Rebuilt Engine Break-in

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Well, it goes back into the shop tomorrow morning to have all these items checked. This is a non-turbo, but everything else will be checked. I have a suspicion that this may be due to a badly-timed injector pump, but time will tell. The engine is very flat from a standing start, and is flat on the top end, but seems to have more-or- less normal power in between.
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Non turbo...
1. Valve adjustment... if too tight, you lose compression and power.
2. Fuel injection timing is off... it goes on one way but if timing chain is off on the injector pump, it is real possible.
3. Timing chain is off... very unlikely if this is done by the pro.
4. Vacuum pump... non turbo diesel still uses vacuum to control a various functions that does affect engine performance.
Let us know what was the problem.
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Will do, and thanks for this list.
As of this afternoon, the shop informs me that it is changing the cam shaft. I would have thought that the cam shaft specifications would have been checked during the engine rebuild, but at the moment, I am trying not to second-guess the M- B technicians. It does make sense, that if the cam was out of tolerance, then it would be difficult to time and to time the injector.
I should have another report in the ongoing saga tomorrow.
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Keep us up to date. I would like to know what was the real culprit.
If the camshaft was worn, the valve would not open as much as it should have and less power. But you gotta have a really badly worn cams to get to that level of performance you described...
Before you had it rebuilt, was the engine that bad in power? You know what I mean... performance wise?
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Actually, no, not that bad. (It had a hell of a lot more power than it does now.) It wouldn't start--that was the problem. This shop claimed that the valves were all set tight, and that as a result, there was no compression. Then we went into the rebuild. What irks me is that the cam wasn't replaced during the rebuild, especially if it turns out it was that far out of tolerance.
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On Thursday, August 27, 2009 10:54:14 PM UTC-5, Tiger wrote:


Greetings-- a resurrected thread,I guess Just had my 617 rebuilt by Thunderbolt Engines Houston Tx, after the old one seized w an oil pump malfunction. Mechanics are completing the reinstal l this week. What is the best way to break the rebuild in? What do I look f or? The manufacturer suggests 500 mi at normal speed ( what is "normal spee d"), then an oil change, adjustments etc. Anything specific beyond that? Thanks and Best Regards
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I diagnosed a no start problem on a newly rebuild head for a Mercedes gas engine to valves that would not allow the valves to close. He was assured by the rebuilder that the valves were adjusted correctly. With this he assumed that the problem was in the block. Sadly, he pulled the engine bought another and put it in before he talked to me.

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What a waste... that valve problem is easily shown to that guy by compression test gauge.
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Yup. He did a compression check and saw low compression. He must not have done the shot of oil test to see if the compression rises. Like I stated before, he was assured that the valves were adjusted correctly on the rebuilt head and assumed that the lower end must be the problem.
I guess that some people do not know as much about about mechanics as they think they do.

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The shop is now replacing the cam. A question: After paying $5,000 for an engine rebuild, would you or would you not have expected that a new cam would have been installed? If not, would the old cam not have at least been inspected for meeting M-B tolerances for a rebuild?
Thanks,
Randall
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Yes, should have been included... and damn! $5000 is alot of money. And yes, it should have at the least been measured by the machine shop before reinstalling.
You already paid everything, They messed up big time. They have to eat their own profit... which is still a huge number depending on how many parts they reuse.
It is just I suspected... your old engine ran alot better than rebuilt one.
Hard starting is usually due to valves not adjusted properly, glow plug system not right or poor compression which requires rebuild.
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An update in the Unfolding Saga...
The shop has now discovered that there is a failed part within the injector pump (the injector pump has always remained a mystery to me, as I avoid tampering with it to any degree) that functions to advance the fuel delivery. Evidently, they replaced the camshaft, and could get the engine to start briskly, but still could not obtain power at the high end. So now they (we) are waiting for a part from Mercedes- Benz.
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