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  #1  
Old 09-05-2003, 03:01 PM
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Some leakage from fuel mixture screw

People:

In attempting to adjust my fuel mixture screw (on rear of fuel distributor (3mm alen; 77 450 SEL K-Jetronic system CIS), I found that it was all the way tight in. Meaning, as far as it could go in clockwise.

When I loosened it to back off, I startewd getting some drops of gas from around sscrew flange. I quickly re-tightend screw, and seems to have stopped the droplets from oozing. But it's again in the all-the-way-in super rich position. I'm wondering if that's why the original owner had it in there tight, and thus rich. so the screw wouldn't leak.

anyway, has this happened to anybody else? any suggestions, other than just getting a whole new fuel distributor for this ridiculous situation?
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  #2  
Old 09-05-2003, 03:32 PM
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Does the fuel drip when the car is running? I would think the vacuum during operation could only leak air to the intake.

I wonder where the slop is. Perhaps damage is confined to the threads of the needle screw, which means only the needle needs to be replaced. I've actually made needles by finding the right size screw and sharpening the tip. The screw is clamped in a drill chuck and ground on a grinding wheel, while operating the drill.

Or perhaps there's a compound like loctite that can be put on the threads to take up the gap, yet allow for adjustment.
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  #3  
Old 09-05-2003, 03:45 PM
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Leaking slightly when car is running and off. It's just some droplets, btu certainly not aceptable.

I'm ipressed by your idea and ingenuity, but think it's beyond me.

Will screww come out altogether?

If so, will gas come rushing out?

Also - if I use locktite, then how can I further adjust screw?

any alternate suggestions?

Thanks!!
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  #4  
Old 09-05-2003, 04:17 PM
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Until someone comes up with a better answer, I don't think there should be gas there at all! My understanding is that the screw simply adjusts the mechanical offset or ratio between position of the airflow meter plate and the plunger in the fuel distributor that apertures the metering slits. I.e., gas would only be present if there was already a leak past the plunger, and it dribbled down to the screw.

Steve
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  #5  
Old 09-05-2003, 04:38 PM
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Stev:

Maybe I've got the wrong screw. I'm talking about the one on the BACK upper section of the fuel distributor, facing towatds the rear (and side mounted). Mine is K-jetronic CIS system. Have I got right screw? Or is there another one, and I'm in the wrong place?
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  #6  
Old 09-05-2003, 04:47 PM
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Look at the pic of the airflow meter with fuel distributor removed here:

190e Air flow meter plate. can anyone tell me whats under there?

Is the part shown as the mixture adjust assembly what you refer to? Note it pushes down on a lever, and does not acually protrude into the fuel distributor.

Steve
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  #7  
Old 09-05-2003, 04:51 PM
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No, Steve. That assembly is separate, I know, and is in front of the fuel distributor.

I'm talking about a rear /back screw on fuel distributor, which is the larger item behind the pictured asembly, and has all the fuel lines running in and out of it.

Are you familiar with that? And can you read back my inquiry, and now tell me if i'm dealing with the rigfht screw?
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  #8  
Old 09-05-2003, 06:31 PM
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Why don't you post a pic and point it out. I'm probably just ignorant of the CIS configurations earlier than ours, but I was unaware of a different mixture screw.

Steve
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  #9  
Old 09-05-2003, 06:42 PM
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Don't have pic: Steve B., can you help?

Don't have pic. thanks for your honesty. Need advice from someone who is intimate with this earlier, though common, K-jetronic CIS system.

If they read my earlier description (above), they'll be able to set me straight about which screww I messed with - and what to do.

thanks!!
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  #10  
Old 09-05-2003, 07:26 PM
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I believe you are on the wrong screw. The mixture adjustment is down in a hole between the fuel dist and the air intake. It is an inch or so down in this hole. If you adjust it, go slow (no more than 1/8 turn and let the engine stablize.
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  #11  
Old 09-05-2003, 07:30 PM
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Thanks, Paul. But: ??

Paul - thanks.

When it stops raining (we have tropical storm right now), I'll take off air filter housing and look.

Have you seen M-117 engine up close? Is your description from eprsonal experience, hands-on?

Just asking.
Thanks.

Bob
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  #12  
Old 09-05-2003, 07:55 PM
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Got a 76 450SL in the shop right now. And I have a 84 500 SEL.
Both have basicly the same engine and fuel system. If you don'
t find what I am talking about, let me know.
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  #13  
Old 09-05-2003, 09:13 PM
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Thanks, Paul.

i'll look for the "hole"!!

Report back later....

Bob
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  #14  
Old 09-05-2003, 10:23 PM
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The mixture screw is between the mass air flow sensor plate and the "tower" where the injection lines attach. The screw you are messing around with is NOT the mixture adjustment. There no way this screw can leak fuel, there is no fuel anywhere around it.

The mixture screw will also have an anti-tamper device of some sort -- on the M103 it is a metal cover pressed into the top of the "stem"' above the screw.

The fitting the 3mm Allen goes into is a spring loaded key, at least on the M103, so you must press is down to engage in the actual adjuster. I assume the one on the M119 is the same.

Peter
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  #15  
Old 09-06-2003, 09:16 AM
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Peter:

Could this,on mine, be in a hole covered by a reular-head screww? There is this like 1/3 inch regular head screww in that approximate location, which I thought had beent he air mass sensor adjustment screww. It is screwed all the way flush, but it easily screwws coutnerclockwise. I've never screwed it all out. Is this them one that should be removed and then allen screww will be below it?
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