Further to my previous postings on misfire at idle /opus/ colourtune I’ve
now found something out of spec on my car. The stall current from coil neg
to earth is only 3.6amps. Manual says 5 amps plus.
So I ran a lead direct from battery pos to ballast resistor and it shot up
to 4.6 amps.
The stock feed to the ballast resistor is through battery lead to a small
busbar, then to ign switch where the single feed also braches off to do
fuelpump etc, then through two more sets of multipole lucar connectors and
then to the coil. No fuses anywhere. Cleaned up all conections and struggled
up to 4 amps with stock wire, this 4 amp would no doubt reduce when more
load taken through the igntion switch terminal if i tunred on more bits and
pieces.
Proposal one:
I’m minded to fit a relay and fused supply close to the ballast resisitor to
supply the coil directly and lighten the load on ign switch and existing
wires. This 25% increase in coil power is probably what i’ve been looking
for to clean the spark up.
I did some volt drops on the main battery cables whilst cranking. Got 0.25v
on the earth and 0.7v on the starter feed. Looks to me like the starter
motor feed lead needs beefing up as well to get a faster crank.
Proposal two:
I wondered about running a new heavier lead direct from battery to starter
solenoid so avoiding the busbar, and leave the existing busbar to starter
cable in place to backfeed the busbar and rest of the car.
Further to my previous postings on misfire at idle /opus/ colourtune I’ve
now found something out of spec on my car. The stall current from coil neg
to earth is only 3.6amps. Manual s…
Further to my previous postings on misfire at idle /opus/ colourtune I’ve
now found something out of spec on my car. The stall current from coil neg
to earth is only 3.6amps. Manual says 5 amps plus.
Assuming you are referring to the E-type ROM, don’t take it too literally,
as it probably only describes the first model of ignition coil which was
used on very early cars (the ROM was apparently not updated after 1971).
[snip]
This 25% increase in coil power is probably what i’ve been looking
for to clean the spark up.
It is unlikely that this has any effect on a misfire at idle. The combined
resistance of the coil and ballast resistor are significantly greater than
the cable resistance in the coil feed.
Assuming that the cable resistance is not varying rapidly, it should not be
causing the occasional non-appearance of spark you reported earlier.
BTW, have you checked your ‘spark tester’ on another engine to ensure that
it works reliably?
I did some volt drops on the main battery cables whilst cranking.
Got 0.25v
on the earth and 0.7v on the starter feed. Looks to me like the starter
motor feed lead needs beefing up as well to get a faster crank.
Did you check that the connections are clean? I don’t think that is
excessive anyway.
Proposal two:
I wondered about running a new heavier lead direct from battery
to starter
solenoid so avoiding the busbar, and leave the existing busbar to starter
cable in place to backfeed the busbar and rest of the car.
It can’t hurt, but I can’t see any practical benefit.