Chasing down a misfire

« **on:** August 14, 2013, 02:40:54 PM »

so...where to start...ok i just have a few general questions so i have info to dig into!

1) what happens when a ballast resistor goes bad? and how to test?

2) what happens when a distributor condencer goes bad? and how to test?

3) what happens when a coil goes bad? and how to test?

4) what happens when a alternator goes bad? and how to test? ** tested last night put meter on back of alt and was charging @ 15volts**(i believe this is too much, dont you think) 1 wire alt!**

these parts i havnt changed yet and im about at my witts end trying to chase down this missfire problem... ( starts to missfire off idleish 1500-1800 rpms to 4000)

460 ford, dual point mallory, 850 holley dp
1 rewired engine side of wire block, new wire-new connectors.
rewired bat wire, ground, and ignition from wire block to dash
new battery terminals / new battery @ 12.5 volts as tested
extra block ground to battery
new fuel pump 6-7 lbs of fuel pressure now

help a brother out, i NEED to go boating!

« **Reply #1 on:** August 14, 2013, 03:13:30 PM »

Coils are generally pretty reliable. I had one go bad once and it just stopped working. There was no sign it was going out before it stopped working either. As far as testing it I just pulled the wire off and used a spark tester to see if it was sparking.

Replaced it and everything works fine now.

What kind of alternator do you have? One wire? Three wire?

Test the voltage at the battery when it's running and it should be at least 14v. On the three wire alternator it's common for the alternator to have 15 volts at the back if you're losing voltage in the charge wire to the battery.

For example if you're losing 1 volt between the alternator and battery then the alternator needs to put out more voltage for the battery to be at 14.

« **Reply #2 on:** August 14, 2013, 07:01:04 PM »

Any luck yet Chromey

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« **Reply #3 on:** August 14, 2013, 07:23:16 PM »

Quote from: CHROMEY on August 14, 2013, 02:40:54 PM

so...where to start...ok i just have a few general questions so i have info to dig into!

1) what happens when a ballast resistor goes bad? and how to test?

2) what happens when a distributor condencer goes bad? and how to test?

3) what happens when a coil goes bad? and how to test?

4) what happens when a alternator goes bad? and how to test? ** tested last night put meter on back of alt and was charging @ 15volts**(i believe this is too much, dont you think) 1 wire alt!**

these parts i havnt changed yet and im about at my witts end trying to chase down this missfire problem... ( starts to missfire off idleish 1500-1800 rpms to 4000)

460 ford, dual point mallory, 850 holley dp
1 rewired engine side of wire block, new wire-new connectors.
rewired bat wire, ground, and ignition from wire block to dash
new battery terminals / new battery @ 12.5 volts as tested
extra block ground to battery
new fuel pump 6-7 lbs of fuel pressure now

help a brother out, i NEED to go boating!

Ballast on mine went bad, and you knew it, on the under side the little coil was fried.Condensor is something I have changed when I have changed points, and not sure how to check. Coil, when mine went, it went, dead! For me checking an alt is putting the meter on the batt while not running, then putting the meter on the batt while running. 12.6 or so not running, 14.2 or so running. Just my .02

« **Reply #4 on:** August 14, 2013, 07:25:18 PM »

Also, how new are the points

« **Reply #5 on:** August 14, 2013, 07:42:11 PM »

15 seems high. Is that when the alt is idling or excited at rpm?

« **Reply #6 on:** August 14, 2013, 09:52:06 PM »

Chromey, pull apart the top part of that dizzy. get down into the mechanical advance unit. Sounds like a tossed spring on there to me. If that's the case, call, I can walk you through how to fix that with a pair of pliers. (Learned how from an original IBM Exec when I'd have spring issues on typewriters years ago.......)

If that ain't it, and all is well and good under there. I'm gonna guess here. You have THE Unilite dizzy Moo ran for years, no issues. So if it ain't the mechanical advance tryin to a$$ fuck with you, double, triple check the timing set on the cam. Pull the Dizz and see that the gear is OK, and the pin ain't sheared.

Are you absolutely sure you didn't flatten a lobe or two on the cam? Lifter Failures?

Ray

« **Reply #7 on:** August 14, 2013, 10:04:52 PM »

which cylinder is it. an easy way to find out is to raise the rpms up till it misses an pull spark plug wires off dis cap till you find it. pull one off put it back on pull next so on and so forth. then olm check wire if good check for vacuum leak if none check spark plug, compression,
dis cap for crack. stick to the basics and it should be easy to track down.

« **Reply #8 on:** August 14, 2013, 10:14:51 PM »

Last time I pulled a plug wire off a distributor on a running motor I watched that dam thing arc almost a foot out onto the intake and shocked the sh!t outta me atleast 50 times before I could jump off the motor.

« **Reply #9 on:** August 14, 2013, 10:18:36 PM »

Quote from: SoCalPSD on August 14, 2013, 10:14:51 PM

Last time I pulled a plug wire off a distributor I watched that dam thing arc almost a foot out onto the intake and shocked the sh!t outta me atleast 50 times before I could jump off the motor.

Video or it never happened.......

The best way to do this is to pull the caps back on the distributor cap and use a grounded 12v test light and short the wire terminals one at a time until the engine rpm does not drop.

GT

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« **Reply #10 on:** August 14, 2013, 10:55:11 PM »

Quote from: GT Jets on August 14, 2013, 10:18:36 PM

Video or it never happened.......

The best way to do this is to pull the caps back on the distributor cap and use a grounded 12v test light and short the wire terminals one at a time until the engine rpm does not drop.

GT

Sent from my SAMSUNG-SGH-I927 using SoCalJetBoats mobile app

At least jets don't run mags like outboards....I lost a bank a few weeks ago and carefully, with a pair of insulated pliers, started pulling wires to see which side was dead...holy fawk! That shit hit hard....still can't feel the tip
of that finger...

« **Reply #11 on:** August 15, 2013, 07:16:54 AM »

If your worried about being shocked, hold a buddies hand when you pull the wires off.

« **Reply #12 on:** August 15, 2013, 07:58:11 AM »

i regaped the plugs to 32ish, switched out my distributer to my backup/backup, rechecked the firing order and made sure all wires were on, got it to pop off last night around 10 so i know timing is in the ball park, will time it at home and go test it tonight @ the lake and see how she runs....wish me luck

Thanks again GT JETS for the hour long conversation! steered me in the right diretion.... added a little Karma your way sir,

« **Reply #13 on:** August 16, 2013, 08:02:38 AM »

well boys, thanks to this sexy guy Brad i know...he came over to look at things and were pretty sure we got it figured out..

all the problems listed above had needed some sort of attention...and in the end it appeard to be getting too much fuel in the primaries and would bog down @ around 3k
not sure if the power valve was bad so we took apart the carb and made some adjustments
switched out the 2.5 power valve and the 86 jets up front, the rear had a block off and 89 jets
** installed 6.5 valves ft and rear and squared up the carb with 82 jets ** bog and missfire went away on the trailer and sounds crisp..we will see how it goes on saturday
now lets boat!

thanks for everybody imput! thats why i love this place everybody has an opinion and give you something to look into to figure out your problem.

« **Reply #14 on:** August 16, 2013, 11:33:21 AM »

Last weekend my boat developed a random misfire, usually under a load above 3500 RPMs. Went through it all, pulling plugs, wires, distributor, etc. All looked good until I looked at the plugs closely. Cylinder #6 had a hairline crack in the porcelain. Further inspection found where the spark was leeching out from the wire boot. Threw in new plugs and wires last night and pretty confident she'll be back to running bitchin' this weekend.

CHROMEY

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