MEP002A Oil Pump

[Boonies]

Sorry I accidentally posted this 3 different times. That was unintentional.
MEP-002A I did and oil change. The generator ran normally for 1.25 hours and then suddenly died. While it was running I checked the oil pressure gauge several times. It was was registering just under 60 PSI consistently and steady. I know that is a little high, but I have had the generator since 2013 and it has always been 60 PSI every time I have ever checked it. When I move the start switch to the start position the generator will crank and start and immediately die. There is no movement at all on the oil pressure gauge while this is happening. Sounds to me like the oil pump? Do you agree? Is there anything else I should check first. I will check the oil pressure cut-off switch, but if the pressure gauge is not registering any pressure, the switch will not be closing anyway.
The technical manual is a little sketchy on the oil pump removal and install section. Can the oil pump be replaced from the end under the governor without removing the oil pan? If the oil pan must be removed, any suggestions on how to approach it. It looks like a monster job. The parts manual lists 3 different thicknesses for oil pump gasket. What do you measure and how do choose the right gasket.

 

[Scoobyshep]

If it were me id make sure there was no oil pressure (low oil can also cause issues) controls wise oil or temperature can cause an unexpected shutdown. Both can be jumped for testing purposes.

Sent from my SM-G973U using Tapatalk

 

[Ray70]

agreed. try jumping the temp switch first. Then if still no start, Jump the oil pressure switch.
To remove the oil pump you have to remove both the timing cover and the oil pan, and if I recall correctly you also have to pull off the gear on the crankshaft because the oil pump body is trapped behind the crank gear. This requires a couple long 1/4-20 bolts to make a puller as well as a little bit of heat, most likely.
So first you need to be 100% sure the oil pump is the problem.
Its fairly odd to go from 60psi to zero on your next startup.
Verify the simple things first.

 

[Chainbreaker]

Just out of curiosity...What year -002a and how many hours on Hobbs?

In the years I've been following the MEP-002a/-003a's here on SS I haven't heard of anyone experiencing an oil pump failure, if they have it hasn't been mentioned here that I recall. Does not mean it can't happen though.

Seems odd that after an oil change this problem came up. What viscosity oil did you use when you changed it? Any other changes other than oil chg?

Wondering if some internal crankcase crud somewhere broke free and is restricting the oil pressure sender. With your noted high oil pressure readings maybe there has always been a slight restriction somewhere causing elevated oil pressure readings?

 

[Boonies]

Thanks Ray, I jumped the temp switch and no start. I jumped the oil switch and it started and ran. Nothing on the Oil Pressure gauge (No bouncing or anything, just zero). I stopped it immediately in case it is the oil pump and no oil circulating. I removed the oil pressure cut-off switch and tested it with compressed air. The contacts close at less than 20PSI air pressure. I cranked the engine with the oil switch removed and no oil squirted out of the port where it mounts.
Also there is an error in my original post. I said the oil pressure while it was running was 60 PSI. The gauge does not even go to 60. I read it wrong. It was registering just under 40 PSI.

agreed. try jumping the temp switch first. Then if still no start, Jump the oil pressure switch.
To remove the oil pump you have to remove both the timing cover and the oil pan, and if I recall correctly you also have to pull off the gear on the crankshaft because the oil pump body is trapped behind the crank gear. This requires a couple long 1/4-20 bolts to make a puller as well as a little bit of heat, most likely.
So first you need to be 100% sure the oil pump is the problem.
Its fairly odd to go from 60psi to zero on your next startup.
Verify the simple things first.

 

[Boonies]

Just out of curiosity...What year -002a and how many hours on Hobbs?

In the years I've been following the MEP-002a/-003a's here on SS I haven't heard of anyone experiencing an oil pump failure, if they have it hasn't been mentioned here that I recall. Does not mean it can't happen though.

Seems odd that after an oil change this problem came up. What viscosity oil did you use when you changed it? Any other changes other than oil chg?

Wondering if some internal crankcase crud somewhere broke free and is restricting the oil pressure sender. With your noted high oil pressure readings maybe there has always been a slight restriction somewhere causing elevated oil pressure readings?

There is something different about the oil change. 8 years ago I installed a spin oil filter adapter. The filter I have been using the last 8 years is a Napa FIL1085 (It is a full flow filter as the TM specifies for the MEP-002A). When I did this oil change, I didn't have a FIL1085 available. The FIL1515 is identical except it is a little longer. The mounting hole and threads are ¾-16 for both. The gasket is the same diameter. They are both full flow. The only difference is that the 1515 is 59 cubic inches and the 1085 is 39 cubic inches. I don't see how this could cause a problem?

Also I had just completed replacing the genset rotor. The rotor end bearing had come apart and the exciter rotor collided with the exciter stator. The exciter rotor was shorted to the rotor assembly. The engine would run normally but there was no output power. I did not do anything to the engine during this process except the oil change. After the oil change and rotor replacement the generator ran strong as a horse under load for about 1.25 hours and died abruptly. I checked the oil level about 15 minutes into the 1.25 hours of running and it was to the full mark. (It is still at the full mark) I checked the oil pressure gauge several times during the 1.25 hours and it was constant at just under 40 PSI (In my original post I said 60 PSI but I had read the gauge incorrectly).

You asked about date and hours. I will have to go up the hill and get the date, I don't have it written down. In August of 2014 the hours were 871.9. They are now 6413.8 That is about 38 days per year average.
You also asked about the oil I use. It is Chevron Delo 400 heavy duty 15W-40. I have used this the entire 8 years I've had the generator including this last oil change.

 

[Guyfang]

7-13. OIL BY-PASS VALVE.
a. Test on Equipment (see figure 7-20). High oil
pressure may be caused by the by-pass valve plunger
sticking closed. Low oil pressure may be caused by
the by-pass valve plunger sticking open. If these conditions
exist, clean and inspect by-pass valve.

This is from the -34 TM. I would suggest you read the whole procedure. I did not copy it all. Like ChainBreaker, I have never seen a oil pump failure. But sure have seen a by-pass valve come apart, (twice) and dirt in the by-pass valve (twice).

 

[Guyfang]

I am confused. What gaskets? Page #, item # and figure #?

 

[Boonies]

I am confused. What gaskets? Page #, item # and figure #?

ARMY TM 9-6115-584-24P Parts Manual. Listed under:
KIT, GASKET. ENGINE Part #168-0135 (Page 17 There are 3 listings:
GASKET. OIL PUMP..003 IN THICK
GASKET. OIL PUMP..005 IN THICK
GASKET. OIL PUMP..009 IN THICK
They all 3 refer to Item #9 in Fig #50
There is not a separate part number for the 3 gaskets, just the kit #

 

[Boonies]

7-13. OIL BY-PASS VALVE.
a. Test on Equipment (see figure 7-20). High oil
pressure may be caused by the by-pass valve plunger
sticking closed. Low oil pressure may be caused by
the by-pass valve plunger sticking open. If these conditions
exist, clean and inspect by-pass valve.

This is from the -34 TM. I would suggest you read the whole procedure. I did not copy it all. Like ChainBreaker, I have never seen a oil pump failure. But sure have seen a by-pass valve come apart, (twice) and dirt in the by-pass valve (twice).

Thanks, I read the procedure. Sounds much easier than replacing the Oil Pump. Do you think that this could cause 100% stop on oil flow? It was also very sudden. I happened to be monitoring the oil pressure gauge and it was stable and constant at just a little below 40 PSI for 1.25 hours of run time prior to dying. (In my original post I said 60 PSI but I was reading the gauge wrong, it doesn't even go up to 60) If I remove the Oil Pressure cut-off switch and crank the engine not a single drop of oil comes out of the port the switch screws into.

 

[Ray70]

Seems very odd, but it is sounding like an oil delivery issue.
In that system I believe oil flows from the outside of the filter into the core then through the 3/4-16 tube and into the oil filter adapter housing, feeding the switch, the gage and the oil cooler as well as the engine.
Check the oil bypass and if this issue started immediately after you did an oil change I would also check for a defective filter.... I've seen it happen before.
You could try loosening the filter and start it for a second and see if oil sprays out from around the gasket, indicating a blocked filter.

 

[Chainbreaker]

Followup post deleted. Nevermind, I re-read your earlier 11:56 am above post and now see you already did the pressure switch jumpering.

 

[Guyfang]

Seems very odd, but it is sounding like an oil delivery issue.
In that system I believe oil flows from the outside of the filter into the core then through the 3/4-16 tube and into the oil filter adapter housing, feeding the switch, the gage and the oil cooler as well as the engine.
Check the oil bypass and if this issue started immediately after you did an oil change I would also check for a defective filter.... I've seen it happen before.
You could try loosening the filter and start it for a second and see if oil sprays out from around the gasket, indicating a blocked filter.

Indeed. This is where you should start. The by-pass or filter could cause this type of failure. The oil pump itself is very dependable. And, yes, its much easier to check the other things before going to the pump itself.

 

[Guyfang]

Now I see why I was confused. The 3 different gaskets are to compensate for wear in the pump. Looking at fig. #50, I was thinking about a simple gasket between the pump and engine. And could not remember ever replacing one. Having never in my whole time working with this set, never seen a pump go bad, or even taken apart, I forgot that the gear wear is to be measured, to figure out what gasket to use.

 

[Boonies]

Seems very odd, but it is sounding like an oil delivery issue.
In that system I believe oil flows from the outside of the filter into the core then through the 3/4-16 tube and into the oil filter adapter housing, feeding the switch, the gage and the oil cooler as well as the engine.
Check the oil bypass and if this issue started immediately after you did an oil change I would also check for a defective filter.... I've seen it happen before.
You could try loosening the filter and start it for a second and see if oil sprays out from around the gasket, indicating a blocked filter.

I decide to install a brand new oil filter just to be sure. It started and I held the start switch on so it would crank long enough to fill the new filter and build up pressure. Nothing on the pressure gauge and it died immediately when I released the start switch. I wanted to be sure I cranked it long enough to fill the oil filter so I removed the new filter and there was not a single drop of oil in it. I cranked it for about 15 seconds.
So my next step is the oil bypass.

 

[Boonies]

I decide to install a brand new oil filter just to be sure. It started and I held the start switch on so it would crank long enough to fill the new filter and build up pressure. Nothing on the pressure gauge and it died immediately when I released the start switch. I wanted to be sure I cranked it long enough to fill the oil filter so I removed the new filter and there was not a single drop of oil in it. I cranked it for about 15 seconds.
So my next step is the oil bypass.

In this last post when I said I cranked it 15 seconds to give the oil filter a chance to fill up. The engine was actually running 15 seconds, not just cranking with the starter. The start switch by-passes both the temp cut-off and oil pressure switches so it can start and run and it will stop when the start switch is released if either temp or oil switch are open.

I'm not sure what to do? When I was being encouraged to check the oil by-pass, I was not registering that the by-pass is behind the flywheel. I was thinking it was behind the gear cover by the oil pump on the other side of the engine. I must remove the generator and the flywheel to check the by-pass. This is a lot of work and if that isn't it, then I have to take the other end apart to get to the oil pump. Are there any other suggestions on how I can narrow it down to one or the other before doing extensive disassembly.

 

[Chainbreaker]

OK, just throwing some thoughts out here...

Wondering if its possible that the new oil filter had some foreign debris in it that came out after initial start up after the oil change, or something entered system during oil change, and plugged an oil passage?

It doesn't take much to block an oil passage. I once was changing oil in a motorcycle and while drain plug, oil filter and fill port were open & exposed a June bug beetle managed to somehow crawl inside and I didn't know it and it later clogged a breather tube return passage that made an oily mess. Stuff happens!

I haven't tried this... but perhaps you could remove the oil filter and blow some compressed air (I would start with a lower psi setting ~30 psi) to see if you can establish any air flow though oil passages where the filter spins on? You could also take off the oil pressure switch and blow compressed air back through that port. I would also blow air backwards through oil cooler & its lines. Maybe take apart the oil breather assy and clean it while off and blow air through its passage. There might be other locations to access oil flow as well. If there is anything lodged in those oil passages it just might free the blockage long enough to allow it to run to confirm & then re-drain oil.

It just seems odd that this started after your new oil/filter change and right after oil change it ran for over an hour & suddenly quit, knowing now due to apparent loss of oil pressure.

 

[Boonies]

OK, just throwing some thoughts out here...

Wondering if its possible that the new oil filter had some foreign debris in it that came out after initial start up after the oil change, or something entered system during oil change, and plugged an oil passage?

It doesn't take much to block an oil passage. I once was changing oil in a motorcycle and while drain plug, oil filter and fill port were open & exposed a June bug beetle managed to somehow crawl inside and I didn't know it and it later clogged a breather tube return passage that made an oily mess. Stuff happens!

I haven't tried this... but perhaps you could remove the oil filter and blow some compressed air (I would start with a lower psi setting ~30 psi) to see if you can establish any air flow though oil passages where the filter spins on? You could also take off the oil pressure switch and blow compressed air back through that port. I would also blow air backwards through oil cooler & its lines. Maybe take apart the oil breather assy and clean it while off and blow air through its passage. There might be other locations to access oil flow as well. If there is anything lodged in those oil passages it just might free the blockage long enough to allow it to run to confirm & then re-drain oil.

It just seems odd that this started after your new oil/filter change and right after oil change it ran for over an hour & suddenly quit, knowing now due to apparent loss of oil pressure.

Thank you for the tips. Do you know if there is anyplace where I could cause damage by doing compressed air

OK, just throwing some thoughts out here...

Wondering if its possible that the new oil filter had some foreign debris in it that came out after initial start up after the oil change, or something entered system during oil change, and plugged an oil passage?

It doesn't take much to block an oil passage. I once was changing oil in a motorcycle and while drain plug, oil filter and fill port were open & exposed a June bug beetle managed to somehow crawl inside and I didn't know it and it later clogged a breather tube return passage that made an oily mess. Stuff happens!

I haven't tried this... but perhaps you could remove the oil filter and blow some compressed air (I would start with a lower psi setting ~30 psi) to see if you can establish any air flow though oil passages where the filter spins on? You could also take off the oil pressure switch and blow compressed air back through that port. I would also blow air backwards through oil cooler & its lines. Maybe take apart the oil breather assy and clean it while off and blow air through its passage. There might be other locations to access oil flow as well. If there is anything lodged in those oil passages it just might free the blockage long enough to allow it to run to confirm & then re-drain oil.

It just seems odd that this started after your new oil/filter change and right after oil change it ran for over an hour & suddenly quit, knowing now due to apparent loss of oil pressure.

Problem solved!!!! I tried the compressed air and could not find any blockages. I was not looking forward to either doing the oil pump or the by-pass valve because of the major disassembly involved. I decided to flip a coin and the oil pump won. I removed the blower fan and took off the gear cover and a gear dropped on the ground. It was the drive gear for the oil pump. It had sheared off of its shaft. I unbolted the oil pump but the oil cup that extends down into the oil pan cannot fit through the oil pump opening. I think this is why they say you have to drop the oil pan. I fiddled with it a while and found I could unscrew the pipe between the oil cup and the pump and get the pump out. If anybody ever has to do this in the future, be careful when you unscrew the oil cup because if you drop it back into the oil pan, you are screwed. Might be able to fish it out with a magnet if you are lucky.
One other thing is that when you put the oil cup back on the new pump you must be extremely careful that you get it in the correct orientation. If it is not in the right position in the oil pan the crankshaft could possibly collide with it and the you have some big problems. (I haven't done this part yet).
Since I got the oil cup off I do not have drop the oil pan and the repair suddenly became pretty simple. I was not too concerned about debris from the failure in the oil pan since the gear that sheared off is totally outside of the oil pan and external to the pump. Just to be sure I took a magnetic parts pickup wand and fished around all over the inside of the oil pan through the oil pump mounting hole. There was nothing on the magnet!
Don't know why the gear sheared off. There was some minor damage to one tooth on the pump gear. Looks like it could have happened during the process of it shearing off. No damage to the inside workings of the pump itself (I took it apart).
Found a pump for $99 but 10 to 15 days shipping. I need the generator ASAP. The next best was $299. Should be here Wed, Thu, or Fri. I will let you all know when I got it installed and running!
If anyone wants photos, I can supply them.
Thanks to everybody for all the help!!!!!
One more thing. In my original post I mentioned the different sized gaskets in the parts manual. Those gaskets are internal to the pump and don't have anything to do with mounting it. The mount is inside the gear cover so they did not need or use any gaskets. So the only time you would need to be concerned with those gaskets is if you wanted to rebuild the pump. I guess Guyfang already pointed this out.

 

[Chainbreaker]

Wow glad you found the problem! This is the first ever oil pump failure I have heard of on a MEP-002a/-003a. I wonder why the oil pump drive gear decided to break off at 6,414 hours? Wonder if there was an inherent defect in the gear shaft metallurgy all along and years of heat/cooling thermal cycling plus time took its toll? Glad that it didn't suffer a more catastrophic failure with significant engine damage!

If you have the time it would be great if you could post some close up photos of where the break occurred on that gear shaft and of the gear toothed portion.

 

[Chainbreaker]

Here is some info I pulled from a copy of an Onan DJB manual that may help:

"OIL PUMP The oil pump is mounted on the front of the crank case behind the gear cover and is driven by the crankshaft gear. Rem oval: 1. Remove gear cover and oil base. (See ENGlNE 2. Unscrew intake cup from pump. 3. Remove crankshaft lock ring and gear-retaining 4. Loosen two cap screws holding pump and DlSASSEMBLY section.) washer. . remove' pump.

Repair: Except for the gaskets, component parts of the pump are not individually available. If the pump is defective or excessively worn, replace it. Disassemble the pump by removing the two cap screws holding the pump cover to the body. Inspect for excessive wear in gears and shafts. To improve pump performance, adjust the gear end clearance by changing the gasket thickness between the pump body and cover. Use the thinnest gasket that permits free movement of the pump shafts. Oil all parts when assembling the pump.

Installation: Before installing, fill-the pump intake and outlet with oil to be sure it is primed. Mount the pump on the engine and adjust the 0.005-inch (0.127 mm) lash between the pump gear and crankshaft gear. Mount the intake cup on the pump so it is parallel to the bottom of the crankcase.

Here are some torque settings that may be helpful:

TORQUE SPECIFICATIONS Ft.-Lb.

OIL Pump Mounting Screws 15 - 20 Ft Lbs