Cylinders Not Firing Please Help!

[ndavis175]

Hey, I am new to the site and from what I have seen this is a great forum with a lots of info. In advance, thank you to everyone for any input that y'all give me. I have a 2001 Bayliner 175 with a 3.0l mercruiser. I have replaced the fuel filter, spark plugs and wires already this year before I got ready to take it out. But when I was running it on the muffs in the yard I notice the motor was running like it was skipping. I started pulling off each plug wire until I notice that cylinders 3 and 4 weren't firing. I did a compression test on all the cylinders and the compression was good, between 160-175 on each cylinder. Also I'm getting fire at the distributor cap. So, my question is what is wrong? or where to check next? Thank you again and sorry this is so long.

 

[Don S]

Re: Cylinders Not Firing Please Help!

You didn't mention replacing the cap and rotor ??????
What kind of spark plugs did you install? Did you gap them?

 

[ndavis175]

Re: Cylinders Not Firing Please Help!

No I didn't change the rotor or cap. And I put champion rs12yc spark plugs in it.I had the guy at the marine shop where I bought the plugs gap them for me.

 

[Don S]

Re: Cylinders Not Firing Please Help!

Replace the cap and rotor, and the spark plugs. Use either the AC MR43LTS or the NGK BPR6EFS plugs.
I have replaced more champion plugs to fix misfires than you would believe.

 

[ndavis175]

Re: Cylinders Not Firing Please Help!

Ok thanks! I will try it this week.

 

[ndavis175]

Re: Cylinders Not Firing Please Help!

Don, I was thinking today and why would I need to change my rotor and cap if im getting fire.

 

[Oldskool]

Re: Cylinders Not Firing Please Help!

You can get fire to some but not all of the cylinders when the cap or rotor is in need of replacement. The cap could have a hairline crack which can cause a misfire to one or more cylinders.

 

[26aftcab454]

Re: Cylinders Not Firing Please Help!

I had # 6 & # 8 not firing on my 7.4.
after replacing plugs( one was burnt down) still missing on 1 cyl.
with the motor running under load(tied in slip)
I pulled 1 wire at a time using long needle nose with good handle untill figerd out which one was still not firing.
I did wind up with new cap,rotor & new wires.

 

[ndavis175]

Re: Cylinders Not Firing Please Help!

I was wondering if there was a way to test the ignition module before I bought a new rotor and cap.

 

[ndavis175]

Re: Cylinders Not Firing Please Help!

So i replaced the rotor and cap... and cylinders 3 and 4 are still not firing.. whats next??

 

[Don S]

Re: Cylinders Not Firing Please Help!

and cylinders 3 and 4 are still not firing

Do this, remove #3 & 4 spark plugs, hook the plug wires to them and ground the base of the spark plug and crank the engine over. Is there spark on those 2 spark plugs?

You keep saying they aren't firing, but I am wondering if they are actually firing, but your problem is that when you pull the plug wires off the spark plugs when the engine is running that there isn't any change in the sound of the engine.
Is this true?

 

[ndavis175]

Re: Cylinders Not Firing Please Help!

Yes correct, when the motor is running I'm pulling off the plug wires and there isn't a change in the motor.

 

[Don S]

Re: Cylinders Not Firing Please Help!

Did you check to see if you have spark on those 2 cylinders?

 

[Fishermark]

Re: Cylinders Not Firing Please Help!

Also I'm getting fire at the distributor cap.

How exactly are you checking it AT the cap itself?

Are you sure you didn't damage the wires when removing / replacing them?

I too dislike Champion plugs. If you don't want to buy new plugs again, you might try pulling all of them again and seeing what they look like. Then put them in different cylinders and see if the miss follows the plugs.

 

[ndavis175]

Re: Cylinders Not Firing Please Help!

I haven't checked to see if I am getting spark to the plugs yet. But I know there is fire at the cap bc when I pull the wires off while its running it shocks home sweet hell out of me. Is there a better way to test the cap other than that? And I have tired pulling the plugs out and see is the miss fire follows the plug but it didn't.

 

[dan t.]

Re: Cylinders Not Firing Please Help!

Did you ever think that you may have 3 and 4 mixed up, check your firing order. To short out a cyl with out getting a zap use a test light, ground the lead, slide the probe between the wire and boot,do not pierce the wire or boot. the light will not flash but it will ground out the spark, you wont get a zap because of the resistance in the bulb.

 

[ndavis175]

Re: Cylinders Not Firing Please Help!

So here is an update on what I have done in the last few days. I have replaced the spark plugs, plug wires, rotor, cap, ignition module, pick up coil and the ignition coil. And still cylinders 3 and 4 aren't firing. The firing order is correct. I have swaped the plugs around as well and the problem didnt follow the plug. So my question is now what?

thanks again for all the input on this I know this is taken forever but thank you!

 

[Don S]

Re: Cylinders Not Firing Please Help!

Try adjusting the idle mixture screw on the carb. Is the choke working right? Does this happen with the engine cold, warm, or both ???

This is probably one of those jobs that if I could actually look, feel and hear the engine, it would be fairly easy to determine what the problem is. But short of doing that, you get to "Try" different things.

 

[ndavis175]

Re: Cylinders Not Firing Please Help!

I have adjust the idle mixture screw. But I need to adjust it back to the stock setting. and It does it both when it starts up cold and after it warms up. How do I adjust the screw back to the stock setting? Im not sure if the person I bought it from may have adjusted or not and it may be way out of wack!

 

[honeys money]

Re: Cylinders Not Firing Please Help!

I doubt if you have 2 cyl. not firing at all, on a 4 cyl. I don't think it would even idle.