PeachParts Mercedes-Benz Forum - OM617A Rebuilder question

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Quote:

Originally Posted by Brian Carlton (Post 1799539)

X2.

barry123400 PMed me I am trying to write an answer. In my previous post I was describing part of what is done when the pump is off of the car and in the fuel injection shop to be rebuilt. My point was is that the Plunger and Barrels are not routinely replaced when a IP is rebuilt as they are some of the most expensive parts on the IP and as long as you have good clean uncontaminated fuel the plungers and barrels will oulive your engine. They are replace when they are no good.

Quote:

Originally Posted by Diesel911 (Post 1799700)

It would seem to me that the plungers and barrels suffer wear over many millions of cycles. Since there is no seals, the very slightest bit of wear will cause a drop in pressure in the barrel and the performance of the IP will be off.

It would appear that the shops don't make the effort to actually measure the plungers and the barrels..........relying on the fuel delivery at idle as a measure of performance.

This is a bit disconcerting.........to pay $1000. for a "rebuilt" IP with plungers and barrels that have 250K on the clock doesn't seem quite right to me.

Quote:

Originally Posted by barry123400 (Post 1799531)

Can you describe paremeters of the start up test on the plungers and barrels? Also if you are static timing a pump just with gravity feed fuel oil on a car. If you reach your normal shutoff point but the element continues to leak as you go by it at say a drip a second. Is that that plunger and cylinder still considered serviceable?
I personally would think not. If it leaks that bad with virtually no pressure what is going to happen when expected to work at normal operating pressures? A partial flood past the piston? Also I would think it might indicate some other bores or pistons in the injection pump could be even more worn. Less worn is a possibility as well i guess.
How is this going to affect milage as well if you have this kind of wear. One last question since I am a little on a roll here with a guy who has worked proffesionally on piston injection pumps. It seem reasonable to me that a pump internally leaking in this fashion also would even have more difficulty if it was hot. Therefore making hot starts even harder or impossible.
Any comments welcome as we very seldom if ever have the presence of an individual that has worked on the pumps at sometime or another.
Please also excuse what I would think are pretty elementary questions to you. The urge to know the answers is strong though perhaps by many on this site as well as myself. Sorry about the semi hijack of this thread as well.
Metric rebuilders just might know where there is a recent rebuilt engine of theirs with very little time in a car that is either for sale, smashed or whatever. This may be worth talking to them about as well.
The engine warranty might even be transferable. Butter them up with I would not like to see an engine that I had rebuilt go to waste either if possible. Chances are nobody else may have taken this approach . Whats there to lose?:rolleyes:
Also dropped diesel 911 a private message to please drop back here if he has a little time. His past experience, knowledge and hopefully advise are more than welcome. Just thought he may not normally cruise down this thread again. We cannot risk him being the one that got away as well at this point. :D

Can you describe parameters of the start up test on the plungers and barrels?-- I was describing what was done when the pump is on the test stand inside of the shop not on the car. The idea of the test is to duplicate what the fuel output during a hot start. I do not know the specific spec. on these particular pumps but the pump is run from 300-350 rpm (also there is a set of calibrated test injectors hooked up the pump with the hard lines). You hit the button and the machine gathers 1000 strokes of fuel output from each of the pump elements into graduated measuring tubes. You compare that amount of fuel to the spec. sheet. If it is not putting out enough fuel the plunger and barrels in the pump are worn out (and if the pump was on a car after it gets hot the car may have trouble starting).
So the fuel either goes out to the injectors or it squeezes by the plunger and barrels; when the pump and the fuel is hot more of it squeezes by the plunger and barrel.
Also if you are static timing a pump just with gravity feed fuel oil on a car. If you reach your normal shutoff point but the element continues to leak as you go by it at say a drip a second. Is that that plunger and cylinder still considered serviceable?- The static pump timing (also called I believe the Drip Method) is used to check the start of delivery of the fuel that would be going into the injector. If you have reached the degree mark on the engine damper (as per the Manual) and you are getting more drops per minute the Manual tells you the injection pump timing is not correct and you need to rotate (advance) the IP until it meets the manuals specs. Not much of the above has anything to do with fuel leaking past the Plunger and Barrel (due to wear) as the gravity feed pressure is not enough to effect it.
The 2nd paragraph starting with -I personally would think not. And Ending with--Therefore making hot starts even harder or impossible.---Again gravity feed pressure used on the static timing has nothing do with the worn plungers. If the Plunger and Barrels are worn enough and enough fuel is leaking past them less fuel gets to the injectors and makes it hard to start the car when the engine and fuel system are hot. When the fuel is hot it is thinner and more easily flows through the clearances.
If you have an IP that has an extremely large amount of miles on it, or you know that water (especially if it sat inside IP for several days), or dirty/contaminated fuel got inside the IP, you have eliminated all of the other less expensive causes, and having hard or no start when the engine and fuel system is hot you might begin to suspect the IP as the problem.

I am not familiar with Metric Motors but all rebuilder are looking for good cores to rebuild with.

The main point of my origional post was that when an IP is rebuilt the pump will be calibrated to the origional/or updates specs. but Plungers and Barrels are reused unless they are no good.
If you want the Plungers and Barrels replaced you need to ask them to replace them (the cost will go up) and make sure they do not give you and exchange pump. It is also a good idea to tell them that you want the old parts saved and given back to you. It is also a good idea to get an itamized list of parts replaced; an invoice with something like "pump rebuilt $1,000" and nothing else dose not tell you much.

Quote:

Originally Posted by Brian Carlton (Post 1799706)

In practice it works ok. I described only part of the process of the rebuild the way they did it in the 1st shop I worked for (close to 5 years). I worked for 3 months at another shop that had a contract with a Internationl Dealership. On the Dealership pumps we replace all of the P&Bs.
Some things cannot be measured; as an example a tiny piece of something goes into the P&B and scores it. If the score mark is not on the side of the plunger where the fuel is metered (the Helix side). It may not put the fuel output out of spec. That same score mark on the fuel metering area will cause erratic fuel delivery meaning you may have good fuel delivery at idle but when you test it at full load the delivery quantity will be low. So you adjust that element to give the correct full load fuel delivery; but when you drop back to idle not the idle quantity is too high. So you need to get rid of that P&P and put in a new one.
As for measuring the P&Bs the tolerances are to close to be measured manually. The shop I worked in did not have one of these but the Air Gauge uses compressed air and you measure I believe how much air flows around the mating parts. Shops that rebuild the Cummings injectors where the hone the old injector bodies to fit oversized plungers have that sort of equipment.
P&Bs where I worked were inspected visually (with a magnifier) and you ran your thumb nail over side of the plunger up at the top where the Helix is. If it was scored you could feel it with your thumb nail.

One of our customers owned a bunch of trash trucks and was a maintenance fanatic when it came to oil and filter changes. He wore out 3 engines using the same IP on all of them one after the other. Finally the advance mechanism inside of the pump just fell apart and he had to bring the IP in.

I think your last paragraph really says all that needs to be said.

I have changed pumps more than once on my cars at the advice of mechanics who did not know enough to really say. Replacing a pump has never solved any of the problems being chased...hence I have good pumps lying around as a result.

It will take a huge amount of convincing to ever get me to change another pump on a 616 or 617 engine.

I will change mechanics before I will ever change a pump again.

Tom W

i rebuild my own engines,only the cranks are outsourced if they fail the specs.
problem with my service is that i havent got the history behind me yet,25k is the most miles i have on any rebuild,that one (91 350sdl will get another trip from louisville ky to key west fl next week)
i plan on offering a service that will be complete for those that want to keep their old diesels,service will only be provided with the engine being installed by my shop.
it would be interesting to hook up with some one who drives like 50k a year to use one of my engines as a trial unit.
will keep the forum informed.
larry perkins lou ky

Quote:

Originally Posted by larry perkins (Post 1799943)

it would be interesting to hook up with some one who drives like 50k a year to use one of my engines as a trial unit.
will keep the forum informed.
larry perkins lou ky

..........Craig is your man........