Engine was cranking without starting, but now nothing happens... - PeachParts Mercedes-Benz Forum

gisenberg · #1 12-24-2005, 10:26 AM

I have been attempting to get my '67 250S started. It would crank but would never fire up. But now I have taken a step backwards. The lights, radio, etc all work fine, until I try to crank the engine. It makes a single click sound maybe from the starter and then the whole electrical system goes out. In about 5 minutes or so, or if I hook up my battery charger just for 1 second and disconnect it all of the electrical comes back to life. Could this be something with the starter?

Thanks,
Greg

Also, I am jacking up the front end, but I am not sure where to put the jack stands? Any help would be great.

MunichTaxi · #2 12-24-2005, 08:01 PM

The original wires were "toasted', but still working. Since the manifold was off, I replaced the 6 wires. The 7th wire is for the power antenna, so it was capped. I used rubber tape (an amazing, cheap product) to further insulate the wires. Plan to invest some time on this project.

Additionally, as a starter wears out, the excessive play at the shaft bushings causes the starter to draw too many amps.

Tomguy · #3 12-24-2005, 11:04 PM

Sounds like a bad battery terminal or connection to the terminal. Take the clamps off, clean them out and resecure them tightly. Make sure the ground on the chassis is good, as is the connection on the starter, if need be.

gisenberg · #4 12-25-2005, 09:35 AM

It was the battery cable going to the start that was burned out. I replaced it and she is cranking again. Now my next issue:

When I have my Dist. Cap off, should there be any sparks in the points? I am guessing not since the Coil is not connected at that point. I was getting an intermittant spark on 2 of the dist. plugs, but none from the other 4. I attempted to change the points, but the points that I bought were not exactly correct. Also, how do you adjust the points when putting new ones in? I have a new dist. cap on order and new plug wires. I have a new rotor, coil, and plugs. Is there anything else that anyone can think of that I might need to change in order to get consistant firing?

Thanks

ctaylor738 · #5 12-25-2005, 10:29 AM

You set the point gap at .012" with a feeler guage. Turn the engine to get the rubbing block on the points close to a point on the dist shaft, and then turn the shaft by hand against the advance to get it exactly on the point. Then adjust the point gap with a screwdriver in the little slot and tighten the screw.

You should see a spark across the points when the engine is cranked.

Some other things to check -

- Are you getting voltage to the + side of the coil when cranking?
- Did you replace the condensor as well?
- Do you have the right cap and rotor combination?
- Are you getting gas? Can you see a squirt from the little nozzle in the primary venturi when you pump the gas?

gisenberg · #6 12-25-2005, 11:47 PM

You should see a spark across the points when the engine is cranked. - Even with the distributor cap off?

Some other things to check -

- Are you getting voltage to the + side of the coil when cranking?
- Did you replace the condensor as well?No, but I will
- Do you have the right cap and rotor combination?I told the auto parts store what year and make of car I had, so I am assuming that I have the right cap and rotor. Is there a way to tell?
- Are you getting gas? Can you see a squirt from the little nozzle in the primary venturi when you pump the gas?I unhooked the line that goes into the carb. and gas was coming through.

ctaylor738 · #7 12-26-2005, 07:39 AM

Yes, you should see a spark across the points with the cap off.

Easiest way to check the cap/rotor is to set your meter to ohms. Put one lead in the coil whole and one in a cylinder hole. Crank or turn the engine and watch the reading go to "no resistance" as the rotor contacts the lug inside the cap.

Gas to the carb is a good sign, but you should still check for a squirt from the accelerator pump.

Arthur Dalton · #8 12-26-2005, 10:24 AM

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When does the rotor ever contact the lugs in the cap??

ctaylor738 · #9 12-26-2005, 11:08 AM

Is this a trick question?

The rotor goes around in a circle. Each time it contacts one of the cylinder lugs, current is transmitted to the spark plug and you get ignition in that cylinder.

Arthur Dalton · #10 12-26-2005, 11:56 AM

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Not at all.
The rotor never contacts the cyl lugs in the cap .. The spark jumps an air gap.
So, you will not see contact between the two with an ohm meter.. plus the primary has resistance in the cap, so again, you will not show zero rexsistance continuity.

ctaylor738 · #11 12-26-2005, 02:12 PM

... learn something new every day.

MunichTaxi · #12 12-26-2005, 03:54 PM

I always wondered about the air gap at the rotor/cap interface.

About 16 yaers ago, I had a Toyota Landcruiser parked a remote mountain hiking trail. I took the Rotor with me on the hike (to prevent vehicle theft)

I thought I was smart and crafty. Well, the thieves were smarter than me. They stole another rotor from another parked Toyota car, and drove away.

When I recovered the vehicle (without a 12 gauge shotgun), the Rotor was 1/8" SHORTER than the original. I drove the Landcruiser over 200 miles before I discovered the "swap".