MCI Engine Manual, Oil pressure sending unit location

[JPonLKN]

Does anyone have a 4 cycle Robbin engine tech manual specifically for the MCI engine? I have one that I used for a pre-mci rebuild, and most of the differences are identified with pop out windows labeled as "Newer Model". One of the differences that is not identified in the manual is the placement of the oil pressure sending unit. Both of the MCI engines I have here have the sending unit on the side of the engine case cover. The manual shows it on top of the case side cover. If anyone has a newer manual that shows the set up for the oil sending unit on the side of the case side cover, can you please post a clip of set up? Better yet, if someone has an MCI engine case side cover off the engine and can photograph what the pathway is between the old oil sending unit location on top of the case cover to the side. Did the check ball and spring move as well, or is there simply a passage that extend over to the side from the original check ball location?

Also, can we re-use the head gasket on these engines? Has anyone done it with success? This engine may have to come apart several times....had to have to buy a bunch of head gaskets for it if it isn't needed.

Thanks

[trig123]

Originally Posted by JPonLKN

Does anyone have a 4 cycle Robbin engine tech manual specifically for the MCI engine? I have one that I used for a pre-mci rebuild, and most of the differences are identified with pop out windows labeled as "Newer Model". One of the differences that is not identified in the manual is the placement of the oil pressure sending unit. Both of the MCI engines I have here have the sending unit on the side of the engine case cover. The manual shows it on top of the case side cover. If anyone has a newer manual that shows the set up for the oil sending unit on the side of the case side cover, can you please post a clip of set up? Better yet, if someone has an MCI engine case side cover off the engine and can photograph what the pathway is between the old oil sending unit location on top of the case cover to the side. Did the check ball and spring move as well, or is there simply a passage that extend over to the side from the original check ball location?

Also, can we re-use the head gasket on these engines? Has anyone done it with success? This engine may have to come apart several times....had to have to buy a bunch of head gaskets for it if it isn't needed.

Thanks

I have never seen the the engine manual just for the MCI engine but not saying there is not one out there.

They only made these engines four years so I would think they would be hard to find.

I have a MCI engine torn apart less the block and flywheel at my shop
I can snap a picture later today of the cover if you want.

I know people who have used the same head gasket and nothing happened. I have never did this but yes it has been done.

CP241 fought an oil pressure issue with one he had a while back.

You shouldn't have to prime these pumps when rebuilding but I always do in case it don't start with pressure. I also don't trust the oiling system on the MCI engine but once working they seem to be good. It don't take but a second to trash the head and cam if it is run very long with no pressure.

I also know there was a o-ring shipped with some gasket sets that was too thick and caused issues. It was too much space between the oil pump cover where it bolts up causing cavitation . I think I got the original oil pump cover and o-ring off this engine also. I will have to look later today

[JPonLKN]

Originally Posted by trig123

I have never seen the the engine manual just for the MCI engine but not saying there is not one out there.

They only made these engines four years so I would think they would be hard to find.

I have a MCI engine torn apart less the block and flywheel at my shop
I can snap a picture later today of the cover if you want.

I know people who have used the same head gasket and nothing happened. I have never did this but yes it has been done.

CP241 fought an oil pressure issue with one he had a while back.

You shouldn't have to prime these pumps when rebuilding but I always do in case it don't start with pressure. I also don't trust the oiling system on the MCI engine but once working they seem to be good. It don't take but a second to trash the head and cam if it is run very long with no pressure.

I also know there was a o-ring shipped with some gasket sets that was too thick and caused issues. It was too much space between the oil pump cover where it bolts up causing cavitation . I think I got the original oil pump cover o-ring off this engine also. I will have to look later today

Thanks Trig123. CP241 sent me links to his nightmare, and another, and I have found others. I think there are several issues that cause the various problems, all stemming from the need for the pump to create suction to pull oil up to the pump rather than having a pump in the sump to push oil. I'm curious if the movement of the oil sending unit also moves the check valve, or if the two locations are simply connected by a passage. Using a mirror and flashlight, I can see up in the hole the sensor came out of, but can't really tell what I am looking at, or more likely, can't see clearly enough to tell what is in there. That pick of the inside of the side cover in that area would be fantastic. I have a feeling CP241's issue was the ball and spring, which he swapped out along with his rod caps just before the issue went away. Of the two, the ball and spring at the sending unit seems more likely. I'm curious if I am having the same issue. I'm going to pull the valve cover and turn it over to see if I am getting oil up to the top of the engine in a bit. If I am getting oil to the valve train, then its simply an oil sensor issue.

The other possibility is that the oil pump o-ring is the issue. I'm not sure who rebuilt the engine, but I know it was one of the shops in Appling GA, near Augusta. It was done a couple years ago, got delivered without a flywheel, fan, and cover, and sat on the bench for two years. Fast forward two years, I "acquired" a flywheel from a generous BGW member , and an ignitor from another generous BGW member , installed the engine and fired it up, only to find an oil light. Yes, I put 1.5 qts of oil in it. As I understand it, reading through the threads, the rebuild kits being used by M&M on these had a period of poorly sized oil pump o-rings. That was about the time this thing was re-built, so that could be the issue. Who knows if they installed the o-ring at the top of the case. Considering that the engine came back without all the parts, I am not confident they put everything back together inside correctly, or with OEM parts. I was hoping not to have to tear the engine apart, but its looking more and more like that is what will have to happen. If you have the oil pump cover and o-ring, I might be interested if the price is right.

I'm gonna go and check to see if I have oil at the top of the engine first...

[CP241]

I did swap the check ball and spring in mine. Twice actually. And found pinhole in the side cover in the oil pump housing. And numerous other issues. I worked on that POS for way too long and took it apart far too many times. I traded that cart for a blown up 2016 Honda foreman and couldn’t be happier bringing in a different POS but... at least the new POS was something engineered correctly. Just abused.

Despite being in that (and other) mci engines more times than I can count, I still have absolutely no clue how that cam gets lubrication.

I’d start by pulling the oil pump cover off and look at the o ring. If it’s big and fat and sticks over the top of the recessed ridge, it’s not right. It should be pretty much flush. And check the cover for any signs of bending or distortion at all. The MCI oil pump covers are thinner than the pre-mci ones and have a tendency to distort easier causing issues.

I scrapped the spare side cover I had with the pin hole. But I’ve got a side cover fir a Kawasaki FE290 in my stash

[JPonLKN]

Originally Posted by CP241

I did swap the check ball and spring in mine. Twice actually. And found pinhole in the side cover in the oil pump housing. And numerous other issues. I worked on that POS for way too long and took it apart far too many times. I traded that cart for a blown up 2016 Honda foreman and couldn’t be happier bringing in a different POS but... at least the new POS was something engineered correctly. Just abused.

Despite being in that (and other) mci engines more times than I can count, I still have absolutely no clue how that cam gets lubrication.

I’d start by pulling the oil pump cover off and look at the o ring. If it’s big and fat and sticks over the top of the recessed ridge, it’s not right. It should be pretty much flush. And check the cover for any signs of bending or distortion at all. The MCI oil pump covers are thinner than the pre-mci ones and have a tendency to distort easier causing issues.

I scrapped the spare side cover I had with the pin hole. But I’ve got a side cover fir a Kawasaki FE290 in my stash

No need for the Kawi side cover...thanks though. LOL

Quick update: I went out to my other running MCI machine, pulled the oil cap, and turned it over a bit, just to see if oil would show itself at the cam. It does, and it kinda squirts in from above the cam on the oil cap side of the head. I did the same with the engine I am currently working on, and again...I get oil at the cam. Good news, she is pumping oil. How much pressure, I don't know, as it isn't getting to the sensor. I'm guessing the ball and spring are simply stuck, not letting oil in the passage. I wonder if simply running the engine might free it up over time, or clear whatever debris is in there causing it to stick.

[JPonLKN]

Update: I need to do some wiring evaluation. I have oil pressure to the valve train when running as evidenced by lots of oil in the head over the cam, viewed from the oil fill cap after running...runs fine. Need to do some adjusting as it is real jerky on take off. Might be belt, primary clutch, or the throttle/accelerator cable, but it starts and runs great.

Whenever the accelerator microswitch engages, the gas gauge maxes out and the oil light comes on. Clearly, something is either shorted, or mis-wired. We will see.

[trig123]

Originally Posted by JPonLKN

Update: I need to do some wiring evaluation. I have oil pressure to the valve train when running as evidenced by lots of oil in the head over the cam, viewed from the oil fill cap after running...runs fine. Need to do some adjusting as it is real jerky on take off. Might be belt, primary clutch, or the throttle/accelerator cable, but it starts and runs great.

Whenever the accelerator microswitch engages, the gas gauge maxes out and the oil light comes on. Clearly, something is either shorted, or mis-wired. We will see.

Page 129 of the manual I sent you has the wiring diagram in it . Here is a screen shot of it

[CP241]

Just note, the oil light and gas gauge are both wired to the key switch. The key switch gets power from the microswitch in the pedal box. So if the pedal is not depressed, there is no power at the key. Ezgo wired it this way on purpose for some reason. Everybody else feeds power to the key switch first.

But this is also why the gas gauge and oil light will only work when the pedal is depressed. It can be wired differently so key switch gets power first, I’ve done it several times to power stereos and stuff. But just keep that in mind while you’re tracing it down

[JPonLKN]

Originally Posted by trig123

Page 129 of the manual I sent you has the wiring diagram in it . Here is a screen shot of it

Thanks Trig123!

[JPonLKN]

Thanks CP241!