phughes69

I am putting my other engine back together and when I was priming the pump tonight, I could feel the gears chattering or binding. I'm using the Melling 10778 pump in this motor. My other engine that I rebuilt that has the same pump didn't not make or feel like this. The noise happens EVERY revolution with the drill motor. I even spun the drill slowly and I can feel it. I even put a pair of vice grips on the priming tool and while turning it by hand I can feel it. It is not the misalignment between the pump and driveshaft. The noise is happening every 360 degrees. Has anyone else had problems with melling oil pumps. When the pickup was welded to the body, the bottom plate WAS removed to not damage the spring. If the pump body was warped from the welding heat, wouldn't the pump feel stiff ALL the time while turning. This stiffness is ONLY once per revolution.

Budman II

iTrader: (1)

phughes, saw that you tried to PM me. Sorry, did not know my MB was full. Cleared now.

I imagine you are going to ask me about my issue with the same pump several years ago. In my case I am pretty sure a piece of slag might have gotten into the pump from when the pickup was welded on. The guy who welded it got a little carried away with trying to get good penetration. I'm not absolutely positive that this is what caused it, because I also had severe spalling on several cam lobes that send metal throughout the motor, so it is possible that the pump ingested this as well.

The second time around I had a local builder braze the pickup, and for extra insurance I fabricated a bracket that was tack welded to the end of the pickup, and then went under one of the cover bolts to ensure that it won't go anywhere this time.

If you think the pump is an issue don't run it. It is not uncommon to feel a little bit of "catchiness" with the gears, but if it is binding, there is probably something wrong. Pull it apart and get the gears out of it and check them over.

Good luck with it.

phughes69

Yes I was going to ask you the same thing I wrote. I have felt pumps before that do have the "catchiness" but that feels smooth and it happens more frequently than this issue I'm having. The motor is coming back out to at least pull the pump off. When the pump body was welded, the gears and bottom plate were removed.

mike tkach

iTrader: (3)

did you prime the pump before bolting it on the main cap?if yes,how did it feel then?EDIT IN.also,did the pickup get welded all the way around or just partially?

phughes69

I did not prime the pump before bolting it to the main cap. The oil pump bolt is still there original one, not a ARP replacement bolt. The pickup was just partially welded to the body, maybe about 1/4 of the way or less. The place that did the welding only does welding, so it was not their 1st time

phughes69

The jerkiness I felt started right from the beginning

mike tkach

iTrader: (3)

mellings instructions say to prime the pump by hand with oil before installing it on the maincap.also,the 10778 is a cnc body and runs tight tolerances.if to much heat is transfered to the housing during welding it can distort it.just food for thought.if you go on the mellings website they have some very good information that is worth reading.i only do a partial weld on the pickup and try not to get the housing to hot.i have done a lot this way with no problems.my guess is mellings will deny a warranty claim on it after the welding.

mike tkach

iTrader: (3)

most oil pumps will feel that way if turned without oil in it.that goes away with oil,at least it is suppost to.

phughes69

I pulled the pump out tonight and found the cause of my problems. Initially when I would turn the pump by hand in a bucket of oil, you could not feel anything, Then I clamped the pump in the vise with the outlet partially blocked (to create pressure) and you could feel a slight hesitation. When I disassembled the pump I found impact marks on the drive gear. The impact marks just happened to line up in the same sport where the pump would get stiff They were large enough to feel with your nail. I got a new pump and disassembled it and inspected the gears. I found very slight marks on that one too but they were not as bad. I smoothed the nick down with scotch bright and it went away. I'm going to see if I can get Melling to warranted the pump.
Here is a picture of the drive gear with the worst mark. I think I counted a total of 4 marks on the gear.

mike tkach

iTrader: (3)

when you clamped the pump in the vise you really distorted the housing rendering it junk.i really doubt they will warranty that pump.