89 30hp missfire after 10min warm up

[wormz]

Re: 89 30hp missfire after 10min warm up

yes, there is a teraml sending unit. i unhooked it so it thinks its cold. it doesnt change anything. magnets look ok i guess. it runs to great when its not acting up. the magnets were scratched from the power pack making contact at one point. it charges fine so i figure the magnetrs are good.

 

[jbjennings]

Re: 89 30hp missfire after 10min warm up

Just my two cents--
I'm thinking that if something was grounding like a plug wire it would most likely do it from the get-go, at least from my experience which I'm sure is not as extensive as others who already posted. Also, why was your old ppack rubbing? Anyway, I'd wait until that sucker started that annoying stuff after it warmed up and take a plug wire off and see what happens while it's idleing. then try the other one. If it's a bad coil on one cylinder, which is my suspicion, it will die when you pull the good coil wire. But you have to wait until it gets warm and stops working. There seems to be no other explanation to me other than something heating up and expanding, breaking continuity. Other than the p-pack, the coil is most likely the culprit. But then again, that's just my idea. You've probably already tried alternately taking the plug wires off, right?
Good luck--I hate electrical problems,
JBJ

 

[wavrider]

Re: 89 30hp missfire after 10min warm up

Timing light,

I chased a intermittent miss for a few days, swore it was fuel related, finally i decided to check the spark with timing light, I tested spark not running with spark tester, all were good.

hooked timing light and found intermittent fire on one coil, inspected plug wire found small white dis-coloration at the coil, under the wire where would not be normaly seen, replaced coil no more miss.

Inspect your wires real well, do a resistance check, could have a bad wire, heats up increases resistance and causes power loss by no spark, measure wires cold for a base measurement, start the engine run it until it starts acting up then measure resistance of wires again, compare readings.

 

[wormz]

Re: 89 30hp missfire after 10min warm up

if one cylinder/coil/ or wire is bad, wouldnt it still rev up with just a loss of power. this thing is just cutting off like a kill switch until the rpm gets back to low/just above idle.

i will check the resistance of the wires and see whats going on there.

 

[wormz]

Re: 89 30hp missfire after 10min warm up

ok, got the plug wires ohmed out. one of the wires has an open circuit if you move/bend it around. i have new ones on the way!
ill let you guys know how it turns out.
will one wire make it do this? i figure one wire would make it just miss on one cyliner not completely cut out.

 

[iwombat]

Re: 89 30hp missfire after 10min warm up

That's why I had you check for arcing. A bad plug wire should have been arcing from coil-end to powerhead.

At least it's _A_ problem even if not THE problem.

 

[ezeke]

Re: 89 30hp missfire after 10min warm up

Interesting thread. Might be over-rated. But, "All's well that ends well."

 

[wormz]

Re: 89 30hp missfire after 10min warm up

ok, new plug wires, resistance is good... 20 minutes in and same ol problem! at least i did find a small problem which could have led to a big one.
this thing is amazing.
still thinking maybe the coil under the flywheel that goes to power pack?

 

[wavrider]

Re: 89 30hp missfire after 10min warm up

I think you are thinking good

You eliminated the spark plug wires now the next in line is?
Need to check the spark when it does mis-behave, when the problem occurs.
that would seem to be the next step, if it runs for 20 minutes before fail, I would think this eliminates fuel, unless the vent on the tank is bad?

New power pack, new wires, good fuel, magnets good, only thing left is coils that I know of.

 

[ezeke]

Re: 89 30hp missfire after 10min warm up

Could you describe the condition of your spark plugs just after the condition arises?

Are you certain that the engine is not overheating?

Are you using Champion QL77JC4 plugs at .030?

Are the spring clips in place on your floats?

Is your fuel fresh?

 

[wormz]

Re: 89 30hp missfire after 10min warm up

i can get a coil for $25 so i can swap it between the two to see if it helps.

definately not overheating. water out "pee hole" is cool-warm at touch and

you can place your hand anywhere on the engine with minimal heat.

champion ql77jc4 plugs was first replaced when the problem occured.

spring clips on floats~~~have not removed carb bowl since it runs so good for so long, after shutting it off for couple minutes it does fine.

fuel is fresh, have een thourgh about 10 gallons attempting to fix it, new batch every two gallons. fuel can is vented...sometimes i leave cap off while working with it.

running out of options, hopefully when its fixed this can help someone in the future! im not giving up yet! hehe thank you guys so much for your advice

 

[ezeke]

Re: 89 30hp missfire after 10min warm up

Sounds good except for:

"spring clips on floats~~~have not removed carb bowl since it runs so good for so long, after shutting it off for couple minutes it does fine."

That's exacly what would happen if the float valves were sticking a little.

 

[iwombat]

Re: 89 30hp missfire after 10min warm up

I'll admit. I'm kind of confused as to what's been found as the symptom in all this.

Can you put a timing light on the plug wires and actually see it stop firing when this happens? If that's the case, it's electrical. If the plugs continue to fire normally while this occurs, then it's fuel.

 

[wormz]

Re: 89 30hp missfire after 10min warm up

i didnt think of that..... let me put a light on it and see where that goes. it got cold today, its only 35 degrees and a freeze warning tonight. i dont think im going to run it with water yet. unless i can find a way to run it in the garage!

 

[wormz]

Re: 89 30hp missfire after 10min warm up

ill also check for the spring clips....to make sure, thats the float in the carb bowl?
hate to sound dumb...but i may be missing something easy.

 

[HighTrim]

Re: 89 30hp missfire after 10min warm up

Is getting confusing isnt it??

Just to throw my 2 cents into the pot...

- I would not want to over look why your power pack was rubbing the magnets.

-Are you positive that she's not breathing exhaust?

Is the flywheel off still? Could you post a pic?

You may very well have more than 1 demon that you are chasing!

 

[wormz]

Re: 89 30hp missfire after 10min warm up

the new one isnt rubbing. not sure why the old one rubbed.
ive owned it for two years, the dealer i bought it from said they couldnt duplicate the concern three times while charging me $90 diag each time.

i can remove the flywheel easily, defiately no exhaust fumes, it wont do it with the cover off... it starts sudden when it acts up and wont go away until shutting down for a littel while. its litterally like when it runs good wide open, its like hitting the kill switch for 1 second and when rpm drops to above idle it kicks back in full blast. its just crazy it will be fine for so long to act up so bad and just get better all of the sudden after shutting down.

 

[wormz]

Re: 89 30hp missfire after 10min warm up

justa thought, bad t-stat would cause it would it? open all the time...never gets hot above 100 degrees from "pee-hole".

 

[wormz]

Re: 89 30hp missfire after 10min warm up

you want a picture of flywheel or the power pack. what angle you looking for?

 

[HighTrim]

Re: 89 30hp missfire after 10min warm up

if i take the cover off it runs for an hour without missing. with the cover on it takes a couple inutes and it cutts off again.

it wont do it with the cover off...

Only reason I ask about the exhaust