Logo
FULL SITE MENU

Chrysler LM 318 starting problem

M

michael.stinson

New member
I am working with a 1980 or 81 Chrysler LM 318 in a Silverton 31 Sedan Bridge. It started out stalling at low idle when trying to dock of course. Thought it was a fuel problem so I changed all the fuel filters. When done the starboard engine started right up and runs beautifully. The port engine however has not restarted yet. I have good spark to begin with, but after a few seconds of cranking the spark at the plugs is gone. The spark from the coil is good and strong. My mechanic buddy narrowed it down to the pickup inside the distributor. I replaced the pickup, with the proper .006 gap. I replaced the distributor cap and the rotor and yet I still have the same issue. It does not start and after a few seconds the spark at the plugs is gone.

Where do I go from here?????
 
but after a few seconds of cranking the spark at the plugs is gone. The spark from the coil is good and strong.
Click to expand...

Ayuh,.... If the coil is firin', the coil wire, the cap, the rotor, the spark plug wires, 'n the spark plugs, are what's 'tween the coil fire, 'n the spark plug fire,....
 
If the battery has a weak cell it won't have endurance to supply the starter and provide adequate voltage for a good spark for extended periods of time. The alternator will be tying to charge a battery that will not hold a good charge. If the problem moves to the other motor and the original problem motor works well, then the battery was the problem. If the problem motor works well for a short period of time and then starts stalling with a different battery, then the alternator on the problem motor could be suspect.
 
Last edited:
Right on! Put a voltmeter on the + terminal of the coil and see what voltage you're getting as the spark goes away. I suspect it will nose dive.

During cranking, the voltage to the coil comers from the starter solenoid's 'S' terminal. If the solenoid is bad, that would cause this. Cheap to replace. The ECM gets its power from the ballast resistor (and needs to run on less than12 volts. Learned that the hard way!) If the ballast resistor is bad, or open, the motor won't run after you release the key.

Jeff

PS: You MUST have a BLUE spark at lease a 1/2 inch long for proper operation. If it's orangy, or less than 1/2 inch, it's not enough.
 
Last edited:
So it turns out the previous owner shopped for replacement parts at auto parts stores. The electronic ignition module that was in the boat was for a car and not a marine application. The difference is car has 5 pins, boat has 4 pins. Put the new CORRECT module in and she runs great. Thanks to Joe at Cobe Marine in Passadena MD for the troubleshooting help and to all here that assisted. Six Knots is back underway and it couldnt be a better weekend for it.

See my new thread "Chrysler LM 318 fuel filter issue" for the next project!!!
 
Glad to hear you're running fine, but those 4 and 5 pin modules are interchangeable. Had one of each on my twin 360s powered boat for years.

Jeff

PS: You simply had a bad module. It happens.
 
Back
Top