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MG Midget and Sprite General - Part 2,...MY dissy is super hot...and is a probl

Hey guys

This is a continuation of my last post called """why is my dissy and coil super hot

So here is what Ive got, the coil tested out fine, and gets a really nice blue spark running from the coil to grounded metal

BUT...Nothing from the dissy... as in no spark

It has the pertronix chip, starts great when cold, runs perfect ... smooth, even, no missing, no issues, but after 1/2 hour, and turn it off... it will not fire and the dissy is SUPER HARD CORE HOT

I tested out the coil to see if its working ... it key off... no volts, key on and running at cold about 12.65 volts, when hot and running 11.78 volts

Im just confused why this is, its perfect running until you shut it off, then you have to wait several hours for the dissy to cool off

the weather is super hot here in mid missouri, so im thinking heat soak from the engine, an issue with the dissy like a bearing ???...what would make it get so hot

I figure Ill pull the dissy tomarrow and give it a good cleaning and re greasing ... AND Im going to drill some holes in the fenders, to vent the heat, the heat from the engine bay is off the charts....Opening the bonnet really fast is like getting smacked in the face by a rodeo bull

im also wondering if I go back to points and condenser will the heat effect the points and condenser in the same way as the pertronix chip

prop
Prop

btw...

Im supposed to be leaving for wisconsin in about 28 hours from now for a 10 hour drive... aka on the road at 2 AM,

So im really nervious about this issue, as Ive never heard of a Super HOT DISSY, let alone tring to figure out why it is and how to cool it back down


OH another BTW... ALL the wires are cool, and yes the coil is still HOT, but it is funtioning fine...Im leaning heavly towards engine bay temp. just being off the ricter scale ... Im going to re-Install the coil inside the passanger side cockpit and see if that makes a differance to how hot it .

Prop
Prop

Prop-
The coil should not be as hot as you say, and the dizzy should not be any hotter than the block it is stuck into. IF the coil is that hot, it is either the wrong coil = NOT a 12V coil; or, the electronics are effectively increasing the dwell to unacceptable levels. IF the dizzy IS hot, it is because the electronics are leaking excessive power to ground. Neither piece is long for this world at those temperatures.

What coil is it, what are ALL the markings on it, and what is the resistance across the two LT terminals?

Do you have an IR heat gun to measure real temps? Or, a contact thermometer so we have REAL temps?

I wouldn't set out around the block with that Pertronix & coil.

Give me the answers to my questions and put the points dizzy back with the points gapped at .015", but the coil must be correct or it will cook the coil AND the points.

I will try to check back here over the next few hours.

FRM
FR Millmore

Its the same coil ive had for the past 8 years

I compared it to the exact copy at auto zone....its a 080, non - ballsted resistor. it read just slightly higher then, the new....i think it read 6.5 ohms at pos to neg on the coil and 3.6 ohms at pos. To LT...The coil is cooler then the dissy,

The coil was giving a great spark but the dissy is not giving any spark.....when hot.

Thanks frm

Prop
Prop

"Its the same coil ive had for the past 8 years"
Good sign it is a suitable coil, though I suppose we have to discount a lot of the "eight years"!

"I compared it to the exact copy at auto zone....its a 080, non - ballsted resistor."
OK, not a "standard coil" as in OEM then. And the numbers mean nothing to me, since I don't know even who made the thing.

"it read just slightly higher then, the new....i think it read 6.5 ohms at pos to neg on the coil and 3.6 ohms at pos. To LT..."
Thinking or "maybe remembering" is not how to diagnose stuff - we need measurements. Even though it seems like it is maybe the right coil, it could have partially shorted windings, which you might catch with measurements. The numbers you give are out of the normal ballpark, but the description is goofy. "LT" means low tension, which is the positive and negative connections on the coil. The remaining connection is the one for the fat coil wire; that is the "HT" or high tension connection.

The coil is cooler then the dissy,
I think the apparent temp is a confusing issue here. Normally it would be notably to uncomfortably warm, but when it is 100 deg ambient, it could seem really hot.

The coil was giving a great spark but the dissy is not giving any spark.....when hot.
How are you checking this? If you get spark out of the coil wire when cranking, but not out of the plug leads after plugging the coil wire back in, then the spark is getting lost from the rotor or cap. This can easily be heat related, especially the rotor.

FRM
FR Millmore

If you haven't done anything else, and it just went like this suddenly, forget about engine cooling stuff.

Although if the engine bay really is that hot, you sound like you have more than a fender hole problem.

Ambient heat, where do you live, death valley?

Your problem appears to lie within the Dis. Take the dis out and rotate it manually. Take the cap off a look at the guts of the dis body. If it sprins freely, nothing catching or rattling (unlikely since it runs for 1/2 hour before problems), then it aint mechanical.

You say the Dis is super hard core hot. which part? All of it or just the body?

If it runs for 1/2 hour strong spark and no missing, I would think the coil and cap are ok, as are all HT and LT leads.

When you say runs. Do you mean tick over or at higher revs?

Any cracks in the dis cap? What's the rotor arm like?

If this is the same coil you had when it was points, then put the points back in an test again.

If not go back to your original coil, whack the points in, go for your drive and sort it out when you get back.
Lawrence Slater

Lawrence - just in case you don't know - this is a new build engine, and, as such, anything that happened before is now totally irrelevant! He does live in a very hot area of the USA, and is now panicking to get his car ready for the trip to Midget50!

PROP - for pete's sake BREATHE!!!!!

Now, get proper temperature measurements - don't do anything stupid - that was DO NOT!!

I'm assuming that this has only raised it's head since you put your bonnet back on? In which case, then yes, the engine bay temperature will be a factor, however, in a 1275, it shouldn't be such a major one to be panicking just at the moment over .... and that's just another diversion against you.

Now - have a cold drink - breathe a few times - and get the facts that we can help you with!
rachmacb

Going to pick up a lazer heat gun when the store opens in a bit
Ill pick up a points and condenser / rotor and being auto zone has the coil made for my car, I may go ahead and pick it up as insurance...even though I dont think its the issue

My apollogies for the lack of exact specs. Ill re-test for those specs, anf report back. the only markings on the coil, is ...080 and 12 volt, do not use a resistor,,,,but it was made for the midget

I tested the spark on the dissy and coil by air gap grounding the HT wire from the coil and the #1 & #3 spark plug wires

Thanks guys

Prop
Prop

It's definately non-ballasted? I mean, you know I trust you and all, but, then again - you do do the odd mad thing ...!!!!!

Hope you're chilled a bit now!

And that a heatgun is something lost in translation ... :P
rachmacb

Rach, I think he means an IR temp gun. and he'ss not going to be much cooler here. 97 in the shade at the track today and more forecast for this week...
Tim Michnay

Lol Tim I was rather hoping that ......!

Glad it's going to be nice for you - have an awesome time :)
rachmacb

Well, I don't know Prop, and I don't know his engine, (or that it is a recent rebuild), but since he describes his dis as hot and not the engine, and that it runs fine for 1/2 hour, my instict is that not much is wrong.

I'm intrigued to find out what it is(was) that's for sure.

And what was the cycle cable all about? Red herring?
Lawrence Slater

Many people - and, I'm sure, Prop - use a cycle cable for a throttle cable as it gives a much smoother "ride", whilst uncommon in the 1275, it is a great improvement on the 1500 one, which is prone to being snatchy.

If you wish to know prop - go and look in the archives - his entire re-build is in there!

You will never know what is the cause for certain, mostly coz Prop never knows!!!!!!!!!!
rachmacb

Ah throttle cable, right that explains it. True too at least for me, never had any problems with the cable on my 1275.

I will indeed look at the archives, any particular thread, it's a big archive? Or should I just search under Prop?
Lawrence Slater

Just search for Prop! See you in a month or two :)
rachmacb

such much huh? --- maybe not then.:P
Lawrence Slater

This thread was discussed between 17/07/2011 and 18/07/2011

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