360 motor loses ignition when warm

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nitronut

nitronut

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I have a small block 360 motor in a '69 Valiant. It fires up immediately when starting cold but a few days ago out cruising the motor died after warming up. It would crank but not start. Very weak spark. After waiting two hours for it to cool down, started right up and died again after running five minutes until warm. Then it just turns over with nothing-no hiccups, rough running, nothing. I can start it all day long (cold motor) but when the motor gets hot it dies. Any suggestions? ballast? coil? One person said it was a heat sink in the distributor...no points, Mopar orange box electronic ignition....HELP!
 
points?....electronic ignition....MOpar ecu?....

gotta give us some info.......
 
no points....Mopar electronic ignition (orange box) with an MSD Blaster coil...
 
I had an Orange box go bad. It would heat up and expand the circuit board causing the engine to die. Cool down and it would fire up. New box fixed it.
 
Interesting I have one that does that it is very irritating. Cold it starts like a champ, if I drive around stop for gas or something and shut it off it is a crap shoot if it will start again or not. I have not yet started throwing parts at it yet, so some inside information may go along way.
 
This is classic coil failure. But it certainly could be the ECU. I'd try a coil first
 
Also remember no matter what box you get or have, the case needs a good ground.

No ground, no work.
 
had the same symptoms; it was a defective Accel Super Stock coil . . .
 
Check the reluctor gap in the dirstributor. If it's too wide, the spark won't go.

Adjust it with a .007"/.008" brass (non-magnetic) feeler gauge.
 
I chased a symptom just like this a few weeks ago.....

COLD - start right up.....

Warm - starter would/wouldnt engage....sometimes make weird noises....

Then....it got to where it would only FIRE in the start position....:banghead:

I thought my ignition switch was going bad.....got on here, searched around....

Checked the Relay - Good....

Removed my steering wheel...checked the switch.... - Good

Inspected Column Harness..:cheers:..BOOM...loose connection...Problem Solved.
 
I've had similar problem. Mine was coil would get hot and stop working. After coil cooled it would run for another 15min. My problem was in my engine harness bulk connectors
 
It's an electric conduction problem of one type or another. Which means in your case with electronic ignition it could be the coil, ECU, or the ballast. Problems like that can be hard to find because usually the part causing the issue will test just fine when cold. But when the part heats up its getting out of spec, either conducting too much or too little.

I had a problem with MANY brand new condensers on a dual point mallory. As soon as the car warmed up the condenser would stop working and the points would fry. I practically went through a case of them before I found a one that would work. Quality control on stuff like that sucks nowadays. And of course, they test fine cold, so they're hard to catch unless you're actually heating them up.

With the electronic ignition it could be the ballast, coil or ECU. Those would be my prime suspects. Ballasts are cheap and fail pretty frequently, easy to replace that. Coils are a little more, but even just a quick substitution of a known, used coil will tell you what you need to know. Modern made orange boxes are junk. I've had issues with several brand new orange boxes. It would be my prime suspect in your case, but they're more expensive, so it may not be what you want to replace first.
 
Check with member trailbeast and get his hei conversion and eleminate all the chrysler bull **** and have a great system. I think there like 150 for the plug and play kit.
 
It sounds like you have a parts mismatch with the orange box and the Blaster coil.
The orange box is supposed to have a stock type coil. What's the ohm rating of the resister?
They come .25 thru 1.25 as I recall. You might be over heating the box.
 
tekslk said:
Check with member trailbeast and get his hei conversion and eleminate all the chrysler bull **** and have a great system. I think there like 150 for the plug and play kit.
Click to expand...

If the fault is in the harness connector under steering column or anywhere besides in the ignition system.. that 150.00 will be by the curb too.
Diagnose first.
 
dodge71demon said:
and what would getting warm have to with this
Click to expand...



I put a distributor in straight out of the box without checking the gap. It was at .030". It would start cold, but not hot. After setting it to .007"/.008" with a brass feeler gauge, I never had a hot start problem. Apparently .030" gap is just enough for the spark to jump cold, but not hot when it expands a little from heat.... :banghead:
 
Thank you everyone for your help and suggestions...I'm going to replace the coil, ignition box w/a Mopar Chrome and the ballast...
 
He might as well have spent the 150 for good stuff because he didnt chck anything first. Check gap in the dizzy at least 7-8 thous this might be simple dont throw the money till you have to.
 
Might want to check that the wires to the coil are not reversed. If they are you will have a VERY weak spark and hard starting when hot. Easy mistake to make if you've changed anything around.
 
Reversed coil wires will not prevent a car from starting or running. In fact, unless you know what to look for, it might not be obvious
 
I had the motor fired up yesterday idling, then bringing the rpms up and down, repeating for about twenty minutes which brought the motor temp up to 200 degrees which is warm for this motor when I'm driving it. I shut it off and started it up at least ten times with no issues whatsoever. Started up immediately every time like it was cold..figured for the $100-$130 bucks to replace the coil, ballast and ignition to give me a little peace of mind was worth it. What else could it be? Distributor?
 
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