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Mechanicals / Re: Excessive control pressure...
Last post by Feather535 - 05 February 2023, 12:01 PM
This is Part 2.  The cleaned and reconditioned WUR is back on the car, but control pressure is still 5.5 bar cold.  The engine won't run long enough to test warm CP. 

revilla recommended 3 tests "Very slowly unscrew the return line at FD head...does the pressure go down? Repeat the same exercise...but this time unscrew the fuel pressure regulator on top/front of your FD. Lower pressure? Unscrew more but never completely. Pressure goes down? Same exercise but this time with the 12mm line on the side of the pressure regulator." 

When I do this the CP stays the same for the first and third tests on the return lines, but it goes down when the fuel pressure regulator assembly is loosened, going lower the farther it's unscrewed.  revilla thinks the FP regulator is the source of the problem and asked for a picture; here's one, and I can provide more. I replaced all the o-rings with new ones from raueda1.  There are 2 shims on the assembly.  I don't have a micrometer, but one is thin and the other is thick, about 1 mm.  And that's where it stands today...
Mechanicals / Excessive control pressure (co...
Last post by Feather535 - 05 February 2023, 11:46 AM
I initiated 2 threads related to excessive control pressure that had grown to multiple responses over 2 pages.  To reduce confusion going forward, I'm starting a new topic, beginning with a summary of the problem and what I've done so far. This is part 1.

The car in question is a 1977 280SE, sold new in Los Angeles California.  It hadn't been  on the road in 10 years when I acquired it.  The seller had replaced the fuel pump and filter, distributor cap, spark plugs and wires and got the engine running, but the car wasn't drivable.

The problem I'm trying to solve is lean running.  The engine is hard to start cold.  When it does start, it pops back through the airflow plate and dies if the throttle is opened.  When the weather was warmer, I could keep the engine running long enough to reach operating temperature and then it ran well enough to drive at low speed. I haven't been able to do this now with cold weather and snow.

Before considering fuel injection, I eliminated other potential causes, mainly vacuum leaks and ignition timing. 

The fuel delivery volume is adequate and base system pressure is 5.5 bar. The cold start injector is working. I have gone through the rest of the test sequence in the CIS Diagnosis and Adjustment manual and it passes all tests except these: cold control pressure = 5.5 bar, warm control pressure = 5.5 bar, full load vacuum enrichment 5.5 bar.

Since then I removed the WUR, disassembled it, cleaned the screen on the inlet side and reassembled it with new parts from  Because the inlet screen was visibly plugged with sediment, I was optimistic that this would restore the correct CP, so I didn't try to reset the fuel cell height, which is about 2 mm above the WUR surface.

Now the WUR is back on the car, but nothing has changed: CP is still basically the same as system pressure.

This is already long, so I'll describe the latest tests in Part 2.

Mechanicals / Re: Just secured a 450 SEL 6.9...
Last post by rumb - 05 February 2023, 09:41 AM
Mechanicals / Re: Just secured a 450 SEL 6.9...
Last post by andrewk - 04 February 2023, 10:04 PM
A little bit of time spent waiting for parts and a weekend away in the country delayed some work on the car.

I wish Mercedes published a description of their bolts other than "bolt" (e.g. M12 x 40 mm x 1.0 - 10.9 Zinc) so I didn't have to remove something from the car, go to the bolt shop then reinstall some time later, or wait for an order from W├╝rth or worse, Mercedes.

So, i'm going to start a catalogue of the bolts, their locations and size (and indicative torque value with a technical reasoning) - coupled with a cross reference to MB part numbers, which in many cases are no longer available. Such was the case for the differential mount to chassis bolts, only two were available at the time of purchase. They come pre-coated with a thread locking compound and should not be re-used after removal, especially when used on drivetrain, suspension or braking system mountings. The bolts from the differential to the mount were a whopping $29 USD/piece from Mercedes Classic. Around 3x what a typical high tensile (10.9/ ASTM A490,A354, Grade 8D) bolt might cost.

So, I have re-assembled the fuel system, the refurbished rear suspension valve, installed a new differential mount and serviced the differential. I carefully cleaned out the brake fluid reservoir which had a lot of black disintegrated rubber particles in it. It is very important that these particles don't end up in the callipers or master cylinder. They are likely from the seals to the master cylinder and also the seal inside the cap. I have a replacement master cylinder to install once the system is flushed out with plenty of ATE SL brake fluid.

The process to clean the tank was as follows:

Emptied old brake fluid (yuck), flushed with small quantities of absolute ethanol until blue dye from fluid was removed, used a degreaser compound (Decon 90) on the inside and out with warm water (fill, shake and drain a few times).
Then I carefully used acetone on a long cotton bud to directly remove the black stuff which was accessible. Following that, I filled and rinsed several times with deionised, ultrafiltered water, several times with the absolute ethanol, then blew out the housing with compressed air, left to air dry. I'll check the float switches with a multimeter and replace the lid which is still available from ATE (PN: 0004315433 - 64), as are the two grommets (PN: 0004310950).

Mechanicals / Re: Inside the WUR
Last post by Feather535 - 04 February 2023, 04:37 PM
There are 2 threads going on this topic, so to avoid further confusion, I'm starting a new one combining this one and "WUR fuel cell height and control pressure".  Stay tuned.
Mechanicals / Re: WUR fuel cell height and c...
Last post by Feather535 - 04 February 2023, 04:32 PM
Quote from: raueda1 on 03 February 2023, 10:01 AMit looks like a lot more has gone on and we're now to 2 threads on the topic.  Feather535, at this point it might be helpful to take a step back and summarize what's been done thus far and the results to date

Good idea.  I'm going to start a new thread combining this one and Inside the WUR and provide a summary of what I've done so far.  Stay tuned.
Shop / Re: Gorgeous 450SEL
Last post by daantjie - 03 February 2023, 09:16 PM
Man that's nice  8)
Mechanicals / Re: Idle Air Connector Hose Re...
Last post by daantjie - 03 February 2023, 04:41 PM
Nice ;)
Mechanicals / Re: Idle Air Connector Hose Re...
Last post by nblewi0 - 03 February 2023, 04:26 PM
Thanks for the quick reply!  I did replace the hose.  It was really brittle.  I actually ended up cutting it off with a box cutter and then I was able to slide the new one in without removing any of the other components. 

I have watched that video from MercedesSource.  It helped me immensely with this task.  I'm replacing all of the rubber components and I am testing/cleaning my injectors at the same time.  It has been a fun learning experience for me.

Thanks again,