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Thread: MEP 805A Fuel Help Please!

  1. #11
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    So here is my update after about 4 more hours of aggravation this afternoon! I started with the MPU. Upon touching the wires one of them fell out of the connector so I quickly repaired that thinking I had found my issue. No difference! I checked the ohms and only get around 1.3 ohms between the 2 wires so I’m guessing it is bad anyway? I am completely hard headed and could not get it through my mind how this could stop my fuel when I had run a 24v jumper straight to the injection pump shut off in theory bypassing the complete starting system on the machine. I had to dig a little deeper! I removed the top cover from the IP that houses the electric solenoid and found everything inside completely frozen up from water I suspect? I sprayed everything with blaster and began to pry things back and forth ever so slightly. Then I moved the shut down linkage to the point I thought should be on and I immediately got fuel out the injector side of pump! After a little bleeding I was able to fire it up! The internal linkages are still kinda tight to slide back and forth so I coated everything good with penetrating oil and left it to sit. I wanted to see if the generator would generate but not sure it will work before I replace the MPU? I don’t know the exact startup procedures for this unit? There is no documentation on the unit that I have found? I guess I will see what I learn tomorrow!

  2. #12
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    You are assuming. Don't assume the MPU is bad, till you test it. What you need to do is read the TM. But since you won't, try testing the MPU. Disconnect both wires from the MPU. Connect a multimeter to the wires set up for AC voltage. Have someone use the S10 dead crank switch to spin the engine over. You should get 3 volts AC from the MPU if it's adjusted right. Having seen Roberts pictures, you can see, the MPU can pick up grease, dirt and metal chips. I would pull the MPU first, to ensure that it dosnt look like Roberts picture. That can and will through off readings. Clean it first. Then screw it down until you bottom out. Turn it back 3/4 turn, (I always do a full turn, as I am that way) then lock down the nut, hand tight. Have someone spin the engine. What you want is 3 volts AC. If it's low, then turn it in, a tad. Test. Low, turn it in a tad. You get the picture. Turn it too far in, you get to buy another one. Get it adjusted right, lock it down.

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    Macondo (08-26-2019)

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    I did remove it after to check and everything looked clean. I saw someone had posted the ohm reading should be I think between 900-1200. Mine being only slightly over 1 I was already sourcing a new sensor? I have been reading through the 300 page books but by the time my internet gets one downloaded and open, and I search through it, I’ve just not run across the right one yet. I will get the sensor sorted later this afternoon I hope as well as freeing up the internals on my injection pump so we can start checking for voltage. I found last night, I have a parts unit about 20 miles away at a neighboring fire department that quit generating but has a good running engine so at least I have a few parts available! Thanks

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    I was able to pull up each manual Regis morning before my kids got up and overloaded my internet speed! I will re check ohms in the control panel this afternoon as well as voltage and see where I get from that. Any additional tips on freeing up the governor or shutdown parts in the top of the injection pump? I’m not 100% sure how free these linkages should be or if I need to go further down the IP to clean any of the rusted areas up? This is a great website and I’m so glad I found it! Hopefully by hurricane time this year we can be ready!!

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    4 Star General Guyfang's Avatar
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    I would get a good MPU and install and adjust it. You can by one from trucking repair shops. There is a thread where 155mm had the same problem and where he bought his replacement. Perhaps Robert can also chime in here. Then give it a try. Since you have removed the actuator, keep in mind that it has to go back in right. The yoke has to slide in just right, to actuate the IP. If you get it in wrong, wont start. So look at it real good before you start, take your time. Once you do it one or two times, its easy. Unless the top of the IP is rusted up, it should be OK. The MPU is the key to the whole set. It doesn't work right, NOTHING works right on the set.

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    Search msp6729 on the big auction site. It is 3/8-24 unf-2a. Should be under $20.

    Robert

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    Guyfang (08-24-2019)

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    Another helpful hint is this. If you find a mag Pickup that fits the hole, it should work. They are all about the same.

  10. #18
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    So here is what I have learned today. The top of the IP does have a fair amount of rust. After soaking last night in penetrating oil, everything moves a little more free than it did but it still needs more soaking/ working! I re installed the MPU per TM direction and then disconnected the two wires from the governor control unit and had approximately 1.3 volts while cranking. I re adjusted it and got it up to 2.3 volts by screwing it in 1/8th of a turn. I still have the top off the IP so I’m controlling the engine rpm and shutdown manually at this point. I started the engine and let it warm up a few minutes and tried to close the switch to activate the generator and nothing?? I tested the bulb and it does burn. I found the info in the manual on ohming the switch and it seems to work fine. Have not found what lines I should be seeing voltage on or how to check that? The 6 connector switch only has 4 wires hooked to it. I have 24volts on the #2 and #3 connection but nothing on the ones hooked to #5 or #6. No idea how to even begin diagnostic testing on the generator side? I have slight electrical knowledge but do have a decent digital meter? I will start reading through the info in the TM’s for my next move on this? Thanks again everyone!

  11. #19
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    Would I be better off to start a new post to get responses about the electrical side? I know it is moving off topic from my original post??

  12. #20
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    I know I am going to sound like a nag again. But you need to read the book. In the operators manual it explains how this set works,

    When you turn S1 on, to the start position, a number of things happen. But the MPU drives them all.
    1. The MPU tells the Electric gov. To start the engine. Without the apron 3 VAC signal, the from the MPU, the electric Actuater will not get a signal from the elect gov, set will not start.
    2. At a predetermined RPM, the MPU tells the electric gov to kick the starter out of operation.
    3. You have to hold the S1 up longer on TQG's to get excitation, so when the starter gets kicked out, the MPU also tells the electric gov to allow the initial excitation to happen. That voltage comes from the S1.

    The he most commen reason no output voltage is people do not hold the S1 up long enough. So if you did not hold up S1 for 4-5 seconds longer then the starter ran, that might be a reason.

    Also, is the Quad MWO installed on your set? Have you checked the fuse?

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