510 with L20B

[Swampwild]

I have a barn find 72 510 with an L20B
I has no spark. The wiring has been brutalized in the engine compartment. Looks like they never got it right. In fact the starter wasn't even working as it had no ground. I have a good coil. Power from the ballast is good. There is only the 12V on the + of the distributor. I'm trying to paste some picks here but so far nothing works. If you look at the 510 wiring for an Lb16 and imagine an LB20 in there now, what advise can you give me? The last guy didn't even use the relay. From the LB16 diagram the BY wire from the relay should attach to P2 on the distributor. Is that just ground at the distributor? Looks like this relay is activated by a CARB SW. Is this not used now? Like its only vacuum? Also, is this ballast Res supposed to reduce the voltage? It doesn't go down from 12V. I'd rather not burn out my coil. Ignition checks out good.

[iceman510]

If you look at the 510 wiring for an Lb16 and imagine an LB20 in there now, what advise can you give me? The last guy didn't even use the relay. From the LB16 diagram the BY wire from the relay should attach to P2 on the distributor. Is that just ground at the distributor? Looks like this relay is activated by a CARB SW. Is this not used now? Like its only vacuum? Also, is this ballast Res supposed to reduce the voltage? It doesn't go down from 12V. I'd rather not burn out my coil. Ignition checks out good.

Sounds like the wiring for the retarded set of points may still be hooked up? Those can be eliminated.

The ballast resistor reduces normal voltage during running (black/white wire), ignition switch and wiring (black/blue merging to black/green) bypasses it in start position.

[Swampwild]

Thanks. The most confusing thing to me now that I read little more is how I should be wiring this distributor. Now I understand the ballast resistor and the ignition. But have a look at the 510 diagram for the 1.6. See the BR wire runs off the distributor. It goes to the negative on the coil and the P1 on the distributor. Also a BY on the P2 distributor cap going to the relay.

So are you saying the only wire to the distributor and cap is the BR with power? The negative off the coil BR to the relay isn't needed? The BY to the relay isn't needed either? Does the question make sense? And why is the L16 so different from the L20B?

[Swampwild]

I have spark now. Not sure yet if it's going to run because the firing order was wrong and I ran out of time and battery. Just goes to show the little car never ran after they dropped in the motor.

[510rob]

The differences between an L16 and an L20B? Federal emissions rules came into effect and then ramped-up over time, necessitating a bunch of tricks from the manufacturers, like dual point dizzys that have advanced or retarded timing depending on what gear you are in, whether you are on or off the throttle, etc...

[iceman510]

Disclaimer: I have never had a 510 that had/still had a dual point distributor or the relay intact and functioning, so somebody correct me if I am wrong.

Does the car still have the dual-point distributor? That's what P1 and P2 indicate on the diagram, two sets of points. If you remove the BY wire and route the BR only from coil negative to P1 it should work on the main set of points, eliminating the relay from the circuit. In static condition it should not matter as it should only operate the second set of point when driving (I think third gear as the sw on the diagram indicates).

The BR line is the is the circuit breaker that when the points open allows the high voltage of the coil wire to the distributor cap to fire. The system should function with just one set of points.

You have spark at the plugs when you ground one?

[Byron510]

I e only had one car with a functioning dual point system, and that was a long time ago!
The ignition system won’t care which motor it’s running on, the functionality won’t change.
As noted above, you’ll find that two + wires; one is hot when the ignition key is in the run position, the other wire is hot in the start position. The hot start wire was to allow a full 12V to the ignition system (bypassing the ballast resistor) with the ignition switch in the start position for a stronger spark, and switching to use of the ballast resistor with the ignition key in the run position, which will drop the voltage through the points giving them longer life.
The exception to the rule above is that 1968 cars did not have the ballast resistor. They have only one wire to the coil. But with out the ballast resistor, shorter point life is noted.
I also believe the dual point feature, which is an emissions related change, began in 1971 model Year cars. And as you can tell from the comments, most of these systems were bypassed for simplicity. In the 70’s through 80’s, changing to the use of just one set of points. In the 80’s, factory Nissan electronic distributors (EI) were readily available on newer models of Nissan products and most owners began upgrading to these units as they have longer reliability (no points to wear out) and stronger ignition spark. Today, you can buy EI conversion kits for your original distributor, or even replace the distributor with an aftermarket EI unit all together. But that’s not to say the OEM distributor won’t work, it will work just fine when set up. You just have a consumable set of points to maintain. My 68 L13 car still runs its OE point distributor.
Regarding your comment on photos, the site limits the photo to 250 kb, so the photos need to be reduced in size before submitting.

I hope the information above helps you. Please post some photos and post back on your progress.

Byron

[Swampwild]

Thanks everyone! This is great. It's single points. I'm using a timing gun to check for spark and it's there. Maybe if I'm really lucky the old girl will go today. I changed all the fluids. Hope I don't have to rebuild the carb. If it goes I'll be trying to tune it next.

[datzenmike]

The second set open 5 degrees later than the first set so the timing can be retarded at will this amount. What I would do is wire the second set on at all times and re adjust the timing on the opening of the second set. This way you have increased the dwell time by 5 degrees.

[Swampwild]

No luck starting it. I have spark going to each plug in the correct sequence. No misfires anymore. It is not firing most of the time. When it does it's backfiring through the Carb. I tried cleaning the jets. The float works, and I've got clean fuel going through. The spark plugs are wet after I try this. Each time. Some oil on them sometimes. I lost the adapter to my compression gauge so by finger test seems good. But I do have a leak down tester for 4 stroke motorcycles. I'm not experienced using it but here's what I think it tells me. With cold engine. My little tester says 95% all 4. What hear is Cylinder 1 -some slight exhaust, 3- some slight carb & exhaust, 4- slight exhaust, 2 -slight carb and exhaust. Nothing from the valve cover vent, no bubbles in rad., no air from other spark plug ports.
So question is, if it's the carb then why are my plugs wet? Lean creates backfire through carb right?. I should try this more and watch the plugs. Maybe I have to remove the valve cover and check and adjust the valves. Then look at the cam chain position. I'm suspect of the distributor. I can advance or retard it and the position plate doesn't move with the distributor. It's stuck in one place. My points and rotor seem fine, distributor cap looks good. The condenser is outside the distributor and looks pretty old.
Here's something you have to know. I have another L20B long block with a Carb that is supposed to be functional. It's on a pallet in storage. The carb is pretty different. I didn't want to strip it at all. My original plan was to pull out the motor that's in there and put the pallet one in. But the one in the car seems like it should work. I mean, I don't know why it won't go. I'd rather have two good working engines!
Look forward to your ideas. I'll find a compression tester but seems ok.

[James]

Have you set it to TDC, and does the rotor point to the #1 wire? Are you 100% on the firing order? Your problem is more than likely timing/ignition related. Its the most common issue.

[abisel]

The L20B in my 510 has a "matchbox" electronic distributor. See if you can find one and you can do away with the ballast resistor. Then have a much more stable spark for both start and run. Two wire hook-up with switched +12 volt and negative from the coil. Here are a couple links: http://datsun1200.com/modules/mediawiki ... e=Matchbox
and
https://ratsun.net/topic/50151-electron ... -matchbox/

[datzenmike]

It's L20B. There is no such thing as an LB20

If getting sounds out of exhaust or intake check the valve clearances. Although 95% sounds pretty damn good.

Set to TDC then back the engine up to about 10 or 12 degrees Before.

Pull the coil wire off the distributor cap and stick an old plug in the end. Have someone hold it against the head to ground it and where you can see and hear it. Loosen the distributor adjustment for setting the timing so the distributor can be rotated by hand. Turn ignition on. Rotate the distributor forward and back and you'll notice the spark jumps when you turn it clockwise Narrow this spot down by turning it slowly. Stop when the spark jumps. The ignition is timed pretty close, close enough to start it and you can check and set it perhaps more accurately once running.

[Swampwild]

Have you set it to TDC, and does the rotor point to the #1 wire? Are you 100% on the firing order? Your problem is more than likely timing/ignition related. Its the most common issue.

Yes, but I'm going to try turning it over with the starter while looking with the timing light. See if it's really firing right. I've seen carbs do strange things but only on small engines and old tractors.

[Swampwild]

The L20B in my 510 has a "matchbox" electronic distributor. See if you can find one and you can do away with the ballast resistor. Then have a much more stable spark for both start and run. Two wire hook-up with switched +12 volt and negative from the coil. Here are a couple links: http://datsun1200.com/modules/mediawiki ... e=Matchbox
and
https://ratsun.net/topic/50151-electron ... -matchbox/

Thanks, I'll be at the stage of buying stuff pretty soon I hope. It has spark at the plugs.