Starting problem when hot

[toneypenna]

Hello to everyone:
64 230 SL:

My new problem is car starts immediately when cold.  When it's warmed up or hot will not start.
Example, yesterday I started the car let it run for about 1/2 hour shut it off, won't re start.
I have read the technical manual, and many thread's regarding this.
I have tried 1/2 and full throttle with no positive result.
I have recently changed the TTS with a Bosch switch. It wasn't bad, at the time had difficulty starting when cold. I found a broken wire at TTS switch, repaired it and that solved cold start  problem. I only  changed the switch because one of the terminals was loose due to the bakelite or whatever that is on top of the switch was broken and the terminal was loose.
Yesterday, expecting that the engine would not start when hot, I rigged up a momentary switch to the CSV to see if that would help, but never got to try it. Before I tried to restart when it was hot I put a test light to the CSV expecting no power,  however I did have  power while cranking, from what I understand this is not correct, the CSV is only supposed to activate for cold starts. Activating the CSV at this time with the momentary switch would be redundant. Please correct me if I'm wrong.
Car has a new battery and even though it cranks well hot and cold, grasping at straws I put a charger on it thinking possibly if it would spin faster, it may start. No difference.
Although I don't think this problem is related, I have recently removed the head and had the valves and guides re done to solve a smoking problem

Any ideas of where I'm going wrong or additional tips on how to correct this.

Jim

[Pawel66]

The CSV is activated also when hot. For a brief moment, but it is. It is called a Cold Start Valve, but it also helps in hot start, the name is misleading.

My issue with hot start was clogged fuel filter causing fuel starvation. One of the experts here wrote once that hot start is the leanest condition the engine is ever in.

During restoration I had an intermediate in-line fuel filter installed between the tank and pump. I measured fuel flow at the end of return line, got poor result and that in-line filter was the first I looked at - it was full of debris. I replaced it, hot start came back. But it was just my case.

[ja17]

Jim,

First perform a fuel pressure and volume test. Next determine if your 230SL has version 2 or version 3 starting aids, (the 230SLs could have either). Version 2 uses a time switch along with the thermo time switch and one second relay. Version 3 uses no time switch. Report back on your findings.

[toneypenna]

Jim,

First perform a fuel pressure and volume test. Next determine if your 230SL has version 2 or version 3 starting aids, (the 230SLs could have either). Version 2 uses a time switch along with the thermo time switch and one second relay. Version 3 uses no time switch. Report back on your findings.

Interesting thought, I will check it out.

Thank you Jim

[toneypenna]

Jim,

First perform a fuel pressure and volume test. Next determine if your 230SL has version 2 or version 3 starting aids, (the 230SLs could have either). Version 2 uses a time switch along with the thermo time switch and one second relay. Version 3 uses no time switch. Report back on your findings.

Joe

I believe I have version 2, there are three relays on the inner drivers side fender. The first  (front) controls the CSV along with the TTS, the next I believe is windshield wiper relay, and then a round one that I believe control's the Injection pump solenoid. Does that denote Version 2?
I'll have to read up  in the technical manual on the fuel pressure and volume test, probably won't get to actually checking that out until Saturday. Will get back to you with results.

As always, thanks for your input.
Jim

[ctaylor738]

My 63 has four relays:  cold start valve (via TTS), injection pump solenoid, windshield wipers, and the round one second relay for the cold start valve.  The injection pump solenoid moves the rack to full rich when the starter is turning and in my experience is the most important in getting a 230 to start.  I have seen a couple of cars where this relay was removed, so you might poke around and see if there is an extra four-pin socket or some taped-off wires in the vicinity.

Good luck.  This can be a frustrating problem.

CT

[ja17]

Look for the Thermo Switch to identify Version 2. The thermo switch is a sensor which has only one wire going to it. Only version 2 will have the thermo switch. Both Version 2, and Version 3 have the Thermo Time Switch that have two wires going to them. Counting the relays will not identify the Version. Only the earliest 230 SL Pagodas had Version 2. Most 230SLs had Version 3.

[ctaylor738]

Hmm.  Sorry for hijacking the thread, but is this Version 0?

My '63, number 133 has two thermo switches.  One is the standard time switch with two wires.  The second (in the back) has a single wire.  Both provide ground to the cold start valve relay.  I believe the single wire switch was for engines up to #404.

Cheers,

CT

[BobH]

Hello to everyone:
64 230 SL:


...Before I tried to restart when it was hot I put a test light to the CSV expecting no power,  however I did have  power while cranking, from what I understand this is not correct, the CSV is only supposed to activate for cold starts. Activating the CSV at this time with the momentary switch would be redundant. Please correct me if I'm wrong...


Jim

As i understand it, on your car, the intake starting valve (CSV) receives a one second pulse from the time switch/time relay/one second timer, the round relay.  This happens regardless of engine temperature.  The contacts should provide a signal to the starting valve during cranking for one second only, as an aid to warm starting.  If you are receiving a signal there for more than one second, perhaps the thermal coil is open circuit and the contacts are remaining closed, if it is switching the intake starting valve for the full duration of your cranking, then the engine may well flood.  Perhaps unplug this timer relay and then see if it helps with your warm starting problem.  For cold starting the TTS provides the signal to the starting valve, so the one second relay doesn't play any part in cold starting

[rwmastel]

Look for the Thermo Switch to identify Version 2. The thermo switch is a sensor which has only one wire going to it. Only version 2 will have the thermo switch. Both Version 2, and Version 3 have the Thermo Time Switch that have two wires going to them. Counting the relays will not identify the Version. Only the earliest 230 SL Pagodas had Version 2. Most 230SLs had Version 3.

Correct me if I'm wrong, but I believe what you wrote could be rewritten:
Version 2 = single wire thermo switch
Version 3 = single wire thermo switch plus dual wire thermo time switch

[BobH]

Hmm.  Sorry for hijacking the thread, but is this Version 0?

My '63, number 133 has two thermo switches.  One is the standard time switch with two wires.  The second (in the back) has a single wire.  Both provide ground to the cold start valve relay.  I believe the single wire switch was for engines up to #404.

Cheers,

CT

Hello Chuck, from what i've read yours is version 11, i'm not too sure if there was a version 0 or 1?  Early cars up to late 63 had the thermo switch, a simple switch which opened the ground contact when the coolant temperature increased, and also the thermo time switch, which did the same, but also had a heater coil built in, which also opened the contact after a predetermined period of cranking.  i don't quite understand why both switches were fitted, it would be interesting to find out.  The one second timer relay was also fitted to assist in warm starting.  From what i understand the thermo switch was subsequently removed in late 63

[ja17]

Mercedes had five versions of starting aids for these mechanical fuel injected engines. Version I was an early system used on some other models produced before the W113 cars. Version 1 was never used on the Pagoda engines. Version 2 was an early version used on the next  models including the earliest 230SLs. This version 2 can be identified as having a thermo-switch). Don't confuse this with the round "time switch" which is simply a 1 second relay. By far the most common version used on the pagoda engines was version 4 (late 1965 to sometime in 1970) . You cannot gather all this information in one BBB. You would need to study both. The best source of information is our technical manual which has graphs, diagrams and pictures. Much of the information is original from our group and cannot be found anywhere else. In addition Version 2 can be modified to perform the same as version 3. Also Mercedes produced a factory modification kit for version 4 to improve starting if needed. It can be complex to understand all the versions. My personal notes on "starting aids" is a loose leaf binder with about 200 pages of information!

[rwmastel]

My personal notes on "starting aids" is a loose leaf binder with about 200 pages of information!

I'll be over this weekend with a mobile photo copier!   

[mauro12]

Could be also leaking delivery valves on the injection pump . They don’t keep enough pressure and fuel is boiling inside the tubes . You need to crank several times in order to build up pressure in the lines .
Correct me if I’m wrong .

[rwmastel]

Yes, that's possible.  There are a lot of things possible.  We just need to suggest good tests to narrow down and eventually identify the problem.

[toneypenna]

Look for the Thermo Switch to identify Version 2. The thermo switch is a sensor which has only one wire going to it. Only version 2 will have the thermo switch. Both Version 2, and Version 3 have the Thermo Time Switch that have two wires going to them. Counting the relays will not identify the Version. Only the earliest 230 SL Pagodas had Version 2. Most 230SLs had Version 3.

I stand corrected, which i'm getting real used to with this car. It appears to have version three, just the TTS with two wires, I looked all over the block and could not find another one with one wire.
I did find this (picture attached) it's on the inside of the right front fender. Looked in the tech manual, couldn't find anything there either, maybe I'm using it wrong or didn't look in the right place.
Hoping to get to the fuel tests on Saturday, and will report back.

As always, Thank You

Jim

[ja17]

Jim, that is the voltage regulator.

[BobH]

As i understand it, on your car, the intake starting valve (CSV) receives a one second pulse from the time switch/time relay/one second timer, the round relay.  This happens regardless of engine temperature.  The contacts should provide a signal to the starting valve during cranking for one second only, as an aid to warm starting.  If you are receiving a signal there for more than one second, perhaps the thermal coil is open circuit and the contacts are remaining closed, if it is switching the intake starting valve for the full duration of your cranking, then the engine may well flood.  Perhaps unplug this timer relay and then see if it helps with your warm starting problem.  For cold starting the TTS provides the signal to the starting valve, so the one second relay doesn't play any part in cold starting

If you're getting power at the intake starting valve (CSV) all the time when you're cranking, that's not correct, you'll also be getting power at the injection pump solenoid, (if you have one) so will definitely flood the engine

There will be a problem with the starting aid system, the relay or the time switch, pictures of both are on here

https://www.sl113.org/forums/index.php?topic=36601.0

Easy to investigate these first, either unplug the timer and see what happens, or disconnect the wire at the CSV and pump solenoid (if you have one, depending on your pump type) and see if that improves the warm start

[ja17]

Chuck, you do not have two "thermo switches" the one with two wires is a "thermo time switch".  Rodd, Version 2 has both, a single wire "themo switch" and a two wire "thermo time switch". Version 3,4,5 do not have a single wire time switch. You can look at my graphs in "The Starting Aid Tour" and see what device is activated, how long it is activated, and at what temperatures it is activated according to the Version. I made and posted charts for versions 3,4 & 5.

[toneypenna]

Jim,

First perform a fuel pressure and volume test. Next determine if your 230SL has version 2 or version 3 starting aids, (the 230SLs could have either). Version 2 uses a time switch along with the thermo time switch and one second relay. Version 3 uses no time switch. Report back on your findings.

Joe

Finally got to do the fuel pressure test  yesterday.
Looked all over couldn't find a TS so I would think this is version 3.

My findings, fuel pressure 19lbs. Volume:  allthoug I didnt actually measure the1 litre in 15 seconds flow rate, there is a good flow and from experience I believe it would qualify for those specs. Additionally, I have timing set about 32/35 any further and it wants to kick back on the starter.
The following is my experience with it yesterday: Starts cold no problem, after reaching operating temp, it started difficult once with promting by holdoing accelerator open. After that wouldn't  start at all, just cranks like ther is no spark, however when I check for spark there is.  Put a test light on the cold start valve and it lit for a second or two during cranking, from what I've read this is correct. Hooked up momentary switch to the TTS held it on during cranking, light stayed on, however had no effect on it starting. Left it and haven't gone back to it, but when I do it will probably start right up.

I'm lost with this, any help you can give would be greatly appreciated.

Jim

[ja17]

Your making progress. Next check the starting solenoid on the injection pump. It should activate for at least one second on any cold and hot starts, with version 3.

[toneypenna]

Your making progress. Next check the starting solenoid on the injection pump. It should activate for at least one second on any cold and hot starts, with version 3.

Joe
It appears this car wants to do me in. Pulled the coil wire so it wouldn't start while testing the injection pump solenoid. put test light on it and it lit for about 3 seconds during cranking. While I was at it I thought I would test the CSV again, test light also lit for a bout 3 ,seconds. I  plugged the coil wire back in turned the engine over and it wanted to start on the initial revolution but didn't. Sounded like a carburated engine would if you tried to start it with out stepping on the accelerator. ( Initially fire off but immediately stall) Tried again this time holding the throttle open various degrees, no luck. Left it sit for about 20 min same result, checked for spark again, it has spark.
Naturally never got a chance to test the injection pump solenoid when at operating temperature.
Had to leave, going back later will try to start it then.

Jim

[alchemist]

You may search "Mercedes Hot Vapor Lock" which was and still is a notorious problem in the 1970's and for a variety of Mercedes models such as 450SL. It has to do with bubbles in the gas lines when the car is hot. Good Luck.

[toneypenna]

Joe

Tried again to start it, no go. So now it looks like I have to fix a cold start problem before we can adress the hot start problem. I believe I'm  getting a gas odor after trying to start. Also in snooping around looking for something I noticed that  the CSV has a crack in it,  the valve doesn't look that old but looks like someone previously tried to  repair it as I see what appears to be glue on it. The crack is in the housing only almost like the ear was broken and they glued it back on. I'm attaching a picture. Can't see how this would cause my problem but stranger things have happened.

Thanks,

Jim

[alchemist]

Smelling gas is an indication of flooding. You may check the spark plug after cranking and smell it. If you find sign of flooding, then you need to adjust the knob at the back of the injection pump. Turn it counter clockwise few notches when the engine is not running.