Not so good results from 4spd swap - Page 4 - PeachParts Mercedes-Benz Forum

Bajaman · #1 04-08-2008, 04:42 PM

sorry, somehow I missed that...

Bajaman · #2 04-09-2008, 07:06 AM

I rebuilt this engine two years ago. Compression is around 405-410 on all cylinders. Injectors were new last year, but I intend to check them again. The only thing thats left is the injection pump. This thing has never run right, and I suspect something may have been wrong with it when I bought it. Cleaning the delivery valves is next. If that does not solve the shake, then I will swap in another injection pump.

JDmills · #3 04-09-2008, 01:38 PM

Quote:

Originally Posted by Bajaman

I rebuilt this engine two years ago. Compression is around 405-410 on all cylinders. Injectors were new last year, but I intend to check them again. The only thing thats left is the injection pump. This thing has never run right, and I suspect something may have been wrong with it when I bought it. Cleaning the delivery valves is next. If that does not solve the shake, then I will swap in another injection pump.

What are the symptoms of a bad injection pump? and what wears out on them when they do go out the door? the 1300RPM shake on my car has just developed since january.. I would be curious to do a compression test on the car, but don't have a diesel compression tester, and have not made it a high enough priority to invest in one..

Bajaman · #4 04-09-2008, 02:47 PM

I don't know, I am targeting it because its the only thing left. I would assume that injection pump problems are going to be noticeable at low RPM just like a bad injector due to the low injection volumes and lower kinetic energy at the flywheel. Fundamentally they are all combustion related events that exhibit themselves as a vibration. These can be related to the following:
Compression
Injector spray pattern
pre-chamber problems (loss of ball)
delivery valve sticking/ improper seating
improper valve lash
Injection pump malfunction (wear/misadjustment)
Feel free to add to the list, I'm just listing the most obvious to me.
I am sorry to hear about your vibration, but at the same time I'm glad to hear that I am not the only one with these symptoms.

JDmills · #5 04-09-2008, 06:29 PM

Quote:

Originally Posted by Bajaman

Feel free to add to the list, I'm just listing the most obvious to me.
I am sorry to hear about your vibration, but at the same time I'm glad to hear that I am not the only one with these symptoms.

If this car was trouble free, I would be bored and not learning anything.. so I am not "glad" to have this vibration, but curious never the less, as to where it originates.. and I am also comforted not to be alone in that particular forest...

this weekend I will dig in and start exploring some driveshaft solutions.. and thinking about the engine miss.. in greater detail..

Bajaman · #6 09-25-2008, 07:17 AM

After trying everything I can think of, I have a new theory. But first I'll list everything that I have done to remedy the vibration.
New stuff:
trans mount -auto version
cross member 240 auto version
flex discs (2)
centering bushing (2)
center support and bearing

The only thing that I have not done is replace the u-joint, and the driveshaft has not been balanced, but it has zero vibration when there is no torque on the shaft, so I don't see how it could be out of balance (again the vibration is the worst under light to moderate torque from 1600-1900 rpm).

New theory: The springs in the clutch are too weak for the larger 5 cylinder motor/lighter flywheel. One thing that led me to think about this is that the springs really do seem too light because sometimes I get a nasty surging when I slow to say 1200 rpm then hit the accelerator. A critically damped system would not oscilate like this. The clutch springs seem like the biggest contributor here. The only other thing that would be a big factor would be overall drivetrain slop. There is some for sure, but it doesn't seem excessive.
Bottom line, is there a clutch available with heavier springs?? Or am I reading this completely wrong? Where are our vibrations guys?

#7 09-25-2008, 07:27 AM

Quote:

Originally Posted by Bajaman

New theory: The springs in the clutch are too weak for the larger 5 cylinder motor/lighter flywheel.

Nope. If that were the case then a few dozen converters and almost half the 300D's in europe would be having the same problem.

I don't have any vibration problems worth complaining about. I'm very happy with my conversion.

Stevo · #8 09-25-2008, 10:02 AM

Your sure you got the drive shaft back together just the way it came apart?

Bajaman · #9 09-25-2008, 11:47 AM

Almost everyone who does the swap complains about vibrations. I don't think its a coincidence.

No, the driveshaft is custom, but if it were the culprit, it would not just show up under load.

Stevo · #10 09-25-2008, 04:01 PM

Maybe its just a consequence of the 616 F/W being seven pounds lighter than the 617 flywheel, least thats the number that I remember from somewhere.

bgkast · #11 09-30-2008, 11:11 AM

I don't mean to sound like a tree hugging hippy (joking

) but I filled up with biodiesel yesterday, giving me about a B50 blend in the tank, and my vibrations have noticeably decreased. I used to be able to rattle my sunroof if I lugged it too much, but now I can't. Maybe it has something to do with biodiesel's less "violent" combustion?

Bajaman · #12 09-30-2008, 11:44 AM

BG your comment about biodiesel combusting slower than diesel would fit nicely with the hypothesis that the flywheel is the culprit. A heavier flywheel would tend to dampen the vibration caused by quick combustion.
On a similar note, I have noticed a dramatic increase of what I will call 'lurching' since I "upgraded" to 265 nozzles. What I mean by lurching, is when I am driving slowly in 1st or 2nd and accelerate gradually, the car will lurch violently (like they do in movies when a kid is learning to drive a stick shift). This only occurs under light to moderate acceleration. Heavy acceleration does not yield the same results.
This lurching is what initially got me thinking about clutch springs being too light. I suppose that I have somewhat more torque than stock. Significantly more at lower rpms do to the VNT swap.
I just wish it drove more like my Scout. You can lug that thing right down to idle and get NO vibration whatsoever. Not that I seriously lug my engines, I just like to shift to a higher gear when cruising around under low torque conditions... saves fuel.

bgkast · #13 09-30-2008, 05:53 PM

I get that too. I believe it is play from a few hundred thousand miles on the diff and transmission. I have had the same thing happened in other manual cars I have owned.

Bajaman · #14 10-01-2008, 08:27 AM

gears certainly wear over time. I wonder if the backlash in the diff. can be adjusted by adding shims behind the pinion.

SW · #15 10-01-2008, 01:10 PM

Quote:

Originally Posted by Bajaman

gears certainly wear over time. I wonder if the backlash in the diff. can be adjusted by adding shims behind the pinion.

Adding shims to the pinion will change the depth of the pinion relative to the ring gear. If backlash is too sloppy, what you want to do is tighten up the pre load on the carrier bearings. On the benz diff you will have to add shims to the carrier bearings or maybe even change them out. Not hard, but very tedius.