Priming my oil pump

[ocwd]

I purchased and RMC engine a few months back. The engine came from a generator set. I should be removing the GPW engine from my M38 sometime next week. After that I will install the RMC engine with the bell housing and starter to check compression on the RMC engine. The RMC engine has been sitting around for a while so I will be draining the oil and replacing it with fresh oil. Also, I will put some oil in the spark plug holes and turn the engine. I did a search here using "priming AND oil pump" with no results.

What is the proceedure for priming the oil pump?

Thanks,

Dave

[Ryan_Miller]

check out this thread.

Read the last posting as it is a good way to pre-oil the system. I am planning on doing this myself on a freshly rebuilt engine soon.



Ryan

http://www.willysmjeeps.com/v2/modules. ... pic&t=2165

[ocwd]

Thanks Ryan. I knew I had read that post before but it was not coming up in a search.

[wesk]

You can also use a pressure pot and plumb it to one of the left side oil gallery plugs.

[ocwd]

Having never done this before, I am not familiar with a pressure pot. From the thread that Ryan posted, it looks like I can fill the oil pump with oil than turn the engine over. Is there a section in any of the TM's that describes this operation.

I got the GPW engine out with no problems. It's amazing that the starter was able to start that engine as some of the teeth on the ring gear were in bad shape. I never noticed any starting problems. In fact, the engine started up strong every time. I guess i'll be looking for a new fly wheel too. I suppose I could buy the ring gear and have it pressed on the old flywheel. I'll try Midwest Military.

[Ryan_Miller]

Hey,

I am not sure what a pressure pot is either.

Yes you can buy a new ring gear and have it pressed on.

John should have them.

[wesk]

A pressure pot is a steel bottle you fill with oil and then attach an air hose to pressurize the bottle and then the oil will feed under that pressure through a hose used to attach to the oil gallery on the engine.

When a rebuilder or manual specifies the need to "Pre-Oil" they are referring to the act of pressurizing the entire oil system of the engine adequately enough to ensure a positive flow of oil goes to all parts of the system. The priming of the oil pump and cranking the starter with the plugs out is the crude shade tree mechanic method which is usually adequate but remember the oil pressure gage tap is only 3" aft of the oil pump and just because the gage needle moves slightly is no guarantee you have oil throughout the system!

You really don't press the ring gear on. You heat and tap the old one off then you freeze the flywheel and oven heat the new ring gear and the new gear will tap right on.

There are 3 jeep ring gears. The 97, 124 and 129 tooth. WWII and CJ2A use the 97 tooth with the small frame MZ4113 or MZ4124 starters. Early M38 and CJ3A use the 124 tooth with the small frame starter that uses 1/2" mounting bolts. Late M38 use the 129 tooth as do the M38A1, late CJ3A, CJ3B, CJ5/6 and so on. This 129 tooth ring gear is used with the large frame, closed nose starter that mounts with 5/8" bolts.

[ocwd]

I bought a 129 tooth ring gear a few months ago. Then I realized that I have an early RMC engine and an early starter so I now have the wrong ring gear. I was going to use the ring gear from the GPW engine until I pulled the bell housing and noticed the damage to some of the teeth. I have two willys engines in storage that still have the ring gear attached so I'll check those out to see if they are the right size before I buy one from John.

Now that I think of it, the bell housing may be incorrect also. The aftermarket 12 volt starter was mounted with two large bolts. I did not measure the size.

[maeserik]

I filled the oilgallery and turns the engine in the oposite way so the oil goes into the oilpump, i filled the rest of the oil in the crancase, put a mechanical pressuregauge on the engine, and crank it with the starter without plugs ( no compression ) and you will see the pressure build up, easy to 10 psi. ( the oil is still cold ).Then you can be sure the pump is primed and gives pressure. put the plugs in and fire the engine up....

when there is oil in the pump ( no air ) she will start to pump when you turns the engine in the right direction

easy to do

Erik

[ocwd]

Thanks Erik. Hopefully, I will get to my engine this week end some time.

Dave

[wesk]

The 129 tooth late M38 ring gear uses the bellhousing with the 5/8" starter mount bolt holes. This 129 tooth ring gear fits too tightly in the early bellhousing and actually rubs on some and the 129 tooth ring gear is not to be used with the early small frame starter which uses a bell with 1/2" starter mount bolt holes.

[ocwd]

Wes,

I'll have to count the teeth on the ring gear that was on my GPW engine. The top bolt that held the starter on was definately bigger than 1/2".

Dave

[Cacti_Ken]

Here is how I pre-oiled the engine. Use starter to rotate crank while pushing oil into galley.

http://www.surfacezero.com/g503/showpho ... hoto=43311

[maeserik]

An old club friend of mine, just put oil in the pump before assembling it on the engine. He filled the cranckase with the right amount of oil, start it up and after a few seconds he had oilpressure. No priming at all. After a rebuild there is enough oil on the parts for 30 seconds on idle speed he said. He rebuilded several engines in the past( cj3a willys, GMC Belgian Army). When you stop the engine, after a few hours the oilgallery is nearly empty. So every cold startup the pump has to fill up some oil into the gallery before you get pressure. Therefore it is not good to push full trottle directly after the start. With some egines you hear the rods knocking for a little moment when you do this. That is his opinion ( 75 year old ex military mechanic )

just as info.

[Cacti_Ken]

The reason for me doing what I did was because the engine was not installed and run for almost 4 years after the rebuild. I did it as a precautionary measure.