Ignition problems Legacy 2.5 NA 1997
Discussion
Engine starts to run rough then eventually won’t run at all. Pull a plug lead and there is a spark to the block. Pull the plug and hold it against the block there is no spark at the plug gap. Hold the plug away from the block and the spark jumps across but still no spark at the plug gap. Increase the air gap and eventually the plug will start to spark at the gap.
Conclusion duff plugs.
Fit a new set (expensive) and after ten minutes the same happens. Engine was not happy when on the fresh plugs so I knew this was not going well.
First set of plugs were quite new BoschFR5DPP222 second set NGK PFR6B.
Thinking perhaps the coil was duff and allowing the plugs to foul so it was replaced.
Thinking the Ignition ignitor may be the next culprit but there is little info on what it does exactly. The fact I have a full set of sparks may be proof enough it is working or is it supposed to amplify the spark? Further investigation seems to indicate they are not readily available and it was inferred to me that was because they never go wrong.
The engine is in a Kitcar but has not thrown any relevant codes.
Any ideas what is going on?
Many thanks
Steve
Conclusion duff plugs.
Fit a new set (expensive) and after ten minutes the same happens. Engine was not happy when on the fresh plugs so I knew this was not going well.
First set of plugs were quite new BoschFR5DPP222 second set NGK PFR6B.
Thinking perhaps the coil was duff and allowing the plugs to foul so it was replaced.
Thinking the Ignition ignitor may be the next culprit but there is little info on what it does exactly. The fact I have a full set of sparks may be proof enough it is working or is it supposed to amplify the spark? Further investigation seems to indicate they are not readily available and it was inferred to me that was because they never go wrong.
The engine is in a Kitcar but has not thrown any relevant codes.
Any ideas what is going on?
Many thanks
Steve
I'm a little vague on them as the only one I looked at was years ago on a 2.2L that was sat in the back of a VW camper. As I remember it, it acted as an amplifier/isolation between the ECU and the coil.
Didn't go into much detail on it as the fault was easy to spot - it wasn't earthed at all!
You're right - you'd need a sampling meter or 'scope to have a look at what the output is like relative to the input. I'm assuming you're thinking down the lines of it being very unusual for a spark to only happen once you increase the gap!
Are you sure the spark you're observing when you've got a big enough gap is every rev (or 2, I can't remember if these are wasted spark or not)?
Didn't go into much detail on it as the fault was easy to spot - it wasn't earthed at all!
You're right - you'd need a sampling meter or 'scope to have a look at what the output is like relative to the input. I'm assuming you're thinking down the lines of it being very unusual for a spark to only happen once you increase the gap!
Are you sure the spark you're observing when you've got a big enough gap is every rev (or 2, I can't remember if these are wasted spark or not)?
The Handbook shows what I think was 2 transistor symbols which I don't understand as I was expecting it to be more complicated than that.
Also, if it is just 2 transistor circuits then why would both circuits fail unless there was some other common circuitry.
The coils seemed to be firing in the correct order/rate and yes they are wasted spark.
Steve
Also, if it is just 2 transistor circuits then why would both circuits fail unless there was some other common circuitry.
The coils seemed to be firing in the correct order/rate and yes they are wasted spark.
Steve
Sorry - didn't spot the reply. How are you getting on? I'm afraid I might not have much to offer, was just trying to ask the right questions to help.
If it's the same handbook I found, the transistor symbols may well just be to imply the functionality of the unit rather than being exact circuitry (the ECU also has 2 depicted as drivers).
They do show a common ground and the coils have a common live feed. Perhaps you could confirm you're getting 0V at '3' on it?
If it's the same handbook I found, the transistor symbols may well just be to imply the functionality of the unit rather than being exact circuitry (the ECU also has 2 depicted as drivers).
They do show a common ground and the coils have a common live feed. Perhaps you could confirm you're getting 0V at '3' on it?
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