MEP-531A surging/hunting

[djdalfaro]

Hi guys, new to the forum. I just picked up this MEP 531a and I'm trying to get it running smoothly. I've gotten to the point where it stays running after starting, but it's surging an hunting and not smoothing out. I have read what I've found on the forum concerning ensuring the oil is not too full, and I drained the old oil, and have added about 600mL of fresh oil which brought up the level to the full mark with the dipstick screwed in. Any advice or suggestions to point me in the right direction would be greatly appreciated.

MEP-531a rough running

 

[LuckeyD]

Good Day: Open TM 9-6115-673-13&P to page 0013-1 and 2. Follow the steps. this will either resolve the issue or narrow it down to a couple possibilities. It is usually a fuel issue, or something related to it. Let us know what you find! Cool!

 

[djdalfaro]

Good Day: Open TM 9-6115-673-13&P to page 0013-1 and 2. Follow the steps. this will either resolve the issue or narrow it down to a couple possibilities. It is usually a fuel issue, or something related to it. Let us know what you find! Cool!

Thank you. I've got new filters and fuel line coming in so I will replace those, flush the fuel, and start with the troubleshooting list.

 

[FarmingSmallKubota]

do yourself a favor and make sure the fuel line between the filter and fuel pump is clear so that you can see air in the line and bleed accordingly.

 

[djdalfaro]

do yourself a favor and make sure the fuel line between the filter and fuel pump is clear so that you can see air in the line and bleed accordingly.

Thank you. Yes, I had seen the recommendation and new Tygon line should arrive tomorrow along with new fuel and air filters. One thing I know is contributing to my issue which will get fixed is the port elbow for the fuel pump supply is missing an o-ring, and so I know I'm getting air in the fuel system at that point. I noticed some sputtering at that point and when I hold the elbow down the running characteristics do change. I'll replace it when I do the rest of the fuel system in the next couple days.

 

[2Pbfeet]

Thank you. Yes, I had seen the recommendation and new Tygon line should arrive tomorrow along with new fuel and air filters. One thing I know is contributing to my issue which will get fixed is the port elbow for the fuel pump supply is missing an o-ring, and so I know I'm getting air in the fuel system at that point. I noticed some sputtering at that point and when I hold the elbow down the running characteristics do change. I'll replace it when I do the rest of the fuel system in the next couple days.

Good catch. These engines are quiet intolerant of air in the fuel.

All the best, 2PbFeet

 

[djdalfaro]

Ok guys, I've got an update. I went ahead and purchased a new Yanmar injection pump as my existing pump suction elbow had failed and was allowing air into the fuel at that point. I'll probably send it off to have it repaired so I can keep a spare on hand. This appears to have solved the issue of allowing air into the fuel line, and the hunting/surging issue...

However, I still seem to be running at higher RPMs and I'm getting weird readings from my multimeter (hz setting attached to 120v output). My generator hz meter is still pegged when running. This leads me to believe I have an issue with the governor. According to the manual, with the switch in run, the governor lever pointer should be centered. My old pump just had "o c", my new one does have a center mark, and when the governor is in run, the pointer is WELL to the right of center. The only way I am able to get the pointer aligned to the center mark is by extending the adjustment screw on the fuel injection limitation screw well past the specified dimension. I would appreciate if someone could open their access cover and post a picture of where their pointer sits both at run and at stop. The manual just states that if the motor is over RPMs to check the internal governor for damage. I had a thought that replacing the springs on the governor might work, and I will try that with some springs I have sitting around, but if there is an internal governor issue, I will have to dig into the motor deeper.

Video below:
MEP-531A high RPM

 

[Guyfang]

Ok guys, I've got an update. I went ahead and purchased a new Yanmar injection pump as my existing pump suction elbow had failed and was allowing air into the fuel at that point. I'll probably send it off to have it repaired so I can keep a spare on hand. This appears to have solved the issue of allowing air into the fuel line, and the hunting/surging issue...

However, I still seem to be running at higher RPMs and I'm getting weird readings from my multimeter (hz setting attached to 120v output). (What are Weird readings?) My generator hz meter is still pegged when running. This leads me to believe I have an issue with the governor. (What you need to do is establish what you have for a Hertz reading on the gen set output. Then you can decide what to do. Just because the meter is pegged, doesn't mean that the output is to high. And "still seem to be running at higher RPMs" is not proof that it is. ) According to the manual, with the switch in run, the governor lever pointer should be centered. My old pump just had "o c", my new one does have a center mark, and when the governor is in run, the pointer is WELL to the right of center. The only way I am able to get the pointer aligned to the center mark is by extending the adjustment screw on the fuel injection limitation screw well past the specified dimension. I would appreciate if someone could open their access cover and post a picture of where their pointer sits both at run and at stop. The manual just states that if the motor is over RPMs to check the internal governor for damage. I had a thought that replacing the springs on the governor might work, and I will try that with some springs I have sitting around, but if there is an internal governor issue, I will have to dig into the motor deeper.

 

[LuckeyD]

In TM 9-6115-673-13&P work Package 64 it says how to adjust and put in order the external governor and speed settings. The actual governot inside the engine that acts on the fuel rack on your injection pump is not mentioned well. Recommend trying the WP64 stuff before going inside the engine. You can see the action it does if you remove the injection pump and observe the rack and move the plunger the external speed adjustment mechanism acts on and how that is working. I have an engine book from Yanmar and the actual governor inside is not well mentioned, but it does say how to tear down and rebuild the engine if you have to go there. It will eventually be available in the TM section if it is not already there. Easy to complex OK.

 

[djdalfaro]

Culprit found. New internal governor in the mail. Thanks guys!

 

[djdalfaro]

Ok guys, I've got an update. I went ahead and purchased a new Yanmar injection pump as my existing pump suction elbow had failed and was allowing air into the fuel at that point. I'll probably send it off to have it repaired so I can keep a spare on hand. This appears to have solved the issue of allowing air into the fuel line, and the hunting/surging issue...

However, I still seem to be running at higher RPMs and I'm getting weird readings from my multimeter (hz setting attached to 120v output). (What are Weird readings?) My generator hz meter is still pegged when running. This leads me to believe I have an issue with the governor. (What you need to do is establish what you have for a Hertz reading on the gen set output. Then you can decide what to do. Just because the meter is pegged, doesn't mean that the output is to high. And "still seem to be running at higher RPMs" is not proof that it is. ) According to the manual, with the switch in run, the governor lever pointer should be centered. My old pump just had "o c", my new one does have a center mark, and when the governor is in run, the pointer is WELL to the right of center. The only way I am able to get the pointer aligned to the center mark is by extending the adjustment screw on the fuel injection limitation screw well past the specified dimension. I would appreciate if someone could open their access cover and post a picture of where their pointer sits both at run and at stop. The manual just states that if the motor is over RPMs to check the internal governor for damage. I had a thought that replacing the springs on the governor might work, and I will try that with some springs I have sitting around, but if there is an internal governor issue, I will have to dig into the motor deeper.

I was getting 300-500 hz on my multimeter. It can be seen in the video. However I also noticed at least one of my brushes was broken. I'll be replacing that as well. Thank you.

 

[LuckeyD]

Great job! Lets hope all goes well on the put back together.

 

[djdalfaro]

A little bit of an update. I did replace the governor with no problem. The Yanmar part number is 714770-61700. A couple points to note on the replacement.

1. I used a puller to remove the broken governor. Slow steady pressure and it will pop off the pin that goes through the lubrication oil pump shaft. This pin slides very easily and I could see it getting lost if the shaft it tilted.

2. When you are installing the new governor, ensure you place the spindle in the weights and onto the shaft before pushing the new governor down completely. Once the governor clicks into place on the pin, the spindle is held in place on the shaft by the weights.

3. It sure would be awesome to have this piece made of metal instead of fragile plastic.

I have not run the generator yet as I still have a broken brush to replace.

Searching for the replacement brush referencing the part number found in the TM (640-00000) was not very fruitful, as I believe the part number has been retired. Looking up the NSN (5977-01-105-6201) a new part number was found (BP5255BR00SP) but still no simple source was found.

I found another post on this forum which referenced a brush company (Ohio Carbon Industries) and a part number (111505. After some discussion with the technical experts, there was some initial concern about the carbon composition of DC vs AC brush, however after their review of pictures of my brushes and some discussion in their office, they confirmed the part number and stated the concern was unfounded. Unfortunately it was not in stock however they stated they had the carbon bodies available and would just need to attach the spring, wire, and terminal. I am passing this information on to the community. At the time of posting, the cost was $14.28 per unit, and I ordered 12. I will update this post once my lifetime supply of brushes arrives, with a picture of the new brush compared to the old brush and any concerns I have.

MEP-531A alternator brush
NSN 5977-01-105-6201
TM part no. 640-00000
New Baldor part no. BP5255BR00SP

Ohio Carbon Industry part no. 1115058
Carbon brush grade class MG
.938 x .188 x .188 0/0
Style G3

Ohio Carbon Industries, Inc
1201 Jacobson Ave
Ashland, OH 44805
P: (88 248-5029
F: (419) 207-0088
sales@ohiocarbon.com

 

[Tinstar]

Excellent information

Thank you