w108,107 Parts Hoarder
Date registered: Jun 2010
Vehicle: slc5.0cab 280sl5sp 280se4.5 500sl92 GONE:280sl79 4xW114/5 3x450sl72-3 280slc4sp81 280s69 73,81SLCs
Location: Philadelphia Area
Mentioned: 27 Post(s)
Quoted: 1569 Post(s)
I don't know the injection system that's being used here, but it sounds like your battery is pretty worn, probably due to be replaced. If not providing the volts and amps where needed, even the spark could be suffering.
As for spark, assuming your car has the transistorized ignition like my 1971 (or even if you don't) the points on top of the distributor need to be opening for the coil to fire current to the plugs.
Speaking of plugs, with excess fuel, they could be fouled and not sparking well.
Air, fuel, spark. Assuming you've got air and fuel, it sounds like you can set your focus on the spark.
After you've got a good battery connected...
You can pull a spark plug, connect it to its wire, put the threaded part into a jumper cable, and connect the other end of the cable to the negative on your battery, and then crank the motor to take a look at the quality of your spark. I like to do this to quickly take a look at the quality of the spark on each cylinder.
My dream car is a classic sporty five speed (stick+overdrive) convertible that seats five. If, you want 70's-80's Mercedes tuner wheels, let me know.