Distributor trouble

[carrottop596]

I recently decided to get rid of my old points and put a pertronix ignitor in my '71 Bronco, but ran into some trouble when i did. When i put the pertronix in i had the dash off (fixing some minor electrical problems) so i was unable to drive it, but it started up fine. About a week later i put the dash back on and when i tried to drive it started up fine, but when i was driving it, my RPM's were jumping all over the place and i wasn't getting much power out of the engine. Then i tried just revving the engine and it worked fine. Any ideas as to why my bronco is doing this?
Thanks in advance for your help

 

[broncnaz]

Sounds like the timing is off a little. We might need a little more info as to what its actually doing while driving. Might also have a loose wire double check ignition wires all the way back to the switch.

 

[DirtDonk]

Yeah, describe how your rpms are jumping around like that. You're talking not juts about a tach reading, but the actual engine racing up and down?
Is it doing it only under load, like when accelerating? Or all the time?

Paul

 

[carrottop596]

I just installed an aftermarket tach and wired it to the ignition and the coil and it works fine when im revving the engine. But, when the car is under load (accelerating) the tach is jumping all over the place and i can hear the engine is definitely not running smooth and im barely getting enough power to make it up a small hill i usually do in 3rd gear (original 3-on-the-tree). The engine sounds like it is firing randomly, really fast then really slow then kinda fast etc. It was working fine when i had the points in it (except the point gap completely closed one time and it took me forever to figure out what was going on. I finally found it was the point gap and fixed it and it ran fine again but i decided to put electronic ignition in it to make it more reliable).

 

[broncnaz]

Unhook the tach see if its causing your issues. Normally the tach is only hooked to the coil.

 

[DirtDonk]

x2. Disconnect the tach to see if anything changes. They've been known to be bad right out of the box before. Not often, but all it takes is once, yours(!), to make it a pain.

Another thing is the gap. Did you set the gap on the Ignitor correctly? Re-check just in case. They're known for a bit of erratic behavior if the gap is too large.

Then re-check all your connections to see if anything is loose.

And one last thing. Unless Pertronix has changed their instructions, they can be mis-leading if you are looking at them for the first time.
Although the Ignitor can run off the same terminal/wire as the positive side of the coil, they want you to use a full 12 volts to the Ignitor. In other words, if you're still using a resistor wire (like a stock Bronco coil) or ballast resistor with your ignition, you need to hook the Ignitor to a different point in the circuit. Either BEFORE the resistor, or to a different circuit entirely, so it gets the full 12 volts to the new Ignitor.
Lower than expected voltage can do what you're experiencing too.

Paul

 

[DirtDonk]

Also make sure that your distributor had a good ground contact with the engine block. The clamp area should be clean and the clamp itself should be bolted down tight.
The part of the dizzy that resided inside the engine block is bare and should theoretically make good contact, but an older one can have a buildup of varnish on it and, along with the o-ring seal, might not make for a good ground contact with the block.
If you're ever not sure about how good the contact is, if you're still having a problem with the ignition and you can't find the trouble, try a temporary jumper wire to ground the dizzy to the engine (or anywhere else for that matter) and see if it helps.
I've personally never had a problem with a distributor not making good contact, but have heard it enough times to mention it.

Paul