old fault returned, dead short in ignition coil wireing loom, unable find where

Have been plaqued with this fault below for years now and it comes and goes, can any one give me a second view as my head tonight is screwed, started fault finding at 18-30 and still on it 00-20 midnight


Ok have had a weird electrical problem on my VP .4.3gl v6 carb engine,
battery tested and full of power, when i turn the ignition key to postion 1 my volts drop on the gauge from 12.63 to 10.01 and the volts needel gauge sits off with no volts, there is 12v on other items in the boat like lights and depth sounder and ignition switch, battery show no volts drop at all, the other day i removed the whole engine loom from the boat and checked all wires and connections, nothing found so placed back on the engine.

For weeks now have been checking and ohms testing all loom cables, tonight i done a continuty test across the volt gauge with wires connected and found i had a direct short between the purple and black on the back of the gauges, if i remove the purple wire from the back of the volt gauge that travels down the boat to energise the fuel pump relay, the volts are normal and correct on all gauges including the volt gauge, So i placed the purple wire back on the gauge and it instanlty drop to 10v and needle down fully off there is also sparking from the wire when touched on the positive side of the gauge i can pick up 10v from the common wire, remove the wire again and volts go back up. took a ground wire off and there is still a dead short between the two wies.

while monitoring with meter i then discounneted the loom connector half way down the boat, and two my suprise no short all volts correct on dash dials, reconnected again and a dead short is back.

so then i checked the main engine harness loom block connector(big black one) and the meter shows a direct short between the earh pin and the purple wire pin on engine side, disconnected the coil wires completly and the dead short is gone, volt on all gauges correct, reconnected wires to coil and volts gone down to 10v and lights dim on dash.

useing a Clibrated Fluke meter

Have taken coil out on bench now and between the + and - ohms is 0.8 primary circuit v/p book says it should be 1.25 to 1.4

secondarty circuit is 10.14k ohms book says 9.4 to 11.7.

Inside the coil you can hear lots of fluid is this right could it be a cooling oil?????, all relays are energizing with this issue, fuel pump is running, choke not used and taped up

the boat runs fine or did have not tested the last few days, what confussed me is the large voltage drop when the ignition is turned, the coil is 2 years old.


Has any one got any ideas as were the fault could lie,i am now brain dead with this issue

Possible.What guage is it hooked to?Tach??? They go bad and short out.Try to run it without the guage?
Aftermarket coil?Does it get too hot to touch?Too hot = bad.

coil is a carter, never actualy noticed if it gets hot, i understand the tach issue, but the dead short is still there on the engine loom side, sort on the dials side goes when i pull apart the main harness loom.

the harness loom connector shows a short between pins 6 purple ignition and pin 1 common, the sort is removed when the wires to the coil are also removed, if i re-wire the coil back up, the dead sort across both wires return. and my volts drop on the dash board dials to 10v v/p and the dial lights dim.ignition switch still has 12v in on the main side red wire

Good news hopefully,so far fault found, after lots of loom checking and belling out cables, found the trim beach switch wires running straight over a counter sunk screw which is 2" to long and the two wires have been slowly rubbing over the tread of the screw. this was noticed when leaving the meter buzzing away on the dead short, i accendently activated the trim beach switch and the short was interupted and then i wonderd how can that be.

The wires run to the trim indicator, which has supplied power by the purple ignition switch, this is why i was picking up the short via the ignition side and coil

lets hope this is the end of this extrely time consuming fault,

Let us know if that solves the voltage drop issue.

thanks woodieman, so far all still seems good and no vlts drop, fingers crossed, will let you know, not on the boat now for another week, due to rubbish weather here and work.

mark