all back together, pull the distributor and run the pump with a drill. If the pump checks out I'll feel a load on it and if the gauge stays at zero at that point I know its just a gauge. I just don't want to start the engine again just in case there isn't oil pressure. Really don't want to pull the distributor cause then I'll have to re-sync it with the FI Tech fuel injection, but I don't have any other choice.
 
Pull cap and see if rotor turns when turning over (just for a second).
Put cheapo gauge on before checking rotor.
 
There's probably small burr or debri on the oilpump internal pressure valve or bore, keeping it open. There's still flow, but hardly any pressure.

Or a lifter has jumped its bore, bent pushrod, acting like a big oil leak now internally. But should be very obvious cause engine will idle rough like missing a cylinder.

Pre-lube the engine through the distributor hole after removing the intermediate shaft. You will right away if it's building oilpressure. (Rotate counter clockwise).
 
Did you try another cheap oil gauge? I know I have had more than one gauge stop working.
 
4spdragtop said:
Pull cap and see if rotor turns when turning over (just for a second).
Put cheapo gauge on before checking rotor.
Click to expand...

Since the engine was running, the rotor would have had to be turning.
 
One day while driving my little brothers 70 challenger with my 426 Hemi in it at the top of 3rd gear i bang 4th and the oil pressure dropped to zero.
I instantly shut the engine off and we towed it home.
I had the Dual line Milodon system with the swinging pickup. When we pulled the pan there was The Swinging pickup laying in the bottom.
 
You don't have to pull your distributor to check the pump. Just drive the pump with a drill and see if oil comes out, while its not mounted.
 
Put it all back together yesterday, pulled the distributor and primed the oil system with a drill, pump built pressure and the gauge worked, so I don't understand what happened. Could a high volume oil pump with the external pick-up suck the pan dry? and with the oil being cold just wasn't draining back to the oil pan fast enough? I can't think of any other explanation.
 
JGC403 said:
Put it all back together yesterday, pulled the distributor and primed the oil system with a drill, pump built pressure and the gauge worked, so I don't understand what happened. Could a high volume oil pump with the external pick-up suck the pan dry? and with the oil being cold just wasn't draining back to the oil pan fast enough? I can't think of any other explanation.
Click to expand...

Yes a high volume pump will suck a pan dry but you would have to be 3 quarts or more low on oil. The engine would have to be higher than idle rpm for this to occur. This happened to my 440 this year and I first noticed it with oil pressure gauge flucuating between 75 to 50 psi at 2000 rpm and I was down on oil. The engine had a slight oil leak at the rear seal retainer due to the engine rebuilder using no side seals but a lot of black RTV. I fixed the leak and modified my oil dip stick by drilling 1/8" holes from the add to full lines. This was because the oil was always clean and it was hard to read on the stick.
 
fgpope2000 said:
The engine had a slight oil leak at the rear seal retainer due to the engine rebuilder using no side seals but a lot of black RTV.
Click to expand...
I helped a guy build his 440 to go in a Duster and the gasket set didn't come with side seals. It had instruction to fill slots with RTV then shove these two supplied pipe cleaners (dampened) down in there to complete the installation. I can't remember what brand of gasket set it was. I didn't like it but that's what he had to work with.
 
You must log in or register to reply here.
-

Back
Top