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Brand new oil pump.... no oil pressure

7.5K views 33 replies 8 participants last post by  85lebaront2  
#1 ·
Replaced the oil pump on my 3.0L, because I had the timing belt off and figure why not.

New melling pump. Cleaned out the pickup, put on with new gasket, torqued everything to spec.

Got everything back together. New oil filter, new 5W-20 oil. No oil pressure. Not even oil in the filter.

What went wrong?

I'm going to try sucking at the oil filter housing with my shopvac, maybe that can get things going?

I'm very low on ideas.
 
#2 ·
I had a no oil pressure situation happen once with Castrol Synthetic 5w30.
I drained the pan, added Mobil 1 5w30, and had normal oil pressure.
About a week later at the SDAC-5 convention, we had a tech session with one of the original Super 60 project builders and he mentioned that they had the same problem with Castrol Synthetic.
 
#3 ·
I don't know anything about 3.0L Engines but always prelube pumps before installing.

Why not you ask??

With 2.2/2.5 Engines and others, I think there are more defective new pumps than used.

A used pump has known qualities, a new one needs to be disassembled and checked closely.

I prelube old or new pumps with a thin smear of grease inside to ensure they seal.

Squirt some oil in from the filter end if possible.

This is one reason the SBC and BBC Chevys are so beloved.

The oil pump sits in the deep end of the pan right in the oil.

No suction required, only pushing.

Good Luck!!!

Thanks
Randy
 
#4 ·
Randy:
That's a great point.
We tend to thing a new part isn't going to be defective vs. a used one.
An oil pump is crucial.

I don't know if the 3.0 oiling is designed similar to the 2.2, but the accessory shaft that's connected to the accessory shaft sprocket gear runs the pump.
Is it possible that you didn't engage the gear at the end of the shaft with the pump gear?
That shaft also runs the distributor.
Also: if you have a failure at the gear or teeth missing, that would cause a no oil pressure situation.
 
#5 ·
Thanks for the thoughts.

1) Jim do you think its the brand (castrol vs mobile) or synthetic vs regular? I have O'Reilly 5W-20 nonsynthetic in there. I really just picked up something cheap more or less at random because I intend to swap it out within an hour of running.

2) I surely did not open up the pump, but I did pour some 10W-40 into it before installing it.

3) On the 3.0 the pump is driven directly by the crankshaft and contains the front oil seal. It engages through 2 flat spots on the shaft. It would seem impossible to mount the pump in a way that doesn't fully engage.
 
#7 ·
Thanks for the thoughts.

1) Jim do you think its the brand (castrol vs mobile) or synthetic vs regular? I have O'Reilly 5W-20 nonsynthetic in there. I really just picked up something cheap more or less at random because I intend to swap it out within an hour of running.

2) I surely did not open up the pump, but I did pour some 10W-40 into it before installing it.

3) On the 3.0 the pump is driven directly by the crankshaft and contains the front oil seal. It engages through 2 flat spots on the shaft. It would seem impossible to mount the pump in a way that doesn't fully engage.
Ahh!
you added some 10W40 to the pump then you added 5W20?
How much 10W40?
Different viscosity oils definitely don't mix with each other.
I'll bet that's it.
 
#8 ·
I would drain it all out, completely, remove and replace the filter, then add 5w30 non-synthetic.
Try that.
 
#9 ·
5W-20 is what I filled with, so 5 quarts of that and just a few tbsp of the 10W-40 in the pump. FWIW, I wouldnt be surprised if that had all dripped out of the pump well before I finished putting everything back together and added the 5W-20.

The filter is new and still dry. Oil never made it up to it.
 
#10 ·
I don't remember having problems with oil pumps on any of my 3.0L engines, but did run into an issue many years ago with a GM V6, it was the original 198 ci in a 1963 Buick Special, the owner had the timing chain fail and replaced it, carefully cleaned everything and reassembled it. I don't think he noticed the oil light staying on, but when it ran like crap due to the lifters leaking down he was sure he had the chain on wrong.

After messing with it for a week he asked if I would come to where that car was in a friend's garage. When I got there he had everything laid out and a Motor's manual opened to the timing chain section. I verified correct timing and asked if someone had any Vaseline and proceeded to remove the oil pump cover and pack the pump (a GM two spur gear style) with Vaseline at which point I was asked "what tells you to do that". I took the Motor's manual and turned to the next page where those instructions were in bold print. That oil pump sits low on the right side of the timing cover and is driven by the distributor shaft.

I would suggest first removing the new pump and make sure that everything is proper inside and that the pump drive key or tang is properly installed and before reinstalling the pump pack the insides with Vaseline or very light grease to "seal" the rotors so they can pull oil up the pickup and passages. I would leave the filter off, pull the plugs and disconnect the coil so the engine can spin fast on the starter. which will help it to draw oil.

Good luck with it!
 
#13 ·
It is a thing when you replace the oil pump and it is recommended to do on a turbo car when changing the filter.
(Filling the filter allows oil pressure to build more quickly on initial crank/start)
Did you disconnect the ASD Relay and crank the engine to build oil pressure before you tried to start the engine?
(Removing/Disconnecting the ASD will shut down all fuel and spark so you do not start/flood the engine without oil pressure)
Did you lubricate the camshafts before attempting to crank the engine after the pump replacement?
(The Camshafts are the last things to receive oil)
Have you installed a gauge to see if there is any oil pressure at all?

I certainly hope you have not reassembled the entire engine and you still have easy access to the timing belt/sprockets and oil pump housing.
 
#14 ·
First thing I did was pulled out the fuel pump relay and cranked.
Camshafts were assembly-lubed from when the heads were at the machine shop.

The engine is indeed fully reassembled. So I'm really hoping to find a solution that doesn't involve pulling the front all off again!
 
#15 ·
Whenever I have the timing belt off I always start the engine before I reinstall the accessories and mounts just to be sure everything is OK.

First thing I would do is remove the filter, fill and re-install, then install an oil pressure gauge and crank the engine (with the fuel pump/ASD relay removed) to see if there is any pressure at all.

If there is not any oil pressure check to be sure the relief valve is not stuck open.

I do not know if Autozone or Advance have an Oil Pressure Tester Loan A Tool.



I also assume you have the "Electrical/Fuel/Emissions" FSM for proper distributor installation?
 
#16 ·
OK everyone here's what I did:

I cranked more.

And eventually the pressure came up:
Image


How long to crank in a go is something they def dont put in a book and no one thinks to mention. I was being very shy with my cranking, doing maybe a second at a time, courageously stretching to two. But when I went for a good bout of several seconds, I saw a flicker on the gauge then it went up! Now I do still need to slap on a proper test gauge to check the real value, but the fears of a bum pump are assuaged. I can confirm I get oil up into the heads too, I open the cap and saw oil draining back down.
 
#18 ·
Yes definitely needs to be cranked more than a second or two.
Glad you got it working.
Regarding what NAJ said about prefilling the oil filter, although I never heard that before,
he was an ASE certified mechanic at Chrysler for a long time and they got updated Technical Service bulletins on procedures all the time.
So I'm going to go with that advice when I change my oil, especially when the car hasn't been run for a very long time.
 
#20 ·
Very good point.
It does take several seconds for the pressure to build up and show on the gauge or for the oil light to go out.
The other thing is that oil pressure rises with RPM's and lowers at idle.
Things to check, clean and measure:
Voltage to the sensor.
Resistance of the sensor according to the service manual
Cleaning the connectors to the sensor ( DeOxit contact cleaner is great).
Cleaning the gauge terminals
Cleaning the harness connector to the gauge.

NOTE:
Never use any abrasive tool or material to clean contacts.
This will rub off the anti corrosive coating on the contact and will lead to repeated tarnishing.
Contact cleaners have to be checked for reactions to plastic.
There are some cheap contact cleaners that will melt plastic.

An excellent product to use is Caig DeOxit spray:
 
#21 ·
Related question, but the opposite:

How much oil pressure is too much?

My book says I should be at 6 PSI at idle. I'm at 18. This is with the engine fully warmed. When I rev to 3000 rpm, the pressure is ~72 psi, book says I should be 35-75. So I'm barely in the range. I'm worried that if I'm driving around before the engine is fully warmed up, is my pressure gonna be too high? How high is a damage-inducing pressure?
 
#22 ·
Is there a way to connect another known working, gauge and sender unit just to test the pressure?
It almost sounds like you have the wrong sender for that stock gauge.
 
#26 ·
I posted the Harbor Freight pressure gauge only because I assumed you would not want to spend more for a gauge that you may never use again.
The 6 PSI is the minimum pressure needed, below that the light will come on.
What is the pressure relief spec on the pump you installed?
 
#27 ·
NAJ:
I'm glad you brought up about the pressure relief spec.It reminded me that I read about different oil pressure relief springs, depending on the pump and application.


edthatalkinhors

If the spring is weak, or the pump installed is a high volume pump, then the oil pressure readings could be off.

If the Melling pump is built to stock specs, then it might be a good idea replace the original oil pressure relief spring with a new OEM one.

Also:
They made one stock oil pump for the 1981 through 1985 2.2L.
They made a different pump starting in 1986 and it was the same for the 2.2L and the 2.5L engines.
 
#29 ·
I cannot find a max pressure spec, the only spec I found is @ idle...
11.8 PSI (or more) @ 167 - 194 degrees oil temp.
(From Alldata)
If you are all together, car is running fine, no noises and you have proper oil pressure @ idle I would say you are good to go.
Just remember, with higher pressure it is an indicator of a good/tight engine.