Author Topic: Warm Start Problems  (Read 1616 times)

joe texas

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Warm Start Problems
« on: February 15, 2019, 20:09:24 »
I have '64 230SL  and I was hoping I could get some help.  The car starts great when its cold, but with a warm engine is different.  If its warm I was told by a mechanic, to fully depress the gas and then crank the engine until it starts.  It starts but it will take 15-20 seconds.  I wonder if I am doing damage to the starter and if it is an indication of something wrong.  Has anyone else had this problem and what did you do to solve it.  Thanks

Pawel66

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Re: Warm Start Problems
« Reply #1 on: February 15, 2019, 22:17:25 »
I am not a mechanic, but having experienced a very similar issue I did some studying on this forum to find the potential reasons.

I suggest you perform search (right hand side, top window, type in "warm start" or "warm start problem") and you will find lots of information on potential causes and solutions. It is fairly common issue.

I think the way to start the car when warm is to depress gas pedal about 1/3 and crank.

Are you sure the car is overall in tune? Mixture, ignition, spark plugs, etc. - all this is ok? If so, then I can think of a couple of points.

After 10 or 15 seconds of cranking I would stop and screw out a plug to see if it is wet or dry. If wet - the issue may be electric, then you go the usual way about checking electrical components. This may be confirmed with a gasoline smell after this time of cranking. If spark plug is dry, this may indicate fuel delivery issue. The engine is in a very lean conditoin in this state and fuel delivery disturbances are making it even leaner, causing start difficult.

Sometimes it can help to determine if the issue is fuel when you just switch the ignition, but do not crank for 30-40 seconds. If car starts nice then - the fuel pump managed to fill the fuel delivery lines so the fuel is available.

Fuel delivery topic can be related to e.g. insufficient fuel supply to the main filter (there can be many reasons for insufficient fuel supply, this is just an example). This may be checked by testing of the fuel flow at the end of the return fuel line (should be ca0.8L per 15 seconds). If the test fails - you go along the fuel supply chain looking for troubles there.

The main filter may be clogged.

It may also be a trouble with, actually, Thermo Time Switch that is associated with cold start, but is supposed also to help in warm start. Check if you have voltage on CSD when cranking. If not, try to hook a wire to activate "manually" the cold start valve when cranking warm engine - see if it helps. If yes, the issue is with TTS or wiring leading to activate CSD or CSD. Some Members have a manual switch under dash thay added to help inject an extra dose of fuel through CSD when starting warm. CSD may be checked if it works as well if hooking a wire to it does not help.

These are the simplest check ups that com eto my mind, I am sure more experienced Members will advise better. Then you may get into return valves in high pressure fuel lines, etc., but this I would look if the simple tests fail.

I would do the search as I suggested above.

I would also encourage you to visit the Technical Manual.

In the section for Full Members you have a chapter about engine starting aids - you would have to become a Full Member to get there. it is an investment that pays back very, very quickly, actually.
« Last Edit: February 15, 2019, 22:31:21 by Pawel66 »
Pawel

280SL 1970 automatic 180G Silver
W128 220SE
W121 190SL
G-class

ja17

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Re: Warm Start Problems
« Reply #2 on: February 15, 2019, 23:21:41 »
Good advice from Powell.  In addition the 230SL had two different versions of starting aids (version 2 or 3). You will need to determine which version you have before you can diagnose the starting system. The version two has an additional sensor "time switch" in addition to the "thermo time switch". Version 3 has no "thermo switch" but just a "thermo time switch".  Your first step is to use a 12 volt test light and check to see if the "injection pump starting solenoid"  is getting power during hot starts. Both versions should activate the injection pump starting solenoid during hot starting. Get back with us on the results and we can move to the next check.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

joe texas

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Re: Warm Start Problems
« Reply #3 on: February 16, 2019, 22:29:53 »
Thanks for the suggestions.  I'll report back.

ja17

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Re: Warm Start Problems
« Reply #4 on: February 18, 2019, 04:22:26 »
If your injection pump solenoid does not activate during all starting (hot or cold) your possibilities are; starting device is inoperative, electrical relay is defective, electrical sensor is defective (tts, ts), wiring problem or fuel delivery problem. when you return with results, we'll head you in the right direction. Ask questions, and get back with us with results.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

Skippermitch

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Re: Warm Start Problems
« Reply #5 on: February 18, 2019, 17:34:35 »
I had warm start problems where I would foul a plug after sitting for 5 min or so. I simply unplugged the 1 second relay and the problem cleared up. Have yet to troubleshoot the relay and it remains unplugged right now. I also use a manual switch on the cold start relay. My is a Euro 1964 230
Mitch