Testing HEI magnetic pickup, specs state 800-910 ohms, I test 785 consistency! Is 785 ohms close enough to 800 to consider it p***ing? Thanks in advance!
Have you confirmed your meter to be accurate? The reading is less than 2% off, if you check what accuracy the meter is supposed to have that could actually be within the correct range - or even further off of the meter is incorrect in the other direction.
Also, if it failed before being in service for a lot of hours, check your alternator for AC voltage on it's ouput (leaking rectifier). AC will kill them in short order.
The ohm reading is close enough that I would call it good. In my experience every pick up failure was a result from the lead wires flexing as the advance plate was turned by the vacuum advance. You may want to recheck your ohm readings as you cycle the vacuum cannister with a hand pump. Are your distributor shaft bushings ok?
I’m a little confused. Are we talking about the module, or the pick up coil?? Those are two different things.
You can also bench test the distributor , Attach a positive and a negative to the coil , Touch one of the plug wire terminals and give the gear a spin , Or use plug wire to housing with gap To see if fires / snap
The pickup coil leads flex when the vacuum advance is working and usually break right at the juncture to the coil. Best to apply varying amounts of vacuum while checking resistance. A broken lead may make contact in one position and give good readings, but open when the vac. advance moves the coil ***embly.
My experience with PU coils is I was having a miss at higher RPMs, no vac advance, GM manual gave a broad spec. Something like 300 ohm range. I took the distributor apart and ohmed it out-was fine- but as I wiggled the wires the reading fluctuated. A new one cured the miss. I started taking the PU coil apart an the corrosion was evident. Thing is nothing in the distributor moves, all is fixed.
I've got the Napa Echlin HEI service bulletin saved here in my Photobucket album Photobucket | Gallery This is simple and easy to follow. Some info on testing a module here along with other tests. www.off-road.com/aimages/articlestandard/jeep/512005/261539/article.html It pretty well walks you though testing the Hei units that have four pin modules. I'm of the school that a module is either good or bad and there isn't anything such as almost good or almost bad. In the pickup coil and I have never seen or heard it referred to being a pickup module in the past 48 years the failure is usually in the wires right at the connection to the coil. I had that shown to me by a guy who proved he knew a lot more than I did in 1978. Agreed that if a module fails it is is usually due to an external from the module issue.
I think my 77 one ton with a 454 has a broken lead on the pickup coil right now. It's just convincing myself to climb up on that thing and stretch out across the engine and deal with it.
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