plugs not firing?

[hullofalottatrouble]

merc 260 with qjet carb petronix II and flamethrower coil.

got it to fire up and idle at 700.. got timing set a 8 btdc at idle speed in the driveway after warmed up to normal operating temp..

so its running and seems to have a miss here or there maybe? i dont really know.. but i pulled the plug wire on #1 and it died.. fired it up again and pulled #3 and it died.. fired it up again and pulled 5,7,2,4 and it really didnt seem to have any impact at all.. pulled 6,8 and there was some hesitation.. i pulled the 5 plug out itself and it looks like its been firing.. not fouled or anything.. looks good just like #1... its too dark and late here to do much more so ill need to give em all a look again tomorrow.. i put the timing light on the #5 and it appeared to be getting spark down the wire.. when idling..

so i guess my question is how should the engine respond when i pull a plug wire? should it die like 1,3 or be hard to tell? i had expected it to keep running but that i might hear a decrease in rpms?

compression is 150 all around..

its a muggy wet day today and had a small bit of white smoke out the prop when idling.. it came out about 8 inches then disappeared.. there was more at higher RPMS thou and it smells a bit like gas.. engine doesnt hesitate or anything when revving it up a bit..

it fires up fine.. idles fine. but something seems off?

also no signs of water in the oil or in the cylinders or on the plugs.. but i need to check that again when its lighter out..

 

[John_S]

Re: plugs not firing?

Based on your gas smell comment, but you should also have some black soot plugs, check the fuel pump safety hose. It is clear hose that attaches to carb. If any gas in it, your fuel pump is bad. Also, look down the primary barrels with flashlight while idling. If you see fuel dribling or seems to be access, your carb float needle is probably not seating. The infanous qjet plug leakdown, could contribute, as well. Carb rebuild time.

 

[hullofalottatrouble]

Re: plugs not firing?

pulled all the plugs and 1,3,5,7 all looked similar with a bit of black on them.. plugs 2,4 looked almost brand new.. and 6,8 looked like 1,3,4,7 with 8 mabybe a little darker..

so it appears that 2,4 arent firing?? and also that i am running rich or just have poor ignition all around.. the rotor and cap look fine really.. im not sure what to do next.. i broke one of the plugs when i took it out so definitely need a new one.. i could buy new plugs, plug wires, cap, and rotor but not sure that solves my problem? i did resistance test on the plug wires and they are all at like 2.5k..

i guess ill run the wires again and see if i can solve the problem??

 

[Don S]

Re: plugs not firing?

You could also be getting water in the cylinders which will steam clean the plugs and make them look new. To check it, try this. Assuming you have a raw water cooled system, Disconnect the hoses that run between exhaust manifolds and thermostat housing from the manifolds. Tie them up so the ends are well above the engine and fill the hoses full of water clear to the top so you can see the water. No pressurize the cylinder while the piston is at top dead center on the compression stroke for that piston. Pressureize to around 50 psi should do it, and check for bubbles in those hoses you tied up. If there are, you have a cracked head or blown head gasket or something leaking cooling water into the cylinder.

 

[hullofalottatrouble]

Re: plugs not firing?

update..

i check cylinders 2,4 for signs of water and nothing.. don i dont have an adapter to put pressure in the cylinder like you suggested so havent done that yet.. just wanted to see if massive quantities or water dripped into the cylinders after i shut it down and didnt see any sign of water..

put a new cap on and re-ran the plug wires..

fired it up.. and it ran a bit better this time.. its a warmer drier day here and there was no smoke to speak of coming out the exhaust at idle or higher RPMS.. there was when it first fired up for like 2 seconds but then it was fine after that..

i pulled plug wires from 2,4,6,8 1,3,7 and the engine kept running but there was a noticeable drop off in performance..

plug number 5 however didnt seem to do much it anything at all..

i pulled the wire out of the dist and there is definitely spark coming from the cap.. could be bad wire? or bad plug? strong spark from the cap thou..

i ran it for a few minutes and will let it cool down and pull the plugs out again and see whats what..

might get some new plug wires and plugs and see if that helps at all..

also need to make some carb adjustments i believe..

pulled the plugs and they probably look like plugs should.. just a little discoloration around the tip...

 

[Coors]

Re: plugs not firing?

#5 has a problem; check compression
Don's idea is excellent.

 

[Don S]

Re: plugs not firing?

Sounds to me like you need a full tuneup, plus some plug wires. Basic case of overdue maintenance items.
Everything has to work together. So putting a couple of wires on now, a cap last week, rotor next week, mayby sparkplugs a few weeks ago, adjust the timing next week, week after mess with the carb....................
Come on. Complete tuneup, all at once. Do a compression check, change the plugs, cap, rotor, points and condenser if you have them (No info on year in your posts) then set the dwell, set the static timing, confirm proper advance timing, then adjust your idle mixture, idle speed, get it all done at once and see how it work then.

 

[hullofalottatrouble]

Re: plugs not firing?

don..

its a 1982 260 reman that i just dropped in last summer.. its got a pertronix II with flamethrower coil so no pts etc etc..

the plugs were brand new, rotor new, cap new.. just the wires are from last summer.

compression is 150+ all around.. ive checked it multiple times this summer.. so thankfully all is well there.. ill get the plugs and plug wires next.. vacuum reads about 17 at idle with some fluctuation that i believe is indicating the miss in #5 if not more cylinders.. this is really the first time ive gotten in running all summer.. it hasnt been out on the water since the reman was dropped in.. its salmon fishing time on the lake so i need to get her out there..

thanks for the help..

 

[hullofalottatrouble]

Re: plugs not firing?

okay.. this is my last update until i get er out on the water..

i got it up and running again and adjusted the idle needles and got the vacuum gauge to read pretty much 19.5 ish at 670 RPM and steady up a great deal.. maybe from 19.5 to 20 fluctuation.. so i take that as a good sign.. thou it would be good if somebody with a better ear for tuning the carb could come take a look..

anybody out there around the north burbs of Chicago?? that can tune a carb with there eyes closed?

Thanks all