No spark plug spark... 170 MC , 1985 Sea Ray

[glennj3]

I have neglected to crank her up in several months but it ran great the last outing. Had new tune up early this rear, wires plug points distributor and not driven much.
Engine turns over well but has no fire. I connected a good plug to a wire and it does not spark. I removed the distributor cap, points and rotor look good. With the key on I have a spark on the distributor when grounding with a screw driver. All wires are connected solidly.
Looking for advice on what to do now.
Thanks, its been a while since I was on I Boats!

 

[Scott Danforth]

file your points, then gap your points then verify the dwell and set timing.

 

[kenny nunez]

Something else to check is the “bypass” circuit from the starter solenoid. Get a jumper wire and connect it from the + battery to the + side of the coil and spin the engine over. If you get a spark then the solenoid is the problem.

 

[glennj3]

Could the condenser in the distributor be bad?

 

[kenny nunez]

The best thing that you can do is to obtain a Petronics ignition conversion.
The condensers and other ignition parts are mostly made off shore and are not reliable.

 

[Scott Danforth]

Could the condenser in the distributor be bad?

yes, this would normally short to ground. easy to check with a ohm meter

 

[glennj3]

I popped a hole in the side of the distributor cap so I got a new one & rotor. Also got a spark detector. I tested the coil with the spark plug tester and it sparks each time the engine turns over. The wire is is good from the coil.
I checked & gapped the points @ 23. I don’t have a spark from the distributor cap! I did not change the condenser but it tests OK with the OHM meter.I did not remove the condenser to test it.
What in the world?

 

[Scott Danforth]

if you have spark at the coil butt not at the plugs, its either your plug wires, your distributor cap or rotor. and the rest it going to be working

if you have no spark anywhere then the points are not opening and closing or your condenser is shorted.

points are nothing more than a mechanical on/off switch used to turn power to the coil on and off.

use a dwell meter to set the points. the gap is only a rough approximation. failure to properly set the dwell means that you may not get coil saturation.

 

[glennj3]

if you have spark at the coil butt not at the plugs, its either your plug wires, your distributor cap or rotor. and the rest it going to be working

if you have no spark anywhere then the points are not opening and closing or your condenser is shorted.

points are nothing more than a mechanical on/off switch used to turn power to the coil on and off.

use a dwell meter to set the points. the gap is only a rough approximation. failure to properly set the dwell means that you may not get coil saturation.

Thank you fir verifying my thought.
The most likely culprit seems it would be a shorted condenser then. Whatever happened while it was sitting still, stored.
The spark makes it to th new distributor cap but nothing past that point.
Other only other thing I can think of is the timing. But that should not happen.
Thanks for your help.

 

[Scott Danforth]

no, if you are correct and there is spark being generated at the coil, then the culprit is your distributor cap, rotor or wires.

with points, you MUST re-set timing after adjusting dwell.

 

[glennj3]

no, if you are correct and there is spark being generated at the coil, then the culprit is your distributor cap, rotor or wires.

with points, you MUST re-set timing after adjusting dwell.

Hmmm, I’m baffled. New cap & rotor, wires are pretty new but I don’t have a spark on the cap where the wires plug in! Very very low time on those points and they look very clean.

 

[Scott Danforth]

how are you checking spark?

have you hooked up a dwell meter? a dwell meter will tell you immediately if you have a good gap and if the points are working.

with points, if they sat for a while, they film up. which is why the service manual calls to file the points, rough gap them, verify the dwell, then set timing.

BTW, your point gap should be 0.022" and dwell between 28 degree and 34 degree http://boatinfo.no/lib/mercruiser/manuals/mercruiser3.html#/34

here is the start of the ignition section of the manual http://boatinfo.no/lib/mercruiser/manuals/mercruiser3.html#/218

here is the start of the points section of the manual http://boatinfo.no/lib/mercruiser/manuals/mercruiser3.html#/228

 

[glennj3]

I’ll have to get a dwell meter. I filed the points with a finger nail file. No change.
I’m using a spark plug tester, (in line).

 

[Scott Danforth]

if your getting spark with an in-line tester at the coil, then the points, condenser and coil are working.

the issue will lie with your coil wire to cap, wires to plugs, the cap itself or the rotor.

the dwell meter will help you dial in the gap (dwell) prior to setting timing

 

[glennj3]

I’m typing as I test here now. I just ran a wire from the coil plug connector with the tester in line to the #1 plug. Turned the engine over and it backfired like a gun.
I removed the point and cleaned them with sand paper. Reset them at 022. They look good.
Again, new cap & rotor.
It ran fine when I put her up 3 months ago.

 

[glennj3]

This is my cap, the # 1 spark plug wire is at 3 o’clock or next to the coil. Is this the correct placement?
It just seems something simple is wrong here.

 

[Scott Danforth]

bring the motor up to TDC on #1 cylinder (you need plug out to verify TDC and light up the timing mark)

make sure the rotor is pointing to the same wire that is going to #1

 

[Scott Danforth]

I’m typing as I test here now. I just ran a wire from the coil plug connector with the tester in line to the #1 plug. Turned the engine over and it backfired like a gun.
I removed the point and cleaned them with sand paper. Reset them at 022. They look good.
Again, new cap & rotor.
It ran fine when I put her up 3 months ago.

use a points file or your wifes nail file

sand paper rounds them off too much

 

[glennj3]

bring the motor up to TDC on #1 cylinder (you need plug out to verify TDC and light up the timing mark)

make sure the rotor is pointing to the same wire that is going to #1

I was hoping someone could visually UD its position. I hate pulling those back plugs in this thing. Otherwise I can’t turn it by hand.

 

[Scott Danforth]

unless I personally stabbed the distributor into the side of the motor and made sure a particular tower was aimed for cylinder #1, there is no way for me to ever know how many times the distributor was pulled, or which tower is for cylinder #1

the only true way to know is to pull spark plug #1, rotate around until the motor is at TDC, align the timing marks, then look at which tower the rotor is pointing at.

the other method is to see which wire is currently on cylinder 1, and using a timing light, set timing to that cylinder

what does your timing light show you?