Gerald Morris
Senior Member
I purchased an ostensible Muskegon MM63 NOS oil pump on eBay this Monday, which at $65 looked too good to be true. So it was. I got a reasonably brand new looking pump with a tag lettered with HM63, NOT MM63, but I was willing to allow for that IFF it worked properly. So I removed my venerable, turquoise painted pump which looks like the original for this motor, yet still delivers ~ 55 #/in^2 cold, and installed the "NOS" pump in hope of modest improvement without need to reprime it ever so often such as after Church on Sunday as happened last weekend.
It delivered ~ 47 #/in.^2 for the 30-40 sec. I ran the engine, along with an increasingly UNHOLY loud ticking noise which convinced me a quick shutdown was in order. This noise was NOT anything like my tappets or such, and sounded a LOT like some bit of something hitting something else rotating. Bad as this was, the SHOWSTOPPER came as soon as the motor stopped, I heard a BIG WET **** SOUND of OIL being ejected somewhere it shouldn't have come from. The quart or 36 oz of oil I saw on my nice hiking pad, which I'd used for comfort and cleanliness confirmed this. Oil had come out right around or from the HM or MM 63 Muskegon pump. I went indoors, got on eBay and initiated a return; then contacted Assurant, mindful of Stan's Wise Words on how defective items returned yesteryear now get pawned to folks as NOS when in fact they're DOS w D for DEEEEFECTIVE! Bedtime.....zzzzzzzZZZZzz
In broad daylight this morn, I replaced Mathilda's original pump, again carefully primed with Vaseline and all was back to normal. I noted that this Muskegon pump's pressure relief valve piston is fluted at the far end from the 7/8" hex head retainer, unlike the original, and it doesn't slide as far. I removed and examined this carefully, noting that the spring seems strong, as a "new" spring ought, and that the rotor indeed meets spec tightness in accord with the FSM. My Question now: Would a stuck pressure relief valve cause the noise when running, then the violent ejection of motor oil closeby that I experienced?
Note also that the piston in the original pump freely slides into the second chamber, allowing relief thus I surmise but is solid, not fluted. I will post pictures tomorrow since these certainly will provide more data han my damned prose since I plan to change my oil back to 10-40W for warmer weather to come and I probably will have to help the old pump a little w priming again.... Your thoughts will be appreciated. I know that my last oil pump quandary was allieviated by unsticking the pressure relief valve, and given how simple these pumps are, there doesn't seem to be much else that can go awry with them outside of wear.
It delivered ~ 47 #/in.^2 for the 30-40 sec. I ran the engine, along with an increasingly UNHOLY loud ticking noise which convinced me a quick shutdown was in order. This noise was NOT anything like my tappets or such, and sounded a LOT like some bit of something hitting something else rotating. Bad as this was, the SHOWSTOPPER came as soon as the motor stopped, I heard a BIG WET **** SOUND of OIL being ejected somewhere it shouldn't have come from. The quart or 36 oz of oil I saw on my nice hiking pad, which I'd used for comfort and cleanliness confirmed this. Oil had come out right around or from the HM or MM 63 Muskegon pump. I went indoors, got on eBay and initiated a return; then contacted Assurant, mindful of Stan's Wise Words on how defective items returned yesteryear now get pawned to folks as NOS when in fact they're DOS w D for DEEEEFECTIVE! Bedtime.....zzzzzzzZZZZzz
In broad daylight this morn, I replaced Mathilda's original pump, again carefully primed with Vaseline and all was back to normal. I noted that this Muskegon pump's pressure relief valve piston is fluted at the far end from the 7/8" hex head retainer, unlike the original, and it doesn't slide as far. I removed and examined this carefully, noting that the spring seems strong, as a "new" spring ought, and that the rotor indeed meets spec tightness in accord with the FSM. My Question now: Would a stuck pressure relief valve cause the noise when running, then the violent ejection of motor oil closeby that I experienced?
Note also that the piston in the original pump freely slides into the second chamber, allowing relief thus I surmise but is solid, not fluted. I will post pictures tomorrow since these certainly will provide more data han my damned prose since I plan to change my oil back to 10-40W for warmer weather to come and I probably will have to help the old pump a little w priming again.... Your thoughts will be appreciated. I know that my last oil pump quandary was allieviated by unsticking the pressure relief valve, and given how simple these pumps are, there doesn't seem to be much else that can go awry with them outside of wear.
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