Engine stops

[knirk]

I went for a 35 mile drive today and about 5 times the engine just stopped like somebody switched off the ignition. No misfire, no pre warnings. And when I turn the ignition switch it starts right up again and runs like a dream until next time it dies.

So I figure it must be ignition related. I have checked all cables for tight connections. The only thing I have done lately is changing the ballast resistor (unnecessary) and replaced a blown fuse number 6 (relay for starter valve and relay for rich mixture).

Where should I start looking  :?:



Per G. Birkeland
69 280 sl aut 834
Norway

[Malc]

Could be:
your ignition switch, you should be able to rig up a temporary switch for testing and see if the cutting out stops. Switch wearing out / dirty contacts
Be careful driving around though.

Though the connections in the cables are ok look for cracked and brittle wires especially in the engine bay to and from the coil and distributor. again rig up temporary cables to see if it cures.

A fuse blows for a reason!(excess power drain) did you find out why it blew?

Guess I have a thing for wiring but if your harness is orginal it's getting old and they do suffer from heat / vibration / fatigue damage

Malc

[tuultyme]

Do you have one of those battery quick connectors on the negative post?  I used to have one until one day last summer it lost connection while stopped for a red light.  I easily retightened it, but the momentarily disconnect with the engine running ruined the alternator.

Bruce; 268Blaugrun(green) 1970 280SL; IL

[Naj ✝︎]

Hi, Per,
I'm with Malc. It probably is the ign switch. Gets to a point where any slight movement in the key will turn it off. With the engine running, try moving the key about in that position and see if it cuts out.
A new switch is reasonable enough but you have to take out the steering lock barrel to change it.

naj

65 230SL
68 280SL

[hands_aus]

Driving my car on the highway, when I hit a bump it cut out, then when I hit another bump it started again... bit scary at 100Kmph.

Turned out to be no spring washer under the screw at the input side of the ballast resistor.



Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[jmela]

I'm going through the same issue with my 108. My car seems to kill frequently if it hasn't been driven in a week or two. Activating the turn signal, wipers, horn, causes it to die. Hair-raising if you're in traffic. Fifteen minutes or so of hard highway driving seem to alleviate the problem.

I plan to check, clean or replace all electrical grounds as I can locate in the near future.

[knirk]

Thanks everybody,
If I rig a temporary ignition switch would it be OK then to connect an extra 12 volt cable to the ballast resistor?
I did not find out why the fuse blew last week.


Per G. Birkeland
69 280 sl aut 834
Norway

[Naj ✝︎]

Per,

 

quote:would it be OK then to connect an extra 12 volt cable to the ballast resistor?

In an emergency, you can even connect a jumper from the + on the battery to the firewall side of the ballast.

naj

65 230SL
68 280SL

[ChrisInNashville]

Per,

Sounds like my problem with bad gas a couple months ago.   Here's my experience from the posting back then:

http://index.php?topic=3419

Good luck,
Chris

[knirk]

Chris,
Compared to your events my engine runs perfectly until it dies, and starts right up without hesitation. I will start today by rigging an alternate power source to the coil (via the ballast resistor), and I will also hook up a voltmeter so I can look at the current to the normal power supply when it happens.

I’ll be back  


Per G. Birkeland
69 280 sl aut 834
Norway

[knirk]

I have now driven about 100 miles in two days without a single engine stop. It does not die with movement of the ignition key. All I did was rigging a temporary cable from a 12 volt source to the firewall side of the ballast resistor. I didn't have to use it so it looks like I had the same problem as you Bob S. It must have been a bad screw connection to the resistor (the only thing I touched). I will carry a cable with me for a while just in case.  

Per G. Birkeland
69 280 sl aut 834
Norway

[hands_aus]

Per,
It is great to see it sorted.
I checked both ballast terminals for spring washers, only one terminal was without one.
Much easier fix than pulling the ignition switch.
You will probably never need that wire for the same reason but still worth carrying.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto