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MECHANICALS With a 30 year-old automobile, there will always be discussion here - maintenance, modifications and mechanicals.

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Old 5th March 2009, 07:29 PM
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Default D-Jet cold start problem

My '75 280SE takes a while to start when cold, cranking for ten seconds, then fires and runs great, no problem when warm.
Any guesses?
Where do I find 'thermotime switch'?
Or any cold start accessories?
Any clues chaps?
Chris M.
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Old 5th March 2009, 08:36 PM
B13 B13 is offline
Join Date: Feb 2008
Location: Victoria
Posts: 686
Default Re: D-Jet cold start problem

Do you get a nice audible BZZZZZT from the fuel pump for 1 second before you turn the key from On to Start? If its not properly pressurising the system at that moment there won't be enough fuel pressure to push fuel out the injectors while cranking... it may take a few seconds (10 or more) to dribble enough fuel into the plenum chamber and finally give the cylinders something to fire.

Just my 2c worth.

6.9 #5440 = 20189H , Falcon GT BF2 # 620 = VMB 690
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Old 6th March 2009, 05:15 PM
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Default Re: D-Jet cold start problem

Well the fuel pump is not as noisy on this one as some, but I suspected that because if I leave the ignition on for ten seconds before starting, it fires up ok.
Maybe the pump is just tired and needs a while to get up to pressure.
Can I use a fuel pump from a later '80 model 280E?
Are they interchangeable?
Anyone know?
Chris M.
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Old 7th March 2009, 09:07 AM
AAB AAB is offline
Join Date: Dec 2008
Location: Toorak Vic
Posts: 67
Default Re: D-Jet cold start problem


I think that you have to check that the fuel pump operating pressures are similar.

My 450 has a " cold start " switch that has been known to give me problems, both for not operating, & recently, for not shutting off.

Plays hell with the mixture & fuel economy if it does not shut off.


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Old 8th March 2009, 08:46 AM
John S John S is offline
Join Date: Feb 2008
Location: Sydney
Posts: 639
Default Re: D-Jet cold start problem

How good is your battery? A fully charged battery with a good earth can make a very big difference in starting a Mercedes.
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