Greetings all, I just acquired a beautiful 1980, 450SEL, 180,000 miles in great shape, when I got it (last week) it had bad timing chain slap and intake manifold leaks, I replaced the chain, tensioner and broken rail. Pulled off the intake to access and replace the doughnuts and intake gaskets, I replaced all vacuum lines in regards to the engine at the same time, it starts great, has plenty of power once you get it moving, but, off the line it will barely get out of its own way, almost like plugged exhaust, once you get it moving though it runs great. I took it to my local muffler shop and they drilled a few small holes in the exhaust system and discovered (by using a pressure gauge) that the pre-converters were 70% plugged they were sure this was the problem, I was a little skeptical as it ran great with plenty of power once you get it moving. Well, after replacing the pre-converters I still have the same problem, I have rechecked the timing and even tried advancing it too no avail, I am at a loss as to the next possibility, any one have any idea's? Thanks in advance, Phill

It sounds like the timing advancer mechanisms are not working well.

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Benzmac:
Donnie Drummonds
300E
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM
OWNER OF MB AUTOWERKS .COM

Donnie,

The vacuum advance is working fine, and it is getting vacuum, however that IS what it feels like. I checked all the timing marks after new chain. Spec. calls for 5 degrees BTDC I moved the timing up to TDC still the same, it is a real weird one to be sure!

The 1980 model was the first with lambda control. Be sure the frequency valve is buzzing. If not check the overvoltage protection relay (or whatever they called the power relay in a 116 chassis).

Without the drop in lower chamber pressure the car has no power even though it runs smoothly.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Thanks Steve,
Frequency valve is buzzing, someone suggested low fuel pressure on The MBZ Discussion list, I will check that monday, I read somewhere that volume could be checked by disconecting the fuel return hose at the distributor and running a hose into a container and measuring the volume for a specified time, Monday I will try to look that up, you don't happen to know do you? Or maybe what the fuel pressure should be at the distributor? Thanks phill

Hi Mutt,
If the timing was at 5 BTDC and you moved it to TDC...your going the wrong way. Try for 10 deg BTDC at idle. The engine can handle loads more advance. Give it a try...
Regards,
Randy D.

I forgot to ask if you had checked the "mechanical" advance as Benzmac suggested.

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W.R.Durrance
ASE Master Tech
Mercedes Tech 20 Years
68 250SE
68 SAAB 96 Ice Racer
69 300SEL 6.3
70 300SEL 3.5
81 300TDT

[This message has been edited by WDurrance (edited 10-01-2000).]

Randy,
The vacuum advance is working and I do have vacuum to it.... will get back to you all Monday eve and let you know about the fuel pressure.......

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Regards, Phill
70 280SE
80 450SEL
84 300SD
85 190E 2.3

System pressure should be about 5bar (70psi + or -). The actual pressure is not as important as that it be steady. If you tee into the supply line and capture the fuel at the return you will be able to test volume at pressure which is the whole test.

Be sure the fuel flows through the frequency valve. Disconnect the electrical and the mixture should go lean. It should be easy to see the results. If pulling the connection doesn't change anything I would investigate.

You might want to verify cam timing also (if you haven't already)

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Check the function of the thermal vacuum valve that is located on the front/top of the intake manifold. That valve controls the routing of vacuum to the distributor based upon engine temperature. The valve serves to function as a way to have the ignition retarded while the engine is cold, thus avoiding over-revving while the idle air valve is open. This change in ignition timing will affect performance if it does not go back to normal when the engine is warm. The proper schematic for this is kind of confusing, as it allows vacuum to bleed back into the manifold when warm, which negates the effect, while closing the bleed back when cold which then allows the vacuum to reach the distributor via a 'T' type connection. (this is if memory serves me correctly - take your chances )

Also, check the ignition timing for full advance, and watch the timing as you slowly rev the engine up to 3000 rpms to watch that the timing advances smoothly, rather than suddenly jumping i.e., if the advance weights suddenly become 'unstuck' rather than moving freely.

Please post a follow up to let me know if this resolves the problem - I'm curious...

[This message has been edited by 450 SLC 5.0 (edited 10-06-2000).]

Hello,guess What,bought The Same Car With 190.000 Miles,runs Like A Dream But Only When The Rpm Reaches 1600 1800 And Up,below That Is Very Sluggish,seems To Have Same Problem,i Went Trough Everithing,now I Am Starting To Check The Tranny,see What Goes On There............

Good Luck With Yours,let Me Know Please What Was Theproblem On Your Car,i Will Do The Same When And If I Find Out Where The Problem Is On Mine.

Regards

Marino Alberti

Finally I Found Out Wat Was Wrong With Mine,it Was A Bad Torque Converter,replaced With A Rebuilt One And Now It Run As It Should Be.

Regards

Marino

I had an 80 450 SEL. At 160 hp it is the most underpowered of the 450s. Early ones put out 230hp. Anyway a faulty or worn out transmission can do this. This was the case with mine. Once the tranny was rebuilt there was a world of a difference in power off the line. It was rebuilt at 150,000 miles. 180,000 miles later it developed a leak and the ATF leaking over the hot catalytic converter caused a fire. That was the end of that car. Well, the thing died with 320,000 miles on the clock. I really miss that car, but I don't miss its crappy gas mileage.
Dimitri