Visit our Twitter feed for more great content
TRExp

The Pub - Off Topic

Old school engine diags- Sun machines. Anything new like that ?

Moss Motors
AutoShrine Sponsor
AutoShrine Sponsor
AutoShrine Sponsor
AutoShrine Sponsor

JohnW63 John Williamson
Apple Valley, CA, USA   USA
I need to diagnose a random miss or what ever the cause is for my 65 Mustang to not run as smooth as I want. My Dad got his hands on an old big Sun oscilloscope, but he hadn't used one in about 40 years and we suspect it is not happy with Pertonix units in the distributor. We wanted to isolate each cylinder but it just showed them all and jumped around a lot. Could be the unit is not fully functional. Is there anything like that around these days ? I don't need all the sensors and MAF checks that new cars have. Just a good way to see if all the plugs are firing and it's advancing the timing and all the old stuff. If it works on a Ford 289, it might be handy on my Triumph GT6.

Here is about what we have:




Home of the 1969 GT6+ MK II resurrection project
and a sorry looking 1968 GT6+ parts car trying to stay whole.

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
jacko241 Avatar
jacko241 Gold Member Joe Jacalone
Saint Augustine, FL, USA   USA
There are many shops that have a modern oscilloscope that will work.


Member Services:
Jacalone & Sons has over 40 years experience servicing MG, Triumph, and Austin-Healey. Moss Motors dealer.
grubscrew Avatar
grubscrew grub screw
The suburbs of, Winfield, Maryland, USA   USA
In reply to # 1572323 by jacko241 There are many shops that have a modern oscilloscope that will work.

I don't think John is looking for a shop!



Dave
1970 Spitfire Mk3
FDU 78359L
34/11 (Jasmine yellow/Black interior)

1962 Triumph TR3B
TCF 575L
Signal Red/Red interior

JohnW63 John Williamson
Apple Valley, CA, USA   USA
Nope. Not looking for a shop. Looking to find a modern version of the Sun for tuning older cars. But, it's not my job, just a hobby, so expensive replacements aren't so helpful.



Home of the 1969 GT6+ MK II resurrection project
and a sorry looking 1968 GT6+ parts car trying to stay whole.

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
jacko241 Avatar
jacko241 Gold Member Joe Jacalone
Saint Augustine, FL, USA   USA
You can buy a low cost one for a couple hundred bucks almost anywhere.

In reply to # 1572445 by JohnW63 Nope. Not looking for a shop. Looking to find a modern version of the Sun for tuning older cars. But, it's not my job, just a hobby, so expensive replacements aren't so helpful.


Member Services:
Jacalone & Sons has over 40 years experience servicing MG, Triumph, and Austin-Healey. Moss Motors dealer.
Doug in Vegas Avatar
Doug in Vegas Douglas D
Las Vegas, NV, USA   USA
In reply to # 1572445 by JohnW63 Nope. Not looking for a shop. Looking to find a modern version of the Sun for tuning older cars. But, it's not my job, just a hobby, so expensive replacements aren't so helpful.

Using the tech of the time is often better.

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
The Sun machine should work with the petronix, but would likely give you information that you can't do much about, such as dwell.

Honestly, over and over again I find myself falling back to a simple, home made spark tester and timing light.

To produce a spark under pressure in a combustion chamber requires much more energy the in normal atmosphere.

For a spark to jump .025" in a cyl it needs the equivalent energy that is required for it to jump about 3/8" in the open air.

Many people forget this, and see a spark at the plug, and figure it's good! When really, when in the cyl the spark is marginal, or just not happening.

The timing light we use to set the timing. But often that is all owners use it for.

Increase the revs while whatching the timing marks. Watch the ignition advance. Is the advanve smooth and steady? Or does it jump or move around?

Also check the timing on other cylinders (this may mean marking other points on the crank pulley).


Attachments:
IMG_20180911_164212.jpg    21.3 KB
IMG_20180911_164212.jpg

JohnW63 John Williamson
Apple Valley, CA, USA   USA
What I like about the old Sun scopes is the trace of all sparks. You can see issues with the shape and size of the spark all at once.

I've got what seems to be a random miss on my Mustang. Changed plug wires, checked for bad plugs, checked for vacuum leaks around the carb, got the Edlebrock carb adjusted by a guy with a Dyno. Just can't get it to run smooth. Can't really tell if it is ignition or fuel caused. Even removed the Pertronix module and put points back in it and swapped to a stock coil. My Dad has an old Sun 1011 , but the scope was not stable, so I'm not sure if it still works properly. I got a PDF of the manual for it and some troubleshooting sheets and schematics.



Home of the 1969 GT6+ MK II resurrection project
and a sorry looking 1968 GT6+ parts car trying to stay whole.

clshore Carter Shore
Beverly Hills, FL, USA   USA
A TV high voltage probe connected to an oscilloscope will do what you seek.
You can actually build a 1000:1 voltage divider pretty cheaply.
And USB oscilloscopes for laptops or even smartphones are cheap as well.

To see all cylinders at once requires a multichannel scope and a HV probe for each one.

That gets kind of pricey, and a 2 channel scope is more than adequate.

JohnW63 John Williamson
Apple Valley, CA, USA   USA
Yeah, I could just note the height and shape of each spark plug and find the high or low ones or the ones that seem to be inducing the miss, if it is ignition related.

As I tested the one one we have, I've found the lead you put on the #1 spark plug wire is not being picked up or is not working. It shows the same graph with out without it hooked up. I can get continuity from the wire to the plug inside, but I haven't tested the inductive clamp yet. Not sure how to that, without just putting a multimeter on the end of the cable where it plugs into the Sun unit. I hope the voltage induced is relatively low and not full spark levels.



Home of the 1969 GT6+ MK II resurrection project
and a sorry looking 1968 GT6+ parts car trying to stay whole.

tapkaJohnD Avatar
tapkaJohnD John Davies
Lancaster, Lancashire, UK   GBR
The modern equivalent of the old diagnostic machines is the PicoScope.
This a black box that turns a PC, lap or desk top, into an oscilloscope. Their products include specific automotive kits and they publish useful guides:

https://www.picoauto.com/products/automotive-oscilloscope-kit/overview
https://www.picoauto.com/library/automotive-guided-tests

They vary in price from a simple two channel box with two leads at £100, to a complete kit at $1000

To sense and display spakr plug lead energies, you would need a special HT connector: https://www.picoauto.com/products/ignition-accessories/ht-extension-lead

Hope that helps!
John



Edited 1 time(s). Last edit at 2018-11-09 02:50 AM by tapkaJohnD.


Attachments:
picoscope 2-channel-automotive-oscilloscope.jpg    38.6 KB
picoscope 2-channel-automotive-oscilloscope.jpg

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
+1 Sun should work with Pertronix. You've probably got a broken wire in the pickup lead. The induced voltage isn't very high, but I'd still check for resistance/continuity first.



Randall
56 TR3 TS13571L Once and future daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

JohnW63 John Williamson
Apple Valley, CA, USA   USA
I had checked for continuity on the wire and it seemed good to the first circuit board. I then hooked a multimeter to the line, with the pickup around a spark plug wire, and got nothing on DC volts. I then swapped the inductive pickup from the line that normally goes to the coil -> distributor cap and Still got nothing. Putting the plug inductive pickup on that wire gave me a stubby square wave in the scope. It has me thinking a bit. If the line I'm testing gives nothing with either pickup, then perhaps the connection between the lead and the pickup is not good. Or... my digital multimeter isn't able to pickup the pulses that fast.



Home of the 1969 GT6+ MK II resurrection project
and a sorry looking 1968 GT6+ parts car trying to stay whole.

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
Hmm, never checked, but I assume the pulse is very short, just a few milliseconds per firing (basically the spark burn time). I can't explain how you found a square wave, unless it was something else (like 60Hz hum). Most likely, your DMM doesn't respond that fast.



Randall
56 TR3 TS13571L Once and future daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

JohnW63 John Williamson
Apple Valley, CA, USA   USA
I re-read my last post and realized it wasn't clear on one point.

I took the inductive clamp that was supposed to be in the #1 plug wire and put it on the coil to distributor wire and got a short square wave. I never got any output on the lead that is supposed to go to the #1 plug wire.

After thinking about the meter settings, I think I'll try testing in AC volts. That should be able to see at least 60hz and the spark plug doesn't fire 60 times a second at idle. I'm pondering putting a little wad of tin foil between the clamp and the lead to make sure they have a good contact in the connector. I wonder if anyone has spare parts for these. I think my Dad got it for free.



Home of the 1969 GT6+ MK II resurrection project
and a sorry looking 1968 GT6+ parts car trying to stay whole.

. Hide banner ads & support this website by becoming a > Gold Supporting Member <

To add your reply, or post your own questions




Registration is FREE and takes less than a minute!


Having trouble posting or changing forum settings?
Read the Forum Help (FAQ) or contact the webmaster