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my 1957 dodge truck cutting out while accelerating

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my 1957 dodge truck cutting out while accelerating

moparjoel moparjoel
New User | Posts: 5 | Joined: 10/09
Posted: 02/12/11
09:44 PM

i have a 1957 dodge d100 pickup that i put a 1978 360ci in, that when im accellerating around 2000 and 4000 rpm the truck starts to cut out, i believe its electronic since my tach goes immediatly to 0 and then right back up with in a second when it cuts out and truck resumes normal operation. but when truck warms up the problem goes away. the problem is getting worse, before it just did it a few times when i first started up and drove it, then it started doing it more often, now today it started back firing badly scaring other cars right off the road along side me, i have swapped the ignition box out with a good one i had laying around but no difference. a fellow mopar guy at a car show i talk to said that there is a part in the distributor that commonly does this but he didnt have enough info to help. my coil, ignition box and distributor are all mopar performance. any one can help i dont want to buy a whole distributor which is what im thinking it might be its only a year and a half old but this truck is my daily driver so she does get used and abused any help would be great thanxs so much       Joel  

waynep7122 waynep7122
Enthusiast | Posts: 643 | Joined: 08/09
Posted: 02/13/11
10:28 AM

i did post a how to test mopar electronic ignitions..  but i will go over it again...

do you have a digital volt meter....   8 buck to 25 buck versions will *** you really don't need to spend more than that... if you don't have one...

set your digital volt meter to 2K ohms.   thats 2,000 ohms scale... but its always printed on the meter as 2K ohms..    measure the pick up coil resistance... 500 to 1500 ohms is expected...  

don't disconnect...  flip the switch to 20 volts AC setting..   spin the distributer shaft...  or have someone crank the motor.. you need to see close to 1.0 volts AC being produced by the pickup coil as the reluctor spins...  
why...  the reluctor is a weird piece of metal.. it will retain some magnetic field.. when it gets old.. rusty.. sand blasted.. chipped.. solvent sprayed.. it looses some of its abilities..  

when the reluctor is not working as expected... it does not maintain a large enough magnetic field as it spins.. reducing the AC seine wave output of the pick up coil....  

the power transistor needs to see over 3/10 of a volt AC RMS in order to turn on to charge the primary windings in the coil...  so that when the seine wave passes 0 and starts to go negative the power transistor then shuts off..  the magnetic field in the primary winding in the ignition coil collapses through the secondary winding and creates your high voltage spark.....

reluctors are easy to change...   warning.. small block and big blocks use the same reluctor..  but one turns  counter clockwise.. the other turns clockwise..  this is why there are 2 slots for pins in the reluctor..

if you get it backward... the spark will be produced when the rotor is between the outer terminals in the cap...  this will make for a weird running motor... if at all...   you will be able to spot this failure if you look at the burn patterns inside the cap.. and on the tip of the rotor...   the burn patterns should be even across the tip of the rotor and the outer terminals inside the cap...    if the patterns are all to one side...  the reluctor may be on backwards...  

waynep7122 waynep7122
Enthusiast | Posts: 643 | Joined: 08/09
Posted: 02/13/11
10:28 AM

i am taking that you have a digital volt meter....

this test will find some problems... that might be causing your truck to misfire when the engine is running at speed..

start the engine.. let it idle.. turn on the headlights...

take your digital volt meter.. set it to 20 volts DC scale..

measure from the negative battery post... to the engine block....  0.04 volts is expected..

measure from the negative battery post to the   body...............   0.02 volts is expected..

measure from the engine block to the firewall........................   0.02 volts..

measure from the battery positive.. to the starter relay / battery terminal on the firewall/ starter battery post..

this also should have close to 0.04 reading..

this tests can be continued to the positive side of the coil...

or... if the other tests show up with something really close to the readings i posted...

i am thinking that you have a bad ground between the battery and the engine..  or the engine and the firewall.. or the engine and the bolts that hold the ignition module down...

it takes a lot of current to power the coil at the speeds you are describing as its giving you problems..

the ignition coil could also be failing internally also...  

sicksatellite sicksatellite
User | Posts: 67 | Joined: 01/10
Posted: 02/24/11
08:33 PM

almost sounds like a bad ground somewhere  

moparjoel moparjoel
New User | Posts: 5 | Joined: 10/09
Posted: 02/28/11
03:55 AM

well i took my cap off and started looking around in there didnt see anything obvious but my center contact on the cap for the coil wire looked really black and burnt so i took some sand paper to it and  then did not drive it for two days, then did not warm it up ran long enough to build oil pressure and went and nothing happend ive been driving it a week since and nothing i doubt that the cap was the problem. just hoping that it either stays away for good (probably will not) or stays doing it constantly so i can look into it more.... oh well thanx for all your guys help