thanks for the advice on the scopes. These are things I know nothing about. I was figuring 'why spend
Hundreds of dollars on something I will use so rarely.'
Hundreds of dollars on something I will use so rarely.'
cylinders 1 and 7 are cold
- Thread starter OC_
- Start date
Seymour Snerd
Lifetime Supporter
You sure don't need to for garage use. But any simple way to visualize what's going on with a wire, although needed rarely, when you need it, it's a life saver. IAE we're probably off topic so if you want to pursue this off line send me a PM or e-mail.
Or we could start a new thread under "GT40 tech, garage and tools".
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I'll start a thread in the GT40 tech, garage and tools area.
John, I responded to your posting re. what type of scope (oscilloscope) to buy, now, apologies I just scanned this, am i right in saying that she's misfiring on 1 and 7, what you could try is to put one of the old timing lights on the plug feed to 1 and 7 and see if the flash is regular, therefore telling you if there is a spark issue. Clearly this will only work at low revs, but you may be able to see if there is a spark pluse or an irregular pluse (flash) compared to one of the good cylinders?
If you strobe the light on the timing marking, you may be able to see the irregularities at hight speeds, strobe effect.
Keith
If you strobe the light on the timing marking, you may be able to see the irregularities at hight speeds, strobe effect.
Keith
Keith, I have done this and noticed missing. It was hard to see at first, but I filmed it with a high speed camera and you could clearly see it.
I guess now that I'm confident that it has a proper air/fuel ratio, it has to be ECU/spark related.
I have learned that my dwell time might be too short and could be causing a weak spark. I need to play with this and see if that makes a difference. But this doesn't explain why it would only be on cylinders 1 and 7..
I dont know how i got so far off at looking at the intake manifold all the time.
I guess now that I'm confident that it has a proper air/fuel ratio, it has to be ECU/spark related.
I have learned that my dwell time might be too short and could be causing a weak spark. I need to play with this and see if that makes a difference. But this doesn't explain why it would only be on cylinders 1 and 7..
I dont know how i got so far off at looking at the intake manifold all the time.
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John, no real need to view the schematic, just pop the ECU cover off and inspect your solder joints, particularly the hand soldered parts. My MSPNP has 4 injector drivers. Two were not soldered well and had open connections between the driver and the board. I am batch firing also.
I also used a simple Fuel Injection Noid light to confirm my suspicions. It won’t tell you that the Fuel Injector is bad, but confirms that it is getting power and the switching signal (also known as the Fuel Injector Pulse Signal). Without any of these two signals, the fuel injector will not work or work intermittently if there is a problem with your ECU.
Howard Jones
Supporter
Wet soot plugs + 300F pipes = intermittent firing = electronics = ECU issue. OR cables/ connectors/ pushed pin/etc, to injectors.
How about making up a simple jumper connector so that you can try to run one of the offending injectors separate from the harness? This might tell you that at least that part of the harness is the issue. And of course if that works try the other cylinder. Look hard at the pin seating in the two plugs on the injector end. Pins can be pushed and then look OK when you un-plug the connector to have a look. They just don't "latch" in the connector housing and then push back away from the other pin (on the injector) when you re seat the plug.
If the harness is good, then I would be swapping out the ECU, if you can. Even using the stock one just to see what the difference might be at idle.
You might be able to rent a o scope for a day/week/month if you really want to "see" the injector pulse. Another way might be to make up a light bulb jumper and simply drive a light bulb instead of the bad cylinder injector. If you do plug it into one of the good cylinder injector plugs first just to see what a good one acts like. Then do a bad one for a comparision.
My bet is a intermitant injector pulse at the two bad cylinders. Qualify harness first then swap out ECU. If it's not that then it's interminttent ign signal to ditributor but I don't see why the same two plugs don't fire correctly all the time if it's the electronics though. Still, then I would suspect HV distribution. You must have swapped plugs and wire by now as well as ditributor, so I'm back at fuel again.
The ECU might be going full rich on two cylinders intermitantly? Fouling plug? Hummmm........ Again ECU swap in your future.........good luck.
How about making up a simple jumper connector so that you can try to run one of the offending injectors separate from the harness? This might tell you that at least that part of the harness is the issue. And of course if that works try the other cylinder. Look hard at the pin seating in the two plugs on the injector end. Pins can be pushed and then look OK when you un-plug the connector to have a look. They just don't "latch" in the connector housing and then push back away from the other pin (on the injector) when you re seat the plug.
If the harness is good, then I would be swapping out the ECU, if you can. Even using the stock one just to see what the difference might be at idle.
You might be able to rent a o scope for a day/week/month if you really want to "see" the injector pulse. Another way might be to make up a light bulb jumper and simply drive a light bulb instead of the bad cylinder injector. If you do plug it into one of the good cylinder injector plugs first just to see what a good one acts like. Then do a bad one for a comparision.
My bet is a intermitant injector pulse at the two bad cylinders. Qualify harness first then swap out ECU. If it's not that then it's interminttent ign signal to ditributor but I don't see why the same two plugs don't fire correctly all the time if it's the electronics though. Still, then I would suspect HV distribution. You must have swapped plugs and wire by now as well as ditributor, so I'm back at fuel again.
The ECU might be going full rich on two cylinders intermitantly? Fouling plug? Hummmm........ Again ECU swap in your future.........good luck.
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Howard, the ECU is only using 2 injector drivers. One driver fires cylinders 1,3,5,7 and the other 2,4,6, and 8. When it fires, it fires all injectors on that side. Because of this, i can use the connectors that fire the good cylinders and swap them with the bad ones.
If there is a fuel problem, its being caused by a interference and the only way I'm going to be able to see that is with an o-scope... I'm thinking its more of an ignition related problem. I can swap and move around everything, except the spark plug wires....
The factory ECU just isn't going to work. That one was tuned for 18lbs injectors and I now have 37lbs injectors. Its most likely going to flood the engine as soon as i start cranking...
If there is a fuel problem, its being caused by a interference and the only way I'm going to be able to see that is with an o-scope... I'm thinking its more of an ignition related problem. I can swap and move around everything, except the spark plug wires....
The factory ECU just isn't going to work. That one was tuned for 18lbs injectors and I now have 37lbs injectors. Its most likely going to flood the engine as soon as i start cranking...
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I have been pretty busy as of late, but I got a chance to play with the Oscilloscope and to put it on the car. Everything is looking good but I noticed some peculiar behavior on the HT leads going from the distributor to the plugs.
If I put the scope on the lead going from the coil to the distributor, the wave form looks like the classic ignition shape:
(this is not my car, but it looks just like this)
But, if I put the probe on the plug leads, it looks something like the attached pic. (sorry for the crappy drawing. I will see if i can get the PC interface to work so i can get a real screen cap later.)
It looks like it could be sort of noise or something happening in the distributor? It was like this on every plug lead i tested... Any ideas?
If I put the scope on the lead going from the coil to the distributor, the wave form looks like the classic ignition shape:
(this is not my car, but it looks just like this)
But, if I put the probe on the plug leads, it looks something like the attached pic. (sorry for the crappy drawing. I will see if i can get the PC interface to work so i can get a real screen cap later.)
It looks like it could be sort of noise or something happening in the distributor? It was like this on every plug lead i tested... Any ideas?
Attachments
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Hi John, it would be interesting to see Ch 1 on the LT side and Ch 2 on the HT so we could see the 2 waves on the same time domain trace.
As the HT trace represents the breakdown of the air/petrol mixture, I would expect it to be a 'dirty' waveform, as the current flow would be related to a series of ionic breakdowns, like fork lightning, as the current makes its way across the gap it will make the jump in a series of hops, possibly not even in a straight line. Perhaps some others can help with their actual experience of what the traces look like. In short I think it looks generally right, the voltage seems to peak, then drop (almost exponentially) as the mixture ionises and the charge is dissipated, then decays away. I am on hols until Sunday, but I can scope an ignition upon my return to reality, then we can compare notes?
Keith
As the HT trace represents the breakdown of the air/petrol mixture, I would expect it to be a 'dirty' waveform, as the current flow would be related to a series of ionic breakdowns, like fork lightning, as the current makes its way across the gap it will make the jump in a series of hops, possibly not even in a straight line. Perhaps some others can help with their actual experience of what the traces look like. In short I think it looks generally right, the voltage seems to peak, then drop (almost exponentially) as the mixture ionises and the charge is dissipated, then decays away. I am on hols until Sunday, but I can scope an ignition upon my return to reality, then we can compare notes?
Keith
Keith, i will try to get a better image of the waveform in the mean time. But the strange thing, from my understanding, the waveform taken at the HT coil wire should look the same as taking it from the plug wire... its the same circuit with the same flow of electricity....
Hi John, I am not sure I understand your last statement:-
"...But the strange thing, from my understanding, the waveform taken at the HT coil wire should look the same as taking it from the plug wire... its the same circuit..."
can you clarify with a diagram where the trace was taken, sorry I has assumed it was on the HT lead going to one of the plugs? There is also another spark jump in a traditional distributor. K
"...But the strange thing, from my understanding, the waveform taken at the HT coil wire should look the same as taking it from the plug wire... its the same circuit..."
can you clarify with a diagram where the trace was taken, sorry I has assumed it was on the HT lead going to one of the plugs? There is also another spark jump in a traditional distributor. K
The spike is the coil collapsing
In the red pic #2 the ocillations you have ,then fading into a straight line is the plug firing.
The drop at the end is the coil turning of and the small oscilations are normal as the coil is shutting down.
The flat base line is the coil building up again and the cycle continues.
Your ocillations in the plug firing line is the plug strugling to start the propergation of spark across the glug gap.
It can be caused by spark plugs,wrong heat range plug, lean mixtures bad swirl in the chamber ect.
It is a condition that is occuring at the end of the ign cycle in the chamber.
Your primary pattern is perfect.
If you can
put the scope + and- across the battery,when you crank no ignition spark you should get the occilations for the starter motor voltage draw, it will be high lows.
Each high low is compression on each cyl.
Put the second channel to the primary wire if you have one coil.
Disconnect the injectors
crank it over and check the primary signal is turning on at the peak of the starter wave on the first channel.
This will point out if the cylinders are firing in the same spot in the cycle.
Use the curser function if you have one to measure the milli seconds between ig on and the crank peak.
360 divide by 8 = 45 deg between peaks
the ms between peaks on crank draw is 45 deg
It is a good thing to check first then you can move through it methodicly.
Its like a dynamic compression issue
You do a comp test and it will show ok because it cranks at 3-400 rpm.
but when running the valve dont have time to seat because its at 800 rpm
I have seen cams do this type of thing, missing lobes that sort of thing.
Jim
In the red pic #2 the ocillations you have ,then fading into a straight line is the plug firing.
The drop at the end is the coil turning of and the small oscilations are normal as the coil is shutting down.
The flat base line is the coil building up again and the cycle continues.
Your ocillations in the plug firing line is the plug strugling to start the propergation of spark across the glug gap.
It can be caused by spark plugs,wrong heat range plug, lean mixtures bad swirl in the chamber ect.
It is a condition that is occuring at the end of the ign cycle in the chamber.
Your primary pattern is perfect.
If you can
put the scope + and- across the battery,when you crank no ignition spark you should get the occilations for the starter motor voltage draw, it will be high lows.
Each high low is compression on each cyl.
Put the second channel to the primary wire if you have one coil.
Disconnect the injectors
crank it over and check the primary signal is turning on at the peak of the starter wave on the first channel.
This will point out if the cylinders are firing in the same spot in the cycle.
Use the curser function if you have one to measure the milli seconds between ig on and the crank peak.
360 divide by 8 = 45 deg between peaks
the ms between peaks on crank draw is 45 deg
It is a good thing to check first then you can move through it methodicly.
Its like a dynamic compression issue
You do a comp test and it will show ok because it cranks at 3-400 rpm.
but when running the valve dont have time to seat because its at 800 rpm
I have seen cams do this type of thing, missing lobes that sort of thing.
Jim
Jim,
Did the battery and crank thing you were talking about.. Heres a capture of it. I'm collection more data now.
Did the battery and crank thing you were talking about.. Heres a capture of it. I'm collection more data now.
Ok looks like it firing after tdc but it maybe the delay between rotor and cap.
if you have coil packs it definitly ATDC as the trigger is the falling signal.
If its coil and distributor I would do the same test with the scope on the secodary if you have accesories to do it and that would prove a point, It looks late to me John the trigger signal is usually in front of the peak crank signal because that is max cyl pressure.
I work with coil packs and that is how the test comes out. in front of the crank peak.
If this has a module there are different types, a dumb module and one that has an advance
ign element built into it, if it has the latter it can take control and delay the timing even though you are programing it to fire at another point.
Non advance module is generally required for a programable system, but check you instructions and part #.
I have not read back through all the info on the issue so excuss me if its been covered.
On capture 5 on your pic something happened but it was on both so I think it may have been a connection or you on the key maybe.
If that is there all the time and the crank signal is normal that trigger is longer.
Thats a problem
Jim
if you have coil packs it definitly ATDC as the trigger is the falling signal.
If its coil and distributor I would do the same test with the scope on the secodary if you have accesories to do it and that would prove a point, It looks late to me John the trigger signal is usually in front of the peak crank signal because that is max cyl pressure.
I work with coil packs and that is how the test comes out. in front of the crank peak.
If this has a module there are different types, a dumb module and one that has an advance
ign element built into it, if it has the latter it can take control and delay the timing even though you are programing it to fire at another point.
Non advance module is generally required for a programable system, but check you instructions and part #.
I have not read back through all the info on the issue so excuss me if its been covered.
On capture 5 on your pic something happened but it was on both so I think it may have been a connection or you on the key maybe.
If that is there all the time and the crank signal is normal that trigger is longer.
Thats a problem
Jim
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Jim, the gap in the capture is the end of the 'scan' that's moving across the the screen. Please disregard that.
The red line is the probe on the battery and the yellow the primaries.
The bottom of the valleys on the red line is where the starter is drawing the most power - hence where the engine is making compression.
You can see that the yellow line dips before those valleys, thats where the ignition is coming on. So, I'm pretty sure that the ignition is firing before TDC. The capture reads from left to right... You have to look at the inverse of the capture (or the bottom side)
I don't think this is the problem..
But anyway, I did make a discovery tonight working on the car. I found that the ENTIRE drivers side of the engine has a very weak spark... so cylinders 1,3,5,7 are all weak and Its hard to even get a reading from them. All of the even cylinders are much better or have a very strong signal. What could be killing that entire side?
The red line is the probe on the battery and the yellow the primaries.
The bottom of the valleys on the red line is where the starter is drawing the most power - hence where the engine is making compression.
You can see that the yellow line dips before those valleys, thats where the ignition is coming on. So, I'm pretty sure that the ignition is firing before TDC. The capture reads from left to right... You have to look at the inverse of the capture (or the bottom side)
I don't think this is the problem..
But anyway, I did make a discovery tonight working on the car. I found that the ENTIRE drivers side of the engine has a very weak spark... so cylinders 1,3,5,7 are all weak and Its hard to even get a reading from them. All of the even cylinders are much better or have a very strong signal. What could be killing that entire side?
Ok I was looking at the highs.
My scope is different.
I gather you have tried adding fuel to the 2 cyl.
Or if you cant I use LPG out of a bottle.
You have been at this for a while.
I will go back and read your threads.
Jim
My scope is different.
I gather you have tried adding fuel to the 2 cyl.
Or if you cant I use LPG out of a bottle.
You have been at this for a while.
I will go back and read your threads.
Jim
Im Back
On page 1 Randy asked you to back the valves of to zero.
You said another shop checked it.
YOU need to check it and You should back them of John.
This reeks of valves sitting off the seats.
You will get a good compression test because the oil pressure is low and the valve springs will bleed it off.
But when running its different.
It could be the push rods are just a tad long or something like that.
have seen HP oil pumps make it worse
I know they looked but what did they look at.
Mechanics can be lazy, I would know I have been one for 36 years
The intake manifold ends at the valve seat John, if the valve is riding it is an air leak and as most have stated this rings of air leak.
You seem confident that the manifold is good then I recon this is mechanical
Makes sense to because same heads and mechanical parts , it maybe picking on those cyl because of oil feed or a machining issue I don't know the answer to that.
Jim
On page 1 Randy asked you to back the valves of to zero.
You said another shop checked it.
YOU need to check it and You should back them of John.
This reeks of valves sitting off the seats.
You will get a good compression test because the oil pressure is low and the valve springs will bleed it off.
But when running its different.
It could be the push rods are just a tad long or something like that.
have seen HP oil pumps make it worse
I know they looked but what did they look at.
Mechanics can be lazy, I would know I have been one for 36 years
The intake manifold ends at the valve seat John, if the valve is riding it is an air leak and as most have stated this rings of air leak.
You seem confident that the manifold is good then I recon this is mechanical
Makes sense to because same heads and mechanical parts , it maybe picking on those cyl because of oil feed or a machining issue I don't know the answer to that.
Jim
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Well, when i was taking about the shop that checked the heads, they only checked the heads themselves when they were not on the car - They just went over them to make sure they were sound when they resurfaced them. They made sure they had good guides, no damage and the likes.
There could be an issue with push rod lengths. I tried to check this the best I could when I put the heads on the engine. But, with hydraulic lifters, you know how hard it can be to check. I even put one of those weak springs in place of the valve spring so that you don't compress the lifter.
I have set the lash many times, i guess i really cant tell whats happening when the engine is running... I do have a high volume pump, but the engine has been clearanced for it and pressure seems normal when its warm.
There could be an issue with push rod lengths. I tried to check this the best I could when I put the heads on the engine. But, with hydraulic lifters, you know how hard it can be to check. I even put one of those weak springs in place of the valve spring so that you don't compress the lifter.
I have set the lash many times, i guess i really cant tell whats happening when the engine is running... I do have a high volume pump, but the engine has been clearanced for it and pressure seems normal when its warm.
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Jim, How could pushrods that are too long cause the valve to stay open? I could see it happening if I adjusted the lash to tightly, but I don't see how it would make a difference based on pushrod length. The same would happen if my pushrods were to short and I had the lash adjusted to tightly...
I'm going to see if i can check what my compression is when idling.
I'm going to see if i can check what my compression is when idling.
