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Cadillac 500 Reaching out to Potter or Water Thunder and all

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ditchdr

Well-known member
Helloooooooooooooo oh crap. I have my Cadillac 500 set in the rigging,wired it and fired it up,and I have no oil Pressure. The motor as reported from the former owner has had a recent rebuild (stock) with a mild cam up grade. The motor has been sitting either in the car in a shop or on a stand in my shop for about 4-6 weeks. With a lift plate installed
The only thing I have done to it is remove the fuel pump to place the mounts..
Also hey WATER the Carter Elect. pump is running fine. I have it plumbed to the orginal one will I need a regulater it seems to flow alot of fuel.
THANKS IN ADVANCE
RCM
 
I would check oil pressure gauge connections if electric and prime oil pump with electric drill prior to starting to see what pressure builds before any damage can be done, regardless of electric or mechanical gauges.
 
jdotson makes the best suggestion first.if that is not the case if it is a new melling pump the pressure relief plunger is probably stuck.i think this has happend to almost everyone that has put a new one on a caddy with out it beeing massaged.if that isnt the case they may have busted a lifter during break in or those p.i.t.a little oil plugs in the lifter vally pop out sometimes that is why alot of guys thread them and plug em.and the oring between the pickup tube and block sometimes poops out on ya.olf art makes a good point as well some guages don't mix well with senders.
 
Same here ! Prime the system! cost less that way ! If it dont prime that way ! Pull off your oil pump ! CHECK YOUR PRESURRE VALUE ! More toasted motors that way ! :D
 
Bondsman brings to light some good points. It's hard to tell what the previous owner did on the rebuild so I would double check everything. The proper oil pump gasket (paper thin) is essential for proper clearance between oil pump gears and block as well. The following is a valuable link for information on Cadillac engines.

http://www.cowboyseven.us/forum/index.php
 
Yep prime that oil pump. You can use an old screw drive and cut it off or one of the gator sockets.

Caddy Oil pumps don't go out it's more you gauge or electric. If you do replace it don't buy a piece of s**t Melin their oil pump trashed my motor.
 
Thanks for all of the advise......I need to clear a few thing up..Ok its a mechanical with a combo of copper and plastic tubing The motor was running in the truck I bought from, and it had 40 - 60 lbs of oil pressure I saw it with my own eyes.I have pulled the oil galley guage adapter off and there is no oil flowing...The father of the young man I bought it from did tell me it was an Melling.........I am kinda of wondering if as one of yall said the bypass valve or what ever it is could be stuck
and is this something that can be fixed or do I just need to buy a new oil pump. Or is there any other possibilties.
Thanks again this is great help
RCM
 
the oil pump is external as you can see take a 5/16 allen head wrench or socket,unscrew the plug watch out if the plunger is stuck cause the spring pressure will shoot the plug away from you.slide the spring out if you can see the plunger in about an inch it is stuck.you can either pull the plunger out and clean the cylinder or push it back in but i would clean it.put it back together and test for pressure.but if you can tell the plunger is stuck my advise would be to remove the pump and take emery cloth to the pressure bore and deburr it the best you can.mts sells the gasket for the pump without having to buy the rebuild kit.
 
I have run into this problem several times and it is an easy fix!!!! Take the allen head bolt out of the oil pimp. This bolt is on the side of the pump facing towards the starter. When you take this plug out the spring might pop out if it does this is your problem without a doubt. What has happened is you bypass valve has stuck open and this is common with new Melen pumps. Take a phelleps screw driver and push the piston foward and it wll free up, then out the spring back behind the piston and replace the allen head plug. When you start the motor you will have pressure again. These pistons will stck on a motor that has been sitting a while. When I got my motor from Potter I had zero oil pressure the first time I started it and it was because the piston stuck. This motor made many dyno runs at Potters shop with no problems and it has never done it sense that one time but it happens. I have had it happen with two diffrent Cadillac motors but I know other that have never had it happen. This fix is easy and only takes a few minuets.
 
Thanks for the input.......I going to work on it again in the AM....This sounds like a good Idea..........what do you think about the fuel pump should i have a regulator on it?
 
Check the fuel pressure with a gauge at the carb. A Quadrajet needs a minimum of 3 lbs flowing at wide open throttle---5lbs is plenty. 7 is too much for a quadrajet and pushing the limit on a Holley.

Charles
 
Well guys that's not the problem...............Pulled the bypass plug and the valve seems to be working fine.......Then I went and pulled the oil pump off to check it out that seems to be fine and new looking... so its back to the drawing board.I think what I will do next is to place the oil pump back on (AS SOON AS I CAN FIND A GASKET) and prime the pump with a drill and see what happens. If anyone has a better Idea I am open

I guess to get a gasket I will have to order one from Potter or MTS because no one around here has it........NOT EVEN THE CADILLAC DEALER IN DAYTONA
Any thougths on that would help too

THANKS AGAIN
RCM
 
Most likely a spit pushrod and then lifter....on a cadillac, spitting a lifter means zero pressure. Or you could have popped one of the oil gallery plugs next to the camshaft gear or in the lifter valley where the casting knob is. Dont start the eninge until you find the problem. Charles
 
6011263 is the NAPA # for the oil pump repair kit, they will have to order it in for you
 
I could be wong but I think I remimber an O-ring on the pick up tube where it goes in the block. If this was forgotten or fails it would be like trying to drink out of a broke straw. That is the only other thing I can think of.
 
one thing that you need to remember is that when the pump is higher then the oil in the pan and the engine sits for a while all of the oil will drain out of the pump and a dry pump on a caddy will take a very long time at idle to make pressure ......... and since you do not want to wreck the bearings while you are trying to get pressure you will need to help it out ....... first when you go to put the pump back on pack it with Vaseline ..... it is thick enough to stay put but once up to temp will melt into your oil and I would prime the system you can either modify a old caddy dist or use a Chevy one but if you use a Chevy you will need to keep it centered so it does not chew stuff up as the drive rod on the caddy pump has little support on the top ....

I am sure nothing major like a oil galley plug has come out by just sitting but no oil pressure for even a short time will hurt things .......I prelube the engine in my car before firing whenever it has sat for the winter just because the caddy system is a little fussy
 
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