81 chrysler 115 problems

81 charger

Seaman Apprentice
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I have been fighting an uphill battle since last summer with this motor. Last summer motor would start and run great but after long periods of running it would just shut off like you reached over and turned the key off while running wide open. Battery would act dead so i would wait a little bit put in a fresh battery and it would fire up. This happend off and on last summer. Sometimes i could ride all day and it would never cut off other times it would just ruin the day. Took the boat out last saturday got about a mile away and it shut off. after messing with it for some time i found that its not getting spark so now i am thinking that the whole problem was it was losing fire while running.

My question is does this seem like a cdi or a stator? All my wiring looks good, getting fuel, had great spark when it was sparking, great compression.

Dont want to buy parts i dont need

thanks
 

Frank Acampora

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Re: 81 chrysler 115 problems

That sounds like an intermittent short caused by heat. This is the usual mode of capacitor failure, so my initial bet would be on a bad CD box. HOWEVER: The likelihood of two CD boxes going bad on both sides is very improbable so if you are losing spark on all four cylinders, then check for a bad ground from the electronics mounting plate to the block. If you are losing spark on only two cylinders, then check the stator and CD box.

In fact, daisy-chain a new ground from all four coils and both CD boxes to a good ground on the block or run the wire around to the engine terminal ground.
 

81 charger

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Re: 81 chrysler 115 problems

I dont know if this helps but mine only has one cd box. according to the manual mine is the type IV ignition with the motorola regulator. I have put a new ground wire in and did a jumper ground wire from my block to the power strip. if i crank it up and just let it idle it will idle forever and never shut off. when its wot i only have about 10 min of ride time and it will shut off. when it does this and i try to crank it its like i only have a few good starts then sounds like the battery is dead. i can take the battery out and put it on the charger at home and it will read 100%.

thanks for the help
robert
 

Nordin

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Jun 12, 2010
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Re: 81 chrysler 115 problems

Do you have a beltdriven distributer? I think so. You have the Motorola CD box and this is a battery system. The CD box need 12v from battery to charge the capacitors in the box.
It sounds that you have a bad rectifire/regulator or bad stator/alternator. The ign.system needs 12V to work properly and if the voltage drops under 10V it can fail.
Check with a VOM at the AC side and DC side that the stator/alternator generat voltage. You should read about 13-14V AC and 13,5V DC at 2000-2500 rpm. The alternator should start to charge from 1500 rpm. The regulator should start to work at about 16V, more then 16V will cook the battery.
 

Frank Acampora

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Re: 81 chrysler 115 problems

OHHHH! You must have a retro-fit Motorola ignition. from a Magna-Power II ignition. Does it have a distributor? If so, you would probably have either a bad CD box OR a bad pre-amplifier inside the electronic distributor.

I was assuming the Prestolite ignition with two CD boxes and four coils because after 1979 MOST Chrysler engines were Prestolite with the exception of a few models made with Magna-Power II. This ignition (Mag II) was so failure prone that Chrysler offered a Factory retro-fit kit.

In re-reading your symptoms, you put in a fresh battery with no problem starting so-- I believe Nordin is correct. You are draining the battery while running until it gets to the point where there is not enough voltage to charge the capacitors. First look to a bad regulator/rectifier.
 

81 charger

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Re: 81 chrysler 115 problems

i put in a new regulator last summer and no change in the way it acts. and i have checked voltage while it is running from the stator and i get 12.5 to 14 on it. mine has a belt driven distributor.

thanks for the time guys. i want to be on the lake so dang bad!!!!!!!!!!!!!
 

Nordin

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Re: 81 chrysler 115 problems

Well to be absolutly sure it is charging, measure DC voltage at battery when engine is reving over 1500rpm. You should read 12,5 -13V or more. A 12V battery has six cells and each cellvoltage are 2,3V when fully charged. This will theoretical be 13,8V fully charged, but theory and practical are not the same.
If you have a second battery, hook it up when you have the problem and see if it fires up. If it does then there is a battery/charging problem.
If not then it is a CD box or preamp issue.
Next step would be to change the CD box or the preamp.

Well there could be a issue with the ign.coil, if it is tempreture related.
 

81 charger

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Re: 81 chrysler 115 problems

i do get 12 to 13v at the battery even at idle goes more to 12.5 to 13.5 while the rpms are up. when it dies even with a fresh battery it will not fire back up. it use to seem like it was more heat related but last time i went out it would not get spark even after a hour of sitting and it died be for the motor heated up all the way.

thanks for the help guys!!
 

Frank Acampora

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Jan 19, 2007
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12,004
Re: 81 chrysler 115 problems

Are you resetting the black circuit breaker at the bottom of the engine terminal strip?
 

81 charger

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Jul 2, 2012
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Re: 81 chrysler 115 problems

my circuit breaker has never tripped. and i have never had any blown fuses.

thanks
 
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