photos needed of starting solenoid

[n/a]

I have been asked to try and trace the cause of a '67 250 sl having problems when starting warm. From the forum it sounds like it might be the starting solenoid. Is anyone able to post a photo of this part so I will know where to focus my attention. Also are the any other possible causes? After the car has ahd a chance to cool down, 10 to 20 minutes, it starts right up.
thank you,
Rudy

[iceberg]

Hi Rudy,
I had similar problems.  Mine got fixed and it had to do with fuel delivery and not with the starting solenoid.  I can help you identify the starting solenoid, but here is something I jsut posted for another member. It makes sense and is worth a shot before you start poking around and later cursing yourself for it, as I did.

So here it is...and it has worked for atleast 4-5 members on this site,
"I had the exact problem a while back. In my case the symptoms were similar and these were created by a clogged fuel pump or fuel filter. Let me explain! See what happens is that in our injected cars the fuel flows from the tank to the fuel pump through the fuel line to the engine. Any excess fuel is returned back through the return line. Now if the supply is scanty because of, either a blocked line (in line or return line) or a faulty pump, what begins to happen is that since there is little or no flow the fuel in the the lines begins to evaporate due to engine heat, thus choking the engine till it dies of fuel starvation. This is what was explained to me. Now to this end, I took off the fuel pump and looked into it where the fuel enters the pump (by the way, the fuel pump is underneath the car on the rear left side....I have a left hand drive). There was a lot of gunk there pressed up against the mesh. I took a marrow spoon and cleaned it out, put the pump back on and it worked like a charm. Then I got adventurous and took the fuel pump apart. Bad mistake. I managed to put it back together very easily but it just would not stop leaking. This led me to buy a new pump and that was expensive, but never had a problem since. So this is how it was explained to me and I am forwarding it to you. Maybe in your case this is not it at all, but a little trial n error never hurt anyone. Let me know how it goes...if this is the prob which I think it is because of the exact symptons, then you'll be just fine.
Also check the fuel filter.  This is a typical fuel delivery prob, especially given that it happens when the engine is hot.  This means that the trapped fuel in the lines is evaporating owing to engine heat."
Regards,
H
P.S: In the engine compartment where all the relays are on the left front fender, there is a relay in the earlier cars to help with starting. Is that what u are referring to?  That has nothing to do with hot starting symptons.  Anyhow just to tell you it is a black cylinderical casing.  
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[JPMOSE]

The photo in the prior posting is of a "Cold Start Valve" Solenoid (located at the far right of the engine compartment on the side of the intake manifold) and not the Starting Solenoid.  The Starting Solenoid is on the back of the injector pump.  Sometimes there are two solenoids on the back of the injector pump -- the Starting Solenoid is the upper one (the lower one is a Fuel Shutoff Solenoid used on USA cars starting with 1968 250SL).  Here is a photo of the injector pump, posted by Joe Alexander:

http://www.sl113.org/forums/uploaded/ja17/20031023231515_injection%20left%20illus.%203.JPG



Best Regards,

J. P. Mose
1968 250SL
1987 560SL

[hands_aus]

Hey Rudy
One way to start a HOT car is to press the pedal about half way down while cranking then let it off when it fires up. This is what MB recommends in the owners manual or BBB.

There is a relay associated with the COLD START SOLENOID (injection pump) which if the contacts are pitted and worn will not work and will not allow voltage to operate the CS Solenoid.

The solenoid should work every time the car is started (cold or hot).
You can use a test lamp attached between the contact on the CS Solenoid and earth/chassis to see if the relay is working while cranking.
If the test lamp doesn't shine another test is to remove the cable plug from the relay and then push it back on. Do it a couple of times.. you never know might be a bad contact.
Then retry the test lamp again.

The relay can be opened and the contacts cleaned and adjusted, it just needs a firm but gentle hand.

Tell us what your economy is like, the colour of the exhaust pipes,

Sounds silly but these are indicators of the tuning of the air/fuel mixture

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[rwmastel]

quote:Originally posted by hands_aus

There is a relay associated with the COLD START SOLENOID (injection pump) which if the contacts are pitted and worn will not work and will not allow voltage to operate the CS Solenoid. The solenoid should work every time the car is started (cold or hot).

Then why is it called a cold start solenoid?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[hands_aus]

quote:Originally posted by rwmastel

quote:Originally posted by hands_aus

There is a relay associated with the COLD START SOLENOID (injection pump) which if the contacts are pitted and worn will not work and will not allow voltage to operate the CS Solenoid. The solenoid should work every time the car is started (cold or hot).

Then why is it called a cold start solenoid?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

Hey Rodd,
Maybe because it is noticably more effective when the engine is COLD.
Maybe it should be callled 'START SOLENOID'.

Similarly, the 'warm running device' is part of the cold start up system... strange huh?

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[ja17]

Hello,
This can be confusing. Both devices are actuated by a electrical solenoid controlled by an electrical relay. The BBB is not even entirely consistent on the terminology of these devices.

The device on the intake manifold near the intake is most often called the "starting valve". We can call it the "intake starting valve" here to prevent confusion. This device consists of a electrical solenoid and a valve which allows extra fuel to spray into the intake manifold when the engine coolant is cold. Iceberg just posted a very nice photo of the intake starting valve in another string.
 The valve is actuated by a electrical relay which is tripped by a engine coolant sensor in the engine called the "thermo time switch".
There are several different "thermo time switches" and at least two different configurations of "intake starting valves" used on these W113 cars over the years of production. The main difference in function is the temperature range of when the device is actuated and how long (duration in  seconds) it is actuated during the cold starting process. One version has a slightly increased fuel spray in the intake.

The 230SL had three different versions. Page 07-10/12a of the early BBB explains most of the differences and also tells how starting can be improved by replacing the thermo time switch with the later one and modifying the wire ring terminal to fit the new switch.

Later W113 cars had two different size "intake starting valves" one was physically smaller.

Another factory modification was offered to increase the activation time of the "intake starting valve" if cold starting problems persist. The modification included adding a time relay and its wiring harness to increase fuel spray an additional one second.

In all cases these expensive units were the same on most same era fuel injected Mercedes sedans.

The relays which activate these units are located along the hood opening on the right side of the engine compartment. Exact location may vary slightly depending on model W113.

The easiest way to test these units is to use a test lamp on the electrical terminal of the solenoid during the engine starting process. If power is not delivered during starting, the electrical relay is not working or the "thermo time switch" is defective.

In many cases a non working relay can be restored by simply cleaning its electrical contacts.  

The other starting aid on the injection system is most often referred to as "the starting solenoid". To prevent confusion with the "intake starting device" we can call it "the injection pump starting solenoid" here.

The "injection pump solenoid is more simple in function. It activates an electrical solenoid on the injection pump to enrich en the fuel mixture to the engine during starting. It activates whenever the starter is actuated. It is also controlled by an identical electrical relay.  
Here again the function can be tested with a 12 volt test light. During starter operation the test lamp should show power to the solenoid. Once again cleaning the contacts on the electrical relay can restore the function of a non working relay. Test the solenoid on the injection pump by simply jumping a hot wire to its terminal.

On injection pumps with two electrical solenoids, the top solenoid is the "starting
solenoid".

The last device, which is not actually a "starting device" is the "WRD" or the Warm Running Device" on the injection pump. It will effect cold starting if the device is stuck in the hot or lean position. This unit will change the fuel mixture and air intake of the engine at the injection pump. Engine coolant flowing through the unit changes the position of a slide valve and plunger via a "heat feeler" (thermostat). These do get stuck from inactivity. Dis-assembly and cleaning will often restore its function. Page 07-14/3 of the later BBB has some nice photos, diagrams and text on the later "WRD".

The unit is located on the top rear of the injection pump and can be identified by the engine coolant lines going to it.  Listening for air rushing in the small cylindrical air filter during the warm up cycle of the engine can tell you if it is functioning. These air filters must first be checked to see if it is clear. Remove it and test it. Check the function of the "WRD" by listening for the suction at the "WRD" air filter by using a section of rubber hose as stethoscope.

Some of the earliest versions of the WRD had no separate air filter but had an air passage but had a separate air line plumbed back to the main air filter.

The early 230SLs had a injection pump and WRD which was different from the later W113 cars. The function was the same but many components were unique to these early cars.

The last significan factor in engine starting is good strong ignition and proper fuel supply. These items should be checked before diving into the complexities of the fuel injection system. Ham=ving the engine in good tune and testing the fuel pressure and volume will often times solve starting problems.

I will try to fill in some of the blanks here with photos and diagrams in the next few days. I am sure George D. others have musch to add to this info also.

Joe Alexander
Blacklick, Ohio