1978 80 hp Weak Spark

[jonesec]

I've done a good deal of work to this motor, and finally got everything back together. It was leaking water into the bottom cylinder from multiple , so I fixed that and replaced a piston. I have great compression on all 4 cylinders now, but I can't get it to start because the spark plugs won't fire on the bottom two cylinders.

When I hook up a timing light to the #3 and #4 plug wires, I get a signal, but the plugs won't spark. I've cleaned plug wires and connections, but still can't get any plug to give me spark. I have tried plugs on the top two cylinders, and they spark just fine, so I know the plugs are all good.

I'm thinking it might be in the stator or in the trigger, but I'm not sure if I am missing anything simple. Any suggestions?

 

[TripleB]

Re: 1978 80 hp Weak Spark

No fire on Two Cylinders (Top or Bottom Two cylinders):

Check DVA voltage of the stator, checking from each red and blue wire to engine ground. The readings should be fairly equal and approximately 180 volts or more on the blue wires and 30 or more on the red wires. If the readings are not equal (or if a DVA meter is not available) swap the red with the red/white and the blue with the blue/white stator wires. If the problem moves, replace the stator. If the problem stays on the same cylinders, swap the trigger wires from top to bottom, # 1 for #3 and #2 for #4. If the problem stays on the same cylinders, replace the pack.

 

[jonesec]

Re: 1978 80 hp Weak Spark

Awesome response. I did both of the tests. The stator came out being OK. When I moved the trigger wires on the switchbox, the top cylinders didn't have any spark, and #4 didn't have any spark. I take it the trigger is bad, but since I don't have any spark on #4, I'm not sure I can rule out the switch yet. I do thank you very much for your response.

 

[jonesec]

Re: 1978 80 hp Weak Spark

Just a follow-up. Got a new trigger and cleaned all the connections to #4 coil and got fat, healthy sparks to all cylinders. Connected the fuel and she fired up just fine. Load tested each cylinder and it is running on all 4. Now I can put it all together and water test it.