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New Owner Need Help please


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Hello there!!

I recently bought a 76 Datsun 620 with the intention of fixing it up a bit and making it driveable 2-3 times per week.

So i started today by changing the fuel filter, spark plugs, spark plug wires, distributor rotor, and distributor cap.

After i changed everything the engine would turn over but not start.

Checked the chilton manual and switched the wiring to match the picture then it made a weird noise and there was a little smoke coming from the distributor. Thats when i decided i should stop before really messing something up.

I think my spark plug wiring is all screwed up or maybe i messed up the rotor???

Just to clarify: the #4 spark plug is located closest to the firewall and then the wire would be run from there to the corresponding socket on the distributor correct?

Im pretty lost and would appreciate any help i can get.


Im fairly new to cars and working on them so any help at all would be appreciated.


Thanks in advance for the help. I tried searching but couldnt find a thing.

Thanks again!!!

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Was this running before you swapp the capm wires ect.....????????sometimes putting in new points you eneded up groundeing soemthing out. Put the old stuff back in.


76 is a point distributor right? make sure points are gapped.


open the oil cap so ou can see the cam lobe. close to the 9 oclock position and dial the crank up to TDC zero on timminplate cover then where the rotor points on the distributor that will be # 1 and go 1 3 4 2 counterclockwise fire order.


this will help

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OK thanks for the quick replies!!!

It was running before i did all the changing of parts.


Banzai- What exactly do you mean by place near chassis ground??

Thanks again for your time help and patience. Im still just learning here.

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You are doing the right thing asking specific questions here on Ratsun. However, if you having seen this site: http://www.davidcmur...lddat/index.htm there is good tech info on 620s. You might skim those pages and see if there is something which might help you. Good luck! Probably something fairly easy, although it never is for me.



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the remote start will work also but rememebr to tell him to have the Key to ON.


620 coils is close to the drivers door. to reach in butt I DONT know if its like a 510/521 where its on the left hand side of steering wheel



mos ttime sif i swp points I installed them wrong (get no spark) the points where insolater is is grounding out of soemthing like that

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Good point Hainz.....yep, gotta have the key "on" to see if any sparks is happenin :)

Unlike the earlier trucks and the 510, the 620 has it's key switch on the right side of the st.wheel.......no go unless you're Elasta-dude and gots a strechie arm! :D



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OK so here is the update...I pulled the sparkplugs to see if they were gapped right and they were. When i took out #4 it smelled like gas and had black stuff all around it.

Got me kinda worried now.

Originally I had the distributor wires crossed up but now thats all good. There is spark from the distributor wire i unplugged it like suggested and tested in near a ground

Still not starting tho and im pretty sure i flooded the carburetor :(

Steep learning curve for me haha

What next???? Do i need to unflood the carb and get a new sparkplug?

This is fun im enjoying learning while i go.

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I don't know if spark plugs are different than "when I was a boy", or (more likely) modern gas with ethanol is to blame, but it seems to me it is really easy to foul plugs with gas to where they won't fire. I've had some success burning fouled plugs off with a propane torch, but buying new plugs is a safer bet. Most guys on Ratsun will tell you to get NKG plugs. A local mechanic here swears Autolites foul much easier than NKGs. First you want to be sure you have good spark to the plug and the float level in the carb is correct so you don't foul a new set of plugs. If you have a torch, it won't take long to try burning the plugs you have and see if the engine will fire. Or go a get new plugs.



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if this was running and you havent changed anything besides the cap ,rotor and points,plug wires.


try swapping out spark plugs. dont give it any gas or anything.



thats a bad ass truck. I would go over and help if I lived closer to keep this on the road.


Did you change the plug wires 1 at a time???????


if your positive you had good snapping spark. then its the plug wires but they look like the correct order if the rotor is pointing at TDC. valve lash maybe flooding out but you said only one plug was bad. The other 3 should still fire.

Put new NGK plug and dont give it anygas and see it it fires off.


after all that try just pouring a little gas in the carb and see if it fires.

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Im pretty sure its an L20b but when i look near the #4 spark plug i dont see any engine info. It looks like they soldered it where the info should be

I didnt change the points, just the rotor and i have no clue what TDC means or how to do that


Im gonna swap out the bad plug today and see if it helps.

When i switched the plug wires i got all confused so i ended up switching them all at the same time. They are back in the right place now

How do i know if the rotor is pointing at TDC? IM pretty sure i ended up not putting the rotor back in place exactly like when i took it off


Thanks for the nice comments and i hope i can have it running soon too

Hopefully wont need to see a mechanic

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When i switched the plug wires i got all confused so i ended up switching them all at the same time??????


this is a big clue.

If you just swapped the rotor and the cap this is good to know.

The rotor can only go on 1 way.


you can try the spark plug but i dont think that will be it.

I think you got the wires wrong.


you need to watch the vid I posted above. How to to TDC ? watch i watch it watch it watch it


But if your truck dont start. I think put plug # 1 where #4 is then go 3 4 2 counter clock wise like what posted on your fire wall it that might do it.


if your lazy just watch this part 6 ,my motor is already at TDC

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He has never done this before hainz, the wires are messed up, the trouble is that he doesn't know where TDC is, and he doesn't know about cam lobe position on #1 cylinder either, so basicly he is lost.

First thing that has to be found is TDC(top dead center), there is a pulley(what the fan belt goes around) on the bottom front of the engine, it has a mark/notch on it, you are going to have to find that small notch, there is also a small plate near the pulley that has marks on it, one of the marks is a "0", you are going to line the notch up with the "0".


Now you will have to remove the valve cover, there is a cam going the length of the engine that has lobes on it, the photo below is of a cam lobe, see how the shiny part is shaped like a egg and sticks out from the cam shaft.


Number 1 cylinder has 2 lobes, one for the exhaust, and one for the intake, the but the lobes need to be pointed at 10am and 2pm, in other words, pointed slightly up evenly, if they are not pointed up, you will have to turn the engine over one complete turn so the lobes will be pointed at 10am and 2pm, see photo below.


Now after it is at TDC, you will pull the distributor cap off and look at where the rotor is pointed, that will be number 1 cylinder plug wire, the next dist. cap post going counter clock wise will be #3 wire, next is #4, and the last is #2, the center post is the coil wire, that needs to be connected also.

Now if everything is the way I just described, engine at TDC, cam lobes at 10am and 2pm, and #1 plug wire is where the rotor is pointed, and 1, 3, 4, 2 is the firing order counter clock wise, then put the valve cover on by removing the distributor cap, remove the coil wire, and lay the cap on the battery so the wires are out of the way, install the valve cover, make sure the rotor is on, put the dist. cap back on, put the coil wire back on.

This engine should start now.

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most L20s I seen the rotor will point in the back if spindal is installed correct at TDC. Dosent mean it is .

But swapping the wires is about a 30 sec job. then he can lean about TDC.

also one doesnt need to take the valve cover off

Just open the oil cap. dial the motor up till you see that LOBE right there till about 9 oclock poisition then look at the crank timming mark and dial it up to Zero. The lobe should be close to 10 o clock. This is TDC comp stroke. then look where the rotor is pointing at. That will be assigned the #1 plug spot then go 1 3 4 2 counter clock wise.

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So today i went and found the pulley to turn but saw one problem. Looks like a tight squeeze to manually turn it.

Do you remove the bumper and radiator? Is there some trick to it??

Thanks guys. Hoping to tackle this tomorrow.


you need to find a way to turn it, you can use the starter, but it is difficult to get it to the timing mark that way, I generally use the belt and fan blade to turn the engine.

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