plug not firing

[hullofalottatrouble]

so any reasons for a single plug not firing beyond a bad plug or a bad plug wire?

 

[ron7000]

Re: plug not firing

did you initially start this thread asking about setting timing?
this board is wierd.


bad distributor cap or rotor, or incorrect rotor.

 

[hullofalottatrouble]

Re: plug not firing

yes it was but i got the answer i needed on that from another board.. so i thought since no answers here yet and insteand of new thread i would just change it..

the cap is new..

the rotor is 1 year old now.. only thing on the rotor is that there is a good bit of side to side play in it.. i can wiggly it back and forth a bit.. is that normal? i guess i was expecting more of a solid snug fit....

but could it be bad and only affect 1 plug? i guess anything is possible eh..

 

[KaGee]

Re: plug not firing

The 3 basics required are Spark, Fuel, Compression.

If you have the other cylinders firing, then the motor has spark. If that plug has no spark it will not fire. Cause? Bad plug, bad plug wire, bad socket in the disrtributor cap.

Other cyliders firing, so the motor is getting fuel. Is that cylider getting fuel? We don't know. Is the plug wet or dry? If the plug is dry time to pull the valve cover and inspect for valve opening.

If the plug is good and has spark and is wet (gas, not water), then time to check compression.

 

[Reel Poor]

Re: plug not firing

What motor Mercruiser, Volvo, OMC?
4, 6, 8 Clyinder?
What year?

If it has points and a lot of side to side slop it can drop one cylinder.

I would recommend doing a compression test to make sure you don't have a mechanical engine problem with that cylinder.

 

[hullofalottatrouble]

Re: plug not firing

sorry.. 1982 merc 260 5.7l v8 reman.. just dropped it in.. havent run on water yet.. compression tests have read 150 on all cylinders..

it has a new pertronix ignitor II and flame thrower coil..

ill pull the plugs again when i get home.. i believe it smelled like gas.. but was not overly wet..

 

[Gary H NC]

Re: plug not firing

I had a defective cap cause that before.
Can you pull the plug,ground it out and turn the engine over to see if spark is jumping across spark plug?

 

[hullofalottatrouble]

Re: plug not firing

i swapped out all the plugs on that side.. because i was not smart enough to pay enough attention to which cyl i pulled the plug from..

and battery still dead.. or too weak to start the boat.. turns it over barely but no spark from coil.. so need to get that fixed then ill check out the plugs..

 

[hullofalottatrouble]

Re: plug not firing

its a mallory dist with a pertronix ignitor II and flame thrower coil..

the rotor wiggles a bit on top it is aligned correctly with the notch.. but i can wiggle it side to side.. and this is without the shaft itself moving.. is that normal? anybody else with a mallory v8 dist for mercruiser?

 

[ron7000]

Re: plug not firing

get a new rotor.

it sounds like what your describing with the wiggle is the mechanical advance of the distributor. I think the rotor will spin clockwise, or for whatever direction it does with the engine running, you'll be able to turn it by hand in that direction just a tad. If the rotor "wiggles" in a manner other than this, then it isn't secure and a problem. You may have a poorly made mass produced part, or your distributor may be old and need some work.

 

[hullofalottatrouble]

Re: plug not firing

the rotor is definitely not secure..

ordered a new one today with the correct part number.. wish the current one had a part number so i could try to verify..

the last tune up was done last summer by a shop that i am not very confident in.. so we'll see if its just a cheap bad part..

thanks