• Hello there guest and Welcome to The #1 Classic Mustang forum!
    To gain full access you must Register. Registration is free and it takes only a few moments to complete.
    Already a member? Login here then!

Pertronix troubeshooting and going back to points?

G

gsxrken

Member
Could use a sanity check here. Son's new to us 69 2-barrel 351w Cougar started misfiring and popping through exhaust. Since this was immediately after some (ahem) unsupervised parking lot donuts, I first thought he might have jumped a tooth on the timing gear or bent a valve or pushrod. However, a compression test had every cylinder at 165-170 PSI. I also checked rotor backlash on the timing chain slack and it.s maybe 5 or 6 degrees max. So I think the mechanical valve timing is cool. Would anyone disagree?

Moving on to the distributor timing, I found it was at almost 19 degrees initial, going to 30 total at 3,000RPM so only 11 or so mechanical advance. This is without vacuum advance hooked up. I don't know what the timing was before b/c the car is a with us a week and I never checked it before. This is also somewhat suspect because the car is running like crap and needs 1000 or so RPM to idle on its own with popping and missing.

We just soaked and rebuilt the edelbrock carb and installed new fuel filter. Ordered a new gas tank due to rusty particles throughout carb and inside cut open fuel filter. No change at all. (Well it's a lot cleaner... )

I'm beginning to suspect the pertronix... Just because it's there and it's voodoo. I read about making sure the gap is correct on the unit, and the height of the push on magnet ring is the same as the pertronix unit... Checked and tweaked both and still no dice. How do you troubleshoot these things?

Oh and one Other thing- let's say I pop on an old distributor with points etc and the one wire as a diagnosis aid. This car has a full 12.3v to the hot side of the coil. Isn't that too much for points? Does the black wire from the points go the negative side of coil? It's been many many years since I've screwed with points
 
Yes, black wire goes to negative side of coil with points. 12.3V when the engine is running is about right if battery/alternator voltage is about 14V.
 
Is there a solid spark at each plug? The original Pertronics has always been real dependable in past. In my case, they either worked or didn't. The timing was always right on and performance was better than points. Have you checked the coil? How are the plug wires.
 
Thanks for the help so far. While I doubt it, maybe the crappy running just happened to coincide with the probable over-rev in the donut session?

Pete, when we saw the old coil leaking, we were stoked and sure we found the problem. Until the $40 new one made no difference.
The wires, cap and rotor look like recent updates. Slight carbon tracking in the cap that cleaned up easy with electronic cleaner. We did install new plugs.

I've also addressed some petrified vacuum lines and just found that the vacuum modulator on the FMX doesn't hold vacuum much at all. Intake gaskets don't seem to leak as tested via spraying carb cleaner along the manifold to head surfaces and listening for idle to pick up.

How about fuel pump delivery? Is there a spec for how much they should output, not in PSI but in volume.

It's been a good father and son collaboration and diagnosis, but he's getting frustrated as the "smoking gun" remains elusive.
 
The fuel pump could have issues based on the dirt/rust from the tank. If the issue is at idle too, I would doubt the fuel pump though. When this type issue pops up, I generally start the entire tune up process from the beginning. Going back to the basics and not thinking anything is correct helps me find the issue.....even though I may never know what was fixed.
 
check your oil and smell it.Maybe you have gas in your oil cause your fuelpump is bad.
check your electrical ground of the engine.
trigger wires that are damaged by rubbing again the engine block ?

Just some idea's.
 
1- don't get frustrated.
2- get back to basics. Check fuel, spark and timing. Adjust as needed. Start with timing light first then air - fuel mixture since the carb was just rebuilt. Follow the mfg directions on adjusting the carb. Then check all plug wires including the one to the coil by replacing a known good one. One at a time. You say you cleaned the cap, do it again. I use a pencil eraser. Get some emry cloth after the rotor.

You've replaced the plugs, so before you do anything run the car a bit and pull the to see what is going on. Report back.

3- don't get frustrated, just work through it.

You need spark delivered at the correct time with the proper amount of fuel mixed with the correct amount of air for an engine to run right. Basics.

Did you check the firing order? When you replaced the plugs one wire could be swapped. Make sure all wires are snug and making contact.

Mel

Sent from my DROID RAZR HD using Tapatalk 2
 
Thanks again for the ideas. I have an inline spark checker we can check on each wire. I can recheck firing order but remember car was running well until it wasn't. We changed plugs as a diagnostic and proactive measure but they made no difference. Redoing grounds is always a good idea so I'll show him that too.

Our next approach is:
  1. Install the old points distributor
  2. Re-time engine and adjust carb
  3. Check fuel pressure with car running
  4. I have an infrared laser temp sensor and may be able to check cylinder to cylinder header primary temps
  5. R&R gas tank and fuel sender when they get here next week. Start with fresh gas
  6. If I have gotten to this point and still don't know WTH is going on, I also have an older LM1 wideband O2 sensor and could weld a bung onto one of the header collectors. I've only used it for carb tuning before but maybe it'll tell me something I don't know.
 
Did you check the cam timing by bringing number one to top dead center and verifying the valve position and timing marks?
 
AzPete said:
Did you check the cam timing by bringing number one to top dead center and verifying the valve position and timing marks?
Click to expand...

Yep. And to these 48 year old eyes, they appeared to be closed and not moving when the balancer's indicated TDC mark lines up with the pointer. But by design both valves are closed for quite a long time as the piston comes up on compression stroke, and they remain closed for quite a few more crankshaft degrees on the power stroke before the exhaust valve begins to open. So I don't think a timing chain skip to the next tooth would be obvious at the rockers without a piston stop, degree wheel and and a dial indicator.

Believe me, the timing chain is not exonerated yet. The age of the motor and the shenanigans the moment before the stumbling, won't idle, and popping out the exhaust began still make me suspect it. But the almost remarkably even 165PSI across all 8 cylinders has diverted my attention from bent valves, pushrods, and timing chains. And while I can't find a spec for it, 6 degrees of crankshaft-to-rotor movement (rotating the motor CCW by hand until the rotor moves, and then rotating CW and observing on the timing marks how many crankshaft degrees it took for the rotor to move again) doesn't sound excessive. Even when new, there's some slack.

If doing a timing chain wasn't such a PITA, for the $50 or so I'd do it. But I don't want the kid to have to go through all of that, outside in the driveway, in the NY winter, unless I'm out of ideas. First things / easy things first, right? ;-)
 
If you think the push rods are bent that is super easy to check. take the valve covers off and take the push rods out and roll them on a flat surface and see if they are bent.

Mel
 
A bent pushrod will actually raise the compression on a cylinder in most cases. The valve just doesn't open, or if the pushrod is bent but still in place the valve only opens partially. Usually the pushrod bends and falls out of place. Another very common result from an over rev is a broken valve spring. It will run just like you describe, but normally will show up on a compression test. You might put a vacuum gauge on the intake and watch it. If it bounces distinctly then you may have a valve related problem.

I have seen failed Pertronix units. If the engine internals are good then you are spot on by changing the distributor to check it. The points wire just goes to the neg side of the coil. The coil just takes whatever that particular coil is designed for. If it has a correct voltage at the coil now, then it will not change by installing the points distributor.
 
I'm not one to just randomly buy parts and swap them in to try and diagnose a problem but in this case why not just buy a new Ignitor unit and plug it in if that is what you suspect? Worse case you have a spare which you would one day need. I'd rather spend that $70 or so and the few minutes it takes to install before I would go through all the hassle of swapping distributors.

If the problem really did start immediately after his antics I would take a very close look at valve train components. They are the most likely to fail on an over-rev and would cause the symptoms you are seeing.
 
Pertonix's have always been a great replacement for points, eliminating the mechanical wear factor. That being said the little magnet wheel that slides on the shaft over the points cam has had failures. I had one installed in my 67 for 8 years before it died electrically, and the magnet wheel had a bad magnet out of the box. Luckily I can grab another off the shelf. On conversions I now use Crane Xr-i, it picks up off the stock points cam so has no magnet wheel, and has a dial-in rev limiter. Also, it's about the same price. Great part.
 
It's the "shenanigans", not the Ignitor. My son's 69 351W Mustang SportsRoof ran like crap until I found the Pertronix Ignitor I back in 1995. It was a worn distributor. The car still runs beautifully on the same Pertronix. My 69 302 convertible has had an Ignitor I since 1998 when I bought the car. It's been to the drag strip many times and has crossed the country and back and I've never had a problem with that Pertronix either. BTW, your 19* initial is a little advanced (stock is 6*) but the 30* at 3,000 rpm doesn't sound so terrible. My vert is 14* initial and 35* @ 3,000 rpm. It depends on the cam that you are running and the distributor curve. Just guessing here, but if the problems showed up after your kid was abusing the car, perhaps you have already found the smoking gun. These old car are really not sprung for all of the donuts and sideshow antics that kids seem to want to do today. Buy him an old Prelude or Civic and he'll be able to do all the donuts he wants to and the risks to him and the car will be a lot less serious.
 
Probably not the Pertronix, but I have no faith in them. I've had 3 of them. And all three failed, and failed in different ways.
#1 failed after about 7 months. Just bellied up and died
#2. Had misfire under a load fromthe gitgo
#3. Ran fine when cold , when it got hot it missed or just died.

In all three cars, a return to points fixed the issue permanently.

They are cheap and cheaply made. No thanks.

Z.
 
Were they the Pertronix I or the Pertronix II? The Pertronix II seems to have a lot more problems than the version I.
 
My three strike outs with Pertronix were all #1's. I never went back for the later versions.

I'm not against electronic ignitions pet se. I have points in my Galaxie 500 because it is all stock and has no need of a different ignition system to function properly. My k code Mustang is a different story. It has a different cam, bigger valves, and a carburetor system that likes to run rich at idle. It needs all the help it can get by way of more voltage at the plugs, when I had a series of vintage Paxton equipped GT350's it was the same story. So I've been using the same MSD digital 6+ ignition box and MSD distributor for about 16 years / 95,000 cumulative miles with no issues.

Z.
 
Last edited:
You must log in or register to reply here.
Back
Top