Cold Starting Valve

[Mpgeslak]

Hi all, I have been having problems getting my 250SL to start and have been reading the Starting
Aid Tour and following the diagnosis instructions.  I have determined that the CSV is getting power, but it only seems to last for a second or two.  Based on the Tour and a bunch of things I have read on the forum, it seems my TTS might be the problem.  If this is the problem, is there anything that can done to repair it or will I need to replace it (from what I see this can be an expensive option). 

Also, can I rule it out it isn’t a problem with the relay?  I have opened it up and cleaned the contacts and done the rest of the tests and everything else checks out other than the power from #87 only lasting a couple of seconds,

Any assistance would be appreciated.

Michael

[ja17]

Hello Michael,  also check the starting solenoid on the injection pump. It should energize whenever the starter is activated.

[wwheeler]

A couple of questions first. You say hard to start. Are you talking about cold, hot or both? How long does it take to start? The CSV should stay on longer if it is really cold. How cold is the engine when you start it? If kept in a climate controlled garage, then that would be the temp inside.

No, you cannot "repair" the TTS. But you can do a ohms test to determine if its working or not. That should be in the tech manual as well.

[Mpgeslak]

Thanks for the responses.

I will check the starting solenoid next, thanks.

It is not in a climate controlled garage and the the temperature is in the low 50’s.  Car will not start at all at this point, so it is a cold start.

Thanks for the responses, have spent a lot of time reading and testing but still can’t figure it out.

[wwheeler]

At 50 degrees, the CSV should stay on much longer than 2 seconds. I would test the TTS and may need to remove it to do so accurately. Not starting at all cold could be a much wider range of problems. I would think a failed starting solenoid would not be the lone fault of the engine not starting. May need to step back to the basics and confirms those - ignition and good fuel flow. Was it doing anything odd before this?

[Pawel66]

Bear inmind you can attach a jumper wire to power your CSV during start to confirm its powering is the root cause of the issue. Please also note that CSV is supposed to be working during warm start as well, it is not just a cold start.

A lot of Members have additional switch to do it while cranking.

[Mpgeslak]

Thanks for the suggestion to step back and go back to basics, I may have gotten my head down following the Starting Aid Tour.

Basics:
Bought the car at auction a couple of months ago.  It didn’t start, I replaced the ignition system with a 123 Electronic Ignition and it started on first turn.  Also replaced the Starter which was failing with a smaller After Market 1.5kw version.  It did start after this, but then stopped.

Battery is charged at 12.6v, getting 10.5v when cranking.  Getting spark to each plug, should note I do have some oil on the threads of plugs. 

The injectors and fuel lines were old and frozen together, replaced both.   Checked fuel flow, which is fine.

Any advice on where to go next?

[Pawel66]

I do not want to side-track you, I am not a mechanic, but if a new or cleaned set of spark plugs does not help, it may be down to fuel delivery issue. The CSV test with a wire is easy - you will see if keeping it activated longer helps.

With 123 - just make sure distributor cap sits ok on the casing, they have weak springs. If the car was running nice, the leads and plug type are ok probably. If you get a nice blue spark - electric side is probably ok. Can always crank it in the dark garage, look for blue "thunders".

Fuel delivery - we measure at the tank end of the return hose (is it how you did it?). Clogged filters (there are 3 or more) or lines, including the return line, often cause starting difficulties.

Do you smell gasoline when you crank a bit longer than usual?

[ja17]

Check the fuel pressure, I would also check the injection  pump rack to make sure it is not stuck.

[Mpgeslak]

Thanks everyone for the advice, very helpful.

Will re-check the distributor cap, I had noticed the clamp is not very tight.  I have not heard the term “blue thunder”, i assume this checking the spark colour for each plug by cranking in the dark?

Will re-check the fuel delivery at the return line.  I do smell fuel when cranking it for a period of time.  How do I check for stuck pump rack, I have researched this but couldn’t find how to diagnose it.

Again, thanks all for your assistance.  With so many variables in the fuel injection/delivery system I am finding it difficult to isolate the issues.

[teahead]

Clean the relay for the TTS.  I.e. open up the box and check the contacts, etc.

BTW, I have a brand new CSV (Bosch) that I'm not using.

Looks like this:

https://www.authenticclassics.com/product-p/auth-003022.htm

[Pawel66]

Sorry for my poor English - by "blue thunder" i meant - when you crank the engine in the dark and there are shorts in the ignition leads, cap or connectors, you may see it as blue sparks between those elements and ground. The good spark on the spark plug should be seen clearly in ambient light.

I had the cap spring gone lose on my 123. It caused cap being lose and this in turn caused broken coal connector between the cap and rotor. Then I heard from other Members about this springs going lose - that is why i wrote about it.

Stuck pump rack - if you go to this link:

https://www.sl113.org/wiki/Fuel/Injection#Pump

and take a look at the first picture under the chapter Operation, you will see where the access is to the pump rack is. The picture does not show the cup that covers this access and needs to be unscrewed. If you have this M4 threaded hole in the tip of the rack, screw in an M4 screw and push the rack backwards gently - it should move backwards with some resistance, but smoothly and then (as it is spring-loaded) it should return. This rack is a toothed bar that moves back and forth causing the Fuel Injection Pump pistons to turn and move. if it is stuck, it means one or more pistons are stuck and are not working. You can try to push the rack in without the screw, but then it may be dificult to pull it back out in case it sticks.

I am enclosing a good guide to work through starting topics systematically, which saves time vs. "shooting from the hip", that even I can understand and follow. Of course not 100% for our cars, but gives a general idea where to start.

[Mpgeslak]

Thanks Pawel for the detailed response.  Will work through the diagnosis step by step on Saturday morning.  Will probably start by going through the set up steps of the new 123 Ignition system I installed.

Just so I am clear on what I see and read on access to the Injector Pump Rack,  can I access it without removing the pump from the car?  From what I see I think I can, but wanted to make sure

Thanks again.

[Pawel66]

Yes, you can access the rack without removing pump. For example look here: https://www.sl113.org/forums/index.php?topic=30088.0

There were a lot of posts about this. Try the search function for FIP for instance.

[Mpgeslak]

I went back over all the basics today, still doesn’t start.  Here is what I found:

Battery:  12.9v and over 10.5v when cranking

Coil: 2 ohms primary resistance, 9 ohms secondary resistance

123 Ignition:  re-checked the set up, all seems fine, only thing I noticed is the rotor has more play in it than I would have expected

Plugs:  seem to get a good spark on all of them.  There is oil on all the threads

Fuel: did the test and got 1 litre of flow in 15 seconds, and which seems good

IP Rack:  I could easily push it in an inch or so and it came right back out

Compression Test:  did a compression test and 4 were low, two down near 40%

My current thinking is the oil change on spark plug threads and low compression means a bigger problem, guessing head gasket?

Thoughts?

[ja17]

Might want to check the valve adjustment to see if all the valves are closing. Remember, if you have spark on time, fuel and compression, it should run.

[Benz Dr.]

Plugged cold start valve.

[Pawel66]

You have some clues here to follow what BenzDr. is suggesting:

https://www.sl113.org/forums/index.php?topic=840.msg4024#msg4024

[Mpgeslak]

Thanks for all the help, The suggestions on the basics of spark and fuel were spot on and I finally figured it out.

I had tested the plugs using an inline tester with a light and they tested fine.  Given I have oil on the plug threads, I got to thinking maybe the oil was stopping them from sparking as well as a simple light test suggested.  So I figured I would look at the spark myself and tested the plugs out of the cylinder and  I found a couple weren’t sparking well.   Since I had already tested the new ignition and it was all fine I cleaned the plugs really well and it started almost immediately.   

Good news it is starting again, bad news is the oil leak is probably worse than I thought. 

I have removed one of the ball studs and the threads were totally dry, plus there doesn’t seem to be oil on the outside in the spark plug well.  I am guessing head gasket?  I have never removed a head before, but I have read the Workshop Manual and searched the forums for information.   

The thing I am most worried about is doing something wrong and making the situation worse.  Thoughts on how big a job it is for someone who hasn’t done it before?

Again, thanks for all the help, it has been fantastic.

Michael

[Mpgeslak]

A bit of an update.  Now that it is starting I have been able to observe more of the symptoms relating to the next problem of oil on the spark plugs.

-  There is grey smoke that gets worse as the car idles
-  the car seems to be idling at a high RPM, but other than that no obvious noises coming from the engine
-  no misfiring
-  I checked the threads again on the ball studs above the spark plug wells and they are all dry. 

What doesn’t make sense to me is how that much oil is getting into the spark plug threads.  I have searched the forum and from what read it seems like the piston rings or the valves.  Suggestions on next steps to diagnose?

Sorry for the newbie questions, thanks again for the help!

[Benz Dr.]

There are three ways oil can get into the combustion chambers: past the rings, down the valve guides or around a loose guide, and more rarely, around an exhaust ball stud. The first two symptoms will show smoke at idle with deposits on the spark plugs. Leaking exhaust ball studs will also produce smoke at idle but the spark plugs will remain clean and dry because oil will only enter the exhaust port and not be burned in the combustion chamber.

[ja17]

If yours is an automatic, smoke can be caused by  a bad modulator diaphragm in the automatic transmission. Top off all fluids and observe. Large amounts of engine and transmission fluids can enter the exhaust manifold and end up in the mufflers. Eventually these fluids will burn off when the exhaust is full temperature. Your problem is find out where the fluids are coming from. A bad head gasket may cause rough running, loss of coolant, smoke and problems maintaining engine temperature.

[wwheeler]

Didn't you say on a few posts back that your compression readings were not very good? I forget, did you ever posts how many miles this engine has?

[Mpgeslak]

Not sure on the mileage as there was no service records with the car.  What I do know is the engine was replaced with another 1967 engine from an SE, but not sure when the replacement occurred.   The mileage is 107k, but no idea how many miles this engine has on it.

The car is a manual.

[FGN59]

Hi,
Once you solve the oil/compression issue, should you wish to replace the TTS, there are several replacement parts (new) on the market, at least in Europe, made by either VDO (the original manufacturer of all the TTSs I have seen) or by Bosch, going for about 70 to 200€:

https://www.theslshop.com/parts-shop/mercedes-benz-r107-350sl-c-w113-thermostat-time-switch-0015459224.html (VDO)
https://www.niemoeller.de/en/search/D%2008%20551 (VDO again)
https://www.sls-hh-shop.de/main/de/mercedes-230-280sl-w113/15-motorelektrik/07-c-elektrische-regulierung/thermozeitschalter-bosch-bauart-siehe-bild-p-134504 (Bosch)

Hard to believe the same part can be found for either 70€ or 200€ from two reputable vendors, so may need to be checked before ordering.

Best of luck with the repairs.