Do I need to replace my constant speed solenoid?

[sgp]

Hi folks!

So here's a question for you:

Do I need to replace my 000-072-01-00 constant speed solenoid?

Background:
My 250sl automatic has had some idling issues ever since I bought it 5 years ago. These issues can be summarized as a loss of power and cut-offs after driving it for more than 15-20 minutes (it works well in N and in P). When I get to a stop sign or a red light the car's rpms drop and it starts to cut-off unless I accelerate it. Sometimes, specially in hot weather the car just doesn't turn on or cuts off very easily at a stop. Not to mention the car completely cut offs when I put in reverse backing into my garage after driving it for 15-20 min. I regularly have to manually push it to its parking spot after a drive.

Yesterday I took my car to Mercedes tech who is a friend and he fiddled around with the solenoid tightening some of its screws. Immediately I felt the car perform much better. Today I took it out for an hour drive around town in morning rush hour traffic to test if these "fixes" worked. The car performed very well during the first 40 minutes in stop and go traffic but on the way home I felt it begin to lose power when accelerating it off the line from a red light. Then when I got home and tried parking it in reverse it completely cut off again.

The car is behaving "better" and withstanding longer drives after my friend fiddled with it. However it still cuts-off and is not reliable as I would like to be. So I ask again: Do I need to replace my 000-072-01-00 constant speed solenoid?

Thanks 

< Picture of the CSS attached >

[Cees Klumper]

From what you describe it sounds like you have more issues than only the constant speed solenoid. Especially the 'losing power after longer drives'. You can check the functioning of the solenoid by having a helper put the car in drive or reverse. while idling (foot on the brake) and you can see whether the solenoid is able to push the linkage enough to maintain the idle speed (should be around 700-800 RPM I believe).

[rwmastel]

... but on the way home I felt it begin to lose power when accelerating it off the line from a red light.

Cees is right, other issues at play here. This particular symptom has nothing to do with the CSS.

[lpeterssen]

Dear SGP

I agree with Cees and rwmastel.  The issues described does not have to do with the CSS (Constant Speed Selenoid). 

Yor gave two clues that are important.

1. Hesitation to start engine when hot
2. Loss of power when accelerating.

The first thing I would go after is the fuel delivery system.

a. Check with proper instrumentation Fuel delivery pressure at the inlet of the mechanical fuel injection.  Go to amazon to buy a pressure gauge.  If I am not mistaken it should be around 4 bar.  Check out value on the pagoda forum technical section.

b. Hesitation to start in hot is always related to a low fuel pressure at delivery point.  If pressure is not high enough, specially on hot weather, fuel evaporates causing VAPOR LOCK.

c.  Check condition of the fuel filter at the engine bay on lower left bumper at the front of the engine.

Best regards

L.peterssen

[sgp]

Thank you all for your great feedback and recommendations.

[lpeterssen]

I am pretty sure that problem is related to a tired fuel pump at the trunk.  It has happened to me many times.  In that case pump needs to be replaced for a new one, or you can try first as this is an expensive item, to buy the rebuilt kits that are listed on Ebay by some Mercedes Classic specialized vendors.  During the process of repairing the pump, new seals, new bearings and new carbon brushes are installed.  This later ones will dramatically affect the speed at which the pump spins and therefore you will have a greater output  flowrate and pressure .  Maybe if the armature is OK it can be rebuild.

[rwmastel]

I am pretty sure that problem is related to a tired fuel pump at the trunk.  It has happened to me many times.

Don't just go changing parts without testing. Collect facts (test results) and then decide what to do.

[lpeterssen]

Yes I agree, first buy the fuel pressure gauge kit, and measure values after the fuel filter and compare against specs listed on the technical section of the forum.  Do that on a cold engine, and also after 30 minutes of driving on a hot hot day.

[lpeterssen]

Here what you need to accomplish the job
Fuel pressure testing kit

BETOOLL HW0138 0-140PSI kit de herramientas para el auto con medidor de presión de la bomba de inyección de combustible. https://a.co/d/1I9pOYV

[teahead]

try the linkage tour (adjustment)