Little bit of help to understand coil signal??? negative ?

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Little bit of help to understand coil signal??? negative ?

Postby DebbieSidera » Tue Jul 18, 2017 6:25 pm

Hi, I used to see the wave signal from the coils a bit different. Today I'm checking a US 1974 Dino 246GT that has been modified. The US version of this car has a different distributor type. The distributor has 6 lubes and a 'single' breaker points (the Euro has 3 lubes and two sets of points, which I like better because it has a large dwell).
The owner was convinced for another shop to upgrade the Original Dinoplex for another type of electronic ignition system (I don't know it, it's all black without any part number). However its trigger for same original 'braker points' system.
The engine is V6 to 65 Degree and has a offset pin crankshaft to compensate. Single distributor with six leads and a single coil.
The car runs well and strong. However when it gets around 5500 RPM and the engine is torquing, a power drop occurs for a couple seconds till at around 4500 RPM power is coming back.
I attached two files of the readings of the coil signal on the 'king lead'. One on idle and the other showing the problem when I'm driving and the engine is on high RPM and it has the 'power drop'.
When I first drove the car, I thought that the ignition breaker points were floating at high RPMs but then when I saw the signal on the oscilloscope, I got confused since all the spark events are on time.
Now I'm going to pull the distributor out and check the breaker points contacts and advance over the synchrograph tester.
Also, I'm going to take carburetors apart and check the floats... maybe is a problem of fuel, and engine is 'starving' on high demand???? (fuel pressure seems ok, because I already check that in the #1 inlet and in to the return outlet) Also, I used the small Amperage clamp on the fuel pump circuit while i was driving but it doesn't seem to move (Amperage is always doing the same pattern because its a self regulating pump).
Why I have a negative spark???? Can I set the oscilloscope to get the complete reading of the pick (-5 isn't enough).
The power drop 'occurs' on page 9 of 13 (4210 ms).
I appreciate your help.

best
Debbie
Attachments
running1.psdata
(4.18 MiB) Downloaded 36 times
idle.psdata
(5.5 MiB) Downloaded 23 times
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Re: Little bit of help to understand coil signal??? negative

Postby STC » Tue Jul 18, 2017 11:56 pm

fuel pressure seems ok


With Respect - I cringe when I hear that word !

Fuel pressure Tester ???

Fuel Flow per minute ???

Does this have an O2 ? If not can we fit one ?


If I recall correctly there was a time when a bad batch of condensers were in circulation from the dealers ?? Causing Havoc !
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Re: Little bit of help to understand coil signal??? negative

Postby ben.martins » Wed Jul 19, 2017 9:28 am

Hello DebbieSidera,

Thank you for your post and it's great to see this beautiful car still going strong! I think initially lets sort out the issue you have with the inverted capture you are seeing. This is a relatively easy fix and all it requires is a change to the probe you are selecting. I have attached a screen shot of where to find this setting.
Secondary ignition pick up.jpg

Also I think it might be worth while upping the number of samples. If you wanted to capture this over a long time base then to help analyse the waveform it would be good to have plenty of detail when we start to zoom in. Also you have a 4 channel scope, why not utilise this and add some extra information onto the screen when the fault happens? As STC's has mentioned including fuel pressure would be nice to see and engine speed but obviously depends on the amount of accessories you have.

Hope this helps for the minute and once there is some more detail we can go from there.

Kind Regards

Ben
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Re: Little bit of help to understand coil signal??? negative

Postby EAAD » Wed Jul 19, 2017 9:39 am

@Ben

What a lovely courteous helpful reply. (Thought I was on Autonerdz for the minute then, not here) Certainly worthy of note imvho.
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Re: Little bit of help to understand coil signal??? negative

Postby DebbieSidera » Wed Jul 19, 2017 10:06 am

Thanks Ben and STC.

About the fuel pressure ,I checked the input pressure on the first carburetor and simultaneously on the last one (Just before the restriction tube before gas returns to the fuel tank). I didn't checked the fuel flow or volume, however I thought that if running strong, the fuel pressure at the return outlet didn't (almost) move, I shouldn't worry about it.
Fuel pump amperage graph was just followed the offset pattern of the impeller. Since it's seft regulated, ampererage is very linear.
What I was really wondering is if the floats weren't properly set and maybe they close before they should. Causing the starvation. However I don't believe it, because it should be move 'gradual' and it can't be posible to drain all the carburetors at the same exact millisecond.
At the file with the coil waves... the signal fails suddenly in one spot in all the cylinders.

My main question was about the understanding of the signal. Because during the 'power drop' signal is very different with much short of the voltage pick.

I'm going to repeat the test with the 'reverse' signal. And spend a bit the time to analyze it.

Thanks again to all

Debbie

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Re: Little bit of help to understand coil signal??? negative

Postby Fat Freddy » Wed Jul 19, 2017 3:10 pm

Hi Debbie.

IIRC you had a timing problem with a Farrari. Did you get an answer to that?

With your latest. Can you do the same capture (running, fault occurring) and include a sync to cyl 1?
What do you think of pg 9 204ms? Advance? I may possibly be having deja vu here(Mick :wink: )

HTH
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Re: Little bit of help to understand coil signal??? negative

Postby DebbieSidera » Fri Jul 21, 2017 8:44 pm

Hi guys,

Well. I pulled the distributor out and I let it spin over the bench on the synchrograph. I connected all the ignition wires on it and I monitored the whole thing.
The green line is the braking points, the yellow is the output from the 'Dinoplex', the Red is the coil lead and the blue is the Cylinder #3.

You can see that that the ignition unit is skipping some of the breaker points events. This happen when the engine speed is over 5400 RPMS.
Ignition wires are getting lots of signal noises. I checked impedance of the ignition wires and the resistance values were all over the place. I'm going to fix them.

I found out the ignition unit is a Perma-tune type. I just sent an email to the unit manufacture, before reporting it to the customer.

best
Debbie
Attachments
IMG_2734.JPG
IMG_2739.JPG
Dino_246_#7724_ignition test2_5400RPM_Jul2017.psdata
(13.04 MiB) Downloaded 17 times
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Re: Little bit of help to understand coil signal??? negative

Postby Technician » Fri Jul 21, 2017 10:26 pm

You know what I find very interesting reading this thread!

This country, the UK (GB) we are told that our vehicles must reach high standards for emissions purposes, looking at zero emissions at the tail pipe and all this technology on our vehicles were we are told must be there to combat these emissions. We are a very small country compared to most other industry countries, yet reading this thread and other threads on other forums about their vehicles over the ponds, they all still have plug wires, distributors and carburetors, where we were told back in the late 1980's that carburetors throw petrol into an engine like throwing a bucket of water over the path when compared to electronic fuel injection, which I agree from an emissions point of view, but we are a very small fish in a very large ocean, why then are all these other big countries allowed to have dinosaur technology on their vehicles today and we have to have all this state of the art electronics?
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Re: Little bit of help to understand coil signal??? negative

Postby Technician » Fri Jul 21, 2017 10:34 pm

I seem to very vaguely remember something from back in the late 1980's over here where some manufacturers, Bosch I think was one that used to have some type of rev limiter built into the ignition distributor to stop it over revving?
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Re: Little bit of help to understand coil signal??? negative

Postby STC » Sat Jul 22, 2017 12:43 am

but we are a very small fish in a very large ocean,

We are (for now) part of Europe and that is where our legislation stems from, so, although we are a little fish but part of a big flock

why then are all these other big countries allowed to have dinosaur technology ?


The Dino 246 GT that Debbie is working on was produced from 1969–1974. If we assume that the engine and ignition system spent just 2 years in R & D then that is 50 years old. A dinosaur in vehicle terms.

dinosaur technology on their vehicles today and we have to have all this state of the art electronics


The Americans, California especially probably has the most stringent emission rules in the world. Martin Winterkorn, one time Volkswagen CEO may validate my thoughts on that.

I digress, knowingly, but In terms of "Bang For the Buck" "Value for Money" it is my opinion that SAAB bought a lot to the table. Very early adopters of Fuel Injection, Turbochargers, ...... ..... to the mainstream in the 70's. Convertibles soon after.

It is all a farce all the while Heinz Baked Bean Tins don't come with a Nappy that has a catalyst built in ?
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