Dead cylinder on 1983 90 Hp Evinrude

[Jack Sullivan]

I have one cylinder on my 1983 Evinrude 90 Hp that is "dead". The cylinder has spark but doesn't seem to combust. I have replaced the stator, timer base, rectifier, power packs, coils and plugs. Cylinder is getting gas and other three cylinders seem ok. Motor runs about 2,500 rpm maximum on the three cylinders. I am out of ideas and need help. Thanks

[Joe Reeves]

All spark plugs removed..........

Check the compression. What are the psi readings of all individual cylinders?

Check to see if the spark will jump a 7/16" gap with a strong blue lightning like flame... a real SNAP!

[Jack Sullivan]

Compression is 100-125 in all cylinders. I will check for spark with wider gap as you suggest. The dead cylinder has a white spark plug after running the motor while the other three appear normal brown. Is it possible for one cylinder to not get gas while the others are?

[Joe Reeves]

Originally posted by Jack Sullivan View Post

Compression is 100-125 in all cylinders. I will check for spark with wider gap as you suggest. The dead cylinder has a white spark plug after running the motor while the other three appear normal brown. Is it possible for one cylinder to not get gas while the others are?

The white spark plug indicates that the plug is not firing, either due to no ignition or no fuel.

And yes, it very possible that only "one" cylinder could not be receiving fuel while the other three are.

There are four (4) high speed jets in that engine, 2 to a carburetor. They are located horizontally in the bottom center portion of the float chambers... way in back of the drain screws/bolts you see at the extreme bottom side section of the float chambers.

The numbering of the cylinders, when standing in back of the engine and facing the spark plugs are as follows. Which cylinder has the "white" plug?

2....1
4....3

You can pick up a air gap spark tester in most auto part stores that test one cylinder at a time... OR...................

********************
(Spark Tester - Home Made)
(J. Reeves)

You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:

..........X1..........X2

.................X..(grd)

..........X3..........X4

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

joe_omc32 | eBay
********************

[Jack Sullivan]

The dead cylinder is number 2. It sounds like I need to dis***emble the carbs and check jets, etc.?

[Joe Reeves]

Originally posted by Jack Sullivan View Post

The dead cylinder is number 2. It sounds like I need to disa$$emble the carbs and check jets, etc.?

No, not yet..... Did you check to see if you had spark to that cylinder and if the spark would jump that 7/16" gap?

The white non firing cylinder (#2 - top port side) could be no spark, a water spray entering cylinder via a failing head gasket, or a no fuel situation.

If water, the water would show up a small droplets on the electrode.

If no fuel.... the mixture must flow freely through the high speed jet for that #2 cylinder before it can gain access to any other pa$$ageway. The bra$$ high speed jet would be located in the top carburetor on the port (left) side way in back of the drain screw on the float chamber, near the bottom center portion of the float chamber.

Carefully clean that jet with a piece of single strand steel wire. This may cure your problem if you have a No Fuel situation..... worth a shot.

[Jack Sullivan]

Cylinder 2 failed the 7/16 gap test. Spark out to about 1/16. Other cylinders p***ed 7/16 test. Also cleaned carb and jets which looked very good and clean. To date I have replaced plug, coil, power pack, stator, timer base and rectifier. I have heard that magnets could fail but have no knowledge in this regard. Where do I go from here?

[Joe Reeves]

Originally posted by Jack Sullivan View Post

Cylinder 2 failed the 7/16 gap test. Spark out to about 1/16. Other cylinders pa$$ed 7/16 test. Also cleaned carb and jets which looked very good and clean. To date I have replaced plug, coil, power pack, stator, timer base and rectifier. I have heard that magnets could fail but have no knowledge in this regard. Where do I go from here?

1983 90hp Evinrude

You've replaced:
Spark Plug
Coil
Power-pack
Stator
Timer-base
Rectifier

That's everything that would apply in the ignition system... nothing to stop it from firing UNLESS some of those replacement parts are used and unknown to you... are faulty.

I feel sure that you've switched the replacement spark plugs and also the coil and power-pack..... if not do so to see if the non firing problem follows the component.

The stator must be putting out the proper AC voltage or else the other three plugs wouldn't fire.

The timer base has two sensors, one of which fires one bank, the other sensor fires the remaining bank. If the sensor fires the #4 cylinder, it would most certainly fire the #2 cylinder UNLESS a broken circuit exists somewhere between the timing sensor and that #2 coil.

Carefully check out all of the continuity of those wires, pins, sockets, and the coil including the spark plug wire.

That's one engine I'd really like to see.

[Jack Sullivan]

Thanks for your support to date. All electronic components are new but I do have some component switching to do to and will recheck all connections. Too, if I am to solve this problem I will report the solution to what has become a mystery inside a puzzle wrapped in an enigma.