WARNING! : DO NOT START WORKING ON YOUR FIP BEFORE YOU ACHIEVE THE BASIC SETUP FOR YOUR ENGINE : CORRECT VALVE CLEARANCE AND IGNITION TIMING AND LINKAGE SETUP !! THIS CANNOT BE STRESSED ENOUGH , OTHERWISE YOU ARE TRYING TO SOLVE ONE PROBLEM BY CREATING ANOTHER ,WHICH WILL DRIVE YOU CRAZY IN THE END ! !.
230SL bad engine running/starting mini tour Part 1 : the basics (
https://www.sl113.org/forums/index.php?topic=38391.msg280468#msg280468 )
230SL bad engine running/starting mini tour Part 2 : Air and Fuel supply (
https://www.sl113.org/forums/index.php?topic=38392.0 )
230SL bad engine running /starting mini tour Part 3 : CSV , injectors and checkvalves (
https://www.sl113.org/forums/index.php?topic=38428.0 )
230SL bad engine running /starting mini tour Part 4 : FIP basic mixture control (
https://www.sl113.org/forums/index.php?topic=38454.0 )
230SL bad engine running /starting mini tour Part 5 : WRD and starting magnet (
https://www.sl113.org/forums/index.php?topic=38504.msg281159#msg281159 )
On a 230SL there are only two electric starting aids , the CSV and the starting magnet at the back of the FIP.(3rd version starting aids)
The starting magnet is sometimes also referred to as "enrichment solenoid" or "solenoid switch" ( BBB fig 07-10/14b)
These are described in part 3 and 5 resp.
Maybe an eyeopener for some : they are both activated at EVERY start, either hot or cold ! Only the duration varies between 1 second to appr. 17 seconds on a really cold engine.
The wiring diagram of the system can be found in the BBB (fig 07-10/14b)
Starting relayCentral part in the starting aid system is the starting relay. It is in essence nothing more than an ordinary heavy duty auto relay.
Between terminals 30/51 and 87 is the actual switch .When closed during starting operation it provides 12 V to the CSV and starting magnet and both will start operating .
In our starting aid system the relay activates by +12 V on terminal 86 during the full time of activation of the starter switch and a temporarily "ground" on terminal 85 ,provided either by the 1 sec. relay (any start) or the TTS ( cold start)
Common problems : burnt , pitted contactpoints causing high resistance, relaycoil failure . Oxidation at plug contacts or wiring problems. Fuse nr 6 , the short 25 A fuse , blown or it contacts oxidated.
TIP 12 : in case of a total relay failure and to avoid high costs , open the housing carefully , remove the old malfunctioning components and solder in a $5 new standard auto relay ,of course respecting the correct terminal positions. Install and seal the cover and nobody will visually notice the difference on the outside.
For ease of explaining how the system operates let's look at the starting aid circuit as if they were two seperate parts :
Note : both parts have a certain overlap ,or common parts if you like , and work in parallel !
1. The part that activates both the CSV and starting magnet each an EVERY start for about 1 second.
See Fig. 1Each start , either hot or cold ,when you turn your ignition key to the "run" position of the ignition switch ,12 Volt is applied via fuse nr. 6 ( 25 A) to the switch contact 30/51 of the starting relay.
The time switch ( 1 sec. relay) contact is still in a closed position so "ground"is available at its contact nr. 85 and at one side of the starting relay coil ( nr.85). The starting relay is not yet activated since there is still no 12 V on the other side of its coil.
Turning your ignition key one step further to the "start" position , 12 Volt is applied to both nr.86 contacts of the time switch and starting relay.
Initially the contact in the time switch was still closed and the startingrelay is now activated and 12V becomes available at its contact nr .87 and now powers both the CSV and starting magnet.
However at the same time the 12 V is applied on the time switch it heats up a bi-metallic contactstrip which opens the contact after appr. 1 second and so now "ground" on contact nr.85 is lost and the starting relay is deactivated causing the CSV and starting magnet to stop functioning. Thats all !
Common problems of the 1 sec. relay are : burnt , pitted , stuck or open contactpoints. incorrect adjustable timing or total failure.Oxidation at the plug ( connector) or faulty wiring may also cause problems.
More on the time switch like testing and tweaking can be found here:
https://www.sl113.org/wiki/Engine/TimeSwitch ( 1 second relay testing and adjusting)
2. The part that activates both the CSV and starting magnet at cold starts only
See Fig.2This part of the starting aid is only active at coolant (!) temperatures below 35 ° C !
This 35 ° C Threshold temperature is "sensed" by the TTS in the cooling circuit and acts as, say, an imaginary on/off switch.
Everything you need to know about the TTS ,like its internals and how to test it can be found here :
https://www.sl113.org/wiki/Engine/ThermoTimeSwitchWhen you turn your ignition key to the "run" position of the ignition switch ,12 Volt is applied via fuse nr. 6 ( 25 A) to the switch contact 30/51 of the starting relay
ABOVE 35° C : the "ground " contact of the TTS is OPEN so no ground is available at nr. 85 of the starting relay from the TTS (ground to the startingrelay will now be provided by the 1 sec. relay, so the system reverts to the "every start" mode as described under 1.)
BELOW 35° C: initially the TTS ground contact is closed , so ground is available via the TTS "W" terminal to one side of the starting relay coil (nr.85). The starting relay is not yet activated since there is still no 12 V on the other side of its coil.
Turning your ignition key now to the "start "position , 12 Volt is supplied to the TTS "G" terminal AND contact nr 86 of the starting relay coil which activates the relay and 12V becomes available at its contact nr .87 and in turn powers now both the CSV and starting magnet
At the same time the 12 V on the "G" terminal starts to heat up a heater coil/bimetallic switch element which opens the TTS ground switch after a certain time interval and thus switches off the starting relay, CSV and starting magnet. . This variable time interval is determined by coolant temperature sensed by the TTS and may take up to 17 seconds in very cold conditions.
Note : multiple repeated cold start attempts may warm up the bimetallic element enough to shorten the time interval of the TTS !
So in the below 35° C condition next to the TTS ,the 1 sec. relay activates as well as indicated above under 1. , but is overridden by the (longer time interval) TTS function during cold starts !
A simple,limited, test of the TTS if
both the CSV AND starting magnet fail to operate at cold starts: before a cold start ,temporarily connect a ground wire to the "W" terminal. Activate the starter switch. If the CSV and start magnet activate with the jumperwire connected , the TTS is most likely your problem. If they don't activate there is another problem like a malfunctioning starting relay ,bad plug contacts ,blown/oxidized fuse nr. 6 (contacts) or a wiring problem.
How I solved my HOT start problems you will find here:
https://www.sl113.org/forums/index.php?topic=38353.msg280324#msg280324Note : I also added a "cabin switch" to bypass the starting relay when needed. Never had to use it ! You can find instructions how to install it elsewhere in this forumboard.
This concludes my 230SL bad running/starting mini tour. Quite some reading, I admit.
I hope it may provide you with a logical and bundled approach to solve most common running/starting problems .
For any additional information please use the forum "search" option, you will most likely find your questions already answered ! ! If you observe anything incorrect in my text please PM me so I can adjust it.
Keep them driving !
Rob ( Rosch)
Halle /Netherlands
