hillman minx coil overheating - cliff

this is driving my old man mad, i know this is an old car but someone may know the answer.

dad's got a hillman minx 1600, 1965 and it has started to misfire when it's hot, after about 5 miles, then it dies.

he's changed the carb, fuel pump, spark plugs, and had the distributor apart, changed the condenser and points.

the engine breather pipe is clear and the spark is nice and strong.

the timing is bang on and the tappets are spot on.

alll this and it's still misbehaving!

the only thing that is odd is the coil gets hot, very hot, like 130 degress hot, hot enough to burn if you touch it, is this normal?

any ideas what could still be causing the misfire/coil overheating?
hillman minx coil overheating - bell boy
make sure coil is a 12 volt item and not a 9v and the polarity is the right way round............
an old haynes should be coil specific and voltage specific
hillman minx coil overheating - Aprilia
Could be..

1. Wrong spec coil
2. Does it have a ballast resistor?? Something gone wrong there?
3. Coil primary has a short - check primary resistance.

Coils should not get that hot - warm, but not so warm that you couldn't comfortably hold it. Something definitely wrong.
hillman minx coil overheating - bell boy
i dont think ballast resisters were used in those days aprilia,thats why they used to be pigs to start if the old black batteries were a little down on puff......
hillman minx coil overheating - Aprilia
Ballast resistors were certainly around in the '60's. I remember the HA Vivas had them (it was a small round one), Hillman Imps and Lotus Elans IIRC. Don't know if this Hillman Minx would have had one though.
hillman minx coil overheating - jc2
If it's a Lucas it should have **12 on the bottom if it's a 12v. coil.
hillman minx coil overheating - Stuartli
This spare parts link may help:

- - - - - - - - - - - - - - - - - - - - -
What\'s for you won\'t pass you by
hillman minx coil overheating - cliff
hi, yes, it's the original coil with 12 on the bottom, i've found a website that explains how to test the coil so he's doing that today, also he'll look for a ballast resistor, he wasn't certain if it had one or not.
i'll keep you posted with the results.
many thanx for the replies so far.
hillman minx coil overheating - henry k
hi, yes, it's the original coil with 12 on the bottom,
also he'll look for a ballast

Having said its a 12v coil forget looking for a ballast.

My Ford 1600E had a ballast resistor as I found out and cooked it.
I found out that when the Tacho was removed for repair the car started but as soon as I let go the key it stopped.
I supplied a direct 12V feed and all was happy for a "short" while then cooked coil.
IIRC ballasted coils were 9V or similar or else the concept will not work..
Start up put 12V on the coil but while running the 12V went through the resistor to supply its 9V.

All part of my learning curve.
Haynes and the full Ford manual ( bought at great expense) were useless.
Haynes had just copied the Ford manual.
hillman minx coil overheating - nick
Beware of assuming that any new parts you have fitted are good. There are lots of mutterings about poor quality condensors, points, rotor arms etc. I've had trouble with perfect-looking but poorly peforming new bits.
It's also worth making and breaking every connection in the circuit. I had a similar problem with a Minor and it turned out to be corroded spade teminals.
hillman minx coil overheating - Screwloose

What was the full coding and part numbers on the base of that coil? Some ballast coils are still marked 12v. Seems a bit unlikely that it's still got the original after 40 years? [Lucas ones are date-coded.]

The crucial test for a ballast coil is the exact resistence between the two Lucar terminals. Did this coil get hot when running, or when left with the ignition switched on? How hot does the condenser get? Is there any current flow in the LT circuit with the points open? [Do a LT terminal scratch test.]

Is this good spark still apparent when it stops and won't restart? Tried taking the filler cap off?
hillman minx coil overheating - cliff
seems the car wasn't fitting with a ballast coil after all.

the rotor arm and dizzy cap are the ones on the car pre-problem, he's examined the arm and cap for cracks, the cap looks almost as new, as does the arm.

with one of those little orange spark testers in the circuit the spark is very bright even when misfiring.

he's tried removing one lead at the time, no change.

he hasn't tried another coil yet but he has tested the one he's got and it appears to be fine, coming back with all the right readings etc.

it only gets hot when the engine is running, don't know how hot the condenser is getting, he'll check. there is no current flow with the points open.

whether the coil getting so hot is the route of the problem of a separate problem remains to be seen.

i'll keep you all posted, thanx for your ideas.
hillman minx coil overheating - pug3
I use to borrow a J4 van many years ago. The van would occasionally break down when warm and only restart after cooling down. I did not know if the problem was fuel or electrics so I drove the van on a small circular route near my digs until the van stopped.

I removed the driver?s seat and engine hatch. As I pulled myself forward to look in the engine bay my hand touched the coil which was very hot. I returned with a spare coil and after ensuring the van still would not start, changed over the coil. The engine started immediately and gave no further problems.
hillman minx coil overheating - bell boy
have you considered fuel vaporisation cliff......?
are you sure the carb isnt blocking up?
i remember when this new fangled non leaded petrol came out lots of cars were having rubber bits in the fuel system turning to a black gloop and stopping cars and all sorts of problems,are you sure the fuel is clean and being pulled down the venturi properly?
hillman minx coil overheating - cliff
quite sure oldman, he changed the carb for a brand new one he bought at an autojumble, same with the fuel pump, new diaphram and all.
you can see the fuel going down the venturi ok.
i'll keep you all posted.
hillman minx coil overheating - robcars
Describe the misfire better?

Does it do it only under heavy load or all time?

Does it start easy hot or cold?

Does it make any difference with electrical load on? Lights wipers etc?

Does weather make a difference?

Any more info?
hillman minx coil overheating - Number_Cruncher
Some thoughts;

What's the battery voltage when running? i.e., is the charging system regulating itself properly? Are the points in the voltage regulator OK, not welded together (assuming a dynamo system - is this right?)

When you measured the current with the points open, which side of the coil did you measure? A short to earth inside the coil would see no current on the CB or -ve side of the coil with open points, but you would see a current on the SW or +ve side.

Did your coil resistance checks include a check between the low tension circuit and earth? Did you repeat your measurements on a cold and hot coil?

You say that removing plug leads made no change - what do you mean by this? I would hope that removing each plug lead in turn from a good running engine would result in a similar rpm drop for each cylinder - not no change - ?

hillman minx coil overheating - cliff
dad seems to have got it sorted.
after it died this time he looked inside the float chamber to find it empty of fuel, by tapping the side of the carb the chamber would fill (with the car cranking) this lead him to assume it is/was a sticking fuel cut-off valve in the carb.
although he had changed the carb for a brand new one it still had a sticking valve, he's put the valve from the old carb back on because he thinks that it doesn't stick as much (perhaps being a bit more worn), anyway he's got to the bottom of the misfire/dying saga.
the coil is still getting warm but we'll try a replacement.
the points in the regulator are all very good and working as they should.
thanx again

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