Bad Plug Wires Or Bad Luck?

[Mike Soda]

Recently I was finally able to bring home my rusty Spring Green 1978 Datsun Deluxe 620 from a friends house where it was slowly being worked on. It's still very far from complete but I was at least able to drive it safely. That is until I discovered the wiring shorts in the steering column made my taillights intermittent at best. That's not my main issue now though, but did lead up to it. That night on the drive home my mom who was following me panicked, claiming sparks were coming out from near the left rear wheel. I checked all underneath & due to the previously mentioned known shorts, figured some wires were to blame.

 

The next day however my father who was also following me was able to confirm that they were in fact coming from it's exhaust. The truck still sounded fine to me so I didn't think it was anything major, since Google lead me to believe it just might be running rich. I know that can foul plugs though so this morning I pulled them, 1 at a time to ensure I didn't mix em up. The last plug, or perhaps the first I'm unsure of order (the plug closest to cab) is very fouled out, rest are fine. I hadn't run it since the night before but now, after removing & putting back the plugs & wires it runs terrible. Being me I doubted myself & proceeded to swap the plugs around, 2 at a time in the reverse order I checked them in, hoping to find the right combination. All of them except one ran worse & that in particular ran as bad as what I originally thought was the correct order.

 

I'm not sure if maybe one of the wires was defective or on it's way out when I first removed it & that's the cause. Neither should be true though as they're only about a year old with not very many miles. Can a plug become severely fouled out from 1 night to the next? Could it be I still have them in the wrong order? I'm just really confused how it can go from running fine but not perfect to sounding like it's falling apart, a mile drive, 24 hours & a spark plug inspection later. I do have a short video clip of what it sounds like in addition to pics of it's bad plug compared to a good 1 in another cylinder. I'm new here though & have yet to figure out how to upload pics or videos on this forum. My friend who helped me do all of the work on the Datsun prior may be able to assist soon but is currently out of state. So any advice y'all can give we'll greatly appreciate it & my apologies if I'm unable to respond right away. This just had to happen while my family is in the middle of moving & dependent on a truck. So we'll probably have to rent another for that but I'll still check back here as often as I can every night because my rust bucket still needs to be running ok soon again for work.

[]2eDeYe]

Sounds like you may have the wires mixed up. This is more important than the spark plugs themselves. Wire order is the firing order.

[datzenmike]

Can you set the engine to TDC firing stroke on the #1 (front) cylinder??? Take the valve cover off and use the starter to turn the engine till the front 2 bumps (lobes) on the cam are at 2 o'clock and 10 o'clock as seen looking at them from the front of the engine. Try to get as even as possible.

 

Now pull the distributor cap off and look at the rotor cap. It should be pointing near to a wire on top of the cap. Call this #1 and follow the wire and make sure it's going to the front or #1  spark plug. Now move to the next wire in a counter clockwise direction. This wire goes to the 3rd plug from the front, The next wire to the 4th or rear most spark plug, and the last wire to the #2 plug. Your plugs are now in proper firing orger. Clean the dirty plug and try it.

[Mike Soda]

On 2/26/2020 at 4:35 PM, ]2eDeYe said:

Sounds like you may have the wires mixed up. This is more important than the spark plugs themselves. Wire order is the firing order.

 

23 hours ago, datzenmike said:

Can you set the engine to TDC firing stroke on the #1 (front) cylinder??? Take the valve cover off and use the starter to turn the engine till the front 2 bumps (lobes) on the cam are at 2 o'clock and 10 o'clock as seen looking at them from the front of the engine. Try to get as even as possible.

 

Now pull the distributor cap off and look at the rotor cap. It should be pointing near to a wire on top of the cap. Call this #1 and follow the wire and make sure it's going to the front or #1  spark plug. Now move to the next wire in a counter clockwise direction. This wire goes to the 3rd plug from the front, The next wire to the 4th or rear most spark plug, and the last wire to the #2 plug. Your plugs are now in proper firing orger. Clean the dirty plug and try it.

Thank you both & I'm sorry for late reply, move has been hectic. I'll try that tomorrow! I forgot to add it's an L20B.

[banzai510(hainz)]

1 3 4 2 counter clock wise fire order

 

one don’t have to remove the valve cover just open the oil cap and look at the lobe and the lobe should be close to the 10 o clock position will be close to TDC and just move the crank to zero notch.then look at the distributor rotor position which should be close to #1.

maybe you need to adjust points or condenser if still running a point distributor. 
 

how about YouTube Datsun L Series

Edited February 29, 2020 by banzai510(hainz)

[wayno]

Are you sure it was sparks coming out of the exhaust?

Did these sparks bounce on the ground?

 

One time a long time ago in another life I was in a gas station parking lot transferring hanggliders from one rig to another at 11pm on a Sunday night(it was very dark out), this vehicle came in and started putting water into the radiator, the engine had a obvious miss, the driver started revving the engine up fairly high over and over and sparks started coming out the the exhaust pipe and bouncing all over the ground in sort of an alluvial fan shape, these little sparks were bouncing 20/30 feet before burning out, we were laughing are asses off, I thought/think I knew what was going on, the engine piston rings were disintegrating right in front of us, fact is the engine ran fairly good by the time the show was over with, I serious;y doubt that engine ever ran right again, it still had a miss when they left but it did sound a little better than when it was having the living shit revved out of it.

Edited March 1, 2020 by wayno

[datzenmike]

If the exhaust was badly carboned up from too much choke and it caught fire it would spit glowing pieces. wayno that's a 'Tijuana tune up'.... dumping water down the carb while revving it up. You've seen how clean a piston is when a head gasket blows and water gets in. You have to have the engine parts HOT and the water explodes to steam and the carbon flakes off. The cheapest  tune up there is. Best way is to use the hose from the windshield squirter and put down the carb throat. Go for a high speed run.

[Mike Soda]

Update I found out what happened, floated a valve & bent a rod. Unsure if it cracked a piston yet.

[datzenmike]

That's..... impossible. If you have a bent rod you would already have seen the piston and a valve impression in the top. No valve is going to bend a rod, it will bend first. If your friends are telling you this they are just guessing. 

[wayno]

I believe they were putting water in the radiator Mike, maybe it had a blown headgasket, it was dark enough that if water did come out of the tailpipe we could not have seen it, them sparks were bouncing a long ways, it was like a fireworks show, like someone was grinding on a piece if metal, it was freaking hilarious to watch/see, if it had not been for the whiplash pain I was starting to have from a head on auto accident I was in(passenger) that would have been a highlight of my life, it still is, but not an entirely positive memory, I was in pain for a year, but when I laid down to sleep or fly my hangglider I was fine, but sitting in a vehicle for any length of time was torture, almost made the 70-100 mile flight not worth it, especially if a lot of other pilots made the flight also and the truck was cramped/filled with pilots to the point there was no room to move around into a different position, pure torture, this happened in the summer of 1989 and that pain is still vivid in my mind, I ended up in the emergency room the next day, I originally thought it was heartburn from eating Frito's corn chips.

[Mike Soda]

On 3/6/2020 at 8:58 AM, datzenmike said:

That's..... impossible. If you have a bent rod you would already have seen the piston and a valve impression in the top. No valve is going to bend a rod, it will bend first. If your friends are telling you this they are just guessing. 

We'll see once they get time to take it apart.