Author Topic: Unusual TTS characteristics and cold start woes  (Read 445 times)

FGN59

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Unusual TTS characteristics and cold start woes
« on: December 17, 2019, 15:02:45 »
Hello everybody,

In a few words, let me express as a new member great admiration and a most sincere gratitude for the wealth of information and experience assembled in this forum, for the accompanying technical manual and support, and generally for everything the Pagoda SL Group provides through the efforts and dedication of its members, past and present.
 
As a newcomer to the MB and Pagoda world, I have read with tremendous interest all that seems relevant to my situation, both to form a good understanding of the objects of our common passion, and to try and solve a few small issues I encountered with my new (new to me) car, a 4-gear manual 280SL manufactured in December 1968 and registered on 1/1/1969 in California. The car was reimported to Europe in 2009, and ended up in my hands two months ago (originally from Paris, I now live in the south of France near Aix en Provence).

The engine suffered a stroke early in 2019, if I may say, and was totally rebuilt from the inside out by a specialist for the previous owner. I purchased it (all matching numbers), after having it verified, before it was even broken in, and have put 1.000 miles on the odometer since, with growing exhilaration (from 2500 rpms at the start to 5500 by now, and still more to come - though I don’t expect to run the engine at such revs after the end of the break in period). It works like a Swiss (or in this case German) clock, and I can’t wait to put the top down when the weather permits.

Except... cold starts. The car starts only after about 10 seconds of cranking (and then it runs as I believe it should). Those 10 seconds don’t seem right, at least in my opinion, given the expectations rightfully nurtured by the gifted and dedicated engineers who have given MB and the German car industry its reputation…

I have succeeded in improving this 10 second-delay from maybe 15 secs when I got the car, after verifying each and every component of the cold start system on the car (CSV, CSS, WRD, TTS, relays, wiring, fuse, seals and o-rings, etc.), but also the timing, spark quality, fuel supply, etc. This was made a lot easier, and in fact simply possible, by the numerous articles and photos or drawings in the technical manual and various posts, so again thanks to all concerned.

I found that the inner o-ring in the CSV was nearly completely worn (replaced it), that the wiring to the TTS was wrong (G and W wires inverted, which I obviously corrected), and that everything else was not only good but running at spec or even better (as an example the fuel pump could supply a 747 at take-off, or nearly, from a crystal-clear tank and with a powerful return).

As it stands now, when I crank the engine, a test light hooked to the CSV illuminates the engine bay for 2 seconds, which is not long enough to get the engine started, although it helps a little bit. When I hot wire the CSV, the engine starts almost instantaneously (from cold, which is about 8-10°C currently around here, ie 45-50°F).

I tested the TTS both in and out of the car, and found that it performs exactly as it should, ohm-wise and degree-wise. I believe it is the ’how it should’ which is the source of my problem.

In addition to the expected marks (‘3.03’ for March 2003, ‘35°c +/-3°c’, ‘12V’, ‘120°C), the TTS bears some other which seem a bit unusual: ‘40W’, ‘20°C 5sec’, and ’36/2/9’ right under ‘120°C’.

‘40W’ seems really high (I seem to have seen 3W on pictures of both older and new or replacement TTSs), ‘5sec’ seems really short, and I have no idea what the 36/2/09 could stand for?

So, after this long exposition, I would be extremely grateful if some of you would advise me on the following:

- I am still missing something in my understanding of what could be wrong with the cold start system on my car?
- does anybody have experience with such an unusual TTS (could it be that it is adapted to freezing climes, like in Canada?)
- assuming it is the TTS which is responsible, is it worth exchanging it for a more ‘normal’ one (Niemöller in Germany sells a Bosch replacement for 67€, which is reasonable) or if a more practical course would be to by-pass the TTS altogether (I will try to maintain a reasonable level of authenticity to the car, but not at the expense of usability, plus cranking for 10 seconds or more as the season advances to colder temperatures is not good for the starter motor, the wiring, etc.), and if so what is the preferred way of doing this? I have thought of running a wire from terminal 85 of the CSS relay to same on the CSV relay, to keep all the cold start devices on the same electric scheme (activated by cranking only), with a manual switch in the car of course for warmer starts.
François

1969 280SL US specs, 4-speed manual, beige-grey (726H), parchment leather
1994 Toyota Land Cruiser HDJ80 4.2L diesel
1955 Massey Ferguson TEF20 diesel tractor 😁
Before
1962 Jaguar MK2 3.8L (4.2L XJ6 engine), black, tan leather interior
1968 Peugeot 204 roadster, white, black interior

ja17

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Re: Unusual TTS characteristics and cold start woes
« Reply #1 on: December 17, 2019, 16:04:54 »
Hello and welcome! Did you test the function of the starting solenoid on the injection pump? It should activate anytime the starter is activated.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

FGN59

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Re: Unusual TTS characteristics and cold start woes
« Reply #2 on: December 17, 2019, 19:06:11 »
Hi

Thanks for the welcome, much appreciated.

I did check that the solenoid is activated (I checked the relay, the wiring, and I can hear the solenoid going ‘clank’), but I don’t know how to check the inside of the injection pump, to verify that the solenoid does indeed activate something. I know (from reading on the site) what it’s supposed to do (push the rack inside the pump to change the enrichment of the mixture entering the engine), but I don’t know how to check that it does what it’s supposed to do.
François

1969 280SL US specs, 4-speed manual, beige-grey (726H), parchment leather
1994 Toyota Land Cruiser HDJ80 4.2L diesel
1955 Massey Ferguson TEF20 diesel tractor 😁
Before
1962 Jaguar MK2 3.8L (4.2L XJ6 engine), black, tan leather interior
1968 Peugeot 204 roadster, white, black interior

ja17

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Re: Unusual TTS characteristics and cold start woes
« Reply #3 on: December 17, 2019, 20:12:15 »
The injection pump starting solenoid should be fine as long as it activates. There is a fine screen, in the fitting going into the CSV (intake), make sure the screen is clean. A partially restricted fuel screen will reduce the volume of the fuel spray from the CSV.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

teahead

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Re: Unusual TTS characteristics and cold start woes
« Reply #4 on: December 17, 2019, 20:31:11 »
Do you turn the key on before cranking for at least 2-3 seconds?  I find that helps a lot.

2s for CSV activation before turning off does seem pretty short.  Did you clean and ensure the cold start relay is keeping the voltage to the CSV on long enough?
1970 280SL auto, AC - aka "Edelweiss"

FGN59

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Re: Unusual TTS characteristics and cold start woes
« Reply #5 on: December 17, 2019, 22:19:54 »
I do wait a few seconds after turning the key, to let the fuel pump flood the filter, injection pump, CSV fuel line, etc., before cranking.

And I did check the CSV itself, opened it, cleaned it, changed the small o-ring to the solenoid, the large one to the air intake manifold, checked the small filter inside the fuel line, checked that the CSV is spraying when activated, that fuel is indeed flowing through the CSV and not leaking to the solenoid when it is mounted (in which case one cannot check that it is spraying, but if fuel is coming to the CSV, and it sprays when not fitted in the the manifold, it would be quite extraordinary if it didn’t spray when mounted on the manifold).

Checked the relay (in fact all 3 relays, including the one which cuts the fuel off when decelerating), both statically (off the car with an ohm and voltage meter, checking that I get 0 ohm resistance between 30 and 87 when the relays are activated) and dynamically (on the car, making sure both the CSV and CSS relays activate with a test lamp), and all the wiring and fuse (nº6) to and from the relays to the CSV (via TTS) and CSS.
François

1969 280SL US specs, 4-speed manual, beige-grey (726H), parchment leather
1994 Toyota Land Cruiser HDJ80 4.2L diesel
1955 Massey Ferguson TEF20 diesel tractor 😁
Before
1962 Jaguar MK2 3.8L (4.2L XJ6 engine), black, tan leather interior
1968 Peugeot 204 roadster, white, black interior

FGN59

  • Full Member
  • Senior
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  • France, Provence-Alpes-Côte d'Azur
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Re: Unusual TTS characteristics and cold start woes
« Reply #6 on: December 18, 2019, 09:00:47 »
Hi again,

My first post was pretty long, and the issue I raised was kind of lost at the end so allow me to repeat it more concisely:

The TTS on my car (a 4-speed manual 280SL from late 1968, US model) bears some of the expected marks: ‘3.03’ for March 2003, ‘35°c +/-3°c’, ‘12V’, ‘120°C.
However there are some which seem a bit unusual: ‘40W’, ‘20°C 5sec’, and ’36/2/9’ right under ‘120°C’.

‘40W’ seems really high (I seem to have seen 3W on pictures of both older and new or replacement TTSs), ‘5sec’ seems really short, and I have no idea what the 36/2/09 could stand for?

I would be extremely grateful if some of you would advise me on the following:

- does anybody have experience with such an unusual TTS (could it be that it is adapted to freezing climes, like in Canada?)

- assuming the TTS is not adapted to the car's new location (southern France), is it worth exchanging it for a more ‘normal’ one (Niemöller in Germany sells a Bosch replacement for 67€, which is reasonable) or would a more practical course lead to by-pass the TTS altogether (I will try to maintain a reasonable level of authenticity to the car, but not at the expense of usability, plus cranking for 10 seconds or more as the season advances to colder temperatures is not good for the starter motor, the wiring, etc.), and if so what is the preferred way of doing this? I have thought of running a wire from terminal 85 of the CSS relay to same on the CSV relay, to keep all the cold start devices on the same electric scheme (activated by cranking only), with a manual switch in the car of course to prevent the CSV firing for warmer starts.
François

1969 280SL US specs, 4-speed manual, beige-grey (726H), parchment leather
1994 Toyota Land Cruiser HDJ80 4.2L diesel
1955 Massey Ferguson TEF20 diesel tractor 😁
Before
1962 Jaguar MK2 3.8L (4.2L XJ6 engine), black, tan leather interior
1968 Peugeot 204 roadster, white, black interior