Mid 60s inline ford, I put a new GM style (cheapy Amazon unit) HEI distributor in it a few years back. Ran fine for a few years, good spark. Took a 3 hour ride the other day and next day she cranks good but won’t start. Definitely getting gas to the carb, so next thing to check is spark. Just want to confirm my coil testing process: Getting about 1 ohm across the red batt and yellow tach terminals. Getting nothing (acting like an open) from batt terminal to rotor. Coil is getting 12v when ignition is ON. Does that fact that I’m not getting a reading at any scale across batt terminal and rotor mean possibly bad coil?
I've never failed a HEI coil but I've had several control modules fail. They are located in tthe base of the distributor and most are what is called "4 pin" style. If you replace it, be sure to apply the heat conductive stuff to the base liberally.
I'd replace the ignition module also. Plus, I'd suggest carrying an extra in case it fails when you are away from home. I buy my 4 pin modules at NAPA. They're guaranteed for several years. Never had a problem collecting with my sales receipt.
Is there any way to test the ignition module before I just go buy a new one? Is there any benefit to spending the extra money for a Pertronix unit versus a cheaper one?
I would also suggest you take a look at the bottom of the rotor, or simply replace it. The early GM HEI had a habit of the coil blowing the spark through the rotor and grounding it through the advance weight pins. The fix is to replace the rotor. The fail will be a black dot burnt spot on the bottom of the rotor near the center of the rotor. The only voltage you should see between the coil post for the rotor and the battery wire will be when the spark is sent out. The spark goes from the coil to the rotor, then out to the plugs as the rotor reaches each plug contact point. For the record, that spark at the rotor will wake your **** up, it will bite hard. Generally, the ignition module fails because the wires going to it break. The easiest test is to jerk on each wire (and don't be a wimp about the jerk). If the wire comes apart, it was already dead. If the wires are good, they won't pull apart. The wires to the module go to the pickup coil on the breaker plate. The plate is always moving, the constant flex breaks the wires.
Factory parts were mostly reliable. As said, the rotors would take the brunt of the high voltage, except on V6, which would burn thru the cap at one of the coil bolts. The later small cap V6 (Fiero and others) would get the green meanies inside. There are proper testing procedures for the HEI, but due to the simple one wire feed design and cheap, readily available parts, most just took things apart, inspected and "replace with known good part (new) and retest" parts shotgun approach. Let's face it, careful testing is the correct way to do it, but 2 cover screws, 2 or 3 quick connectors and it's ready to grab a multi meter. 4 more of the same size screws and it's out. The knockoff stuff is much less reliable. I'd get a quality cap, rotor, module and coil and swap stuff out. Anything that doesn't fix it will be a spare. Anything that does would stay in and another bought for that spares pile. YT channel Low-Buck Garage bought a bottom dollar HEI and spent too much time and effort getting it to work reliably.
Install a new module. If it fixes issue , go buy a spare. If the module doesn't fix the problem, you already have a spare.
Replaced the ignition module and the rotor, still just cranks but no start. Any ideas what I should look at next?
Did it loose a timing chain/gear (have no idea what is in the old inline Ford motor)? Pop the cap off and make sure the rotor is turning while the motor is cranking over. 12 volts while its cranking over would be a good test before dropping more money into it. After that, its the coil, then the distributor pick up.
Bench test , 12v batt , few test leads & a spark plug or 2 , Verify on the bench that it's firing or not. Then test components on bench & specs No point moving to vehicle engine Until Bench testing producers spark, Does not need to be installed in engine. Did not see what Ford in line 6, Will 300 6 fit ? Do you have pick a part , $30 300 6 75- 92 ish
Usually a module failure is heat related, from my experiences getting stranded with a HEI car. ****s out, starts fine when it cools off. I had one that was confounding. I could stop doing errands, but for less than 10 minutes. Go for 15 minutes and it was a **** shoot if it would start, until the engine was dead cold.
Check the wires from the pickup to the module. They can break from the constant back and forth motion from the vacuum advance.
On Gm since 78 to present I have only had like 6 or so modules go bad I did fleet , Gm , Ford Mopar My experience Usually the Gm either good or bad for the module OEM one. Ford & Mopar they would intermittent Work then Not
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