Mercedes-Benz Forum banner

1 - 9 of 9 Posts

·
Registered
1984 300TD
Joined
·
123 Posts
Discussion Starter #1 (Edited)
Installed a used low miles 617 turbo (15K on rebuild) engine of unknown history otherwise and 4 speed in a wagon. This engine sat idle for at least 1.5 to 2 years before this. It smokes way too much, looks blue to me though could be black too.
Warm compression:
1. 400
2- 400
3- 420 (it fired during this one)
4- 390
5- 380

Can compression rings be good but oil rings be bad?

I just put a rebuilt head on it from a good shop.

I just finished a 7 day marvel mystery oil cylinder "soak" with little improvement in smoke.

Timing of ip is 24BTDC.

Turbo seals:
I removed the EGR valve at the front of the intake pipe where boost air enters intake, stuck my pinky in there to check for oil, it's dry, no wet oil, just dry black fuzz. Turbo seals must be good.

Way slow to return to idle:
At 2500 rpm if I release the accelerator pedal the rpms do not drop to idle normally. While stationary it takes 7 or 8 seconds for the engine to drop to near idle. Much worse at speed, its a 4 speed stick and the momentum of the car seems to make the rpms "float" much more so. No slowing down using compression in this one.

Gummed up IP?:
I just flushed .25 litre of lacquer thinner thru the fuel handling part of the IP, no apparent improvement.

Turning the rack damper out half a turn doesn't help. Turning it in half a turn initiates loping and makes searching before full warmup worse.

I guess the next step is install the spare IP from the worn out engine I'm replaceing.... it seemed to work right. Some here say "no need to remove the filter tower" But there isn't clearance, you need about an inch or rearward mobility, the rack damp bolt is too close as is the plastic vacuum gizmo to the rear of the anerod unit.

Has anyone seen this "clinical picture" before, ie smoke with good compression and "floating rpms....?

Thanks in advance.

Please: if you have real training and experience with these things include one sentence about what can be happening and one with the appropriate solution for each cause of the issues.
 

·
Registered
2001 Volvo V40
Joined
·
2,954 Posts
Does the control rod of the IP move freely and easily with the engine off (test by moving the control lever by hand)?

Does the gas linkage move the control lever quickly back to the idle stop?

Is the ALDA still virginal, i.e. not adjusted?
 

·
Registered
1984 300TD
Joined
·
123 Posts
Discussion Starter #3
Does the control rod of the IP move freely and easily with the engine off (test by moving the control lever by hand)?

YES, MY OVERSIGHT NOT TO MENTION, LINKAGE MOVES FREELY BACK TO STOP IMMEDIATELY, ALL THE LINKAGE IS FREE TO MOVE.

Does the gas linkage move the control lever quickly back to the idle stop?

Is the ALDA still virginal, i.e. not adjusted?
DON'T KNOW ANY HISTORY, ALDA IS THE PLASTIC VACUUM CONNECTED GIZMO ON TOP OF THE IP IMMEDIATELY REAR TO THE ANEROD UNIT?
 

·
Registered
2001 Volvo V40
Joined
·
2,954 Posts
Inside the red line is the ALDA. Inside the blue line is a adjusting screw. If it is still virginal, the screw is covered by a black cap, as shown in the picture.

 

·
Registered
1984 300TD
Joined
·
123 Posts
Discussion Starter #5 (Edited)
CAN I ask that you summarize in two (or briefly) sentences how the ALDA can cause floating rpms and what the fix would be, specifically, or how it would could cause excessive smoking at the exhaust and the fix.

Here there is no black cap, just an exposed screw concentric with a hex locking nut associated with that screw. There is no paint or the like on the screw.

No sense in a prolonged exchange of emails each doing a tiny fraction of the job....

Also when you visit Calif bring some of that great hash you guys get there in Holland....
thanks
 

·
Registered
1984 300TD
Joined
·
123 Posts
Discussion Starter #6
ALDA
this modifies the amount of fuel delivered in any moment according to local altitude and boost pressure in any given moment.

Higher altitude = fewer air molecules so less fuel
more boost = more air molecules so more fuel is delivered

Presumably you are thinking sustained rpm (and maybe smoke) is the result of too much fuel.

What do you propose, adjust that screw so less fuel is delivered at any given condition? ... since it seems too much fuel is involved....
 

·
Registered
2001 Volvo V40
Joined
·
2,954 Posts
IMHO there are two possibilities:

the oil scrape ring on the piston is not working properly (as you mentioned). Above the oil scrape ring there are two compression rings, so compression can be good, while the oil scrape ring is not. As a result the engine is partly running on engine oil, which can explain the slow return to idle and the smoke. You should however notice a large oil consumption.

The other possibility is that the linkage of the governor of the IP is not working properly. If the ALDA was adjusted it could inject more diesel fuel than the engine can burn, that would explain the smoke. I don't think adjusting the ALDA by itself can cause the slow return to idle, perhaps some more thingg of the governor were adjusted.
 

·
Registered
1984 300TD
Joined
·
123 Posts
Discussion Starter #8
IMHO there are two possibilities:

the oil scrape ring on the piston is not working properly (as you mentioned). Above the oil scrape ring there are two compression rings, so compression can be good, while the oil scrape ring is not. As a result the engine is partly running on engine oil, which can explain the slow return to idle and the smoke. You should however notice a large oil consumption.

The other possibility is that the linkage of the governor of the IP is not working properly. If the ALDA was adjusted it could inject more diesel fuel than the engine can burn, that would explain the smoke. I don't think adjusting the ALDA by itself can cause the slow return to idle, perhaps some more thingg of the governor were adjusted.
Thank you, you make good sense.

I think the next step is install a spare ip I have on hand from a worn out motor that ran quite well but was getting to become one of those stinky smelly beasts. First I'll try a full turn out on the governor damper bolt, a local rebuilder of IPs suggested half a turn which seemed to make no difference.

Must one remove the filter tower to get the ip out?

Some here say no, the FSM says remove it, inspection reveals the governor adjust bolt would touch the filter tower as would the plastic vacuum actuator (I guess it's shut off related, the one shown in your photo) before you would get enough rearward mobility of the ip to disengage it from its mounting studs.
 

·
Registered
money pits of various forms
Joined
·
5,885 Posts
Those are decent compression numbers, not great but quite passable.
Adjust the valves?
 
1 - 9 of 9 Posts
Top