Oil Pump woes

[garage gnome]

If you've been living under a rock, you probably haven't heard that there have been lots of issues with new oil pumps for your 134 cu in 4cyl. Willys engine. I myself had this issue with the pump locking up and snapping teeth off stuff. Fortunately, mine only broke the oil pump teeth. Some have had the cam teeth break off.

The best way to tell which pump you have is simply look at the cover. The new ones have the pressure release built into the cap. The old style has the pressure release built into the housing.



The internals are totally different too.



One thing I noticed while taking these pictures is the old style pump has an oil galley on the housing so oil can get to the shaft. The new one does not. I wonder if this is the problem with the new ones? You can see the missing teeth on the left side of the gear on the new one.




So here's the scoop, if your original oil pump works fine and your engine had good oil pressure, reuse the original pump. My engine rebuild kit came with the stuff to rebuild the original pump, gaskets and the relief spring.

Mine was properly installed. I had primed it properly and when the engine was running for the first 5 min, it had great pressure, 40 psi, then it shut off because the distributor quit spinning. Mine was a Melling. When I rebuilt the V6 in the Jalopy, I used a Melling pump. I know they make good pumps, but for some reason these just don't work. The drive shaft in my pump is what locked up. The idler gear falls right out into your hand. As you can see in the pictures too, there if very little wear on the cover. So I have no idea why this happened.

[1955CJ-5]

Thanks for those pictures. I still have my old oil pump. I've read so many negative things about the new pumps I wonder if I shouldn't look for a rebuild kit and rebuild/re-install the old pump.

The engine never ran with the old pump since I bought it, the head was already off and I just pulled the engine and had it rebuilt, so I have no idea as to the old pumps  output......

The new pump puts out 40 psi right from startup...

[garage gnome]

If your new pump has been working fine, I wouldn't worry about it. Most people have had them lock up in the first few minutes of the very first startup.

[terryb]

well after looking at the pics. that garage gnome posted,  I do have the new style pump on my willys. it has the relief valve in the cover. its the pump that came on the jeep when I got it and this jeep sat in a barn for about 25 yrs. before my father n law sent it my way for $1.
all the pumps I've found on the internet are the new style, so my question is,  is there anything that can be done to the pumps to keep this from happening again.
thanks again willys lovers,
terry

[David]

Gentlemen, I've been a mechanic and eng builder for 60 yrs. Melling WAS always a good pump. Few people had trouble w/ them. I always rebiuld and blueprint the original pump on every eng I do. Many antique rare engs have no parts available so I make my own. Ocassionally a pump will be broken so I find another used one to rebuild. My understanding from my warehouses is Melling has been having the pumps made in China for the last few yrs. A lot of failures. I always dismantle and verify a new pump when supplied. The seizures and problems w/ the Mellings is w/ pumps for all brand engs, not just these 134s. I suggest the rebuild route. David

[F Bill]

Gentlemen, I've been a mechanic and eng builder for 60 yrs. Melling WAS always a good pump. Few people had trouble w/ them. I always rebiuld and blueprint the original pump on every eng I do. Many antique rare engs have no parts available so I make my own. Ocassionally a pump will be broken so I find another used one to rebuild. My understanding from my warehouses is Melling has been having the pumps made in China for the last few yrs. A lot of failures. I always dismantle and verify a new pump when supplied. The seizures and problems w/ the Mellings is w/ pumps for all brand engs, not just these 134s. I suggest the rebuild route. David

Sounds like you have some experience with the Melling failures...In your opinion what exactly is causing the current crop of Mellings to fail??

[David]

F Bill, All clearances are poor fits. Rough surfaces. Many burrs on housing and gears. Just no quality control at all. Another real problem I've found is the built in pressure relief valve will "hang " open partially or fully and they'll be low or no pressure. this problem can be erratic. I'm seeing this on Flathead Fords and hear many complaints on the subject. That's why I rebuild the originals. Never have a problem. Parts of the Stephentown 3B will live on. David

[Gunslinger]

I cant talk to the Melling pump issues, but I do know that the Felpro Gasket sets that you buy for the 134 rebuilds do not have the right thickness gaskets in them.� I had a good original pump, it generated 40 psi, however when we rebuilt the motor, doing our Due diligence we put in the new gasket, 3 miles later the pump locked up, tore three teeth out of the pump gear, and stopped the motor.� I then purchased a NOS gasket, measured it and put it in the pump, 3000 miles later no issues.� The gasket sets the head space for the pump, if it is too thin it will lock up the pump when the motor warms up.
Gun

[David]

Gunslinger, That's one of the problems w/ people "rebuilding" their pumps. The gasket does not set the "head space" as you called it. (a new term to me). It is the responsibility of the installer to know these things. You can't blindly think the gasket is correct. It usually isn't. The "body to gear" end clearance must be verified accurately taking into account that gasket. Either trim the gears, the body or eliminate the gasket to obtain no more than .002". Orig gskts are typycally .002-.003". Most kit ones are much thicker creating low pickup suction and low pressure. Everybody is worried about lash between gears. It is NOWHERE as important as gear end play. David

[1955CJ-5]

So,

I retrieved the old pump from the storage unit...

It has an aluminum body and concentric gears.

It had .002" end play between the drive gear and shaft housing before I took it apart.

The clearances between the inner and outer rotor are .007, the book recommends no more that .010. and between the outer rotor and the case is .006. Well within limits.

Of course the new gasket is thinner than the old, but only by .001~.002"

I will check the other clearances according to the book...

Then? I don't know.....

[garage gnome]

Thanks for getting the aluminum pump on here too Randy.