3,0 Only Firing on 3 Cylinders

[hoowahfun]

Hey everyone, I discovered today my boat is only firing on 3 cylinders. I discovered this while trying to diagnose a no-start issue which I think was the result of a collapsed fuel filter. Along the way I started investigating the ignition system after I checked off everything on the fuel side and I found out I was only getting spark to maybe 1-2 cylinders. You can read about it in the link below.

https://forums.iboats.com/forum/eng...ines-outdrives/10647285-collapsed-fuel-filter

I ended up buying a new dizzy cap and installed it this evening. In the process I noticed the rotor had jumped out of the slot and was not installed correctly. I must have bumped it when I lubed up the weights and springs in the dizzy while trying to solve my no-start issue. I fixed that and put the new cap in, and was able to start my motor again. Whew!

While it was running I decided to check to make sure all my cylinders were firing. Pulled the plugs off the cap on all the cylinders and got sparks and noticeable engine change EXCEPT on cylinder 3. Bummer. I swapped out the plug wires from one of the cylinders that was firing and it still didn't work on #3. I didn't think to check the plug itself until after I put it away for the night.

Coil looks original and has Pertronix Ignitor system. Hoping it's not the ignition module. 1987 3.0.

Any ideas??

 

[achris]

As far as the module and the coil are concerned, they don't know which cylinder is firing. Firing on any cylinder means they are fine. That leaves, rotor, cap and leads; if it's a lack of spark problem. If you have confirmed you ARE getting spark on all 4 cylinders, I'd be doing a compression test next.

Chris........

 

[kenny nunez]

As Chris said check the compression. When you remove the plugs look closely at #3 plug for water or rust, spin the engine to check for water coming out. If water is present then it could be either the head, manifold or the block. Next check the compression. If the compression shows low in #3 and the the boat was running normal the last time you used it then the exhaust valve could be stuck and the rocker arm stud has pulled up some. These are the most common problems I have encountered when I had my shop.

 

[hoowahfun]

I'm definitely not getting any spark on #3. When I removed the lead from the cap, there was no change in the motor and no spark between the lead and the cap. All the others resulted in noticeable change in the engine and sparked between lead and cap.

The cap and wires are new. I eliminated the wires as a possibility by swapping out the wires for 3 and 4 (didn't just cross them, but actually swapped them) and that resulted in no change for #3, and #4 still sparked. I suppose it could be a dead plug so I may try swapping the #3 plug with another or maybe sticking a bolt in the boot of #3 and seeing if the spark will jump the gap when I try to ground it. The rotor is also relatively new, but I could check that again since it may have been damaged when it got bumped and jumped out of the slot.

Does any of that make sense and sound like I'm on the right track to troubleshoot? Doesn't seem like to be a cylinder issue to me at this point...

 

[kenny nunez]

With the distributor cap removed is there any side to side movement when you push or pull on the rotor shaft?

 

[hoowahfun]

I solved it!

I checked shaft play (which was good) and swapped #3 and #4 plugs with no change. Then I decided to dig into the distributor further and found that the little sleeve that comes with the Pertronix kit had separated allowing one of the magnets to fall out so the module wasn’t getting a signal for that cylinder to fire. Fortunately, I found that magnet under the cap a few weeks ago but wasn’t sure what it went to so I stuck it in my glove box. I put the magnets back in and glued the bottom retainer of the sleeve back on. Everything seems to be working now. I’m getting spark to all cylinders and it’s running much smoother!