Help....again!

[4runneradam]

If you read my last few posts, I had a problem with the #2 cylinder not firing. Traced it down to a bad output on the prestolite cd box. I got a replacement from Standard Magneto out in Chicago. Hooked it up, fired up the motor, and verified spark on all 3 cylinders. Took it out on the lake, and the boat would only run up to 28mph and had poor acceleration. Pulled it back out, and noticed that the bottom carb wasnt opening all the way. fooled with the control rod and stripped out the screws. Fast forward to this week. Got new speed nuts for the throttle rod, and lined up the carbs so they are all fully open on WOT. Pulled the spark plugs and noticed the #2 plug looked like it wasnt firing. Hooked it up to the ears and fired it up. #2 cylinder is not firing, again. Switched output wires to the coils and verified coil is working, but the same output on the CD box is dead again.

Do you think I have another bad box, and it's just a coincidence that it went out the same way, again? Or do you think I have a bad stator or trigger that is causing that output on the cd box to not fire?

I got a repair manual to troubleshoot the stator and trigger, but it tells me I need a meter that will read peak voltage, and that a standard multimeter will not do the job. I have a regular radioshack digital voltmeter. I cant afford to buy a $200 fluke meter just to run some tests on the boat.

I'm going to bring it home next weekend and pull the flywheel to visually inspect the stator and trigger. If I find nothing, I'm probably going to take it in the shop and spend a bunch of money and wait a few weeks to get it back. I really don't want to do that, but I don't know how to check it without buying a new meter, and even then it seems a bit confusing on how to test.

 

[Frank Acampora]

Re: Help....again!

Switch The wires on the new box. You already know that #1 works well. If it now has problems, then the box is bad. If #2 still has problems, then it is not the box. Or: switch the second box that fires #3 cylinder to the #1 and #2 cylinder position. It is unlikely that 3 boxes would be bad especially since one side of the box that fires #3 cyl was never used. If you still have no spark on #2 then in all likelyhood, it is the trigger. Check the wires closely. Since they move when you advance or retard the throttle, they are liable to break.

 

[4runneradam]

Re: Help....again!

I already did that. One box I replaced fires the #2 and #3 cylinders. I switched wires to the coil packs, and the #2 cylinder fires, but the #3 now doesnt, so that means one of the outputs is bad. The unused output on the other pack has nothing hooked up to it, so without rewiring it, it will not fire no matter what you do. And I don't know how to rewire it, so I don't want to hook something up wrong and mess something up. Plus, if theres something thats blowing up the control boxes, then I don't want to damage another box.


You don't think its a coincidence that the brand new box only worked for a few minutes, and then the exact same output on the box went out again? Seems to me that something else is causing it to go out. I dont want to buy another box and ruin it again.

 

[Frank Acampora]

Re: Help....again!

What ignition system do you have? The prestolite uses made up connections and the other system uses a terminal board on the side of the engine on the box side. I don't think you can switch trigger wires on the prestolite system.
At any rate, If you did not switch the trigger wires when you switched the coil wires, you have not conclusively proved that the box is bad. This is because the number 2 trigger is now firing #3 cylinder Thus: a bad trigger wire will make it look like you have a bad box. I forget the trigger wire colors, but the schematic is usually on the block. Test the #2 trigger with a resistance meter. The trigger is a coil that puts out between 1/2 to 1 volt when the flywheel center magnet passes it. This signals the box to dump its stored power into the coil. If there is no continuity, then the wire is broken or the trigger coil is bad.

 

[4runneradam]

Re: Help....again!

I have the prestolite black boxes with the plug in connections.

The wires I switched were the wires coming out of the box and into the coil pack.

What color are the trigger wires? Blue and yellow? I looked at all the wires visually and they seem ok. There are 2 plugs, one had a single blue and a single yellow, and the other has a single yellow. I noticed that inside the plug with the yellow and blue, it has 2 blue wires butt connected together.

Test resistance between what and what? The Cd box and the trigger housing?