Secondary Ignition Waveforms (common faults)


in secondary ignition analysis using the scope I’m using an old-school sung scope the reason I’m using it is just for the ease of showing you guys some different aspects of types of misfire so we’re going to create a couple misfires and we’re going to look at it only two leads I have connected I have one lead connected to the plug wire and this is typical for any scope and have another leads connected by number one cylinder the way that this would work would be every time a cylinder would fire you’re going to have impulses coming out of the coil there’s one quote the whole engine so it’s going to be like this one two three four five six one two three four five six what does the red trigger lead to it coordinates those six so it would be kind of like playing the drums you got one two three four five six one two three four five six this one’s a plug wire this one fires one time for every six of these you send these impulses into a machine that has a program built into it and we can figure out what’s what on the screen so let’s take a look at that and again this is just an old-school Sun machine I like it it’s one of the best ignition just for ease of viewing the ignition system it’s got the firing order on there already this is very similar to what the staff on Barris and the novel Vantage Pro does it would look like this the parade format is nice I can also do this with my Pico which is very nice and the Pico gives way better detail than this thing does but this is just the scope I’m choosing for this right now for now we don’t have a misfire I have my gas analyzer screen up there too which is the other reason I picked this one because I wanted to show you guys the head gasket one but the first one I want to do is I’m going to unplug that same fuel injector right and this is going to be well I don’t know which one will look at it on the screen I just unplugged the fuel injector what do you notice on the screen we don’t see it pretty typical injector problem I don’t see it so how do we recognize an injector problem first off let me plug it back in let’s do a couple snaps take a look at it those are some good-looking signals we pause this go back take a look I might’ve missed it look at where I snap that right there right there’s where I snap the throttle it is normal to see all of these lines increasing that’s the amount of kV the coils building up before the plug fires the reason why they all increased is on a snap throttle your cylinder pressures increase so that line is going to increase that’s totally normal um as we look through them you don’t want to take any one shot and say oh that looks bad this is pretty typical this is a good looking pattern the reason why the spark line which is next to it that’s these lines right here firing lines spark line the reason the spark lines kind of get choppy you could just call it turbulence that thing’s firing and a high compression high swirl environment it’s like a candle blowing and a breeze so the spark jump in that gap it’s going to jump around on us now totally okay to see all that Hoffs in those plug wires sorry in those spark lines during the snaps oh that’s a good-looking snap now let’s go back with the Geo injector and unplug it take a look at watch the injector all right I unplugged the injector certainly can’t see it a title to you I didn’t see any of the change that should be cylinder cylinder six that should be the cylinder six injector which would be all the way to the right do we see any change in that at all man this cars got a dead myth right now right I’m going to snap it this is where you’re going to see it freeze a picture let’s get our gas readings out of the way so you can see it go back take a look the snap and I want you to get used to looking at this this is what a no fuel misfire will do look at this heart look at this spark line right here get a couple more frames of that look at that no fuel misfire that is a classic view of a no fuel misfire this would be figure figure-four in my book page 14 figure 4 will refer back to that minute figure 4 page 14 you know top left picture in the bottom right picture no fuel misfires the theory behind that a couple different views on why it looks like that I’m going to go with this one fuel acts as a conductor in that spark plug electrode if there’s no fuel in that cylinder it becomes more difficult for the spark to jump the gap and so basically what you’re dealing with right here is the spark on these ones is firing the whole distance and on this one it’s only firing right there and this big spike is a large coil oscillation which is energy left over they can’t fire that spark plug will go without it doesn’t matter bottom line what’s a no fuel misfire look like it looks like that and what to catch it you have to understand that the car idling isn’t good enough right you need the car running do a stat throttle you can see it for sure you see it live – the key is the stop no fuel miss pot do you see something like that don’t put a set of plugs and wires in it for sure all right I’ll show you ignition one now this one’s a little bit difficult to duplicate exactly but I’m going to do one there’s so many different variables you can have when it comes to the ignition one’s going to be an open plug wire and I’m going to do this very quickly and pause it because I don’t want to do any damage to the system I’m just going to pull plug wire off let’s watch it and I’ll put it back on that’s frozen that one’s easy I don’t need to snap it what happened why does it look like that an open plug wire there’s no spark line that spark has nowhere to go so what do we get we get a large coil buildup that has no release so you see very very high firing line and no spark line that is an open secondary okay to see the height of that what we want to do is unfreeze this change this to a 50 kV scale and do it again watch it cause that one and actually this test tells you two things one you got an open plug or wire we don’t know which one but at least one of them is right what you can do to identify if it’s a plug or wires you can move the wire to the next cylinder switch the wires to see if it moves with the wire or switch the plug see if it moves with the box honestly when I see that in the field I don’t care what’s Clark it only plugs all new wires if it’s a conventional system like this cap and rotor as well the other thing this test tells you is the coil output so this is how you check an ignition coil for how much energy that it’s able to produce is what’s the height of that spike that line right there that’s 40,000 volts as coils putting out it’s actually burying my scale so is that a good core yes it is this is how you do a coil test – that’s what an open plug wire looks like and that’s how you do a coil reserve voltage test 40,000 volts from that coil I like that I’m going to show you what a shorted plug wire looks like and this can vary you have to understand it was sort of fun liar if it’s a direct short or if it’s a sort with an air gap it’s going to look different if it’s a sword to ground with an air gap it’s actually going to look very very close to what the spark plug looks like and it’s hard to identify those so see if I can show you we try to get an air gap in on this too looks like the other cylinders doesn’t it watch on the staff watches this is key watch the snap watch the other cylinders will you notice they do I’ll go back and take a look at that if you were just looking at this tonight what you’d miss it it’s got a dead cylinder miss from a sordid plug wire it’s just not totally shorted on the snap what we want to see all of those lines should increase and this whole surge see all my firing lines jump up what do you notice about number four staying the same why is it staying the same because it’s not firing in the combustion chamber that’s the answer with that it’s firing it has an air gap it’s not firing in the combustion chamber so that’s what a sorted plug wire is going to look like that does not have a direct sort that has an air gap see if we can give it a full sort actually I don’t think we can yeah and I can’t give this one a full sort and the reason I can’t this is a distributor system they’re still an air gap whereas the air gap inside the cap runner air-gap so I’m sorted out directly now I can’t show you a direct sort on this design because of the cap rotor air gap that I can’t get inside to sort out the road or on the one cylinder that’s good enough some fundamentals of ignition systems you see a real high firing behind those spark guard what is it real high firing line and no spark line you’re looking for an open in the secondary normal-looking tire wear when you snap it the sparkline don’t throw hot injector no fuel misfire you see an ignition waveform looks pretty decent but that’s a change on a snap it’s not firing in the combustion chamber there’s so many different things to look at with these the key truthfully is to get a scope that has the capability of doing this and doing multiple cars knowing good known bad you just start to get used to what what they’re supposed to look like so a little bit of secondary ignition using the scope will do primary next