W111 3.5 engine not firing up at all

[sjefke]

Update and a question:

I was able to set the timing statically to about 3 degree before TDC. By chance, the starter put the white dot I had put on TDC just about 3 degree before the mark on the block. Rotor was correctly pointing to cylinder 1 mark in distributor and a peek in oil filler hole indicated that camshaft was up and valves of No 1 were closed. So I hooked everything up and turned the distributor until I heard a light "crack" indicating spark had jumped in distributor. Tightened everything up and tried starting car. It had a small fire hickup (hope at last!), but that was about it. Tried it several times. On all occasions, engine smelled like gasoline after a while so it seems to be flooding indicating plenty of fuel going in.

So my thoughts were going back to weak spark/ignition.

I measured resistance from main lead in distributor cap to carbon tip and it showed good continuity, so no broken carbon tip or connection.

Wondering whether I had a broken solid core coil lead, I put an Ohm meter on the main lead from coil to distributor and it showed an unexpectedly high resistance. It does show continuity, but Ohms are high. I also measured the spark plug cable from distributor to cylinder 1 and it had less than half the resistance of the coil lead, and I had to push a wire in to get a contact at the back, so it probably was not a great contact either.

Question: The coil distributor cable is a Bosch 7mm silicon cable. Is it supposed to have a high resistance?

One theory I have is that the coil cable may have an internal break causing a weak spark. It was the only cable I pulled off during my slave cylinder repair because I wanted to check that the clutch and transmission internals were fine by cranking the engine without ignition. It was sticky, so I am suspicious whether I accidentally caused a crack/break in the silicone near the distributor end. I did see a long spark earlier, but perhaps that was a fluke spark due to break being accidentally closed when I held is tight together in a plier.

Do you think it is the coil lead?

Thanks,

Bert

[Tony H]

I think my car has correct wires-my coil wire shows 2.26K ohms. Did you pull the distributor when you installed the Pertronix? Did it ever run with the Pertronix?

[sjefke]

Tony,

On a 20K Ohm scale, I read 16.27 on my digital multi meter yesterday. On a 2K ohm scale, my meter indicated "1" - meaning no continuity. Sounds to me like my wire has 8 times more resistance than yours. What type of wires do you have?

Car never ran with Petronix, but did not run anymore before I installed it either.

I did pull distributor, but was VERY careful not to twist it to loose timing. I verified yesterday that distributor is indeed in correct position. I heared the petronix firing (sounds like "tack" in the distributor) when I turned the distributor around yesterday during the static ignition timing with ignition on.

Any more thoughts on coil wire resitance? Or recommendations for replacement? Should I stay with solid core (silicone) or go with copper strand?

Thanks,

Bert

[Tony H]

I thought my wires were correct but maybe not-they are not solid core. If you think it might be the coil wire you could by some solid core wire from the parts store and just make up a test cable. It sounds like the resistance is really high on your wire.

[el sea]

I would strongly question the gas. Double check to make sure you are pumping and trying to run on gas and not water.

Oct 29, 2007 Altanta Speedway ring a bell?

Good Luck,

[sjefke]

Well, after a year of silence, I decided yesterday to take another crack at the old MB that was sitting silent and dusty in the garage. I had put on new wires, rotor, cap, plus Petronix 1 and Flamethrower coil, and now I also had a good strobe light. Fuel gauge read empty, so I dumped 5 gallons of fresh gasoline in the car and tried starting it. And you guessed it, after some sputtering it came to life. The word dumbfounded decribed it best.

I suspect I had a mix of gas and water in the tank that caused the problem.

Moral of the story: make sure you have plenty of real gas in the tank before troubleshooting.

Bert (who is very happy)

[Graham]

Bert - As discussed off-line - I have posted a pic of the Pert connections with switchgear and blue coil still in place. But other than a jumpy tach, no need to not use Flamethrower and bypass switchgear. Then add resistor when you can.

Lower left red is Pert red and upper left black is pert black on my 350SL 4.5L.

If you put the Flamethrower in, I think you have the sketch from an earlier thread. With that, the green/yellow tach wire should connect to coil negative with an inline 7-11 kohm resistor if tach jumps. I still have to do this step, so just going by what Pertronix told me.