Ignition problem???
Hi I’m 17 and building a 90 d150 with a 318 magnum carb swaped. I’m having an issue with my ignition box I believe. Truck starts and runs for a little bit runs great then missfires and dies (can start right back up and runs fine then repeats). I was having a high rpm breakup also but I bypassed the ballast resistor and it seemed to help. Idk if it matters but I’m running an orange box and a blaster 2 coil. only getting 3.5v at the coil when testing with coil ground and 13v if I check with a body ground. I thought it was the carb but I’ve tryed my buddy’s known good carb and it still did the same thing
You are going to have to explain exactly your testing connections and conditions.
If you bypass the resistor (and as mentioned, you should NOT) then with the meter connected from coil + to ENGINE BLOCK or BODY and with the key in RUN but with engine stopped you should get "same as" battery voltage, AKA fully charged battery, about 12.6V
With engine running, and same connections, you would get the charging system running voltage, which is going to depend on condition of charging system, loads turned on, (headlights, etc) and engine RPM
What you SHOULD get with a normal, normally connected system, ............and with a proper ballast
1....Meter from coil + to block, key in "run", engine stopped. Should get somewhere between 6 and 10V. This shows the coil is drawing current through the box, and the resistor is dropping the coil voltage.
2....Meter as above, read meter while cranking WITH THE KEY. Should get "same as battery" and battery will be drawn down some with starter. Should see minimum of 10.5V or higher
3....Coil NEG to block, key in run. Anywhere from 1/2--1V or a bit more. This is the box grounding the coil NEG, but that goes through a transistor and circuitry so there is some voltage drop.
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For "becuz," unbolt the box, scrape around the bolt holes and remount using star lock washers. Box MUST be grounded.
"Work" all connectors in/ out several times to check for tightness and scrub the terminals. ECU connector, ballast connectors, and distributor pickup ESPECIALLY
"Wiggle" test harness in various places with engine running, INCLUDING the ignition switch (key)