bad coldstart or bad solenoid

[r.bartl]

I was on the way to buy a new solenoid but was told to post my symptoms to find the source of my problem (thx. Bob!)

I have a 230SL with automatic transmission. had no problems until one month ago.

- since appx. 4 weeks the car doesn't start well when it is cold.
- sometimes it just makes "clack" and nothing happens
- with the second try it tries hard (oinck, oinck, oinck), often about 15-20 seconds until the engine starts.
- the idle in "P" is about 900 rpm
- if I shift into "R" or "4", the engine often dies and I have to start again.
- until the engine is warm/hot, it always sounds like the idle is too low when having a drive gear in and hit the break. the idle shows appx.600-700 upm
- my mechanic thinks that my solenoid is bad, it does move, when I shift from "P" to "R", but it seems to be weak, he says.
- I tried the "spare solenoid" from Mike Salemi, he bench tested it and electrically it appeared to work, but no difference for my problems, when I installed it.
- once the engine is warm/hot, everything seems o.k. (idle on "P" 900, idle with shifted gear and break 600, idle on "O" 1000 ump
- sometimes when I stop and have a gear in, but hit the breake, the oil pressure goes down to just above 30 instead of 45. if I shift to "O" or "P" it looks normal again.

to me everything has to do with the idle, but if you have other suggestions, please advise.

as the change of Mike's solenoid didn't solve my problems, maybe there are more things connected.

my mechanic did spend 1.5 hours for adjusting idle speed, he told me that there is still "room for improvement", but as I always have a problem starting the car in the morning, I want to change these flaws asap.

thx. for help!

roman

p.s. attached an image of my existing solenoid


Download Attachment: solenoid.jpg
79.14 KB

230SL, 1967
ivory with chocolate brown top

[George Davis]

Roman,

it sounds like you may have a couple of problems: the cold start valve on the intake manifold, and the warmrunning device on the injection pump.

A bad cold start valve makes starting the engine very difficult when it's cold.  There are several possibilities: a stuck valve, stuck solenoid, bad solenoid, bad relay, or bad thermo-time switch.

The warmrunnig device could simply be stuck, in which case disassembling and cleaning it may be all that is necessary.  Or, the thermostat element may be bad, in which case it must be replaced.

Also, before either of these, the ignition system must be checked to be sure it's in good order.

These are the first things your mechanic should be looking at, in my opinion.  Good luck!

George Davis
'69 280 SL Euro manual

[hands_aus]

Roman,
Try letting the the fuel pump prime the inj pump for about 20 seconds before you start the car.

I believe that if the inj pump ball valves bleed-back then the fuel will be depleted in the lines to the injectors and you will have a delay in starting.

If you have a re-built inj pump then it is unlikely bleed-back will be a problem.

My comment about your solenoid... if the borrowed one did the same thing then it is not the solenoid.

These topics have been discussed many times on here. Do a search for 'cold start problems', ' warm running device', 'constant speed solenoid', print out the results for the mechanic and yourself.

There are tests you can do yourself if you are technical.

Also a DIY guy benefits from owning a service manual (known as the Big Blue Book (BBB)). There is lots of good info in the Haynes manual too.

Try the simple basic things before replacing solenoids etc at huge MB prices.

Please keep us informed on how you are progressing.

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

[ja17]

Hello Roman,
As George and Bob has mentioned, make sure the car is in "good tune" before making adjustments on the  complex injection system.

If you are not sure of the mechanical history of your engine you may need to give it a good "physical" before you can accurately diagnose the problem.

Assuming you have no recent history of the following, I would replace the fuel filter and check the fuel pressure and volume. Check the engine compression (warm engine). Remove and replace the spark plugs, re-torque cylinder head and adjust valves. Replace the ignition points and set the timing. Make sure the distributor vacuum cell and the centrifugal advance is working on the distributor. Set-up the accelerator linkage paying close attention that the venturi linkage stop screw is set correctly. Check the air filter on the injection pump and check the oil level on the injection pump.

Change the engine oil if it is due.

At this point you can consider correcting faults in the complex injection system. The warm up device and starting aids along with mixture adjustments on the pump itself.

Ask lots of questions. If you have some mechanical history on your car it would help also.

It is normal for the oil pressure to drop when  a warm engine's  idle rpms become low.


Joe Alexander
Blacklick, Ohio

[r.bartl]

Joe.
thank you for your hints.
yesterday evening I Mike came over and helped me to check some things on my car.
so far we found out:
- the cold starter valve is working (for a couple of seconds after turning the ignition) - there is power coming there.
- if the starter solenoid is acting properly couldn't get tested, it gives a "klack" without crancking.
- as soon as I put in a gear, the motor stalles, event the solenoid for this is pushing

Mike: do you have additional comments, did I forget something?

230SL, 1967
ivory with chocolate brown top

[mdsalemi]

Hello All,

As Roman indicated I went to his home last night armed with a meter and test probe and we got to the bottom of a couple of things.  BTW thank you David Pease for sending the photo--which we didn't need but it was very assuring to have it in case we did.

1)  STARTING.  There was a bit of a communication issue on this.  What has happened apparently, is that the starter motor and solenoid are not working properly.  When the key is turned to start, there are a few clicks from the solenoid, I think, and nothing else--the starter motor is not engaging nor turning.

My experience with this symptom on other cars is that the solenoid is defective, or more likely there is not enough current to engage the solenoid because of poor electrical connection or a bad battery.  Other suggestions?

Now, when this happens on Roman's car, if you turn the key on and off repeatedly, it will catch after a couple of times.  Here's the rub--what Roman was inadvertently doing was NOT turning the key off and on again--but rather leaving the key in the start position!  What this did is to "time out" the 1 or 2 second timer, thus disabling the cold start system.  So when he eventually did get the starter to turn, the cold start was inactivated and there was a very long period of cranking before the engine would start.  Our test probe verified this.

When I did this last night, I immediately turned the key on and off, and thus kept the 2-second timer in check.  As soon as I got the starter to engage and run, the cold start was still working and it fired up immediately.  I did this repeatedly without issue.  Again, verified with the test probe.

While we were at it we checked the cold start relay and its behavior.  When Roman left the key in the on position, the voltage to the CSV would be on for a couple of seconds, then go off as it is supposed to.  True to form, the engine would hardly start without the CSV engaged.  By running these tests we determined that in all likelyhood, the thermo time switch, the 2 second relay, the CSV and relay that drives it are all fine.  The issue is with the starter solenoid or the voltage going to it.

2)  IDLE.  When we did get the engine started, it appeared to have a nice idle at about 800 RPM or so.  I did the "Blacklick" CO test, and it appeared to be OK, however I did notice something a bit odd.  I had to push down on the fuel side of the accelerator quite a bit--a lot of motion--in order to get any change in the RPM, which did go down.  On my car--a later 280SL, when I did this test and pushed down on the fuel side of the accelerator, the RPM drop was almost instantaneous, indicating to me that MY richness is set OK.  My conclusion for Roman is that the richness of the FI pump is probably OK, but all the linkages are a bit off.  Comments?

3)  CONSTANT SPEED SOLENOID.  I have to agree with Aussie Bob that if my spare behaved the same as Roman's then this part is not the issue.  Last night after we got the car started and observed all the issues with the starter and the CSV, I said let's take a look at the CSS.

With the car at that nice 800 RPM idle, as soon as he puts it into gear, the engine dies.  Back to our tester and observation: as soon as he puts it into gear, voltage shows up on the CSS, and you can clearly see the CSS engage and push down on the accelerator.  Problem is it does not push enough.  So, what I tried to do is to manually push that down, helping the CSS so to speak, and maintain the idle.  I was able to do it.  However, the amount of motion I needed to add to this accelerator in order to maintain the idle was very far in excess of the CSS's limited range of motion.

My conclusion on this is that all the linkages need to be set up from square one.  Comments?

3)  OVERALL CONCLUSIONS.
a)  Nothing wrong with the CSV, or anything related to it.
b)  Nothing wrong with the CSS or anything related to it.
c)  Linkages need to be reset.
d)  Starter solenoid issue, probably voltage related.

Any comments?  BTW anyone coming to Roman's home to help him is treated to a restaurant-quality fine meal by his wife Ingrid, and engaging conversation with his lovely 4-year old daughter Francesca!

Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored

[Jonny B]

Mike,

Did you pull the plugs to look at them as a further indicator of the richness/leanness set alright.

I finally got around to that on mine, and they were clean, no black gunk etc. There was a fine coating, but they were not burned away.

Jonny B
1967 250SL Auto

[mdsalemi]

quote:Originally posted by Jonny B

Mike,

Did you pull the plugs to look at them as a further indicator of the richness/leanness set alright.

I finally got around to that on mine, and they were clean, no black gunk etc. There was a fine coating, but they were not burned away.

Jonny B
1967 250SL Auto

Didn't think this was necessary, as we knew there were some other issues that need to be addressed first.

Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored

[hands_aus]

Roman and Michael,
As the car is a 230sl, if it has the 'one second' relay operating each time the engine is cranked, the engine could be flooded because the fuel is not being used. This could cause the extra cranking time.
The thermo time switch will time out because its internal heating element will raise the internal temperature beyond the cold status but the 'one second' relay will contiue to operate the CSV.
To make sure the Thermo Time Switch is working disconnect the plug from the 'one second' relay for starting the car the first time. The CSV will come on and then go off becuase the TTS has timed out.
Once the engine is working and warmed up a bit the TTS will not operate. Re-connect the plug for the 'one second' relay and then test the CSV again when starting. it should fire each time.

On my 250sl the verticle linkage rod that comes up between the inlet/exhaust manifold sections was actually touching the exhaust manifold and using it as a 'stop'. I adjusted the linkages and venturi correctly. This then gave me additional adjustment length for the Constant Speed solenoid.  It might be worth a look with your torch and a small mirror.

It is always re-assuring to make sure the CSV is not leaking.

There is a small 5mm screw in the side of the CSV. You can remove it and with the ignition ON but with the engine NOT Running watch to see if fuel is coming out the hole.
MB BBB specs say more than 3 drops pre minute is un-acceptible.

Remove a couple of plugs and check the colour. That will tell you straight away if the engine is running rich or lean.
I also look at my exhaust pipes... if they are black sooty it is too rich. white too lean.
If they are soft grey the mixture is just right.

These basic tests cost nothing. It will give you lots to talk to the mechanic about.

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

[George Davis]

Michael,

it was very nice of you to go over and help Roman, and nice work, too.

I would agree that the linkages should be checked, starting from square one (i.e., making sure the throttle plate closes properly, then adjusting the rods).

You may have checked the warmrunning device, but if you didn't, the check of listening for air being sucked in at the filter when cold/no air when hot should be done.  If the WRD isn't functioning properly, the engine will run lean until it's warmed up.  Not sure from your write-up if your mixture checks were made with engine cold/cool or fully warm.

Also agree that a bad solenoid and/or low current could cause the starter to not engage.  Other possibilities are poor ground connections from engine to bulkhead, and/or battery to chassis.

George Davis
'69 280 SL Euro manual

[Ben]

Once again we see how this website units owners of these great cars and shows the lengths others are prepared to go to just to help !

Even though Ireland is a small place, there is quite a nucleas of 113's about and most of us met here and have helped eachother over the last few years in one way or another !

Well done Michael, and fair play to Roman and Ingrid for their hospitality...........not forgeting Francesca's input too !   :mrgreen:

Regards,
Ben in Ireland.
'64 230SL 4sp.