75 lbs. oil pressure to ZERO in 10 seconds. WTF?

Mark Barnes

Well-Known Member
Local time
9:07 PM
Joined
Mar 21, 2020
Messages
568
Reaction score
801
Location
MI Thumb
Just fired my 383 last week. Started and broke in very well. New Melling hi volume pump made pressure 75lbs. at startup, drops to 25 lbs.at idle, 60lbs. at 2500 rpm. Took my son up to the parts store to get collector gaskets. Almost drove by the store driveway, so I leaned on the brakes a bit. Oil pressure went to zero, and stayed there. No clatter, no other noises. Shut the motor down, went inside, came back out 10 min. later restarted motor. Ran 5 seconds, no pressure. Shut it down again. Pulled the distributor, shaft is fine. Intermediate shaft, no issue, gears just like brand new. Cam too. Had it towed home. Only thing I can think of is brand new pickup tube broke off, or separated enough to suck air? (I have 2 oil press. gauges, one mechanical, one electronic, both said zero.) Never had this happen before...anyone have a similar issue? I'm lost and pissed. All brand new parts...
 

RemCharger

Well-Known Member
Local time
8:07 PM
Joined
Apr 5, 2014
Messages
3,824
Reaction score
3,571
Location
Sask
At first I would agree with the pickup... but when you say it's fresh with the good HV pump, the 25 lbs pressure is alarming.
Could still be the Crack at the pickup thread, but wondering if the pump got **** kicked with trash going through it.
 

Lefty71

FBBO Gold Member
FBBO Gold Member
Local time
9:07 PM
Joined
Mar 8, 2018
Messages
2,862
Reaction score
3,108
Location
Ohio
If the cam bearing with three holes is tight and spins, won't it cut off signal to the guage pressure as well as the rocker train?
 

khryslerkid

FBBO Gold Member
FBBO Gold Member
Local time
9:07 PM
Joined
Mar 10, 2010
Messages
27,570
Reaction score
45,451
Location
Hanover, Pennslyvania
To continue with the last post, is the valve train noisy?

You could pull the drain plug and look inside the pan for an out of place pickup. Pressure valve in the pump might of stuck open too.
 

Hubbarocks

Well-Known Member
Local time
8:07 PM
Joined
Jun 25, 2020
Messages
188
Reaction score
97
Location
sconsin'
pull the valve covers off , pull the oil pump shaft and spin the oil pump with a drill, see if it's actually moving anything up top ? the cam bearing could have spun.
 

RemCharger

Well-Known Member
Local time
8:07 PM
Joined
Apr 5, 2014
Messages
3,824
Reaction score
3,571
Location
Sask
If the cam bearing with three holes is tight and spins, won't it cut off signal to the guage pressure as well as the rocker train?
No
20220712_155321.jpg
 

Mark Barnes

Well-Known Member
Local time
9:07 PM
Joined
Mar 21, 2020
Messages
568
Reaction score
801
Location
MI Thumb
I just stuck the priming rod back down there and spun it...nothing. Pump or pickup, I guess...
 

AR67GTX

FBBO Gold Member
FBBO Gold Member
Local time
8:07 PM
Joined
Jan 28, 2012
Messages
3,790
Reaction score
2,873
Location
Arkansas
I wouldn’t be to surprised at a cracked/ failing pickup - after just having installed one and having to use vice grips to spin it down tight and to clear the pan.
 

R413

Well-Known Member
Local time
6:07 PM
Joined
Feb 4, 2019
Messages
3,567
Reaction score
7,222
Location
NW USA
If the cam bearing with three holes is tight and spins, won't it cut off signal to the guage pressure as well as the rocker train?
Will just cut the oil to rocker shafts. Gauge will work.


@Mark Barnes drain all of the oil from the drain plug and see if any debris in the oil. Pour it back in if clean. Then remove the pressure relief valve from the oil pump and see if any debris in there. Then try the priming shaft again.


no need to remove valve covers yet.
 

Mark Barnes

Well-Known Member
Local time
9:07 PM
Joined
Mar 21, 2020
Messages
568
Reaction score
801
Location
MI Thumb
Will just cut the oil to rocker shafts. Gauge will work.


@Mark Barnes drain all of the oil from the drain plug and see if any debris in the oil. Pour it back in if clean. Then remove the pressure relief valve from the oil pump and see if any debris in there. Then try the priming shaft again.


no need to remove valve covers yet.
This is perfect, have to change oil anyway. How does the pressure relief come out?
 

gtxrt

FBBO Gold Member
FBBO Gold Member
Local time
9:07 PM
Joined
Feb 18, 2021
Messages
231
Reaction score
117
Location
central ny
it's a stuck relieve valve in the oil pump.
 

Sinitro

Well-Known Member
Local time
6:07 PM
Joined
Mar 6, 2021
Messages
118
Reaction score
109
Location
Southern California
Pull a valve cover and double check the valve train, if a lifter collapses it will pop out a pushrod losing oil pressure..

Just my $0.02...
 

Mark Barnes

Well-Known Member
Local time
9:07 PM
Joined
Mar 21, 2020
Messages
568
Reaction score
801
Location
MI Thumb
Pull a valve cover and double check the valve train, if a lifter collapses it will pop out a pushrod losing oil pressure..

Just my $0.02...
SFT camshaft/ lifters. If one of them collapses I have WAAAY bigger problems that no oil pressure!
 

gtxrt

FBBO Gold Member
FBBO Gold Member
Local time
9:07 PM
Joined
Feb 18, 2021
Messages
231
Reaction score
117
Location
central ny
it takes 10 minutes to take the 15/16 bolt facing the back of the engine and take the spring out and check the valve if it's free
 

1 Wild R/T

Well-Known Member
Local time
6:07 PM
Joined
Jul 9, 2019
Messages
7,199
Reaction score
18,620
Location
California
Screen Shot 2022-07-12 at 11.10.36 PM.png


Relief valve could be hung open or a dozen other possible problems... A lifter out of it's bore, oil pump found a way to suck air, oil pump drive shaft sheared...

In your post you say "Intermediate shaft, no issue, gears just like brand new." did you actually pull the shaft & inspect it? Or looked & saw the gears look good? Cause twice I've seen the drive hex get sheared off...

Have you tried spinning the oil pump with a priming tool?
 

Geoff 2

Well-Known Member
Local time
8:07 PM
Joined
Jul 21, 2014
Messages
927
Reaction score
552
Location
Australia
I hope it is just a stuck relief valve, but........

To check the pump p/up, remove the pump. Blow compressed air into the p/up passage in the block. If you hear air hissing, p/up has broken. If you here gurgling [ oil ], it indicates p/up is ok.
 

1 Wild R/T

Well-Known Member
Local time
6:07 PM
Joined
Jul 9, 2019
Messages
7,199
Reaction score
18,620
Location
California
I hope it is just a stuck relief valve, but........

To check the pump p/up, remove the pump. Blow compressed air into the p/up passage in the block. If you hear air hissing, p/up has broken. If you here gurgling [ oil ], it indicates p/up is ok.
Maybe, maybe not... The hissing I agree, bad... The gurgling, doesn't prove there no air leaking it just means some air is bubbling in the oil, so the pickup isn't fully broken, but it could be cracked....
 

OKDart

Well-Known Member
Local time
8:07 PM
Joined
Nov 9, 2012
Messages
577
Reaction score
598
Location
Oklahoma
I'm not a fan of the aftermarket pickup tubes, I was trying to get mine positioned right and it snapped off at the threads with barely any force. It was one of the gold pickup tubes, looked to be cheap cast metal.
 
Top