Hi All, Just bought a 70 Barracuda with 440 and lost oil pressure half way home. It ran fine for an hour and half before that. I have checked/done the following so far. Verified Gauge Function Removed Valve Covers verified no broken push rods of rocker arms Removed Dist. and Oil pump shaft, neither of which appears to be broken Removed oil filter which was very hard to get off, oil pretty black, oil on dipstick looked clear (i think previous owner changed oil but not the filter) Removed oil pump, seemed to rotate freely so I bought new filter, filled it with oil to prime it, used drill to prime it with oil sending unit off. No oil comes out of sending unit hole. Pulled pan, pickup in place and no apparent cracks or blockage. Only thing that I can think is that the oil pump is bad, is there anything else that I should check. Any help would be greatly appreciated.
did you pull the oil pump rotors out and inspect them? were you priming the pump in the right direction? how long did you drive it /let it run after it lost pressure ?
didn't inspect the rotors, didn't know what to look for but they turned freely primed pump counterclockwise and it never loaded up a minute or so just to coast off the freeway, motor still turns over
Lost oil pressure? All of it? A worn pump will still have "some" oil pressure.... Try checking for oil pressure at a different oil galley location.....
excessive wear between them (feeler guage) pits or breaks on the rotors on my first bb chrysler i started priming the pump and kept trying and trying could not get anything changed direction on the drill and almost instantly it primed up
the gauge is stock High Low gauge, electrical off the sending unit, no oil comes out of sending unit hole seemed to have lost all pressure timing is counterclockwise, I assume I should prime the oil pump in that direction?
Yes, you should be turning the pump counter clockwise on a Mopar big block. I know that you said you pulled the pan and did not see any cracks or blockages with the pick-up, but that is what I am suspecting. It is a straight shot from the pick-up into the pump. Stan
I know you said no busted pushrods or rockers but generally when there is no oil pressure at all a liftes has jumped out of the lifter bore. I would recheck if I was you. A lot of the advice you have is good. Even a worn put oil pump will have some presssure. A broken oil pickup though will also cause this. Often if you lift during a wheeelie with a deap pan and dont have the saftey bumpers on you lower control arms as per my book you will smack the pan enuf to crack the pickup at the threads but the pan will appear scrapped but not dented. (which is why you never ever lift when leaving wheels up. ) After that all you can suck up is air. Don
Oil pumps just don't go bad all the sudden, unless the oil pump shaft breaks. The oil pump on Big Block Mopars is external so if you removed it you have to pack the oil pump full of vasoline to get it to prime again, otherwise it's just sucking air. Same thing goes for AMCs and Buicks. I had a 383 Mopar doing something similar and when I tore it down it had a spun cam bearing.
You said you checked pushrod,etc, but I had a 440 did the same thing and finially found a lifter had popped out .
Yes on this. Dirty filter may mean a little piece of crap on the piston causing it to stick. At least on the B/RB the pump is on the outside where you can get at it.
Had problems with a Pontiac like that... Turned out to be the oil pump pick up screen was plugged.... Maybe too basic, but worth a check...
The 440 6 pack or 6bbl what ever you choose to call them uses a similar pump, but uses the black high pressure relief spring. (They were available in the 'Cuda in 1970-71.)If you pulled you spring out and it wasn't broken, replace it with the black one. Trying to recall if the "cup" comes out with it and having a senior moment here....
I had a similar issue with my '67 383. Oil pressure would be 65 lbs hot running down the road, 35-40 lbs hot at idle. One day after a hard weekend of racing and cruising, oil pressure was 45 running warm, down to 20 lbs at idle, periodically dropping to 0 and coming back up. Replaced the electric sender, same problem. Replaced the pump, same problem. Pulled the pan, and found most of my first main and a good portion of my thrust bearing. Damn thing drove over 150 miles missing one whole bearing. The fix was a new bottom end. Pumps don't just lose pressure like has been stated. You can pop the outer cover off and take a look at the impeller to see if they have any kind of damage. If they don't, or the damage is minimal, you have bigger issues. Put a mechanical gauge on it just to be sure. Dropping the pan is the ultimate way to tell. Unless you sheared the drive off in the pump and you think you're priming it when you're not. That's a real stretch though.
back in the day, my 383 road runner did the same thing...checked all the items you listed...spun cam bearing....= no oil pressure, i hope thats not the case for you but it sure was for me.
Check for broken rocker arm.A lifter may have come out of its bore= no oil pressure ........seen it a time or two.
Hi Everyone, Lots of things to think about. I did pull the pan and can see all the lifters from below are in place? Is that sufficient or do I need to pull the intake. I ordered new pump, pickup and just got them. Will be installing by the weekend and advise. I am hoping it is not a spun bearing. If it is a spun bearing shouldn't I get some pressure or resistance once the pump is primed? I spun the drill (counterclockwise) for several minutes and it never loaded up? Any thoughts?
Just pull the valve covers and you can check the lifters. Out of all the years I ran BB Mopars, I once had a pushrod go through one of the rockers. The motor had well over 100K on it, and still chirped the tires going into second, and sometimes even third. It still ran in the low 14's in the 1/4, too. Anyway, that was my oil pressure problem. I replaced only the rocker, and never had a bit of trouble again.
Yes, with a spun cam bearing, you should still feel the pump load up once primed-but the flow wont go past the spun bearing. if you can pack the pump a bit with some vaseline, it will create suction enough to prime itself. once running, the vaseline will dissipate harmlessly. check the pickup DOUBLE GOOD for any air-sucking cracks-
Since I have the pan off should it take off a couple of the main caps to check out the bearings. Would that harm anything taking one off and then reinstalling/torque it back in place. I know that there is typically a torque sequence, would that hurt anything though. Also when I pull the valve covers again, should there be "no play" when pushing on the rocker arm/push rod or does that depend on the cam position for that cylinder? Thanks again
On priming the oil pump, some are saying a little vaseline, some are saying 30w, some are saying STP. Since I am buying a Melling pump any idea what they recommend for priming?
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