Working on a 250 with pertronix has no spark going to 1 or 6. It won't make my timing light flash, 2-5 flashes just fine. It has new cap, rotor, plugs, wires. I tried moving the plug wires around and swapping with known good ones. I also moved the pertronix magnet rotor and checked the air gap. The miss stays on 1&6. Compression is 145-155 across all 6. This one has me scratching my head. Any thoughts?
250/pertronix miss
- Thread starter cobraguy
- Start date
Probably not this easy or simple a fix, but did you double, triple check the firing order 1-5-3-6-2-4 being that those two cylinders are 180* from each other it may be easier to mismatch 'em...BTDT 
Otherwise I have heard of issues with the magnets being loose in pertronix causing similar issues. Good luck
Otherwise I have heard of issues with the magnets being loose in pertronix causing similar issues. Good luck
Yup the firing order is right. I thought it was wierd too that the two dead holes are 180' apart. When my kid first brought the car over it would barely run. After doing the tune up and replacing the carb. The RBS had been rebuilt a couple of times and still the accelerator was wonky. Anyway, I found the vacuum advance was dead but had it running on all six. I set the base timing at around 18'-20' a little sluggish until the RPMs came up but drivable. He took it to work and came back the next day said it ran OK Going to work but like crap on the way home. The vacuum advance came yesterday and I installed it. Thats when I discovered the miss. My timing light wouldn't fire. I thought it was broken so I tried clipping the lead on #2 and it worked fine so I tested all the plug wires 1 and 6 don't fire the timing light. Unplugging either or both with the engine running has no change in RPM and I don't get the expected snap of the spark finding any ground. I pulled #1 plug it was carboned up so I cleaned it then connected the wire and cranked it to check for spark. It sparks but its weak and brown. Would a carbon fouled plug make my timing light not fire?
thesameguy
Famous Member
Did the problem occur before or after replacing the cap & rotor?
I ask because I have had some weird problems like this on Saabs, where the cap has been defective and the rotor literally won't reach two opposing towers. And I've had this issue multiple times with the same store-brand parts.
I ask because I have had some weird problems like this on Saabs, where the cap has been defective and the rotor literally won't reach two opposing towers. And I've had this issue multiple times with the same store-brand parts.
Check to see if the magnets have fallen out of the round holder that fits over the cam. The magnets are only taped in.
If all the magnets are there, try rotating the holder to see if the problem shifts to another cylinder. I'm not certain on a Pertronix, but some Hall sensors are polarity sensitive so if the magnets were improperly installed there might not be a signal that the pickup can see, hence no spark.
If all the magnets are there, try rotating the holder to see if the problem shifts to another cylinder. I'm not certain on a Pertronix, but some Hall sensors are polarity sensitive so if the magnets were improperly installed there might not be a signal that the pickup can see, hence no spark.
I can affirm that hall effect 'prox' sensors are polarity sensitive. North and South positions MUST be correct, they must be replaced correctly. Offten, the magnets are not visiably different. You have to check using another similar magnet.
Just recently on my road roughness machine, I had to remove and reglue all 288 magnets ...when I put them around the wrong way and my HE sensor wouldn't work.
Just recently on my road roughness machine, I had to remove and reglue all 288 magnets ...when I put them around the wrong way and my HE sensor wouldn't work.
I tried moving the magnet rotor but the miss stays on 1 & 6. None of the magnets is missing the green tape is intact. The car ran ok after getting the swap finished almost 2 years now. The accelerator pump had always been an issue. The car had sat alot in the almost 2 years with only occasional drives. He said it just got worse and quit driving it. Well I'm going to mess with it some more I'll let you know what I find or be back with more questions.
OK so I pulled all the plugs out and visually checked for spark. All plugs firing when cranking. I put the plugs back in and started it up. still runs crappy. I checked for the miss using my timing light now 3&5 aren't firing. I'd mixed the plugs on reinstall. Anyway grabbed two of the old plugs from the trash cleaned and installed them in 3&5. Tadah running on all six now. Idles good but when you take off it launches ok but has a big flat spot through 2500 to 3000 then just flattens out at 4000. I have a Carter RBS (Tomco rebuild) on it. Other then throwing a Jiffy kit in the old one I have no experience with this carb. Any way to dial it in better?
Congrats on tracking it down 8) ...speaking of 'tracking' [groan] :roll:
I'd check the cap for carbon tracks and replace if necessary...all that votlage had to discharge somewhere, and might have spent your cap or come back to bite you down the road.
Don't know much about the rbs...but maybe a accel pump shot or transition circuit issue, if not back to the ignition curve. RBS does have an odd pump (center bowl?...afaik). A member by the handle simon was a fan, and I think posted some info on them. Mike's carburetors has some good info in the 'tech' and 'free manual' section...
http://carburetor-blog.com/?page_id=182
http://carburetor-blog.com/?page_id=335
Good luck
I'd check the cap for carbon tracks and replace if necessary...all that votlage had to discharge somewhere, and might have spent your cap or come back to bite you down the road.
Don't know much about the rbs...but maybe a accel pump shot or transition circuit issue, if not back to the ignition curve. RBS does have an odd pump (center bowl?...afaik). A member by the handle simon was a fan, and I think posted some info on them. Mike's carburetors has some good info in the 'tech' and 'free manual' section...
http://carburetor-blog.com/?page_id=182
http://carburetor-blog.com/?page_id=335
Good luck
It also may be VERY lean , as 1 ans 6 are on opposite ends and are last to get fuel , try artificially giving it more fuel ( spray carb cleaner , or pull the choke flap on slightly
