Upgraded ignition system, Problems

[rmattingley]

Ok here is what I did.
I changed out my points on my 4 cylinder gm 2.5 marine engine for a PerTronix ignitor II electronic ignition. At the same time I changed the wires for sprial core, coil with a PerTronix flamethrower II (as recommended by PerTronix) and changed plugs.

I set the timming at idle for 8degrees btdc as stated in the user manual.
It runs great, but I have lost 700 rpms at the top end. The boat will only do 3600 rmp with this setup.
so to trouble shoot, I rebuild carb, replaced fuelfilters, tried old wires tried old coil. Found that if I put the points and condensor back in it ran at 4300 rpm like before.

I was wondering if anyone had anyexperience with these electronic ignitions and could explain what I am doing wrong.

Like I said before It ran great up to 3600 then it just kind of bogged out.

Thanks

 

[Papa Bear]

governor built into ignition module ??

 

[1 FMF]

I have a pertronix 1 & 2 for my 351w motor in the big boat.

since you had points, what you need to do is wire +12v directly to the coil + side. It will depend on how your boat wiring is, because it can vary. But figure on going from battery + to ignition key switch battery side, run side of key switch goes either directly to coil + side, or to a relay which connects wire from + side of battery directly to coil + side. And the module under the distr. cap connects to coil +/-.

... with your points setup the existing wire to the coil + side is probably a resistor wire. You need to remove that, because it is dropping voltage going to the coil. That was ok and was supposed to be like that for a points ignition to prevent the points from burning up. It operates your coil at around 9 volts. With the pertronix, you want full voltage. You're probably running out of power at the higher rpms. you want full voltage, actually 14 volts when alternator is putting out, going to + side of coil all the time.

There is no governor or rev limiter built into the pertronix module.

If you can go back and forth between pertronix and points and get 4300 rpm on points, it's not the mechanical advance in the distributor so you should be getting full timing advance. Good idea would be to check with a timing light at high rpms anyway, you should see around 24-28 deg btdc. And if you get > 4000 rpm on points it's certainly not the carb.

 

[rmattingley]

Thanks for the reply.
The engine was installed with a balast resistor, which I took out. I assumed that with a balast resistor, there wouldn't be a resistor wire, but I will give it a check. Time to get the old volt meter out.

 

[another Todd]

Call Pertronics. I installed a pertronics unit in my boat years ago and the tach wouldn't work. They were very helpful, gave me exact part numbers for two diodes to install inline to the tach, worked perfectly. There probably isn't a problem they haven't seen before. Their unit worked flawlessly in my setup. BTW, I used an Accel coil, but I doubt if that is the issue.

 

[1 FMF]

todd had a good point, try disconnecting your tach and running the pertronix. you won't see rpms but, you should obviously tell by sound and speed if you're breaking 3600 rpm. would be a quick & easy troubleshooting method.

I was assuming you had a mercruiser. I've read the omc's require some extra doodads to work with their shift interrupter switch, not sure if it applies to you although I don't see how it would affect top rpm.

 

[rmattingley]

Update. I did some benchmarking with a new set of points today. I set the dwell and timing and then ran it through some timing tests.
500 rpm 5 btdc
2000 rpm 20 btdc
3000 rpm 25 btdc
4000 rpm 28 btdc

This is without a load. Later this week I am going to give Pertronics a call and see what they say.

Info: The mercruiser's don't need the diods on the shift interupter switch. Just the omc engines.

 

[mechtech2]

They sure like retarded timing, don't they?

 

[1 FMF]

it's not actually retarded, better way to say it would be they run less (or need less) advance than the typical 32-34 dbtdc of a v-8.

your test with the points is showing the mechanical advance of the distributor to be working fine.
what you need to do next is run the pertronix and see what the max advance is. If you get max timing then, the only thing I can think of is the unit isn't getting full power. But if that were the case I would think you'd get intermittent spark and the engine would run choppy and cut in and out at high rpm. If it runs smooth but only hits 3600 rpm then only thing I can think of is the pertronix II is NG, you've ruled out all other factors. The II unit is supposed to vary dwell and timing, so if it's NG or the incorrect one for your distributor then it's probably giving less timing than you need resulting in the power loss.

I have both the I and II for my motor. They both run fine at high rpms, but I noticed at a 500-600 rpm idle the II would cause idle surge on me whereas the I would idle rock steady at 550 rpm. Found that cause switching them both out on a warm motor. The II definitely affects dwell and timing.

 

[RH+G]

I have found that with PerTronix ignitor II electronic ignition you have to adjust the timing. On a slant six I had to retard it about 5 degs.

 

[rmattingley]

Fire, Fire, Fire

Well, not sure what happened, I took the points out and put in the ignitor and coil and smoke was rolling out of the coil. didn't notice it untill I tried to turn it over. Then there were flames. Good thing I had my glass of ice tea handy. lol.
Coil craked, ignitor looks fine. Im sending both back to company.
I think I have relearned a valuable lesson. If it ain't broke, don't fix it!!!!!!!
Ill see if pertronics will rma my unit so I can continue my experimentation. Otherwise it is back to points system.

later

 

[mechtech2]

The resistor was limiting current flow through the coil, as well.
Oops!
Look into a SCR [silicon controlled rectifier] system for your points ignition system. It takes the load of of them - all they do is switch a very small signal to the unit.
I always had one in my old point cars, and the points never wore, and had a stronger spark, to boot.
I don't know who still makes them, though.

 

[Steve S]

Quote:

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I have found that with PerTronix ignitor II electronic ignition you have to adjust the timing. On a slant six I had to retard it about 5 degs.

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Could you explain?

 

[Steve S]

Quote:

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The resistor was limiting current flow through the coil, as well.
Oops!
Look into a SCR [silicon controlled rectifier] system for your points ignition system. It takes the load of of them - all they do is switch a very small signal to the unit.
I always had one in my old point cars, and the points never wore, and had a stronger spark, to boot.
I don't know who still makes them, though.

---

MSD and other companies make them. Jegs and Summit carry them if you want to look them up.

 

[RH+G]

For whatever reasonit ran better like that. I think the way the unit is mounted in the dist. canges the distributor cam relationship as compared to the points. DOnt know for show. Maybe it just from being more effcient