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  #1  
Old 02-01-2015, 01:33 PM
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Fuel Mixture Adjusted = No More off line stumble. And a fuel line question.

I finally got around to checking the duty cycle at the diagnostic port (round thing with a screw cap on left inner fender) using the no. 2 (-) and 3 (+) pin connection.
I tested the Ign. on / Eng. off test and got 70%. Then tested with engine running at operating temp and got 50.4% at idle with fluctuations at higher RPMs.
Using a 3 mm Allen key - pushing down to engage the adjuster - turned it CCW from 12 o'clock to half way to 11 o'clock. Waiting 10 seconds - the idle duty cycle was now fluctuating between 42 to 49%. I did a few more very very small adjustments but ended back at the first adjustment. This thing is super sensitive. I could not have done this without my Fluke 87V.

After all these years will a slightly high idle and stumble starts from a stop it finally has a normal idle and strong off the line. Amazing how that small adjustment made such a huge improvement. This also fixed the RPM hunting on deceleration.

off topic. I noticed outer rubber on one of the fuel lines is dry rotted. The inner plastic line is not leaking but need to be replaced asap. This is the one that goes into the fuel distributor and routs to the inner fender and down under. (Not the chilled one) Looks like a PITA.
I think the PN is 1264703675. I found the number on the Mercedes of South Atlanta parts site.

Where should I buy one from and how hard is it to replace?

Thanks,

Rich

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1986 560 SEL
1960 Ranchero
1970 Cougar XR7
2002 Crown Vic Sport
1992 F150

Last edited by Ritchie; 02-03-2015 at 08:17 AM. Reason: add PN
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  #2  
Old 02-05-2015, 03:12 PM
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Not easy since it wraps down along the trans tunnel. But if you're brave, notice the hose is just pressed onto the metal portion of the line. I've read of people replacing just the rubber portion with or without clamps.

I'd probably just replace the whole thing just to be safe.
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  #3  
Old 02-07-2015, 01:57 PM
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Thanks Mike.
I thought about just replacing the hose. It is nylon fuel injection line with a rubber outer layer. I was thinking aeroquip fittings and their high pressure fuel line that can handle 100+ PSI.
Baum has a fuel injection line tool but also saw a post where someone (Porsche site) made one out of hard wood. I really like the idea from echrisconnor. And maybe a little heat to help the live go over the barbs.

It is the return line but I still want to use fuel injection line and no hose clamps.

No 23 (From Engine to Return Line) is the line.


rich
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1986 560 SEL
1960 Ranchero
1970 Cougar XR7
2002 Crown Vic Sport
1992 F150
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  #4  
Old 02-07-2015, 05:21 PM
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Ritchie:

The fuel line that you marked in red is the pressure line from the pumps; the return circuit goes through the heat exchanger.
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  #5  
Old 02-07-2015, 06:20 PM
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If that is the case; why is the return going through a pressure regulator? see photo. I think with the 560 SEL gen II it is a return line.
I don't want to mislead future reads with assumed fact.
I'll do some more research but the VIN pulled a diagram and P/N that indicate "return line".
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1986 560 SEL
1960 Ranchero
1970 Cougar XR7
2002 Crown Vic Sport
1992 F150

Last edited by Ritchie; 02-07-2015 at 06:44 PM.
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  #6  
Old 02-07-2015, 06:51 PM
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The pressure regulator IS in the return circuit, as it is for almost all injection systems; in contrast with pressure regulators for carburetors, which are in the supply line.

Pressure in the working components inside the fuel distributor is maintained by bleeding off the excess on the return side. As more fuel is sent to the nozzles in response to increased demand for more power (opening throttle), a constant pressure is maintained by reducing the flow that is returned to tank. And contrariwise when demand is reduced (closing throttle).
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  #7  
Old 02-08-2015, 09:42 AM
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Mercedes Part page

So 17 in the part list and diagram is return and 23 is supply and Mercedes got it wrong?
Anyway looks like Item 23 is the one I need to oreder.

Thanks,
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1986 560 SEL
1960 Ranchero
1970 Cougar XR7
2002 Crown Vic Sport
1992 F150

Last edited by Ritchie; 02-08-2015 at 09:54 AM.
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  #8  
Old 02-08-2015, 09:59 AM
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Some points about the fuel line drawing are in order:

1) The drawing is generic.
2) Only one fuel pump is shown, rather than two.
3) The fuel pressure regulator (FPR) is not shown.
4) The fuel cooler is not shown.

#23 should be shown connected to #11 (supply)
#17 should be shown connected to the outlet side of the FPR and then to #29 (return)
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  #9  
Old 02-08-2015, 01:38 PM
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Thanks Frank

startek diagram shows the line that is red-lined - is the supply line.

Now I'm thinking I need 17. 1264703575

Thanks,

rich

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1986 560 SEL
1960 Ranchero
1970 Cougar XR7
2002 Crown Vic Sport
1992 F150

Last edited by Ritchie; 02-08-2015 at 02:04 PM. Reason: 1264703575
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