Datsun 620 engine doesn’t start

[WhiteRed]

The thing is, I’ve done a rebuild to the engine L20B of a Datsun 620 1976 but the mechanic hasn’t been able to start it properly. Right after the engine was mounted on the truck, the engine was able to work for about 3 hours but suddenly it turned off and the choke valve of the carburettor got stuck. The mechanic took it to his garage and fixed it and it did it maintenance. After that, the carburettor was mounted on the truck but couldn’t been able to get it work properly because the engine doesn’t start it only try to start but won’t start and it get a lot of explosions while trying to start it, but for a brief moment the engine worked but it was right, it sounded very weak and went off. I’m wondering what is making that the engine won’t work. Could be the engine is out timing? Or the firing order it’s not correct? Can anyone know what would it be the problem?

Note: the tank is full, the pump it’s working properly and it got good fuel pressure.

[datzenmike]

If it ran for 3 hours then it's more or less set up properly. After removing and installing the carburetor it's not starting, so start there.

 

Make sure that there are no vacuum leaks between carburetor and intake. This is the stock Hitachi carburetor??? Or Weber???

 

 

You'll need the choke on for cold starting. The choke flap should be fully closed. Pump the gas a couple of times first.

 

 

 

[WhiteRed]

17 hours ago, datzenmike said:

If it ran for 3 hours then it's more or less set up properly. After removing and installing the carburetor it's not starting, so start there.

 

Make sure that there are no vacuum leaks between carburetor and intake. This is the stock Hitachi carburetor??? Or Weber???

 

 

You'll need the choke on for cold starting. The choke flap should be fully closed. Pump the gas a couple of times first.

 

 

 

Ok, I’ll do that, and it has an original Hitachi carburetor.

 

Today, I was looking the spark plugs cables and I noticed that the firing order it’s set as 1-2-3-4, but in the Datsun 620 of 1977 manual says that the firing order is 1-3-4-2. I’m wondering if that could be the cause that the engine hasn’t worked?

[banzai510(hainz)]

On 4/3/2026 at 12:12 AM, WhiteRed said:

Today, I was looking the spark plugs cables and I noticed that the firing order it’s set as 1-2-3-4, but in the Datsun 620 of 1977 manual says that the firing order is 1-3-4-2. I’m wondering if that could be the cause that the engine hasn’t worked?

It wasnt running just by Magic!!!!!!!!!!!!!!! 3 hour mean it was set up correct.

 

1 is front plug 2 and 3 then 4  is in the back 

 

1 3 4 2 is coubter clock wise fire order.

 

 

On 4/2/2026 at 12:25 AM, WhiteRed said:

mechanic hasn’t been able to start it properly

Hes a mechanic he should know himself. what the fuck  pay you mother fucker!

Have spark ? take center coil wire out of dist and place near ground and see if sparks when hiting the starter. should get spark. If not look at points . wires hooked to coil plus minus?

Have gas?. cycle the carb linkage by hand and see if gas squirting in main barrel. Mean you have gas.

recheck the valve lash. lash pad fell out

ws the oil pump fill with oil before intial start up and had oil pressure. I assume yes otherwise it be fried already

 

points adjusted? if still points then check the condensor. is tight.

 

intake manifold bolts snug? carb bolts snug.

 

this is a simple motor. Bushmen in Africa keep these going for fun

 

I approve this message

[Rustbin]

5 hours ago, banzai510(hainz) said:

this is a simple motor. Bushmen in Africa keep these going for fun

 

@banzai510(hainz) you been watching Rat Rods for Africa on You Tube?

[datzenmike]

All 4 cylinders are 1, 3, 4, 2. Or all that matter.

 

If you suspect the condenser just disconnect and try it. Put back if doesn't help.