Cranks but won't fire...need help - PeachParts Mercedes-Benz Forum

mosu · #1 11-22-2014, 09:04 PM

Hi all,

Specs: 68 twin Zenith M130 280S.

Did a couple of things today to help my car start easier but looks like I achieved the opposite. Pulled the distributor and cleaned it thoroughly. It was really dirty and the advance plate was binding. I had marked it's position on removal - about 80% of max adjustment in the clockwise direction. Put it back as I found it.

I also popped the covers off both carbs and adjusted the floats to spec.

After all was put together, it doesn't want to start. Cranks and gets the occasional sputter if I pump the gas several times. If I pump the gas while cranking, I can get some epic backfires.

Pulling the coil lead and grounding against the block gives a nice blue spark. There's gas in the bowls as the accelerator pumps have a strong squirt.

I could use some guidance as to where to start the diagnosis...Got spark, got gas, not sure why it doesn't want to play ball...your thoughts will be greatly appreciated before I pull all my hair out.

Cheers!

Bdub03 · #2 11-22-2014, 09:35 PM

my guess is timing since you pulled the dist. I'm not sure of the proper procedure to static time an M130 but try to bump the starter to TDC and match up plug 1 to your rotor.

Subscribing as I'm new to the M130 engine and need to do a tune-up soon.

Frank Reiner · #3 11-22-2014, 10:16 PM

Although you returned the body of the distributor to the same place, the odds are that you have the rotor off by one tooth in the retarded direction, i.e., the opposite of the direction of rotation.

mosu · #4 11-22-2014, 11:06 PM

Frank, I'm not sure I understand what you mean by one tooth off. The distributor has two claws at the bottom of it's shaft. Although it looks like it can go in at 180 degree apart positions, it only engages in one place along the rotation of the shaft.

Maybe I missed something. Can you provide a little more guidance please?

Frank Reiner · #5 11-23-2014, 12:25 AM

In lifting the distributor, it is possible that the vertical shaft that drives the distributor thru engagement with the intermediate shaft, was lifted along with the distributor far enough to move one tooth before it dropped back in.

How completely did you disassemble the distributor for cleaning?

mosu · #6 11-23-2014, 11:16 AM

Yikes. I went all the way down to the advance weights, including removal of the top section of the shaft that attaches to the sides with the advance springs. Seemed really straightforward as everything was keyed to assemble one way.

Frank Reiner · #7 11-23-2014, 12:03 PM

I may be mistaken, but I think that the breaker cam can be installed 180 deg from the original. The pins to which the springs are attached extend through the driven plate of the cam, and enter limit slots in the driving plate below. I think that those pins are the same diameter and, hence, can enter either slot. If, however, the pins are of different diameter, then they can only be assembled one way.

A quick check on the 180 deg. possibility is to move the spark plug wires 180 in the distributor cap. 1 for 6, 5 for 2, 3 for 4.

meltedpanda · #8 11-23-2014, 05:10 PM

on my no start - same kinda thing, I found I shorted out the condensor to the distributor body - just a thought

mosu · #9 11-23-2014, 06:25 PM

Panda - I have a pertronix in there, points and condenser are long gone.

Frank - the top section of the distributor shaft appeared to only slot into the advance weights in one position. I played around with it so I'm fairly confident it only goes in one way.

I'll turn the motor to TDC on the cam and crank marks and check to see where the distributor rotor points. Will report back.

Bdub03 · #10 11-23-2014, 11:08 PM

So I got mine fired back up today... Ended up static timing the distributor between 0-10 degrees ATDC using my timing light and pow... fired right up!

Even if you're 1 tooth off, you should be able to turn the distributor while someone is cranking and get it to fire up.

mosu · #11 11-23-2014, 11:52 PM

Nice! So you just had a helper move the distributor back and forth? If it is a tooth off, is it worth rectifying or just leaving as is and adjusting from the distributor?

mosu · #12 11-25-2014, 12:22 AM

Ok, I set the engine at compression TDC on the cam index and crank and the rotor lines up almost perfectly with the mark on the distributor body.

The problem must be on the fuel side. I'm thinking of pulling off the carbs, blasting them with carb cleaner and resetting them to baseline settings. When I checked and adjusted the floats as per Frank's advice on a previous thread I noticed one of the needle valves was sticking due to this crusty residue. I had the previous fuel pump leak oil into the gas and I think that formed into this dried mud type residue past the fuel filter. Maybe that stuffed up some passages.

Am I on the right track?

JMela · #13 11-25-2014, 08:48 AM

Pertronix "I" units can burn out if the ignition key is left half turned/in the 'start' position for more than 20 seconds or so.

mosu · #14 11-25-2014, 09:00 AM

Not the case as I'm getting spark from the coil wire when grounding against the block.

Frank Reiner · #15 11-25-2014, 09:54 AM

At the risk of suggesting the obvious, now that you have established the relationship between the crank/cam position and the distributor rotor position, mark the outside of the dist. body for the rotor position at #1 TDC, install the cap, install #1 plug wire at the socket corresponding to the mark, and proceed around the cap installing the plug wires in firing order.

Then check for spark at the correct time, using a timing light on #1 wire, while cranking the engine.