Should I pull the distributor to prime the oil pump?

TrueTexas

TJ Enthusiast
Supporting Member
Joined
Feb 7, 2019
Messages
463
Location
The Woodlands, TX
Hey Everyone,
I cannot decide if I need to prime the new oil pump in my 4.0L

I have had the Jeep out of service for about 5 months to replace the Front Timing Cover Seal, timing chain and gears, RMS, Oil Pump, Oil pan Gasket, entire cooling system, pulleys etc... I did not touch the crankshaft or bearings, other than the rear bearing cap for the RMS. I also replaced the clutch and the AX-15 input shaft seal.

I am finally at the point where I am ready to start the Jeep.

Question is, should I pull the distributor and prime the oil pump to get oil to all of the internals or can I just crank it over a few times to get pressure up, then start it?
 
It's so easy I see no reason not to.
Also if you didn't prime it after changing the pump you will need to anyway. Either way you will feel better turning the key knowing you have good pressure.
 
I haven’t had to replace the oil pump on my jeep but I’ve always primed them on all my other vehicles and would definitely do it to my Jeep as well
 
I primed a new pump with a hand drill on a spare distributor shaft without the drive gear. I was surprised how long I had to spin it before it finally sucked up oil into the pump. I'd hate to run the engine that long without oil pressure.
 
We primed our oil pump in the oil pan before ever installing it, from what I read that was an essential part of the process for the Melling Oil Pump we installed. Once all bolted up we primed it with the valve cover off to see the air bubbles and oil actually pumping through the engine before starting it.
 
  • Like
Reactions: Squatch
Any one have anymore details on doing this? What is needed to drive the pump besides the obvious drill? which way do you spin the pump CW or CCW?

Thanks
 
Any one have anymore details on doing this? What is needed to drive the pump besides the obvious drill? which way do you spin the pump CW or CCW?

Thanks
We bought a really really long flathead screwdriver (biggest one possible probably), then sheared the handle off with an angle grinder, put that tightly into the drill and you'll spin it clockwise. For us, IIRC it took approx a half hour of priming before we actually saw oil pumping all the way up to the top with the valve cover off.

Note: It may not work unless your drill is very powerful and has a lot of juice. So make sure its fully charged and I would say at least 20v. The engine folks that we called beforehand said this method would not work sufficiently enough to prime it, but it did for us in the end.
 
Thanks. I'm definitely going to prime it. I couldnt find a flat end screwdriver socket that was wide or thick enough for the slot in the oil pump drive. So, I bought a 16" long 1/2" spade drill bit from Lowe's this morning. Gonna cut the blade end off and round the corners. It has a hex end on it and tapers so the final end on it will only be about 3/8" wide (the oil pump drive is 1/2").

The factory manual wants you to rotate the engine to TDC. It doesn't seem that I need to do this as long as I mark all of the reference points and reassemble exactly as I take out the distributor. Am I missing something here?
 
Thanks. I'm definitely going to prime it. I couldnt find a flat end screwdriver socket that was wide or thick enough for the slot in the oil pump drive. So, I bought a 16" long 1/2" spade drill bit from Lowe's this morning. Gonna cut the blade end off and round the corners. It has a hex end on it and tapers so the final end on it will only be about 3/8" wide (the oil pump drive is 1/2").

The factory manual wants you to rotate the engine to TDC. It doesn't seem that I need to do this as long as I mark all of the reference points and reassemble exactly as I take out the distributor. Am I missing something here?
For me, I had to rotate it to TDC because it was a whole new engine rebuild process. I believe if your just replacing the parts you may not have to.
 
Wanted to follow up on this thread.

First of all, thanks to everyone that chimed in telling me to prime the oil pump. It was 100% the right decision.

The tool that I made from the long spade drill bit worked perfectly. So for others that cannot find a tool, buy this from Lowes, then cut the blade off and grind it smooth.
IRWIN SPEEDBOR Extra Long 1/2-in Woodboring Spade Drill Bit

I started by using a piece of flexible tube and large syringe to push oil thru the outer hole of the oil filter housing to try to fill the pump. After installing the filter and adding 6qts of oil, I spun the pump with the tool above. I had the gauge come up to 40psi within 10 seconds. Ran it for another 20 seconds to ensure the internals got oil before I started it.

As other mentioned, it was super easy.
 
I read this thread around 10 PM last night before I went to bed. It was just a thread, not a bad one, just a thread. Similar to the 1/2" of snow we had at that time.

This morning I wake up, sit at the computer while eating breakfast and see this thread again. It's like the sun has come up. Totally opposite of the fact that it's still snowing here.
 
  • Like
Reactions: TrueTexas
One more thing, since this was not a new engine build, I did not rotate to TDC. I marked the rotor position on the distributor and then marked the oil pump slot once the distributor was out of the Jeep. Only had to pull the dizzy once to adjust the position of the slot in the oil pump before it just fell back in place.

And here is a picture of the tool I made.
IMG_20191112_163934.jpg
 
Was there an answer to the direction your turn the pump to prime? CW or CCW?

The answer is whichever way the distributor spins, that’s which way you spin the pump.

And now to answer the unanswered from 2019:

I’ll be the counter-point here and tell the story of when I changed out my pump. I read all the threads, watched all the videos. I spun that pump FOREVER and it never primed. I finally gave up and decided to let the engine prime itself, figuring that if I didn’t have any pressure for like 20 or 30 seconds it wouldn’t be catastrophic. When I fired it up I had pressure immediately. If I ever have to do it again, I’m gonna jump straight to this step and see what happens. ¯\_(ツ)_/¯

So to the person who said priming it was “absolutely the right advice,” I can’t say you were wrong, but from a scientific method standpoint you don’t know it wouldn’t have built up pressure immediately even w/o the prime. Likewise I don’t know that mine wasn’t one revolution away from being primed. IJS.

And for posterity and readers from the year 2300 or whenever this thread gets necro’d again, regarding the TDC question you CAN find TDC and re-set your distributor that way OR you can be careful about marking the orientation before you remove it and re-insert it the same way. There’s a how-to about how to replace your distributor the easy way which details this specific process.