150 weak spark on cylinders 1&3

[Todd H.]

Ihave a 1988 yamaha 150 with weak/no spark on cylinders 1 and 3 which only allows me to get to 3000 rpm or so. A yamaha mechanic advised I change the CDI, I did, still have weak spark on 1 and 3 and no ignition. I have checked resistance of pulsar and charge coils, all check okay. I swapped around the ignition coils, still have no spark on 1 and 3. Sometimes, I think I lose a spark to a 3rd cylinder because then the motor barely runs...

I disconnected the control unit thinking it may have been limiting the igition or rpm in some way, but that did not make a difference. I have changed the plugs, no difference. I have checked the resistance on the rectifier, it is okay.

What could this be. I am thinking of replacing the pulsar coils, but since the resistance checks okay I am not sure.

Anyone had an experience like this before or suggestions?

Thanks,

[jb123]

are you pullng your wires while running and listening for sound change/arcing or pulling plugs out and watching ?

[Todd H.]

I have a spark tester and I crank the engine and watch each one. The sparks on 1 and 3 are very weak. I also switched the wires/ingition coils to 1 and 3 and the results were the same so the problem is somewhere back from the ignition wires.

[jb123]

i would try to run it in the dark and watch for any wire leaking as your wires are old and brittle. On my `89 pro-v 150 i had to shrink wrap all the coil leads as they were bleeding.Im sure as you removed and replaced the coils you should have good grounds...

[Todd H.]

Thanks jdb, I checked the wires and I did not see any sparks or cracks. Also, I replaced the ignition coils and they come with new wires...

[Todd H.]

Hi jd,

You will be glad to know that the problem was not in the ignition system. The upper fuel pump was not bolted tightly to the engine and it was not pumping...

[jb123]

another expensive lesson learned about fuel/electronics.