Calling on all SC ignition whisperers

[Harvs11]

Here we go again.   My cars been running fine for ages and today suddenly went to crap. 

Symptoms are loss of power, temp is up a little, slow, rough idle, misfire when trying to accelerate, backfire when the throttle is blipped.

I've checked a few basics like vac hose to dizzy advance is connected, rotor button moves so the advance mechanism isn't stuck, spark plug leads are all in place. The timing light didn't show up any great clues.  The mark on fan shroud was right between the two marks on the pulley.  As the revs get over about 3k it smoothes out a little and the advance increases but not much. 

There's plenty of spark as my still tingling/numb left hand can attest to. 

Any advice on what next to check will be greatly appreciated.  I don't have a multi-meter or vac. gauge so basic visual stuff, please.  

[Dreamr]

Blocked injectors?   ..... probably wouldn't account for backfire but "could" explain loss of power and rough idle .....

Never hurts to run some injector cleaner through. Not that cheap stuff from Supercheap either.

I read somewhere that "Subaru" branded cleaner from a dealer is the one to use ....

Next .....

[Harvs11]

I suspect either an electrical problem or vacuum leak as it started suddenly.  I haven't pulled the injectors or plugs but I will check them for uneven colour. 

[michel]

Sounds like it's leaning out - one cause of popping and backfiring . Vacuum issues and electrical amongst others.

is WUR ok and fuel pump?

i just put liquimoly cleaner through my 76 as it has been behaving in a similar though more distressing vein. 

Also Dizzy advance not fully functional - pulled and cleaned , lubed it. Checked it for correct function

Reset the dwell

found the CDI was working but not great. Swapped it for a rebuilt unit I had - 90% better, though a ground wire issue somewhere still. Recommended to get a partsklassic CDI, if issue not resolved.

checked system for vacuum. Used both smoke and vacuum set to exhaust and soapy water. Found some suspect plumbing. 

Been cleaning all the connections earth's etc to remove any trace of green death. Replaced some wiring.

Cleaned throttle body, air sensor plate and  bunch of parts ultrasonically - real dirty coked up 

running better, getting better electric supply though still need to do more work 

These been my issues as car had been losing power, popping backfiring and after first round of treatment began  to randomly power off. Which was inconvenient to dangerous. 

[Harvs11]

AFAIK the WUR and fuel pump are ok. They've never shown any problems (yet).  Even if they were playing up, I think it would only cause idle and mixture issues, not the misfires. Unless, of course, the WUR is the source of the vacuum leak and throwing out the ignition advance.   No points on this dizzy so no dwell. 

I've pulled the injectors. They are all clean and dry, not dribbling like an old man with prostrate probs. Plugs are all the same colour etc. 

The intake runner seals and gaskets were all replaced when the engine was out a couple of years back-this fixed a number of vacuum leaks. It's been tuned recently and was running clean and strong since.  The problems started suddenly so something has either cracked or fallen off.  Where do I start?

 

[81SC]

How does the shielded green wire from the CDI to the distributor look?

Is the green wire insulation cracked?

[Harvs11]

How does the shielded green wire from the CDI to the distributor look?

Is the green wire insulation cracked?

The wire casing looks in good nick. No cracks,   Soft enough to push a thumb nail into. 

[Fraz]

Maybe check the dizzy shaft bearing. Pull the rotor button off and see if the the shaft has any movement in it. 

Had similar problems as you (non P car) replaced all sorts of things until I found the dizzy bearing was shot which caused the rotor button to spin off centre.

Also check the connections to the wires to the fuse box in the engine bay, your symptoms are almost identical to my mates 3lt car. The connections were tight but had internal corrosion.

[Harvs11]

Thanks Fraz.  The shaft feels ok. No slop or rattling around.   As said above, the advance mech. moves ok and returns to its stop nicely.   The rotor tip and contacts are a bit fried but that could be a result of the poor running. 

Fuses under the cover in LHS of engine bay are all good.  

[Harvs11]

I checked the CDI box for it's telltale hum. More high pitched than I expected but I guess that's normal. ???

 Started OK after letting everything cool down.  As usual the idle settled after about 10 seconds but the misfiring is still happening.  You can hear it in the video. Sounds like a whip crack thru the air box. 

 

 

[Mezger Autosport]

You mentioned it's running warmer, this straight away points to either running lean/ ignition too far advanced. Then u said its misfiring, to start with that cap and rotor in the pics are too charcoal for my liking. Have you tested ignition leads, and are the correct ones fitted?

 

[Stew F]

Just a thought. Is the distributor cap sitting down properly?  I removed my cap to give the rotor tip a tidy up. I thought I'd put the cap back on properly. Started the car and it was misfiring. I rechecked the cap and found it was sitting up a bit on one side. Fixed it and all was well.

[Harvs11]

Leads are the original, externally shielded factory items.  I ran it in the darkened garage and saw no sign of cross sparking. Aside from visual I have no way to test them. 

[Harvs11]

 

@Stew F cap is on OK.  First thing I checked was for any loose leads etc.  It's usually a simple thing which trips us up. 

 @RI technical   timing was at about 3 deg btdc. Spec is 5 deg. 

[81SC]

I checked the CDI box for it's telltale hum. More high pitched than I expected but I guess that's normal. ???

 Started OK after letting everything cool down.  As usual the idle settled after about 10 seconds but the misfiring is still happening.  You can hear it in the video. Sounds like a whip crack thru the air box. 

 

Does the tacho needle bounce when the engine misfires or before the misfire?

 

[Harvs11]

 

I didn't notice any tacho. bounce.  It did seem a bit 'lazy' on the drive home though.  Maybe it was just the engine's reluctance to rev.  Dunno.  

[michel]

Harvs CDI can still hum, though be not as effective. Originally and wrongly I had thought its squealing everything's fine with the CDI, not so.

swapped it for a known good one (someone else's) significantly improved, so put my other unit in. Better than before, but not great.

get Cdi tested or borrow a mates. You obviously are going to tidy/replace rotor and cap.

 

 

[jnr356]

have you check the resistance in the plug connectors ?

[Harvs11]

Harvs CDI can still hum, though be not as effective. Originally and wrongly I had thought its squealing everything's fine with the CDI, not so.

swapped it for a known good one (someone else's) significantly improved, so put my other unit in. Better than before, but not great.

get Cdi tested or borrow a mates. You obviously are going to tidy/replace rotor and cap.

 

 

The CDI might be the culprit. I'm not familiar with a healthy squeal as opposed to a death squeal.  That rotor and cap is playing on my OCD 

have you check the resistance in the plug connectors ?

Do you mean the wiring to the CDI box or the spark plug leads?  I don't have test gear to do this but am getting it all checked out this week.  

[Fraz]

Any progress ?

[Harvs11]

Any progress ?

nothing today.   I'll update later this week.  

[Russ]

I'd be guessing at CDI or coil, might be worth finding someone local with a 'known good' setup and swapping both out - should only be a 5-10 minute job and then you can cross them off the list.

I'd work systematically back from your spark plugs (checking the condition of them by pulling out and looking, or changing them while you're in there) then resistance in the ignition leads (I'm pretty sure it should be 4000 across the complete lead, 1k in the wire and 3k in the connector with the resistor in it), then points (check gapping/condition), cap (check for corrosion), rotor button (check wear on top and tip), distributor postion/gear/lubrication, then CDI (wiring - will also interact with your tacho as mentioned in an earlier post as the CDI runs the tacho and if faulty will make the needle jump) and coil as mentioned above.

I got jack of troubleshooting and replaced everything from one end to the other except the CDI unit, the change was night and day and gave me piece of mind knowing when things were replaced.

it seems like an intake backfire so I'm thinking too much fuel and not enough spark.

 

[jb84911]

Here we go again.   My cars been running fine for ages and today suddenly went to crap. 

Symptoms are loss of power, temp is up a little, slow, rough idle, misfire when trying to accelerate, backfire when the throttle is blipped.

I've checked a few basics like vac hose to dizzy advance is connected, rotor button moves so the advance mechanism isn't stuck, spark plug leads are all in place. The timing light didn't show up any great clues.  The mark on fan shroud was right between the two marks on the pulley.  As the revs get over about 3k it smoothes out a little and the advance increases but not much. 

There's plenty of spark as my still tingling/numb left hand can attest to. 

Any advice on what next to check will be greatly appreciated.  I don't have a multi-meter or vac. gauge so basic visual stuff, please.  

Harvs if you need a multi-meter I can drop one off tomorrow

[Harvs11]

 

thanks JB.  PM sent

I'd be guessing at CDI or coil, might be worth finding someone local with a 'known good' setup and swapping both out - should only be a 5-10 minute job and then you can cross them off the list.

I'd work systematically back from your spark plugs (checking the condition of them by pulling out and looking, or changing them while you're in there) then resistance in the ignition leads (I'm pretty sure it should be 4000 across the complete lead, 1k in the wire and 3k in the connector with the resistor in it), then points (check gapping/condition), cap (check for corrosion), rotor button (check wear on top and tip), distributor postion/gear/lubrication, then CDI (wiring - will also interact with your tacho as mentioned in an earlier post as the CDI runs the tacho and if faulty will make the needle jump) and coil as mentioned above.

I got jack of troubleshooting and replaced everything from one end to the other except the CDI unit, the change was night and day and gave me piece of mind knowing when things were replaced.

it seems like an intake backfire so I'm thinking too much fuel and not enough spark.

 

Thanks Russ.  Plenty to check there.   Electrics are not my best suit,  I prefer mechanicals but I'll work through it and see what I can eliminate.  

 

Anyone in Sth east Melb. got a CDI box & coil gathering dust?

[Harvs11]

I checked the resistance in the leads tonight.  (Thanks JB) They range from 3990-3720 ohms. Close enough to 4K I suppose.  Checking the CDI box wiring requires tracing back each of the 6 wires. The label on the box was illegible so I've no idea what each terminal is. Not going there.  I'm more likely to disturb something else and make it worse.