MEP-003A

[Ray70]

You don't need to test with the lines totally disconnected, just loosened. Things may look a little different than I described if the lines are removed completely off the injectors.

 

[Johncar48]

Thanks for your input. I'll pull the cap and valve out of the IP again and check for correct installation. Even though there is fuel getting to all injector when I pull the lines off, there seems to be no fuel actually getting to cylinders 1 & 2. Absolutely noting coming out of the stack when cranking after heating glow plugs for 45 seconds. I will insure the valve is assembled EXACTLY as the TM shows. If I'm paying close attention, it would be hard not to put it back together correctly. If all this does not work, is it hard to check the IP timing and would you need any special tools please? Also, is it OK to use a little grease around the valve to hold it in place while screwing the cap back on. I did this before and it seemed to work well.

 

[Ray70]

Once you confirm the delivery valve is ok, you can try doing the static timing test as described in the TM. This may show you if the plunger guide has skipped or not. I would assume that you will find the timing to be completely wrong if it has.
While you are in there, try doing a visual check to see if the plunger is both rotating and moving in and out as you rotate the motor by hand from the blower wheel bolt.
AND, just for giggles, look at the tag on the right side of the pump and see if it is an Ambac M-50 ( blue tag ) pump or an American Bosch PSU ( black tag )
And yes, I would think a little grease would be ok to use to hold things in place.

 

[Johncar48]

Looks like it is a Bosch...black tag

 

[Ray70]

Uh, Oh! not a good sign. Now look closer and see if is says M50 or PSU on the tag. We recently found a case where a member had an early M50 that was actually built by Bosch in Italy and had a black tag , prior to Ambac taking over and using blue tags.
The M50 is a serviceable unit, the PSU does not use a plunger guide and if the plunger and drive pin are broken the pump can not be repaired.

 

[Johncar48]

I just noticed, it looks like the engine has been sprayed with black paint. I've never seen one that was black so perhaps the tag was pained over as well. Won't know until I can inspect closed.

 

[Johncar48]

The black tag does say Model 50 with a bunch on alpha/numeric numbers after that and shows a button size as well.

 

[Light in the Dark]

As an aside... I know the Bosch unit appears slightly different from the Ambac unit. Does anyone have both kinds they could photograph to show the difference?

 

[Ray70]

The only external visual difference is the large flat head screw pointing straight down from a boss cast into the center of the main body housing underneath.
PSU has the screw and M-50 only has the undrilled boss cast into the housing.
I have several " Junk" pumps lying around ( unfortunately ) so I'll take a comparison pic. later today.

 

[Ray70]

Here we go... side by side photo. Finger is pointing to the screw in the PSU pump. That is the only visual difference on the outside that I know of.... besides the Tag.

 

[Light in the Dark]

That is excellent, thanks Ray. Its a more easily discernable variation than I realized.

 

[Light in the Dark]

If someone had a bad PSU unit, can the Ambac be dropped in its place? I assume the answer is yes... I've been lucky with air cooled machines thus far.

 

[Ray70]

Absolutely, the Ambac M-50 will drop right in, just need to check the timing button thickness. Everything else is the same.
I'm actually considering taking apart a good PSU ( have 1 good machine with a PSU in it ) and taking the plunger to a machine shop to see about the possibility of getting some new ones fabricated. I have 4 bad pumps that could be repaired if I had access to plungers.
Would be interesting to see what is involved in fabricating a dozen or so new ones.
Need a machine shop with precision centerless grinding capability I assume.

 

[Johncar48]

Hopefully I dodged a bullet. Mine does not have the screw.
Does anyone know of a good MEP-003A mechanic in the San Antonio, Texas area.

 

[Johncar48]

Ray th plunger is moving in and out and rotating as I crank the engine over by hand.

 

[NY Tom]

Absolutely, the Ambac M-50 will drop right in, just need to check the timing button thickness. Everything else is the same.
I'm actually considering taking apart a good PSU ( have 1 good machine with a PSU in it ) and taking the plunger to a machine shop to see about the possibility of getting some new ones fabricated. I have 4 bad pumps that could be repaired if I had access to plungers.
Would be interesting to see what is involved in fabricating a dozen or so new ones.
Need a machine shop with precision centerless grinding capability I assume.

What does the plunger look like?

 

[Johncar48]

Are you suggesting I pull the plunger out? Here is a pic looking into the pump.

 

[Johncar48]

Here's a pic of how the TM says to reassemble everything in order

 

[Ray70]

No, you can not pull the plunger out. You need to disassemble the pump to take the plunger out.
As long as it's rotating and pulsing that's enough for now.
If the plunger guide or drive pin in the case of a PSU was broken the plunger would not turn.
Your assembly sequence is correct.
I'd put it back together and try the static timing test to see if something is way out of whack.

 

[Ray70]

Here is a picture of the PSU plunger from the TM.
It's about 5/16" diameter with a slot on one end, the thru-hole is for the drive pin ( which is why they snap right at that hole )
It pumps the high pressure fuel, so the diameter is precise and polished, I presume hardened based on how they snap....
I will have to disassemble a good pump off a running machine to take exact measurements etc.