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240 Carbed 240, Only 2 Cylinders Firing?

simmy_binker

winning!
Joined
Dec 19, 2007
Location
Hamilton, Ontario
Hola all,

I'm back.

Got this 240 and it doesn't like to utilize all 4 cylinders. #1 and #3 have no boom boom. This was determined by removing the spark plug line to each of these, and the very rough idle did not get any worse than it already was.

The funny thing is that if I partially remove the spark plug line, and lay it strategically on the plug, it DOES bring those cylinders back. keeping in mind, I cannot see under the black rubber jacket, but I am just touching the electrode to the top of the spark plug.

I'm nearly certain that a few days ago it DID have all 4 cylinders. or at least more than 2.

These are new spark plug lines.

And I've got big jumper cables from the block to the negative terminal of the battery to rule out the dinky grounding strap.

Thinking it may still be the spark plug line, I swapped #1 and #2 lines (on both the plug and the distributor), and still #1 did not fire. I checked the gap on #1 spark plug, and it was 0.030".

Thoughts? I'm sure it's an easy fix but my brain isn't working.
 
More info:

It's actually if I remove the lead off the spark plug terminal, and ensure there is a gap. that is, If I'm touching the wire to the spark plug, it doesn't fire. and if I'm too far away, of course, it doesn't fire. Increasing the gap doesn't change the timing does it? I am changing the resistance over the electrical circuit - how does increasing the resistance make the spark plug fire?
 
rotor and cap is new (previous owner installed). No idea on ignition system - it's a 1982.

Under the assumption that pulling the plug wires away from the plugs artificially "delayed" the timing, I then assumed that delaying the timing on the distributor will fix my problems. after a little meddling.... I can't get it to start now :/. I may have flooded it in all my monkeying around - so I'm going to let it sit for a bit.

If I line up the harmonic balancer with 12*, can I line up the distributor arm with the marking on the side of the housing and assume it's close enough to at least get it fired up, so I can drive it to a professional? Unfortunately I don't own a timing light, and none of the local shops rent them out with Covid and all.
 
That won't delay the timing, at least not to any extent measurable by normal equipment. It will, however, build up a bit more of a voltage spike.

I'd think that your ignition system in general is perhaps a bit weak. And that there's something a bit off on either those spark plug wires or the plugs themselves. Try moving the plugs to another cylinder, see if the miss goes with them. Clean and regap while they're out.

Also possible there are other issues with those cylinders - like some low compression? But from what you've said, I'd be sniffing around the ignition system first and foremost.
 
Can you cut off the fuel to the carb? If so pull the plugs and crank it and let it air out, go buy some new plugs for$12usd or $30cad and gap them correctly then try it again.
 
yeah - the leads are new, and I've swapped the leads and the problem persisted on #1 and #3. I checked the gaps on them and they're fine.

ok... now I've got another issue. I have no spark at all now. After messing with the timing a bit, it simply shut off, and wouldn't fire back up - even if I put the timing back to where it had originally been. I assumed the cylinders were flooded, but upon removing the centre lead off the distributor and holding it close to ground while cranking, there is zero spark from the capacitor.

could adjusting the timing have stressed the electrical system enough to have caused a component to fail? and if so, which one is most likely as culprit? when you mention the "ignition system is a bit weak" - which component would cause this, and need replacing?
 
It's a stock B21A

There are 3 skinny wires going to the coil; one brown on the + side, and two black on the other. When the ignition is off, the brown wire has continuity with ground. When the ignition is on, the brown wire supplies 12V.

The black wires are neither continuous with ground or 12V in either key position. When plugged into the coil, these will float and do whatever the brown one does.

That is, with the ignition on, there is no voltage drop across the coil. I have 12V at both terminals.

Does anyone have a wiring diagram for upstream of the coil? I suspect one of these black wires should be pulling down to ground.

I checked the resistance on the coil, and it is fine.
 
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thanks man! I actually found that exact same manual just a few minutes before you posted it!

Found the source of my no-start condition; the small spade connector (black wire) coming off the side of the distributor that is connected to the points was corroded. My hand was on it or near it when the vehicle quit - so this makes sense.

I also found an old TB thread where someone said with confidence that you must use spark plug wires which are intended for vehicles with points. Vehicles without points run on electronics, which must be shielded from the high voltage noise from the spark plug lines. These lines have shielding which is great for electronics, but if you use it on the vehicle with points, you'll get a weaker spark with the greater resistance. Which seems to be my issue. So I guess I'm going to go on a hunt for different spark plug wires...

well, after cleaning up that spade connector, it did attempt to idle rough for a bit - so this I took at a win. I shut it off, put it all back together, and tried to fire it up again, and it's back to not even firing up. However, I have confirmed I do have spark now. so THIS time it's probably flooded. I did remove ALL the spark plugs, inspect, let it air out - but still no start.

I'll try again tomorrow as it's gotten too ****ing cold to work on it.
 
thanks man! I actually found that exact same manual just a few minutes before you posted it!

Found the source of my no-start condition; the small spade connector (black wire) coming off the side of the distributor that is connected to the points was corroded. My hand was on it or near it when the vehicle quit - so this makes sense.

I also found an old TB thread where someone said with confidence that you must use spark plug wires which are intended for vehicles with points. Vehicles without points run on electronics, which must be shielded from the high voltage noise from the spark plug lines. These lines have shielding which is great for electronics, but if you use it on the vehicle with points, you'll get a weaker spark with the greater resistance. Which seems to be my issue. So I guess I'm going to go on a hunt for different spark plug wires...

well, after cleaning up that spade connector, it did attempt to idle rough for a bit - so this I took at a win. I shut it off, put it all back together, and tried to fire it up again, and it's back to not even firing up. However, I have confirmed I do have spark now. so THIS time it's probably flooded. I did remove ALL the spark plugs, inspect, let it air out - but still no start.

I'll try again tomorrow as it's gotten too ****ing cold to work on it.

You might be able to grab a generic V8 non-resistor core plug kit from your local autoparts store.
Then you'll have another spare set of wires that you'll probably never use :lol:
 
Good thinking! thank you.

Yeah, I want to give this ignition system every chance it can get. Any other ideas for a strong, girthy spark? I need it to last for longer than 4 hours.

Does anyone have a troubleshooting guide or procedure for getting this thing idling and running well? I take it one sets the timing first, and then adjusts the carbs second.
 
Hola all,

if I partially remove the spark plug line, and lay it strategically on the plug, it DOES bring those cylinders back. keeping in mind, I cannot see under the black rubber jacket, but I am just touching the electrode to the top of the spark plug.
This much information should lead you directly to 1.)Coil 2.)spark plug wires 3). plugs. Your test delays the plug firing just a bit. Thus, the coil has more time to build up a larger voltage. Wimpy coil, leaking spark plug wires, clogged plugs.


-L
 
If the ignition system uses points, clean them. Like file/sand them. I recently had a very weak spark on our ancient forklift on the farm. It was just from the points with some carbon build up on them.
 
Look into a Pertronix kit to get rid of those points. A friend told me once you can gap the points with a dime if they get out of adjustment on the road.

A dime is real thick! Usually the gap is 0.016-0.020? for most points systems I?ve worked on.
Business card folded over twice works well too :)

And 100% get rid of the points!
 
I swapped my B21A dizzy over from points with a genuine pertronix and never looked back. There are TONS of cheaper chinese copies, but I figured why not splurge on the name brand this time. I was running a Bosch blue coil for a while, but then swapped to an MSD box with an LH2.4 potted coil. I've got the plugs gapped at 0.045" and so far not a single stumble.
 
Well, talking about electronic ignitions is great, once you find your real problem. Everyone here is assuming that the OP has actually looked at all the connections - oops a corroded distributor wire, checked the plugs, checked the spark wires for fraying, cracking insulation loose end clips, checked the condition of the points contacts, verified that the coil gets 12 volts during start and so on. Nothing here will change if you put in a mag pickup except it will eliminate the points from the equation. How about the distributor cap - is each of the 4 contacts intact? Turn the engine to TDC on #1 and confirm that the rotor points to the #1 terminal and #1 wire. If the rotor is NOT pointing to the #1 terminal, then the distributor has been installed incorrectly. Then after everything is running you can think about a mag pickup or an optical system.
-Lazarus
 
Thanks all,

I believe I've mentioned it twice above, but these are new spark plug lines. spark plugs are new and gapped properly. I mentioned above that the cap, rotor and coil are new, but I'm not so sure about that now. In any case, I've cleaned any carbon off them - they're in relatively good shape. I recently even took a piece of fine grit sand paper and fed it between the points for a quick buff. They look fine besides.

The problem seemed to be the spark strength. Very weak, and could be artificially made better by increasing the gap between my coil wire and the plug.

In any case, I finally took it to a real pro mechanic. Within 30 minutes he had it back up and running. turns out it was the condenser (small cap on the side of the distributor). It was one of the only pieces that I didn't have a spare for - and this guy is a Volvo shop - so he's got lots of spares to swap out.

Other things I've learned is that there is an internal resistance to the coil, and a resistance to the spark plug lines - and it's not as simple as saying "go as low as you can for a car that has points". The proper lines should be matched with the coil. The lines that are currently on the car are ~2000 ohms, the ones that were original/older were up around 5000 ohms (and required you to unscrew the cap on the end of the spark plug), and I took the advise of someone on TB and picked up a pack of eight for a 1970s Ford engine. This definitely would have had points, and their resistance was up around 13000 ohms.

If anyone has more information on the resistance of the high voltage system; please send it along. Because it all seems like magic to me.
 
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