• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Oil pump not priming

Black_Sheep

Super Commando
FBBO Gold Member
Local time
12:18 PM
Joined
Nov 18, 2022
Messages
2,850
Reaction score
11,308
Location
Upper Midwest
I’m at a loss here, trying to get the oil pump to prime. Turning the pump CCW (440) I even bought a new 1/2” drill thinking my 3/8 cordless didn’t have enough speed or power to get it done. No joy! I resealed the engine and changed the pan, the pickup to pan clearance measurement was 3/8” so I didn’t mess with the pickup at all. I did disassemble the pump (Mopar HV) to replaced the gaskets and inspect the pump, which looked great inside. I just pulled the oil filter and it’s bone dry. Before I remove the pump, what am I missing?

DBD21B5C-0DD6-4A4F-AB58-4EA911473D12.jpeg
888E897F-1FA3-4970-B3A0-AF8A32E3B64A.jpeg
 
Did you turn the engine over a bit to make sure oil is getting all the way to the top end through the cam bearing hole for the rocker shafts? It should prime before this but I have had a few take that to start sucking. I think sometimes that gives the oil somewhere to push the air out of the system and let’s it start priming and building pressure. Worth a shot.
 
Filter is bone dry so the oil isn’t even getting that far...

image.jpg
 
I always put oil in the filter and then install, and pre-fill the pump with something thick like Hilton's Hyper Lube before installing.
 
Does the oil pressure relief return to the inlet side of the pump?
 
I’m at a loss here, trying to get the oil pump to prime. Turning the pump CCW (440) I even bought a new 1/2” drill thinking my 3/8 cordless didn’t have enough speed or power to get it done. No joy! I resealed the engine and changed the pan, the pickup to pan clearance measurement was 3/8” so I didn’t mess with the pickup at all. I did disassemble the pump (Mopar HV) to replaced the gaskets and inspect the pump, which looked great inside. I just pulled the oil filter and it’s bone dry. Before I remove the pump, what am I missing?

View attachment 1469443View attachment 1469444
What is the history on this motor? Was it running with oil pressure before you started working on it?
 
What is the history on this motor? Was it running with oil pressure before you started working on it?

I pulled it to reseal some oil leaks and clean everything up, it ran great.
 
One of the reviews at Summit says the Milodon gasket is cut incorrectly and blocks one of the holes.
I'd take a look at that first.

Milodon 21591 Milodon Oil Pump Gaskets | Summit Racing

I think you and 3wood are onto something. The old gasket tore when I took off the pump so I probably didn't compare it to the new one. Looking at photos of oil pumps online I see the port that would be obstructed by the gasket from the Milodon gasket kit I used.

61FG-JQl+AL._AC_SL1125_.jpg
 
Last edited:
I resealed the engine and changed the pan, the pickup to pan clearance measurement was 3/8” so I didn’t mess with the pickup at all. Before I remove the pump, what am I missing?

First, if this is a stock pickup, you should have it against the bottom of the pan. They have a built in recess....

565 R (2).jpg

The blue arrows point to what should rest on the bottom of the pan. The red arrow points to the recess. If you're 3/8" up using this type of pickup, it would be like your fuel sender pickup sitting 3/4" up from the gas tank floor. You'd run out of gas with 2 gallons in the tank.
Secondly...I have heard of people that have trouble obtaining a prime but have never experienced it. For my last several builds, I've packed the pump with assembly lube. I've always had good luck with the oil pressure coming up quickly when spinning the drill.
 
45+ years. I have never primed a pump... other than the camp water pump I did a couple of hours ago.
 
First, if this is a stock pickup, you should have it against the bottom of the pan. They have a built in recess....

View attachment 1469463
The blue arrows point to what should rest on the bottom of the pan. The red arrow points to the recess. If you're 3/8" up using this type of pickup, it would be like your fuel sender pickup sitting 3/4" up from the gas tank floor. You'd run out of gas with 2 gallons in the tank.
Secondly...I have heard of people that have trouble obtaining a prime but have never experienced it. For my last several builds, I've packed the pump with assembly lube. I've always had good luck with the oil pressure coming up quickly when spinning the drill.

It's a Moroso 1/2" pickup made specifically for the Moroso pan I'm using. The more I think about it, I'm 99% sure 3wood and OKDart are right about the gasket. I have to pull the pump regardless, so it will be obvious if that's the issue.
 
45+ years. I have never primed a pump... other than the camp water pump I did a couple of hours ago.

The oil light stayed on when I cranked the engine, since the carb and fuel system were dry I had to crank it quite a bit. Usually after sitting all winter the light would go out before the engine lit. Tonight when it fired up the light stayed on, so I shut it off immediately. I pulled the distributor and used the prelube tool to diagnose what was going on.
 
I know it's basic, but are you sure your drive shaft is engaging the pump shaft. It has a hex end, drive shaft, and so does pump shaft.
 
Auto Transport Service
Back
Top