1972 350sl (450)

[afmcorp]

help, i can't get the sl to start.

went to move the sl from the garage to polish it but it is not starting. charge the battery use the 200 amp booster on the charger. engine cranks good but won't start got juice to the plugs although weak yellow spark not a strong blue. the P/O kept super care of this car.

now it's had the same gas for 1 1/2 years in the tank. i've started it a dozen times moving it around. just started about 4 weeks ago just fine after the battery charge.

now don't flame me but i used starting fluid after many attempted trys. won't even kick up or cough on starting fluid. even without gas it should cough and run a second or two. but nothing.

my engine manuals are at work and the 107 cd doesn't show any trouble shooting.

it's been tuned by the P/O, new wires, you name it dist cap so i assume points and actually it has run quite well up to this point. not cold maybe 70 today.

any help would be appreciated
tks
craig

If it won't spit even one drop with starter fluid, I can't imagine that you have any ignition. I know you're seeing spark, but if you had any ignition at all, you would get it to hit at least temporarily with starting fluid.

Keep examining the ignition.

Good luck,

[afmcorp]

hello larry

this is what i'm leaning towards too. now that i think about it during these attempts i would allow the car to spin maybe 15 to 20 seconds and after about 10 or so sec you could see a vapor start to appear so i'm sure there was enough fuel then i would also spritz in some starting fluid and nothing.

both the coil lead and a spark plug showed yellow spark. yep that's what i'll work on is the ignition spark.

thanks much larry for your help
craig

[afmcorp]

well, i'm still working on the 72 a bit at a time. all the coil and resistors seem to be ok. what i'm looking at now is the switch gear.

i can say the ignition system seems to have been up dated. the capacitor has had it's lead sniped off so it's out of the loop as far as the points are concerned.

i've got the benz engine manual, both chilton and hayes and the 107cd and i can't come up with the terminal numbers these books keep referring to. also it's taken all 4 to figure out a real test of the switch gear.

if there is anybody out there that has figured out the terminal #'s and where they are i would certainly appreciate a hint.

tks much
craig

[stevebfl]

If you have spark of any kind the switching unit is switching. Do you have compression? Start with the drivers side.

[dkveuro]

Hi folks...I had this problem with a '78 450SL, it was all the short running times moving it around the yard and into the shop. The plugs fouled out....Pull plugs and spin it over BUT FIRST disable the ignition !!!! Well, it worked for me !
Don.

[afmcorp]

thank you steve and don for your replies.

i did check compression and that was @ 130 (i did this cold and with the other plugs in as i went along). plugs had a bit of soot but not bad at all.

as i am figuring out all the manuals i have as a guide it still seems to boil down to just an old wiring system with an increased resistance. i'm finding wiring that is shedding the insulation. i found the 3 connector block by the battery on the mounting stand for the radiator tank 2 of the screws refuse to come loose. i've used special screw extrators and they just cut the screw without loosening. on terminal #16 the screw isn't even tighten down looks like some else has had a problem here with the ring terminals of the wire just loosley sitting on the screw.

up to this point i am finding the 2 resistors running about twice the resistence listed. the silver .6 is running about 1.2 the blue .4 is running .9 to 1.0. i've replaced several sections of wiring that the insulation just crumbled apart.

1 question i would pose is regarding the resistors it doesn't seem like much of a difference but is it enough to replace them?

i'm going to clean this "age" problem up just for GP.

i see in the haynes book there are several items listed under hard or not starting. "various valves being defective" unfortunately they say what's possibly wrong but point in no direction of what to do.

when i get home tonite i'll post what those items are. i still seem to be having a bit of a problem identifying some locations of these items and their descriptions. i might post a few fotos of some of the items in question.

i will check the actual fuel pressure tonite at the fuel ring. i think that's what it's called. i know fuel is being pumped but i'm sure not at the pressure required.

the symptoms still show just a weak spark. so i've got juice to the plugs just a very weak one. i know fuel is being pumped to the injectors but the old 4.5 won't even offer a cough with starter fluid.

i'm wide open to suggestions.

thanks guys
craig