cold start relay

[rmmchl]

250 sl I think my cold start relay is bad. The cold start switch has been rebuilt already. I have to play with the pedal when starting. Once started it runs great. I had the engine rebuilt recently. All new everything. Balanced the new flywheel to the ground crankshaft, bearings, etc. How do you tell it's bad and how much is a new one? I was told that when you turn on the key, if someone gets under the hood they should hear it click. I didn't hear this.

[jeffc280sl]

Get a 12V lamp and solder two wires to it.  Connect one wire to the CSV and the other to ground.  As you start the engine the lamp should light up.  If it doesn't the relay may be bad.  You can take the relay apart if you are careful and clean the contact points with fine sand paper.

Jeff C.
1970 280SL 4-speed

[A Dalton]

If you do not have the 12v at CSV at Start position, a quick test for both the relay and the TTS [ time/temp sw] is to ground the "W" wire at the TTS . [ this is the  2 wire/coolant temp sensor just above the FI pump]. This   test takes the TTS out of the circuit and energizes the relay coil when the key is in the Start position.  You then retest for 12v at the CSV, as Jeff suggest.
 If you still have no 12v at CSV, the relay [or power feed ] are suspect. If you now have 12v, then the TTS is suspect. Power feed for CSV circuit can easily be verified by checking activation of heater blower , as that is the same circuit [fuse # 6]
 Do not confuse the CSV [ fuel squirter on intake] with the starting aid solinoid on the Injection pump.  That is a different enrichment device that  moves the  IP rack to rich when cranking, regardless of coolant temp.[ and has little effect on cold starts]
 First suspect on poor cold start is CSV circuit ..
[ relay/TTS/CSV/fuse]