No/Intermitent Ignition
 

Greetings Forum Members,


I need help in diagnosing a no start problem that seems to be due to not receiving proper voltage to the spark plugs.
The car is my 1985 280sl with the 110 engine.
I've gone through the testing proceedure according to the MB 110 manual
for the TSZ 8u switching unit.
Everything seem to check out ok.
When I follow the test proceedure for testing the ignition distributor transmitter section leads for ground connection via the green cable I get no ohm reading.
The manual states that each plug on the distributor should read >/= 200k ohms when grounded.
The same test for the TST 4 unit states that the leads should give a infinity reading.
What does an infinity reading on an ohm meter look like?
How can I tell which unit I have?
Supposedly after 1981 I should have a TST 8u unit, but this is a Euro spec car.
The coil is new.
The fuel pump relay plug tested ok per the MB manual.
Can the relay itself be tested with an ohm meter?
Should I suspect the ignition switch as a possible problem? How might I test the ignition switch?
The engine will fire up for a couple of seconds and shut right down.
The plugs are wet, I'm getting fuel.
When testing for spark with my timing light I get a very erratic and some timey flashing of the light while cranking the engine.
Please HELP!!

Thanks,

Knarf

Infinite ohms on a digital ohm meter will look just like it does when you set the meter to test ohms (assuming a multi-meter) without touching the leads together. A new spark plug with no degradation or carbon build-up on the ceramic should read infinite ohms (completely open circuit). Are you using an induction type timing light where you put two leads to the battery to power the light and the third clamp type lead that goes around #1 plug? Sounds like you are and if that is the case you have a bad plug wire or anything in the ignition/distributor.

Ralph69220d,

Thanks for the feedback.
I was beginning to think that no one would reply.
Yes I am using an induction timing light.
I would like to diagnose the problem and not "throw parts" at the problem but I'm limited with only conventional tools.
Is there a proceedure for testing the fuel pump relay with a multimeter?
I've switched the distributor with a supposedly good used unit from Adsit Company.
I suspect a problem with the ignition switching gear.
I've read in posts of persons opening and repairing the switching gear.
If I knew what I should be looking for as a problem I'ld give it a try.
New ones are quite expensive.


knarf