Spark, but no Fire

[MillBubb]

68 Evinrude, 65Hp

I need some sugguestions for the port side not fireing. I have tested the spark to jump a 1/4" with an adjustable tester but number 2 and 4 cylinders are not combusting. (Plugs are wet & black while the plugs 1 and 3 look good, dry, amber). Compression is 95psi for both 1 and 3. Compression for 2 and 4 is 85psi. Also I can pull either 2 and 4 with no drop in RPMs. What's up with that? 85psi should be enough - right?

Any help is appreciated!

 

[jbjennings]

Re: Spark, but no Fire

Do you have two power packs? One for each cylinder bank? If so you may have a bad pack on cylinders 2 and 4. If not, is there something else that cylinders 2 and 4 have in common like a coil? If so, try switching the coil or powerpack and see if the problem follows. Then you'll know what part you need to fork over the dough for.
Good luck,
JBJ

 

[MillBubb]

Re: Spark, but no Fire

It has one power pack and one coil. The distributor has been cleaned and I didn't see any carbon tracks. Points are gapped @ .010. The plugs and wires are new too

 

[jbjennings]

Re: Spark, but no Fire

Sorry Millibub,
I reread your initial post. Is it correct that your spark will jump a 1/4 inch gap with a nice spark for cylinders 2 and 4? If so, you've got 2 carbs, right? sounds like the carb that feeds cylinders 2 and 4 is flooding them out. Maybe you've got a stuck float in that carb.
I'll look up some diagrams on your motor and see what else I can see, if a real expert doesn't give you the correct info. before I get to it.
Hope you find the problem,
JBJ

 

[jonesg]

Re: Spark, but no Fire

Unless your engine is radically different from my 150, a 1/4 inch spark just isn't enough to jump a sparkplug gap under compression.

I know this because all my port cylinders can jump 1/4 inch ok but they misfire when run. Starboard cylinders are all good to 7/16th gap.

If I take the starboard output from the powerpack and move the (primary) wires over to the port side coils the port coils fire good.

I'm told the odds are 10 to 1 its very likely the power pack and am waiting for it to come UPS.

if you try this test remove the sparkplugs.

 

[CharlieB]

Re: Spark, but no Fire

85 psi is getting down there, but with a CLEAN plug of the right heat range it could be made to work for a while yet.

First thing to try is switch those nasty plugs with the other side to see if they will fire at all, they could be fuel fouled and garbage already.

Next, using an adjustable gap spark tester, test BOTH sides, keep increasing the gap to find out the maximum gap that your ignition will fire. The reason that I want you to do this is to find out how well you have gapped the points AND how clean are your points. Just a little dust or dirt will lessen their contact and impede the ignitions peak power. You will be checking to ensure that you don't simply have a problem with the points.

Next is to increase the heat range of your plugs. If you are able to run a standard electrode plug then I recommend an NGK B7HS, possible using the B6HS on the lower compression side.

Also check your fuel pump pulse hose, the actuating hose from the crankcase to the pump, check inside that hose for the presence of gasoline, which could indicate a leaking fuel pump diaphragm, flooding that cylinder, fouling that plug, the recirc system then pulls excess fuel out of that cyl and pushes it into the top cyl, also flooding that cyl.

 

[tashasdaddy]

Re: Spark, but no Fire

this may help you. http://www.boatpartstore.com/page28.asp. also the motor was designed to run on Champion Plugs.
65 (V4) 1968 L76V Surface Gap or QL77JC4 .030

 

[MillBubb]

Re: Spark, but no Fire

Great tips! Thank you.
I have bypassed the mechanical fuel pump with an electrical one for now. I did however notice that the actuator hose will spray a mist if not plugged.(It is plugged now)
The hotter plug idea has got me wondering if I didn't foul the new plugs right off when adjusting the rebuilt carb. (This engine has 1 carb with two bowls) Trying to adjust the Starboard side bowl doesn't make a very noticeable change when setting the low speed needle. (I think this bowl wraps around through the manfold and supplies the port cylinders?)

 

[MillBubb]

Re: Spark, but no Fire

"Next is to increase the heat range of your plugs. If you are able to run a standard electrode plug then I recommend an NGK B7HS, possible using the B6HS on the lower compression side."

So I'm clear, this suggest running NGK B7HS on cylinders 1 & 3, then plug NGK B6HS on cylinders 2 and 4? What would be a good gap for this setup?

 

[CharlieB]

Re: Spark, but no Fire

Same gap as the manual calls for on an electrode plug

.030

 

[MillBubb]

Re: Spark, but no Fire

Sunday update... Installed the NGK B6HS's on the weak side and it started first turn! Without the choke even! Sounded great at idle. Motivated, the wife and pooch boarded and off we went. On initial power-up it sounded a little rough, like bad timeing, but quicky smoothed out and got on plain. We headed out -wot for 15 minutes then took a break at a nice beach/play spot. Checked the engine and it was not overly hot.
When we were ready to go it was hard to start and even died a couple of times when tyring to throttle up. Really rough at mid throttle but after a l-o-n-g hole shot we got on plain and ran well (24mph) back to the ramp. Removed the NGK's to find them black and damp. Sorta at a loss here. Any thoughts??

 

[CharlieB]

Re: Spark, but no Fire

BOTH plugs on the left side look the same blackened/sooted, partially fouled?

If it were only one plug I would expect a carb running rich from too high of a float adjustment.

But your ignition is the common point. One set of points is NOT perfect, the gap is not the same as the other set which does have an effect on ignition timing. The left side is firing late, you are going to find the point gap just slightly wider than those for the right.

They MUST BE gapped the same.