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fuel issues

Author Topic: fuel issues  (Read 3257 times)

rumb

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Re: fuel issues
« Reply #15 on: 30 October 2016, 02:35 PM »
so that could explain both an external leak and the engine running rich?

Do you know where the line connects up front?  what is left of my line is maybe a foot long and ran under the intake upper plenum straight towards the front of the car.  the piece i have is not long enough to reach the front of plenum. 

I guess when I take the plenum off I should see the other end somewhere.....
« Last Edit: 30 October 2016, 02:41 PM by rumb »
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

daantjie

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Re: fuel issues
« Reply #16 on: 30 October 2016, 05:51 PM »
On mine it connects to the rubber breather pipe between the air filter housing and RHS bank.
Daniel
1977 450 SEL 6.9 - Astralsilber

rumb

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Re: fuel issues
« Reply #17 on: 01 November 2016, 02:46 PM »
On mine it connects to the rubber breather pipe between the air filter housing and RHS bank.

It looks like that was a change after engine @3800.  not really sure I would want to dump a ton of gas into the valve cover.  One could argue that it would be sucked into the air cleaner, but I bet a lot of it would go the other way. If the pressure valve was leaking then you would not even know it if it were to vent that way. Though I suppose there would be a real change in the way the engine was running, like mine.

I believe on my earlier engine they just vented it to the environment. Into the valley seems a like a decent place as then it will leak out the bottom drain hole like mine did. I will make a new line that goes back into there. EPC drawing doesnt help show routing of the line. It does show a rubber connector on the far end as though it did connect somewhere.

New part on the way, we shall see soon enough if that fixes all my issues.
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

w116john

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Re: fuel issues
« Reply #18 on: 02 November 2016, 07:05 AM »
hi

on the earlier cars the vent line connected to the front of the engine just below the air intake, i will take a pic when i get my car back its in for a fuel pressure test, starts first time but idle drops quickly for 10-20 seconds idles lumpy then ok, especially noticeable when warm, its there cold as well but the open aav helps, hot starts fine

john

rumb

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Re: fuel issues
« Reply #19 on: 05 November 2016, 02:55 PM »
I can finally call this issue resolved.  The new fuel damper seems to have fixed my problems.

Engine is running reasonably well, but still need tweaking mixture and idle some more.  I think my plugs got pretty dirty and may change them or do more Italian tune-ups.  My idle adjust screw now actually works.

Any sage advice on getting the mixture dialed in?

'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

UTn_boy

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Re: fuel issues
« Reply #20 on: 05 November 2016, 05:09 PM »
If your fuel system is tight, injector seals are new, and there are no intake vacuum leaks or idle air valve hose leaks, then that should take care of any running issues.  If there are still mixture issues, then you'll have to buy a rebuilt warm up regulator, as it's what controls your mixture when hot and cold.  Also, make sure that your coolant temperature sensor is new and/or within spec at both warm and cold temperatures.  K-jet doesn't allow for much mixture regulation at all, if any.  Sometimes people will install a mixture adjusting screw on top of the fuel distributor like the later fuel injection systems had....such as in the W126.  However, it's only a temporary band aid that compensates for a worn/non functioning warm up regulator. 
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daantjie

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Re: fuel issues
« Reply #21 on: 05 November 2016, 07:08 PM »
My 1977 6.9 has the idle mixture adjustment screw on top of the fuel distributor. It is a 3mm in hex bolt which reveals itself after you remove the plug. You set mixture once fully warmed up with small adjustment clockwise and anti as needed and you will clearly hear the idle go up and down as you make adjustments.
Daniel
1977 450 SEL 6.9 - Astralsilber

rumb

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Re: fuel issues
« Reply #22 on: 06 November 2016, 04:20 AM »
Thanks for the info.

My WUR was just rebuilt, so all components of the system are new or rebuilt now.

I was more interested in the small adjustment of the screw by the fuel disti.   Do I just set to smoothest running?  or do I need my mech to use a CO meter to get set so I can pass emission inspection?
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

daantjie

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Re: fuel issues
« Reply #23 on: 06 November 2016, 07:43 AM »
I set mine by ear but then again we do not have to pass smog here anymore. If you start by moving the screw anti clockwise you  should hear the idle go up as you are leaning it out. Then you should reach a point where the idle drops as it leans out too much. This mid point is the basic sweet spot where you want to be.
Daniel
1977 450 SEL 6.9 - Astralsilber