Quote:
Originally Posted by rick winchester
Can a msd 8251 coil test good on a ohmn meter but still cause a misfire . I have replaced cap,rotor , coil wire,plugs, checked all grounds checked all plug wires , new batteries , alt. checking 13.6 @1800 rpm .changed carb checked fuel pressure. set float level. Plugs look dark, or damp. 7al box . really dont know to check it . going to try another dist. in the morning. Rick
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Good morning Rick and to all,
Over the years I've had MSD troubles as well. I had two (2) #8261 coils go bad on me. One right out of the box. At the time Tech West was doing my ignition stuff and Pat said the #8261 coils were made with "offshore" components and suggested I use the #8251 coils, which I did. I have three of them including one on our engine dyno - No problems with any of these.
In the past when I had an ignition problem the MSD box was usually the problem. I have two MSD 7A's and two MSD 7AL2's. All were "tuned up" by Pat and are operating well. The last MSD box that failed - didn't miss, pop, bang, or do anything outwardly stupid. Just wouldn't go fast, went over valve springs, did a compression test, changed the converter , changed the fuel, finally Glenn asked if I had a "spare" ignition , which I did. We changed the box, coil, cap rotor and wires and PRESTO we qualified number 5. Over the next week or two changed back the coil, cap, rotor & wires without any incident.
So to make a short story long, I would suggest changing to a "known" spare MSD box and work your way from there. That was from personal experience. Ignition coils have been know to go bad , but they usually work or don't ! One other point of interest , when was the last time you replaced your coil wire? When you consider you are firing 8 spark plugs through one coil wire with the voltage we run through them you just might want to change that as well. I usually R/R mine once a season. Call it cheap insurance. That's my Two Cents and I hope that helps you.
Have a Great Day
Respectfully,
Henry Kunz 1534 H/SA