Hey guys I'm helping my buddy with a new project car.. Long story short it's having a hard time starting, and it runs pretty rough at idle, and sometimes it just stalls out.. I checked for spark, it's very weak and seems "intermittent".. I don't have much experience with these ugly ass HEI dizzy's, are there any tale tell signs if/when they go bad? Do they just die or do the fade away?? This dude isn't much of a wrencher, I'm just helping him out with getting this thing dialed in and relaible.. You fellas have any ideas if I'm overlooking something?
I should also mention, he just told me that the car has died a couple times on him after it is all warmed up and been running a while..
what year is it? i just had the ignition module go out of my chevy they can just die or stop working when they get hot id check that if you take it off you can have them checked at most auto parts stores
That's what I'm thinking, I just got want to send him on a parts chase if he doesn't need them, you know?
I agree with the coil part but they put a special spark tester out just for the HEI, much wider gap than standard spark plug. easy to build one, just cut the electrode off that bends across to become bottom contact on the gap. A hot coil will shut down, and a coil not getting proper voltage and ground will heat up...
Too many times guys use the old points coil wire for the HEI 12 volt lead. This is no good for that,you NEED to run a 12 gauge wire from a FULL 12 volt source or the HEI will NEVER work correctly. Please check this out before you spend money for nothing
Modules either work or they don't work there isn't any in between. There is a big difference in the quality of the modules that you get from various sources though. You can test the coil with an ohm meter pretty easily. One more thing that craps out on them is the pick up coil or more likely the wires that connect the pickup coil to the plug that plugs into the cap. They tend to break right at where the wires connect to the pickup coil due to the movement of the plate from the vacuum advance. The car might run ok and then cut out and the run again or just quit. That might cause a weak spark too due to not having a full current flow. also take a look at the ignition lead to the distributor to make sure it still has the clip that locks it to the distributor. The clips tend to break when they get old and the connector can jiggle around just enough to break the connection and cause the engine to miss or die. Yep check what WDobos said in post nine. the HEI has to have a full 12 Volts to operate right. I'd be checking the voltage there first and then proceed with checking the other things.
Just pull a wire off by hand, if you wake up on the other side of the room, you have good spark! The wires on the pickup coil have been known to break internally. Some caps have aluminum terminals that corrode. You can buy an Accel replacement for around $150 complete with rotor, cap and coil. A Cardone replacement costs about $80 but doesn't include a rotor cap or coil.
I have had moudles that wouldn't start in cold weather,started but would not rev up well and other problems.I used to think the same as you.
ive seen and test modules that wouldnt work hot but when they were cold they tested ok sometimes they do go all out but dont everytime
Like 48 chev said they loose pickup coils as well as the coil and the control mod. My last HEI dropped the coil first, that is common the coils overheat. Then a week later it lost the control mod. After that the pickup coil went, it was missing on my drive to work with the pickup coil then wouldn't start at all when I went to fire it off in the middle of the night (worked 2nd shift). It is now an oil pump primer.
Exactly right! Not sure what kind of vehicle this is but make sure that 12-volt source wire is not running through any kind of ignition resistor. Like WDobos said, run it straight to a 12 volt source.
Had some similar problems with an HEI. Tested EVERYTHING!!!! Everything except that little carbon button that goes beneath the internal coil and sends current to the rotor. It had broken in half horizontially but was wedged in there tight enough that it didn't fall out when i took the cap off. When i fiddled with it it fell out. I guees that as it heated and cooled the gap grew and shrank and would cause it to sometimes fire and sometimes not. Worth a look.
Just went thru a like problem, I tested every thing multible times and was pulling my hair out trying to figure out why it would die or maybe not even start finally I tapped in a wye connection at the 12 volt power supply to the dist. so I could moniter from the drivers seat.........finally the erratic problem showed up, turns out the fuse panel mounted on the inside firewall which all the wiring passes thru had a problem with the unfused 12 V ignition wire.. it showed 12V cranking and running numerous times then all of a sudden 6V or less, bingo verified 12v between the key and fuse panel and ran a new wire to the dist. problem gone. When I put this truck together about 10 years ago this was not a brand X wiring harness...oh well shit happens......just another point to check, hope you find it
it could be the module, but most times they just quit completely and the motor wont fire. check the pickup coil too, those will work okay when cold but when they warm up the resistance goes sky high and they don't send the needed signal and the module doesn't know what to do.
If you can, try to replace those parts with n.o.s. AC Delco from the mid to late '70's if possible... I think those parts were made here (USA) back then...
those ignition modules are a real pain at times. i used to carry a can of computer keyboard cleaner (air) and when mine acted up and left me stranded roadside i wouls pull the cap and hit it with liberal dose that was enough to get me home. started carrying spare after installing new module and 10 years later spare is still in glovebox of old work truck.
Check and make sure the adv. weights aren't froze and stuck under the plate. If they are stuck then you will adv. the dist too far and it will run like crap. I've had 3 different dizy's jam on me and until an old mech. told me to check the weights I just kept advancing the timing and getting nowhere fast.
This comes from an old tech tip from either Hot Rod or Car Craft magazine... Check your advance weights for red oxide dust. This indicates that your rotor may have a hole burned thru underneath the center contact. Current will seek the path of least resistance, in this case arcing to the advance weights, therefore not giving full spark to the plugs. The red dust is a byproduct of this arcing. As silversink suggested, check the advance weights, Ive seen where the pins that the weights pivot on were worn half way through, causing the advance to jump around.
I'm heading down there to have a look at it in a bit, thanks for all the tips guys!!! You're all rulers. Thanks fellas.
X2 gm hei flame throwers need full 12 volt I got hit by one of the 50,000 volt monsters once and have the scar to proove it
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