'97 4.3LX New Cap, Rotor, Plugs, Wires - but now weird starting problem

NHGuy

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To further clarify, on the Mercruiser caps the OUTER numbers are standard rotation, not the inner.

And to clarify the comment about the distributor rotor possibly being for the 8 vs 6 cylinder engine, you would count the "windows" on the tone wheel that is attached under the rotor. For your engine there will be 6 windows and six blockages to spin past the pickup.
 
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NHGuy

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A problem I once created on a Mercruiser spark plug change was a partial broken plug.

The exhaust manifolds impede the reach of your plug socket and it's possible to snap the ceramic top insulator when installing or removing the spark plugs.
To check try to wiggle the tops of the installed new plugs in place. If they are stationary you are good, if any of them wiggle you could have cracked them.

It's also possible to get the spark plug wire ends reversed. Check the fit of the plug wires at the cap and at the plugs. The ends are different. The cap end contacts push out against the cap terminals, and the plug end contacts grip the little metal nub at the tops of the plugs.

BTW I agree with the other guys. I have goofed up ignition wires plenty of times. The reason it seems like a wire problem is the clank noise may a cylinder firing so early that the combustion pulse is going against the rotation of the engine.
 

jkimball

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Thanks for the advice guys. As soon as my son wakes up so that he can bump the key to help me find TDC I'm going to check the rotor and rewire again.
The part that's not making sense to me is its just doing it when starting and only one or two times then it fires off and purs like a kitten. Does this make any sense to you guys?
 

flipbro

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No! Mabe be4 u fire her up pull the plugs and have a look for water. Almost sounds like a leaking riser gasket and a slight hydro lock.
 

jkimball

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No! Mabe be4 u fire her up pull the plugs and have a look for water. Almost sounds like a leaking riser gasket and a slight hydro lock.

Thanks.
The problem literally just started when the cap/rotor and plugs were changed. And it only does it when there is fire to the ignition. If I pull the kill switch to remove power to the ignituon, it turns over as normal.

One thing I was thinking after reading through Bt Docturs response earlier was the trigger wheel.
I know it has 6 Windows on it, but what if I got a bad one and they're not indexed correctly? Is that a possibility? I may try to pull it and swap it to see if there's any change
 

jkimball

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So I can confirm the firing order is correct, I've used new cap-old cap, new rotor - old rotor, new wires - old wires, new rotor with old trigger wheel etc and a combination of all of the above and the problem still persists.
So I took it to the lake and ran it and it runs BEAUTIFULLY! Probably the best it's ever ran since I've owned it. No bogging, surging or anything. Revs beautifully.
But the problem at the start is still there. Though seemingly less pronounced in the water.
What could this be? Again, it's ONLY when you start the motor initially
 

Fishermark

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I don't know if it would be an issue or not... but it seems like Mercruiser used locktite to hold the rotor cap in place. Not sure why. Just trying to think outside the box here. Maybe the rotor cap is loose and moving? I really can't see that as an issue... but something to look at and see.
 

jkimball

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Has anyone seen anything like this? And if so, what was it
 

jkimball

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Is it possible it's a problem with the starter or flywheel?
That's what I'm wondering... The starter was replaced before I got it and worked its way loose (or wasn't tightened properly) several months ago so I retightened it and haven't had an issue since. And I checked it and it's still tight. But I can't rule that out since it's ONLY during the start.
Maybe it's just a coincidence that it happened after the tune up?

Also, would the fact that I replaced the thermostatic choke have anything to do with it in theory? Can't really see how but I don't know what else it could be.
Maybe wires touching manifolds and arcing? I don't know I'm kind of lost right now
 

FreeBeeTony

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Was just a guess on my part.......hard to determine from print.....
​Doubt the choke has anything to do with your problem.
 

jkimball

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So I was finally able to get the videos loaded to Youtube and have attached the links here.
The first Video:
https://www.youtube.com/watch?v=X1oyf2oa4Fk

Is the first start of the day, you'll see how it kicks back then fires right off.

The second video:
https://www.youtube.com/watch?v=RUXoxrHEuqc

Is immediately following that run in the first video. See how it fires right up, and idles clean?

The third video:
https://www.youtube.com/watch?v=P0OtoWD-NsY

Is the longest, but also the worst Kickback/Backfire and a little choppy idle that smooths out...

Again, this one has me stumped, but I do appreciate all the input/help. Can you please watch the videos and tell me what you think may be going on?
 

BRG25

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I'm not an expert but it looks to me like maybe the carb/choke could be the issue. Does this usually happen during a cold start up? I know when my choke wasn't working properly I had similar issues and my idle was way too high.
 

jkimball

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It happens cold or warm, but as you can see in the videos it starts fine after it does it. It'll do it if I let it sit for 5-10 mins between start ups too. I do feel like my idle is a little high too. On muffs it's idling at about 1k rpm and in the water in gear it's still about 800 or so

Do you remember if it was due to your choke being too lean or too rich?
 

NHGuy

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So on a cold start the choke should be closed, you should pump the gas a couple of times . Then open the throttle a little bit, just to where it will run at a fast idle when it fires off. If it does not start right up it's ok to pump it a bit while you crank-like idle to half or 1/3 throttle a few times.
But since you are comfortable that the wires are right, that clank sure seems like your base timing is wrong. The engine should be able to idle lower than 1000, maybe 750 or less, once it's warm or partly warm.
Only way it could have run well before the wires and not after is if the previous wires were on the wrong posts of the distributor. Some backyard and ol school mechanics do stuff like that and then time by ear. Not the best move! And unless you took pictures you can't prove that.
 

flipbro

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Have you put a timing light on it just to verify timing is correct?
 

bajuski

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Does your distributor have centrifugal advance? It does sound like the timing is advanced, stuck weights could do this and also affect your idle speed!
 
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