MEP-002 Injector pump replacement question

tkmo061

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Picked up a couple of MEP-002's from a third party that were supposed to be in 'running condition' and now I have a new hobby on my hands as they are anything but. Both are original, low hours units but appear to be suffering from lack of use and both have what appears to be bad injector pumps. I have been lurking on the boards for the last month and have learned a great deal this forum...so a huge thanks to those who have gone before in getting these working.

I picked up a couple of new pumps for a great price and am ready to install the first. I have pulled the old pump and was all excited to do my button calculations but now cannot find the port closing dimension anywhere on the old pump. The button size (13) is stamped right where it is supposed to be. Have any of you experienced MEP-heads found the number in a different location? Am I stuck doing timing method #2 or is there a way to figure this out on the old pump? Also, could use some advice on the most gentle method to get the tappet out to get to the button.

Thanks!

Ryan
 

RichardR

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Austin, TX
Ryan,

The Port Closing (PC) dimension of the IP is supposed to be stamped or marked with an electric pencil on the same side of the mounting flange as the button number stamping. http://www.ambac.net/images/IF_No._3136.pdf page 3 shows where the numbers are SUPPOSED to be. But I have often seen them reversed or marked on a different side of the mounting flange. Sometimes the PC dimension marking is VERY FAINT when done with an electric pencil. And the format of the PC dimension is often given with 4 decimal places like 1.XXXX, rather than the 2 decimal places shown in the example.

If you cannot find the old PC dimension and you have to utilize flow timing (method #2), that's not so bad because I believe you can be more confident in the result.

The tappet can be gently extracted by using 2 flat-blade screw drivers on opposite sides of the tappet inserted into the groove around the face of the tappet. You could do it by gripping the tappet with your fingernails in the groove, but you'd have to have really strong fingernails and I cannot do it that way. Anyway, the tappet will come out with only moderate force because it is held in only by a rubber o-ring.

Hope this helps,
Richard
 

tkmo061

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Progress

Thanks for the advice. I took a brass brush and solvent and cleaned off the edges of the pump and found the number so I'm good to go with ordering a #16 button. I also was able to remove the tappet, but could now use some advice on the best way to remove the retaining ring for the button. Thoughts?
 

RichardR

Member
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Location
Austin, TX
epitts is correct regarding retaining ring removal. Just slip something sharp like a dental pick under the ring and it will easily come out before you expect it to do so. The ring is known as a "jesus ring" because that will be the first word out of your mouth when the ring flys out and sails across the room, never to be found again. If/when that happens, you can order a couple of extra jesus rings with your #16 button. The nice lady at AMBAC will know what you need even if you don't have the part number.

Actually, I believe you can read the number off the currently installed button without removing the ring and button. Just tilt the button to one side and the number should be visible as shown here, last picture of this post. You should confirm that the current button is really a #13 before ordering the #16 button.

Richard
 

tkmo061

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Waukesha, WI
Thanks again for all the good advice. To clarify, I finally figured out how to remove the tappet in the brand new pump, not the old one. What I thought was the button, must not be because what I'm looking at looks nothing like the picture link with the button with the number 14 on it. I'm thinking my new pump doesn't have a button installed, which would explain why I'm having a hard time finding it aua. The manual also mentions that a button is not installed by default (makes sense).

I have not been able to remove the tappet in the old pump as it is currently flush with the bottom of the pump, and I can't get any traction on it to pull it out.
 

RichardR

Member
96
3
8
Location
Austin, TX
Yes, the new pump probably has neither the button nor the jesus ring. You can use the ring from the old pump (unless it has magically disappeared during removal), but you'll have to order a new button of the correct size unless you get lucky and one of your old pumps has the correct size for you to re-use. The button is made of very hard material so an old button should be re-usable without wear concerns if it is the right size. However, it sounds like you need a button 3 sizes larger than the one you have, whatever size that is, so you need a new button in any case.

You'll have to be inventive to get the tappet out of the old pump. The basic problem is that everything inside the old pump is stuck from sitting too long with old fuel in it. The piston is stuck in the "up/in" position, which has the return spring compressed so that it can't press out on the tappet. You could soak the entire pump in a solvent like carb cleaner or lacquer thinner. That's very harsh on the seals, but it may not matter at this point. A more direct approach would be to remove the stuff on the top of the piston (see the diagram) and AS GENTLY AS POSSIBLE drive the stuck piston down. The tappet should move with the piston. A solvent/lubricant liberally applied will help.

Then again, none of this matters if you believe the old pump has a #13 button and you need a #16 for the new pump. You'll can just order a #16 button and the retaining ring from AMBAC or wherever you plan to get them. The only reason for dissembling the old pump is to confirm the button size and to retrieve the retaining ring.

Richard
 
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