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450se Motor Bucking

Started by brettj, 23 December 2012, 02:19 PM

wacotech

The setting is of course another factor - which MUST be correct - can't remember off top of head how to set it right.

caleboar

#16
13.25 mpg is pretty standard for a 450?  On my 76 450 SE I'm getting about 10.25 city/14.25 highway. My city could be higher but I don't really warm it up before driving a few mile commute through the hilly, congested Seattle streets.  And I like to floor it whenever possible.

caleboar


Kjhall65

My '76 450 is currently on LPG and gets around 10mpg in the city. I'm the same as you caleboar, I love to floor it when I get the chance.  I didn't buy the car to worry about fuel consumption :)

Tony66_au

Quote from: Kjhall65 on 09 January 2013, 02:15 AM
I didn't buy the car to worry about fuel consumption :)

Thats the point I feel, Neither did I and who could honestly say that they would buy one of these magnificent beasts if they couldnt afford the fuel.

Its the price you pay for owning a large car and enjoying the hell out of it and I have to say that I would often manually select the gears in the 450 to blow the cobwebs out and enjoy the burble and roar as the RPM climbed not to mention the sheer enjoyment of the pull of acceleration.

brettj

I've always looked at fuel consumption as a way of judging if the tuning of the engine is correct. I've also been having lots of gray smoke coming from the tailpipe when the car is first started. That is an indication of running too rich. So between the bucking and the smoking I know my engine is out of spec.

I've ordered from Mercedes a new charcoal canister, suction valve and fuel filter. Still waiting to receive those parts but in the meantime the bucking problem is getting worse. My fuel system must be really clogged up!

Kjhall65

Quote from: Tony66_au on 09 January 2013, 07:16 PM
Quote from: Kjhall65 on 09 January 2013, 02:15 AM
I didn't buy the car to worry about fuel consumption :)

Its the price you pay for owning a large car and enjoying the hell out of it and I have to say that I would often manually select the gears in the 450 to blow the cobwebs out and enjoy the burble and roar as the RPM climbed not to mention the sheer enjoyment of the pull of acceleration.

I took mine shopping today and after it was all done it just seemed to nice a day to put it back in the garage.

So I took to the country behind Canberra and gave the old girl an Italian tune up.   Gave her a good run for about an hour and a half up and down through the hills and some lovely long straights :) She is running much better and the gear box changes more smoothly.

For the fuel conscious among us I did 148 km and used 47 litres of LPG.  I suppose it's a bit much to ask to do better than 10mpg with LPG and the accelerator on the floor.  But it was a great afternoon.

Here is the old girl during my comfort break.





brettj

Hi,

I finally had the time and some good weather to get out and work on the 450SE. I installed a new fuel filter, suction valve and charcoal canister. The fuel filter did not appear plugged. The new suction valve and canister really seemed to make the car more powerful but the dam loss of power and bucking issue has not gone away. I was thinking that perhaps the distributor, idle speed and CPU is not set properly. To solve the problem I increased the idle speed and reset the CPU on the leaner side. So far this adjustment has seemed to help. Anyone have any other ideas?

The throttle switch is my other question. If it is indeed set incorrectly how do you reset that switch. I've read the shop manual directions but still can't figure that one out.

Thanks,

Brett

djenka018

I'm sorry, I have no experience of most of D-Jet specifics.
Vitamin C for SL... the SLC

brettj

I'm still poking around with the bucking issue of my 450SE. The problem does come down to what most of you have stated in previous posts, fuel delivery issue. I must have a clog somewhere in the system. I've been thinking that perhaps I should remove the gas tank and have it cleaned. I was also thinking that perhaps the gas lines themselves are clogged and possibly need to be replaced. Can gas lines be cleaned or do you have to  replace them when they clog? My car sat in the garage from 2003 - 2007. During that time the gas in the fuel delivery system must have turned to shellac  somewhere in the system. With that in mind, I've replaced the fuel pump , filter, injectors you name it. I've never done anything with the fuel lines themselves. Is it an easy job to replace the fuel lines? Is there an additive that I could put in the gas tank to clean fuel systems clogs?

Brett

jbrasile

Brett,

I've never seen fuel lines clogged and replacing them is a big job since you need to run the tubes all the way back to front under the car. Also as far as I know the lines are not available from MB . Start with a good tank cleaning and eliminate all variables before thinking about the fuel lines.

Tks

Joe

brettj

Hi Joe,

Glad to hear that the lines themselves  don't clog. Once the tank is cleaned and if I still have the fuel delivery problem what other fuel system parts should be looked at as the cause?

Thanks,

Brett

jbrasile

Replace the tank filter screen, make sure your fuel filter is new, your pump is delivering proper and consistent pressure and that the fuel vapor vent system is ok. I can't really think of anything else at the moment.

Tks,

Joe

brettj

Hi Joe,

I've replaced the  tank filter screen, fuel pump (Mercedes Part cost me $700.00!), damper and fuel filter. What parts make up the fuel vapor vent system? If the vapor vent system consists of the suction valve that sits on tops of the engine near the injectors and the charcoal canister, I've replaced those parts as well. In my research of the fuel delivery system there also appears to be a valve that is located under the rear seat floorboards driver side. I don't know the proper name for this valve but I know that it does something with fuel vapors. I've already checked with the Classics Center and unfortunately it is no longer available. Anyone have  the correct name for that valve?

Brett