Csv and Thermo time switch

[mauro12]

Hello guys , it seems I have some problems with the cold start . I have to crank many times before it starts . This happen only when the engine is very cold . Once it starts I have no problems at all .
I’ve read many post about the csv , the solenoid and relais . I also read about this Thermo time switch which I don’t know if it’s working or not ( incredibly expensive to buy  ). What is the first things to check ? I really hope is not the Thermo switch because the price is insane . What do you suggest ? There are too many post regarding this topic and make me quite confused . Thank you all .

[Jonny B]

There has been a lot written on the site about this issue. Try the Search function and use - "cold start" issue - as the string, include the quotes as shown. I got four pages of items, but I think you will be able to find what you are looking for without going through all of those.

The easiest first check is to use a trouble light at the cold start valve to see if it getting power when you engage the starter. If no light the relay could be the culprit.

From there things get more complicated, so check the search.

[mauro12]

Can a car start with a malfunctioning csv ? First thing the relay and solenoid right ?

[Jonny B]

Yes, do this first it is easy to check. It is easiest if you have someone to hold the test light (oops on my part, not a trouble light) the kind with a metal point to touch to the solenoid and a clamp to go to ground. Then you just try to start the car, if the solenoid is sending power to the CSV the test light will come on. You only get one try or maybe two tests a day, the car needs to be fully cold.

And yes, the car can start - it just takes quite a few cranks to get it to fire off. I have had this happen a couple of times. The first time, I just opened up the cold start relay and filed the points to ensure they were clean. The second time I just replace the relay, it was not that expensive, and kept the old one as a possible back up.

[teahead]

I always wait like 1-2s after turning the key to the RUN position before you go into the CRANK position.

I replaced my thermo time switch w/a Porsche one.  Seemed much cheaper.

https://www.pelicanparts.com/More_Info/91161711700.htm?pn=911-617-117-00-INT


I just removed those side pegs on the top there.

[franjo_66]

I always wait like 1-2s after turning the key to the RUN position before you go into the CRANK position.

I replaced my thermo time switch w/a Porsche one.  Seemed much cheaper.

https://www.pelicanparts.com/More_Info/91161711700.htm?pn=911-617-117-00-INT

Thanks for that tip ! Very useful to know.

[Bshaunessy]

Mauro12
   I just finished successfully troubleshooting CSV and WRD ( warm running device component of the fuel injection pump).  1970 280 SL auto.
   I agree, there are many posts about the CSV , some confusing and some to the point.   Ditto WRD.   I found the most comprehensive and logical description of both to be in TECH MANUAL / ENGINE/ MAINTENANCE / ENGINE STARTING TOUR. ( an odd place to squirrel this info away but once you find it…very helpful).

   Would recommend using a quality voltmeter and ohmmeter to trouble shoot ( vs a test light), as you will quickly find that your problem is not just Q?do I have 12 VDc? ( if you can solve with a simple test light, then your overall problem is also very simple….lucky you but unlikely)
   In my case: CSV and TTS ( Thermo time switch) were both functional , as was the CSV relay but…..a broken wire somewhere in the wiring loom was the culprit.  So CSV relay would close during cranking and send 12 v to TTS but….12 v never got there.   Replaced wire from relay to TTS so that TTS gets 12 vdc when cranking and….voila: CSV gets 12 v when cranking and sprays gas into intake manifold ( as it should) and car fires up every time now!……problem solved.

[mauro12]

I just overhauled the injection pump and the wrd is working properly . I have to admit that my car has always suffered from cold start issues . Having said that , I have no idea if the thermo time switch is working or not , can they last 50+ years ? Spending 800€ for this stupid sensor seems crazy . I have a 250sl early model , what can be the source for another switch ? From Porsche but you need to have the same specs .
One thing is not clear to me and I also posted in another topic from this forum .
The cold start issue depends 100% from the csv itself . The hard hot start I believe is not related to the csv .  I have been told from the guy who rebuilt my injection pump that hard hot start depends on delivery valves problem ( they don’t keep ideal pressure in the fuel lines ).
Bshaunessy , you had a miss from the key contact to the csv relay , is that right ? If the relay doesn’t have power what can be the cause ?

[mauro12]

The 250sl has the first or second type TTS ? Do they usually fail? I was checking their price and is insane . Also I read many post regarding some alternatives but many of them are no longer available in Europe . If you check on eBay for a TTS they all come from USA and to import in Europe is quite an expensive game .
Could you put some link where to source this item ? Thank you

[teahead]

First, before you buy a TTS, check w/a test light to see if it lights up your CSV.  Have someone help you hold it while you crank.


I'm sure you can find:  911-617-117-00  somewhere in Europe.

[mauro12]

Unfortunately not . All come from USA and they are on the range 200€ plus delivery and duties . I’m wondering if 20€ sensors for modern cars have similar specs to this . Spending 200€ for this thing is a real theft .

[BobH]

These seem to have similar characteristics, but you'll need to check dimensions, thread size, connections etc,

https://www.deloreango.com/uk/delorean-thermotime-switch.html

[mauro12]

There are no characteristics for this item .

[BobH]

The Tech Manual says the original switches were used in several other cars, including the Delorean, so i asked them

The original is 35 degrees C for between 8-12 seconds, the repro is 35 degrees C for 30 seconds

https://www.sl113.org/wiki/Engine/ThermoTimeSwitch?action=download&upname=W113%20Cold%20Start%20Thermo%20Time%20Sensor%20Alternative%20rev%201.pdf

[teahead]

Just get the Porsche switch mailed to you.

Something so tiny, I can't imagine it being THAT expensive.

heck, it's costing me a few hundred US dollars to ship FOUR WHEELS from Austria to West Coast of the USA.

[mauro12]

The Porsche switch is listed on eBay for 300€ right now .

[Bshaunessy]

Mauro12
  Further to my post above and to answer your question:(Bshaunessy , you had a miss from the key contact to the csv relay , is that right ? If the relay doesn’t have power what can be the cause ?)
TO CLARIFY:
My issue was I had 12v to CSV relay when cranking, AND CSV relay functioning ok but a break somewhere in wiring harness between CSV relay and the "W" or "G" contact ( can’t remember which side is hot) on actual TTS.  Ran a duplicate wire from CSV relay output to TTS…..voila….CSV works and car starts easily and always.  ( once I got 12 v to TTS when cranking).
 
 

[FresnoBob]

From my recent experience, you should also check the nozzles of the CSV.  Mine were oriented so they sprayed up and down, when they need to align with the centerline of the intake manifold.  You can also hook a 12 volt light to the CSV and watch how long it activates the switch during cold starts.  I also put a ziplock bag around my CSV and checked that the nozzles were indeed spraying fuel.  I've heard these can clog over time.  I always struggled with cold starting, but with diligence and systematic diagnostics, you will achieve surprisingly good starting for such an old car. 

Good luck!

[Bshaunessy]

Mauro12:
Q? did you find the description of the CSV and  TTS and WRD in the TECH MANUAL / ENGINE / ENGINE STARTING AID ?  There is a very detailed TTS testing procedure I would recommend you follow before concluding your TTS is at fault and buying a new one ($$$$$j.  It is likely your TTS is fine and the problem is electrical and elsewhere.

BTW: I also have 1975 450SL and it has same cold start and thermal time switch circuit.  I had similar cold start issues but concluded I had a failed TTS…..bought used replacement TTS off EBay: that replacement was bad  ( bench testing) and returned to vendor.  Eventually found a different electrical problem that was causing issues with CSV ….my original TTS was fine ( mis diagnosis on my part as I did not have a good resource like the TECH manual here to diagnose for my 450 SL).

[mauro12]

Hi guys , just a quick update on my csv . I checked all electrical connection and relays and solenoid. everything is working fine . The only thing is that somebody has blocked the csv with some bathroom sealant . We unblocked and the car was starting perfectly , the only big problem is that the csv needle and spring are not sealing anymore , for this reason the valve is leaking like crazy with huge black smoke . I decided to buy a new brass valve , spring and o ring . the needle valve has some corrosion and imperfection and I guess this is the reason for the leak. I'm sure somebody before me noticed this problem and instead of buying a new spring and needle , decided to block the csv and solve the problem . if the brass valve is not sealing you will have a huge amount of fuel leak once you turn on the engine or even the key in the first position.
Have you ever had this problem about replacing the needle valve ? thank you