I posted about this probe device I found that allows you to check each COP using an automotive lab scope. The scope is expensive (like thousands of $$'s) and this probe is $230. It allows you to visually see what each COP is doing... how it is firing (or not). What is called the secondary ignition... the spark plug side of the coil. From this you can compare one COP to another to locate a low or completely bad unit or plug.

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So, having more time than money I'm making my own and sharing that with you all. I will use an electronics bench oscilloscope, since I already have one.

This is what I've done so far. Plan to start testing tonight and will keep posting until it's completed and working.



This is a small section of hollow aluminum tubing about 20" long I found in my junk bin. Added the wooden dowel handle. The end is drilled out 3/8" diameter by 1" deep to accept a BNC jack to connect to the scope. A shielded wire will connect the sensor probe to the jack.



Closeup picture of the "probe guts". Basically, I'm using a choke coil as the pickup device. Some padding may be needed after testing to reduce the spike levels if they exceed what the scope can handle.

BTW: My investment so far... around $4.

 

Very cool! I like it.

Now if my Fluke Scope Meter had not been stolen I would be building this too!

 

OH! Be sure to cover the exposed Aluminum with heat shrink or sparky tape!

 

Had a chance to do a quick test now that I have it more or less assembled. Used my 1996 Toyota since that's what I drive to the office. This uses a four output coil not COP's so not exactly the same but, as you can see, it seems to be clearly reading the secondary voltage.



I just laid the tip against the top of spark plug boot. Each one produced a similar result... but then again I know this car runs fine : ). I would have to pull one of the plugs to see what it looks like empty to make a judgement.



What I'm seeing on my bench scope. Set to .1v/division @ .2ms

BTW: Thanks for the suggestion about the tape. Will do that! The tube is not connected to the circuit, however.

 

Take a look at this unit for $80! Very tempting. Even records to a memory card for playback later.

Mini Oscilloscope ARM DSO Nano - Pocket-Sized Digital Oscilloscope | eBay

 

Very cool device.
Thanks.

 

Completed the assembly of the Poor Man's COP scope probe. This is a picture of the tip. The blue being the 1Mh choke coil that acts as the pick up transducer.



You can see in this picture the part of the COP that remains above the spark plug well when it is inserted. This is where I hook the probe tip for best results. Just inside this boot is where the coil connects to the spring that leads down to the spark plug cap.

 

Actual testing of the COP scope probe using my 1999 E-350 van last evening. The oscilloscope can be seen to the left of the van.



Actual picture of the scope representation of a Ford COP in operation. This happens to be cylinder #6, the front most position on the right side. I need to remove the air cleaner components to reach all ten positions for a complete check.



Right now I'm not sure why I'm seeing a double spike. Testing with my Toyota earlier in the day did not show this*. It may just be way the timing is set on my scope. Will need to test more.


*Update: I have just read where some manufacturers, Ford among them, use a "multi-strike" ignition system during lower speeds, such as idling, to reduce emissions. Perhaps this is what I'm seeing, here.

 

On ford COP systems, they do use multiple sparks below 1000 or 1350 rpm (depending on emissions tune). But that doesn't look like what I would expect. When I was megasquirting a modular v8 I spent a fair bit of time scoping the coils with a snapon setup.

The first spark should last .5ms, the second should last .5, then the third should hold until the charge in the coil is depleted (about 1ms on ford stock coils.)

 

Nice project. Does the commercial unit use inductive pickup as well? Most regular ignition probes seem to be capacitive -- usually some metal that clamps around the ignition wire, but does not make a complete circuit.

I've got a regular (cheap) commercial probe of that type and I see spark waveforms as shown in the books. Just curious if you could get to the same place on a COP system.

Great job in any event. It certainly should give you a good indication is the COP is working correctly.

hj

 

I had no idea how they worked. No circuit diagrams that I can find but one recent patent mentions using a magnetized ferrite rod with a coil around it. I was hesitant to connect my $1000 scope directly to the HV ignition system of the van so went with this wand idea.

And that's all I'm really after with this. If it shows a different waveform for a bad coil or spark plug then, for me, it's done the job.

I'm going to test all ten of mine tomorrow and we shall see what happens. I'm fairly sure I've got ignition issues. Whether this probe will find them... ?

Thanks for the support in any event.

 

Scooter gets 10 bonus points for this project.

 

At least 10, more if they're available!

 

Just saw this post and thought it interesting. Scooterspal do the leads of the coil connect to the tubing? And if so are they soldered? What holds the choke in the tubing besides the tape? Do you have any updates on this probe?

Thanks
Dave

 

No, the tubing was only as a way of getting the probe tip way back to reach all the COP's and to provide some shielding from the others.

The leads are soldered to the choke and cap, yes. Also to the connector at the back.

I first used heat shrink to secure the choke to the end of the tube and then followed up with electrical tape to prevent the tube from shorting out anything.

My theory was that a bad COP would show something different from one that was firing correctly. The kind of pulse made no difference as long as the bad one(s) looked different. However, I never got that far. The ones I felt might be bad like #10 as I recall required I remove the air cleaner to get in there.

In the end I ran out of time. The engine had no power and I needed to get it fixed for some important work I had coming up. The local Ford dealer said they would replace all the COP's and plugs (10 of them) for around $500 if I supplied the parts. I felt I could not go wrong by having an expert do the work who had done it many times before and knew what to expect. Discussions on this site clearly stated this was not a job for the faint of heart. Old plugs could/would break off at the threads leaving you to have to remove the heads : (

My van had over 100K and was never properly maintained by the prior owner. Today it runs like a champ.