Little or NO power after bottoming out suspension- 1981 300SD - Page 11 - PeachParts Mercedes-Benz Forum

Silber Adler · #**151** 03-03-2013, 08:21 PM

Have you tried spraying in some WD40 or propane as the engine is idling?
I hope it isn't a spun bearing. Wouldn't your oil pressure be wonky?

kerry · #**152** 03-03-2013, 08:37 PM

Quote:

Originally Posted by Silber Adler

Have you tried spraying in some WD40 or propane as the engine is idling?
?

Deja fuel.

funola · #**153** 03-03-2013, 11:48 PM

Quote:

Originally Posted by ROLLGUY

I am not sure how a spun bearing should act, but Roy seems to think it would still allow a smooth idle, but only cause friction at top RPM. I have no way to prove that wrong (or right, short of engine diss-assembly). I inspected the oil pump when the pan was off, and it looked just fine. Just the rubber part of the pickup was damaged. Roy suggested a problem with the trans as well (pump causing too much friction), but that would be a WAAAY long shot. I am going to go with the oil cap removal first, then the WD in the turbo test, then the belt removal last (well, maybe not last the way things have gone with this car!).

Did you see this and will you try it?

"One more thing for you to try:
Disconnect the emergency shutoff linkage from the throttle and push it in the opposite (shutoff) direction and see if you can get higher RPMs. That shutoff can limit fuel if jammed or misadjusted."

ROLLGUY · #**154** 03-10-2013, 12:46 AM

The other day I told my friend what to do to test his engine (I had to work, and could not perform the tests myself). I had him remove the "U" tube and spray WD40 in the turbo to see if the engine RPM increased. He reported that there was no change whatsoever. I told him to remove the oil cap, and see if that made a difference. He reported that the engine runs the same with the oil cap on or off. The only thing left to try, other than pulling the upper pan and inspecting the main bearings, is to remove the belts. He has not done that yet as far as I know. I will contact him and find out what he has done so far. The more I think about it, I believe that Roy has the correct diagnosis (spun main bearing/s). If that is the case, anyone want to buy a 1981 300SD cheap?

colincoon · #**155** 03-10-2013, 12:54 AM

Why not just replace the engine? 617's aren't too hard to find, and they aren't exactly expensive. A day's work and a few hundred bucks are worth it to keep it on the road.

funola · #**156** 03-10-2013, 12:14 PM

How big a job (# of hours) is getting to the main bearings?

Would draining the oil looking for bearing material reveal if it is a spun bearing or not? If not, what about oil analysis?

I am curious how big a dip in the road your friend went through. Can you ask him for a good description, how fast he was going etc? The info he provides may save some engines down the road.

kerry · #**157** 03-10-2013, 01:03 PM

I'm skeptical that one spun main bearing would stop the engine from revving up. If it was that, wouldn't there be a big cloud of black smoke out the exhaust from the additional fuel not being burned?

funola · #**158** 03-10-2013, 01:21 PM

A spun bearing is not that large of a frictional load. With 120 HP shouldn't it be able to overcome that additional frictional load and reach full RPM? And why would it limit upper RPM and not affect the idle? Shouldn't the idle RPM drop by some corresponding amount?

jt20 · #**159** 03-10-2013, 01:35 PM

Quote:

Originally Posted by kerry

I'm skeptical that one spun main bearing would stop the engine from revving up.

Ditto! But it would not smoke unless there was IP damage.

I am highly skeptical that even if all 6 were 'spun' (incorrect terminology) along with the rod bearings that this would be the case.

I drove well over 50 miles in city with damaged (from oil starvation) main bearings on a turbo 617. It drove great!

It is incredibly unlikely that the bearings are 'spun' after a momentary loss of oil pressure, in this case. You stated that the pressure is currently, and has been, normal.

AND, you said you could spin the crank by hand without abnormal resistance....

jt20 · #**160** 03-10-2013, 02:02 PM

try the good IP with that second set of injectors

max out the rack lever when drip timing.

inspect the fuel filter housing , banjos and clear lines for cracks etc..

whunter · #**161** 03-10-2013, 02:20 PM

Quote:

Originally Posted by jt20

try the good IP with that second set of injectors

max out the rack lever when drip timing.

inspect the fuel filter housing , banjos and clear lines for cracks etc..

Three injection pumps, I suspect his answer will be NO.

.

jt20 · #**162** 03-10-2013, 02:51 PM

Quote:

Originally Posted by whunter

Three injection pumps, I suspect his answer will be NO.

.

Is that your response to technical suggestions? sounds frustrated.

As I recall, it was 2 IPs and it is currently set up with the old one. Its far easier than pulling an engine.

You spoke to him, perhaps you have more info than we do.... Its a strange case for sure, but there's no need to displace the shortcomings onto me.

funola · #**163** 03-10-2013, 03:18 PM

I am still placing my bets on fuel delivery.

whunter · #**164** 03-10-2013, 04:32 PM

Quote:

Originally Posted by funola

A spun bearing is not that large of a frictional load. With 120 HP shouldn't it be able to overcome that additional frictional load and reach full RPM? And why would it limit upper RPM and not affect the idle? Shouldn't the idle RPM drop by some corresponding amount?

The engine is closer to 38 HP at the moment.

This was a 70+ MPH rolling vertical impact (that did not stop the car).
The lower oil pan deformed in the oil pump pickup area.
This oil pan punched the rubber pickup into itself = cutting off oil supply.

My best guess at this point:
* Secondary accessories damage = pull all of the belts and test - run the engine.
* Engine bearing oil starvation damage.
* After reading what he has done + several discussions / diagnostics, the fuel supply system is totally eliminated. If removing the belts does nothing, and he can find another (good used) injection pump, it would be worth trying.

Complete 40 channel accelerometer (instrumentation G-force) impact data from this incident would be highly educational, unfortunately it does not exist.

FYI:
The symptoms have a few similarities with the following thread. Warning: This is huge 855 posts.

wont start for anything! 1985 300SD
wont start for anything! 1985 300SD

As I recall, he went through five injection pumps before the engine was running right.

.

Brian Carlton · #**165** 03-10-2013, 05:35 PM

Quote:

Originally Posted by kerry

I'm skeptical that one spun main bearing would stop the engine from revving up. If it was that, wouldn't there be a big cloud of black smoke out the exhaust from the additional fuel not being burned?

I agree.

The problem is almost certainly not a main bearing. If the bearing was damaged to a significant degree, the engine would not idle without additional fuel. The fact that it will idle, within the governor range, effectively eliminates a main bearing from the list of potential problems.

I'm still curious about the advance mechanism. He stated that he checked it and it appeared to be fine, however, I have my doubts. If there is no advance as the engine tries to climb in rpms, it cannot produce any power.