I recently purchased a secondhand Briggs ignition coil from a seller on ebay. "Yes" I realized the risks involved and "yes" I am now kicking myself. But I really feel like I should be kicking the seller!
The coil arrived and first thing I noticed was the plug boot was badly perished. It was so brittle and rotten it was falling apart in my fingers. Then I inspected the spark lead and it was so hard it could no longer be bent and it had a huge crack in it. I put it on an engine and got no spark at all. Tried it again a few minutes later and all of a sudden I had spark, but it seemed a bit weak. So I went to the trouble of putting on a new lead and plug boot, as I thought that might be the problem. Put it back on the mounts, reset the air gap and tightened the screws. I had spark, but intermittently. Sometimes the engine would try to start then it would not. I put my spark plug tester on it and there was no spark at all.
I purchased a multimeter that day and waited for it to arrive in the post. It turned up a week later. On testing this coil I found the readings to be very erratic. Sometimes the primary coil would read about 8.6, then it would read 19, then it would read 3.6, then it would read 1 (infinite resistance). The secondary coil was giving a reading at times before flicking abruptly to 1. The readings were all over the place. I cleaned all of the posts and terminals with very fine wet and dry paper to ensure a good connection and tried again. Same result!
I wondered if my multimeter might be faulty so I compared it with some coils that I know are working. They all showed the correct readings and were stable on those readings. So nothing wrong with my multimeter. I tried the coil from ebay again and got the same result as before. Readings were unstable and all over the place and constantly changing. I asked an electrician mate and he tested it with his superior quality multimeter. He got the same results. His advice was that the coil is bad. He said it is "on the way out" and might function correctly at times but then fail. It could not be relied on and will soon fail for good.
So I contacted the seller about it and got this fairly "standard" reply: "All my coils come off running mowers before l sell them so l know they are working. lt might be the magneto on your mower that's faulty. I've been selling mower coils for years and never had any one complain of having a faulty one." Blah, blah, blah!
Of course there was nothing wrong with my magneto. I put a coil on the engine from a working machine and it worked just fine.
My first thought was that if he is so sure of his coils and their quality he should be willing to back them up with some kind of guarantee and a refund if they are D.O.A. ("dead on arrival"). No such guarantee apparently. I got what I paid for and just have to wear the costs. I could go through ebay and request a refund, but my guess is this will just be a waste of time and I can't bear putting up with another seller whining forever about his lost revenue. I guess he can argue that the coil is not technically dead. It is just on the way out and this is consistent with an old secondhand part.
My advice to other online shoppers is to spend a few more dollars and buy a new one! If I was selling stuff on eBay there is no way I would even consider selling a coil as bad as this one to anybody. I would not even sell it to my own worst enemy. The coil had not even been properly cleaned. Covered in dirt and muck that took me almost half an hour to clean off. So I ended up wasting a lot of time and extra expense on what was essentially a dead coil!
