Intermittant spark in one cyl, '86 90hp Crossflow

[V153]

Please refresh my memory. Seem to recall I had a similar problem awhile back & it turned out to be a coil. Still have trouble comprehending that. Where I grew up coils either worked or they didn't?

Oh well gonna go get a new one @ NAPA & start shuffling em around. My luck it'll be the 4th one ...?

 

[boobie]

Re: Intermittant spark in one cyl, '86 90hp Crossflow

While your at NAPA get an open air gap spark tester. Set it at 7/16 " and check the spark on all 4 cyl's. This will narrow it down to where the prob is. You could also have a bad pack or timer base.

 

[nphilbro]

Re: Intermittant spark in one cyl, '86 90hp Crossflow

If it's a single spark I would guess isolate it from the plug back to the coil.

If you check and there's intermittent spark on 1 and 3 or 2 and 4 it would likely point to the trigger.

Hopefully it's just the plug or wire (try switching plugs if you don't have a spark tester- best 9 bucks I've spent). If that doesn't work, switch the coils on the bar and at the powerpack and see what's going on. You'll have your answer then. If you have spark it's the coil. No spark - power pack. It shouldn't take more than an hour to do this test.

 

[emdsapmgr]

Re: Intermittant spark in one cyl, '86 90hp Crossflow

As was mentioned, you can perform testing which will help you decide what is wrong. Though the coils are usually a very reliable component, you can swap two of them and see if the problem moves with the coil. Similarly, that engine has dual power packs-each controlling the spark to one head. Those packs are not as reliable as the coils. These can also be exchanged. See what happens when the packs are swapped. Since the pack typically has a higher failure rate than the coil, swap the pack first.

 

[Haffiman]

Re: Intermittant spark in one cyl, '86 90hp Crossflow

Be a bit careful just swapping coils. A shorted coil may even kill a power pack and swapping might then not be a good idea. Before swapping, use a multimeter, preferably with a DVA adapter, and check for voltage from powerpack to coil. Roughly the voltage should be around 230-250Volts (AC Peak).

 

[keefallan]

Re: Intermittant spark in one cyl, '86 90hp Crossflow

You can also check the resistance on all the coils to see if one is different than the other.

 

[V153]

Re: Intermittant spark in one cyl, '86 90hp Crossflow

Thanks for all the input folks. 'Preciate it. Will check coil resistance, etc tomorrow. Before shuffling ...

Fwiw this motor was rebuilt from the crank up about 4 yrs ago. New power packs, non water cooled/warmed voltage regulator, etc.

In the past year or so I've upgraded the stator, rebuilt the starter, new solenoid and 'rectumfrier' too. Could it be the timer base all of a sudden? Hmm ...

Plugs have been checked & shuffled around. Run NGK BR7HIX irridiums, love em. Guess I should get an air gap tester ...

Thanks again for the input y'all.


Doug

 

[kenmyfam]

Re: Intermittant spark in one cyl, '86 90hp Crossflow

Does it only do this when warm or at any time ???

 

[Haffiman]

Re: Intermittant spark in one cyl, '86 90hp Crossflow

Use of any plug with 'R' in the description (resistor), and you run a severe risk of powerpack failure.
NGK BR7HIX !!!

 

[emdsapmgr]

Re: Intermittant spark in one cyl, '86 90hp Crossflow

When cranked, the timer base should output 0.3 volts as measured with a peak-reading voltmeter. Black lead into the "A" cavity and the red lead in the "B" cavity. Crank the engine. Repeat with the red lead in the "C" cavity.

 

[V153]

Re: Intermittant spark in one cyl, '86 90hp Crossflow

Thanks for the info.

Yo Haffiman, please elaborate on the resistor plug problem?

 

[Haffiman]

Re: Intermittant spark in one cyl, '86 90hp Crossflow

Thanks for the info.

Yo Haffiman, please elaborate on the resistor plug problem?

Been discussed endless times, and even stated in the OEM manuals for VRO engines. However the 'quickest' one, check conversion for the QL77JC4 to NGK for Evinrude/Johnson engines. You may even Goggle Supressor vs Resistor plugs.

 

[V153]

Re: Intermittant spark in one cyl, '86 90hp Crossflow

Been discussed endless times, and even stated in the OEM manuals for VRO engines. However the 'quickest' one, check conversion for the QL77JC4 to NGK for Evinrude/Johnson engines. You may even Goggle Supressor vs Resistor plugs.

Forgive me for not researching the archives before asking my silly question. I'd never heard that resistor plugs had an ill effect on powerpacks. Sorry for the intrusion.

 

[Haffiman]

Re: Intermittant spark in one cyl, '86 90hp Crossflow

Was a bit short of time with my answer, busy with other things. However read this thread: http://forums.iboats.com/showthread.php?t=526594&highlight=resistor+plugs