1972 300sel 4.5 no start - PeachParts Mercedes-Benz Forum

robertbrown29 · #1 02-14-2009, 08:46 AM

Yesterday I unplugged the injector points plug next to the distributor and turned the ignition over for about 10 seconds.the car would start before I did this,now it will not.what have I done?

Tomguy · #2 02-14-2009, 09:49 AM

Make sure you plug it back in firmly, it should go in smoothly. If it does not you may have bent one of the contacts - check and make sure all 5 are straight and that none of the wires on the plug are broken.

robertbrown29 · #3 02-14-2009, 10:52 AM

thanks tomguy.checked those things, but this appears to have affected the timing,as if the engine will not"catch',for want of a better term.

Tomguy · #4 02-15-2009, 12:59 PM

Is your distributor loose? Was it tightened the last time it was timed? If not you'll be able to move the distributor clockwise or counterclockwise, and that surely will affect running. If that's the case it will NEED to be re-timed and tightened.

robertbrown29 · #5 02-15-2009, 01:10 PM

Distributor is tight. whatever happened was caused by unplugging the trigger points connector and spinning the engine.It was starting before I did that.

Tomguy · #6 02-15-2009, 01:23 PM

Unplugging the points and cranking the engine doesn't do any harm - all it does is keep the ECU (switchbox) from triggering the injectors at all. The cold start valve does still fire though, but chances that you're flooded from just the CSV are pretty slim. Just to check, pull a plug; if it's wet it's flooded and you may want to crank with the CSV AND trigger points unplugged and your foot floored on the throttle.

robertbrown29 · #7 03-01-2009, 10:48 AM

two weeks ago after spinning my motor over with the trigger points disconnected,I could not get the engine to start.After several checks I found the pin that touches the rotor button(from the coil wire)was sheared.Installed a new one today,same thing happened.What could be causing this?

Tomguy · #8 03-01-2009, 10:53 AM

Yikes, those caps are costly to keep shearing those pins!

Ensure TWO things:
1) Your rotor MUST be pushed down FULLY - if it's not in place right (off to the side a bit) it won't pop in all the way.
2) When reinstalling the cap ensure that you are NOT wiggling from side to side. Push it straight down and it will fit snugly on, and allow you to clip on the sides securely. These clips are installed by just pushing the center with your thumb. Do NOT use a screwdriver!

robertbrown29 · #9 03-01-2009, 11:02 AM

Thanks,guess I need to pay more attention,and order another cap.

robertbrown29 · #10 03-07-2009, 10:40 AM

Replaced distributer cap and rotor.If I keep turning the key with the accellerator(sp)pushed all the way down ,the car appears to be running,but will not "start"

robertbrown29 · #11 03-07-2009, 03:38 PM

perhaps in my eairler post,I should have gone into more detail.with a new distributer cap and rotor,my engine is getting spark to the plugs.I have made no adjustments to anything,Ican here the fuel pump actuate when I turn the key,and the fuel pump relay is working.the engine sounds like it wants to start.what can I check next?

Tomguy · #12 03-07-2009, 07:40 PM

Have you pulled any plugs out to see if it's flooded? The 4.5 floods easily with the heavy-duty injectors and the CSV all spraying fuel into an engine and it not burning.

Gurunutkins · #13 03-07-2009, 08:56 PM

if you push the accelerator all the way down, the TPS reads the position and tells the ecu the engine is flooded and switches off the injectors. dont push the accelerator pedal down at all when trying to start or if needed (and that means something is out of whack) only a little way
cheers
barri

robertbrown29 · #14 03-08-2009, 11:21 AM

Thanks for all the input.current situation is that as long as I am turning the starter,the engine runs(holding the throttle half way down)I occurs to me that just before the (no start)I put half a tank of premium fuel in the drove it about one mile home.I have always had to pump the throttle one or twice for the car to start.Question;could this be bad fuel?also,what does it mean that I have to pump the throttel when on previous FI car I just had to turn the key?

robertbrown29 · #15 03-08-2009, 07:11 PM

I guess what im trying to say is the car starts but will only keep running if i keep the key turned and the throttle halfway or more.