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Thread: Isuzu diesel engine w/ zexel inline injection pump.

  1. #1
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    Isuzu diesel engine w/ zexel inline injection pump.

    Tomorrow I have to fix a fuel leak on a MQ25 wisperwatt generator and I'm looking for a little bit of info. The fuel is leaking out of one of the barrels on top of the fuel pump. I've got the O-rings already and an extra barrel incase its bad to. I wouldn't be to nervous bout this except my shop cant find the manuals for it.
    From what I can tell by looking at the new barrel, all I have to do is take the fuel injection line off, loosen the clamp that locks the 2 barrels together and pull the leaking barrel out?
    Anybody that's done this before that has any tips and info would be greatly appreciated!

  2. #2
    Super Moderator willie59's Avatar
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    I'm not an expert on Zexel pumps, but I'm near certain you're describing a delivery valve (barrel) that is height adjusted for proper flow timing. This is done at an injection shop by spotting the pump timing for each delivery valve and adjusting each valve by screwing delivery valves in or out to achieve proper timing. Once proper flow timing is achieved, the clamps that lock two delivery valves are fitted to prevent timing from being upset.

    About the best you can do in the field is remove the injection line, then take a dial or digital caliper and note the exact height of the delivery valve before you remove the retaining clamp. Upon re-installation, turn delivery valve in until that proper dimension is achieved.

    Remove delivery valve with care, you may find a seat, pintle, and spring inside there.
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    I was always under the impression too that delivery valves were height specific to delivery timing, flow, etc. I was working on an air compressor with an isuzu and I believe a zexel pump that needed a head gasket. When I took off the injection lines one of the DV's turned with the line and I thought I had really screwed the pooch. I turned it back to where I thought it was before and continued. After I got it running that DV leaked fuel. I told the boss and he told me just to tighten it down- it wouldn't matter. I gave it a little turn and it snugged up. Long story short this one just tightened down and it ran like a champ when i got done. I guess I would like to know which pumps use a specific height to the DV like ATCO said and which ones just thread in and bottom on a seal.

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    Thanks Atco. Yea I got to searching a little deeper into it and found a parts manual only so I looked up the nozzel. I saw all the different thickness shims! I think I'm gonna take a torque wrench and find out what torque it starts to break loose, note it down and put a mark on the barrel and the fuel injection housing to try to put everything back where it was in addition to the heighth.

  5. #5
    Super Moderator willie59's Avatar
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    Yep, the shims are how you adjust the flow timing for the whole injection assembly for TDC of #1 cylinder. But each of those delivery valves are set by an injection shop for proper flow timing of each individual delivery valve. The height from base of delivery valve housing to a given point of delivery valve is the best metric you can work with in the field.
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    Thanks...if I dont get rained out on that project tomorrow I'll let you know the outcome

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    Okay so 2 weeks ago this thing was leaking 2 gallons of fuel a day. I show up today to replace the seals and it would leak a drop. I dont know if one of the other mechanic's may have fixed it or if the forman tried to snug it up with a wrench and it stopped. I ran it for 20 minutes today and no leak. So I'll have to wait and see what happens.

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    Would not leak a drop *

  9. #9
    Senior Member rare ss's Avatar
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    I've had afew the bigger zexel pumps leak over the years, the orings fret the housing of the pump and you need to sleave seal surface to get it to last, you can change the seals but generally it'll leak again rather quickly

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