[W126 Coupe] how do you adjust

[Gary]

it was running very rough, then stopped running.  would turn over.  i took it to 
the garage and the fuel pressured it and the FD was the problem.  i probably 
should just take it back to them and have them do the fine tuning since they 
have the tools.    i'll give them a copy of your info, can't hurt.    thanks 





________________________________
From: Dick Spellman <dick.spellman at gmail.com>
To: Mercedes Coupes Mailing Lists <mbcoupes at mbcoupes.com>
Sent: Mon, July 19, 2010 9:37:12 AM
Subject: Re: [W126 Coupe] how do you adjust

Gary,

You need to put a fuel pressure gauge on the fuel distributor (fd).  At a 
minimum you can connect to the cold start valve outlet (upper fd chamber) on the 
fd to obtain overall pressure.  Ideally, you want a gauge that permits 
connections to both upper and lower chambers (two hoses with a shut-off valve on 
one)) so you can measure the difference between upper chamber and lower chamber 
pressures (referred to as differential pressure) in the manual.  Typical fuel 
pressures would be 5.3~5.4  bar overall.  When isolating lower chamber pressure 
it should be approximately 0.4 to 0.45 bar LESS than the overall pressure.  This 
would be your differential pressure which is in the manual.

So, as an example upper chamber is 5.3 bar and lower is 4.9 bar, differential is 
then 0.4 bar.  Without knowing the pressures it is difficult to recommend a set 
of steps to remedy your problem.  Two quick questions:

1. did you replace the rubber o-ring (seal) at the base of the fd when you 
swapped out?  If not, a vacuum leak (large) will likely exist where the fd bolts 
down on the air flow meter housing.
2. what running conditions did you have prior to the swap?

Good luck,

Dick


On Sun, Jul 18, 2010 at 10:57 PM, Gary <garysalas at yahoo.com> wrote:

the fuel distributor.  i put one from a donor car and need to adjust because the 
car just turns and turns   thanks for the help

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