Anyone help me out on this one?

[Datsun84]

1984 Nissan 720 2.4 Manual 

 

Ive been on here a couple times and just wanted to see if anyone could shed some light on where I am, because I’m stumped… 

 

Cranks and cracks and puffs white smoke, I’m getting spark, fuel, and air. I am getting low compression but not enough to think it shouldn't start… one area I’m stumped is there a filter on top of the gas tank that won’t fill up with gas.

 

 Things I’ve checked and done

 new gas, spark plugs, carb, have timed it advanced stock and retarded, I’ve pour carb and starting fluid down the carb and gas. Changed most of the fuel hoses except for the one with the filter on top of the gas tank, still need to change those but it’s not getting gas there anyways from the above comment, it has the correct firing order, most all of the emissions are all plugged off. Coils both tested good on primary and secondary…

 

anyone?

[ggzilla]

Time to do the fuel pump tests, which will test the filter and lines at the same time

 

oh, wait 

1 hour ago, Datsun84 said:

I’ve pour carb and starting fluid down the carb and gas

So after cranking, it didn't fire up? It won't run but a second on starting fluid, but if it doesn't even do that, you have an ignition problem

[datzenmike]

You say you have fuel (I assume at the carburetor) so not the pump or that filter. Fuel filter not showing fuel really doesn't mean much. 

 

You say you have puffs of white smoke so ignition must be firing at least some of the time.

 

 

 

Low compression??? Got numbers? Always write them down. Are two adjacent cylinders lower than the rest???? For example 140, 110, 115, 140? The Z24 is known for blowing the head gaskets. If between two cylinders it's sharing compression losses and won't fire properly.

 

 

 

 

[Datsun84]

9 hours ago, ggzilla said:

Time to do the fuel pump tests, which will test the filter and lines at the same time

 

oh, wait 

So after cranking, it didn't fire up? It won't run but a second on starting fluid, but if it doesn't even do that, you have an ignition problem

it’s a new fuel pump, should I still do one?

[Datsun84]

2 hours ago, datzenmike said:

You say you have fuel (I assume at the carburetor) so not the pump or that filter. Fuel filter not showing fuel really doesn't mean much. 

 

You say you have puffs of white smoke so ignition must be firing at least some of the time.

 

 

 

Low compression??? Got numbers? Always write them down. Are two adjacent cylinders lower than the rest???? For example 140, 110, 115, 140? The Z24 is known for blowing the head gaskets. If between two cylinders it's sharing compression losses and won't fire properly.

 

 

 

 

I’m gonna go ahead and do another compression check and get back with you… I’ll keep this post updated on when I get everything ready. There is a tab on the distributor wires like looks like a ground with a tab and not hooked up. What is that? I plugged it up and grounded it and didn’t change anything 

[Stinky]

White smoke is water.

 

Blue smoke is oil

[datzenmike]

Black 'smoke' is choke on or flooding over rich

 

EVERYTHING grounds through the distributor, usually the mounting bolts and the case. Some later distributors has a dedicated ground wire just to be sure,.

[Datsun84]

5 hours ago, datzenmike said:

Black 'smoke' is choke on or flooding over rich

 

EVERYTHING grounds through the distributor, usually the mounting bolts and the case. Some later distributors has a dedicated ground wire just to be sure,.

thanks Mike, so I’ll see if I can ground that… I took a spade connector and plugged it in the tab and grounded it but it didn’t change anything, I’ll try and find a bilt for it and get it grounded. Could that be the issue? Also I’m going to do a compression test and get back on tonight and give you guys specs

[datzenmike]

If no change then it was grounded. The extra terminal is just Nissan insurance.

 

Take the top off the air filter and hold the choke flap open. Have someone pump the gas peddle. If there is a stream of gas from the accelerator pump then fuel is getting to the carburetor. If you have a stock Hitachi carburetor look for the fuel level in the round sight glass on the front face of the carburetor body.  Got fuel?

 

Take a plug wire off the intake side, put an old spark plug in the end and hold against the grounded head. Have someone try to start the truck. See any spark??? Now do one on the exhaust side, got spark??

[Datsun84]

Here are the compression numbers….

 

1. 75 

2. 125

3. 125

4. 125

[Datsun84]

I have spark on all plugs, when removing the plugs they smelled like gas. Intake side. I am getting gas took the plate off the carb up front and hose next to the carb and it’s getting gas from the gas tank and also into the carb

[Datsun84]

Also, it’s a Amazon carb… had good ratings, I know it was just a quick by to see if I could get it started lol

[ggzilla]

75 is ultra-low. Perhaps why the white smoke, may be a backfire through the valve. The valve may be sticking. Does the smoke come out the air clearner, or out the tailpipe?

 

If it was me, I'd revoved the rocker cover, turn the engine to the TDC mark, and check the valve clearance for #1. If the clearance is way wide instead on one valve possible you could free the valve up by tapping it?

[Datsun84]

18 minutes ago, ggzilla said:

75 is ultra-low. Perhaps why the white smoke, may be a backfire through the valve. The valve may be sticking. Does the smoke come out the air clearner, or out the tailpipe?

 

If it was me, I'd revoved the rocker cover, turn the engine to the TDC mark, and check the valve clearance for #1. If the clearance is way wide instead on one valve possible you could free the valve up by tapping it?

I’ll check that. Quite odd to be 75 and all others be 125. And that would make sense, I’ll bring it to top dead center and check what the valve lash will be.what are the specs? Can I check exhaust and intake at too dead center? I’ll remove the rocker and see if she is stuck

[Datsun84]

38 minutes ago, Datsun84 said:

I’ll check that. Quite odd to be 75 and all others be 125. And that would make sense, I’ll bring it to top dead center and check what the valve lash will be.what are the specs? Can I check exhaust and intake at too dead center? I’ll remove the rocker and see if she is stuck

also the smoke comes out of both

[ggzilla]

TDC with the distributor rotor pointing to #1 spark plug wire. If pointing to #4, rotate a full turn to TDC again

Yes, check both intake and exhaust valve at TDC for #1 cylinder

 

The spec is 12 thousands inch. If you have less clearance that can also cause low compression

 

With stuck valves I have encountered it was more like 25 to 40 psi in one cylinder

 

 

for a full clearance adjustment see

 

[Datsun84]

10 minutes ago, ggzilla said:

TDC with the distributor rotor pointing to #1 spark plug wire. If pointing to #4, rotate a full turn to TDC again

Yes, check both intake and exhaust valve at TDC for #1 cylinder

 

The spec is 12 thousands inch. If you have less clearance that can also cause low compression

 

With stuck valves I have encountered it was more like 25 to 40 psi in one cylinder

 

 

for a full clearance adjustment see

 

thanks brother, I’ll try and see if I can do that. I also finally ordered me a timing light, I almost wonder if my buddy even timed it right… cuz he was just listening and using a timing light. He did advance it. Anyway sorry,

 

I’ll check the clearance on it, distributor rotor is inside the top case correct? And point it to TDC?

[ggzilla]

* turn the crank pulley to line up the 0 mark

* distributor rotor is visible after removing the distributor cap

 

 

 

Initial ignition timing can be done by 1) turn the crank pulley to line up the 5 mark, then 2) remove distributor cap and check if the toothed thing is lined up. If not, loosen the distributor bolt and rotate distributor to line it up. Later after you get it running you can check it with the timing light

 

lined up (yellow arrow points to the two pieces lining up)

[Datsun84]

34 minutes ago, ggzilla said:

* turn the crank pulley to line up the 0 mark

* distributor rotor is visible after removing the distributor cap

 

 

 

Initial ignition timing can be done by 1) turn the crank pulley to line up the 5 mark, then 2) remove distributor cap and check if the toothed thing is lined up. If not, loosen the distributor bolt and rotate distributor to line it up. Later after you get it running you can check it with the timing light

 

lined up (yellow arrow points to the two pieces lining up)

thanks man!! I’ll try and get to it tomorrow, and keep everyone posted. Hopefully we can get this thing started

[Datsun84]

So put it at the 5 inbetween the 0-10 and check the dizzy and then make sure it lines up with the like the one with the arrow… is there a chance I have to remove it? Incase it doesn’t line up? As if the teeth are off inside, or it should just line up?

[frankendat]

On 6/8/2025 at 10:05 PM, Datsun84 said:

1984 Nissan 720 2.4 Manual 

 

Ive been on here a couple times and just wanted to see if anyone could shed some light on where I am, because I’m stumped… 

 

Cranks and cracks and puffs white smoke, I’m getting spark, fuel, and air. I am getting low compression but not enough to think it shouldn't start… one area I’m stumped is there a filter on top of the gas tank that won’t fill up with gas.

 

 Things I’ve checked and done

 new gas, spark plugs, carb, have timed it advanced stock and retarded, I’ve pour carb and starting fluid down the carb and gas. Changed most of the fuel hoses except for the one with the filter on top of the gas tank, still need to change those but it’s not getting gas there anyways from the above comment, it has the correct firing order, most all of the emissions are all plugged off. Coils both tested good on primary and secondary…

 

anyone?

I am not an expert by any means, but I have an 84 720. To run the engine needs gas, air, and spark. If the air cleaner is off and carb exposed, then you have air. Starting fluid in shot into the carb gives gas (as long as you didn't over do it) Try to start it, wait a minute and try again to be sure. If air is good and gas is good, that leaves spark. That is where I would focus.

HOWEVER, white smoke usually means you are burning oil. Add that with low compression and your head gasket could be blown. Check your oil for water and check coolant level. If the head gasket is blown, starting is unlikely, spark or no spark. 

That would be my next steps, if those smarter disagree, listen to them

[frankendat]

Shit. I only replied because it came through my feed and said no one replied. Then I reply and many replies show up (a bunch better than mine) Man what a jip

[ggzilla]

6 hours ago, Datsun84 said:

is there a chance I have to remove it? Incase it doesn’t line up? As if the teeth are off inside, or it should just line up?

It is unlikely you will have to remove the distributor. Most of the talk with teeth and lining up is with the driveline gear below the distributor, which is unique to the L/Z/KA engines

[datzenmike]

If it was running before and the timing cover was never removed, the distributor won't have changed position.

 

 

SO...

 

Was it running before? and did this just happen recently?

Did you or someone just change the head gasket?

[Datsun84]

3 hours ago, ggzilla said:

It is unlikely you will have to remove the distributor. Most of the talk with teeth and lining up is with the driveline gear below the distributor, which is unique to the L/Z/KA engines

okay so, I got to the 5 mark and distributor lines it up correctly, had a bit of a more pop but still just cranking, Although your pin hole on that piece you line it up with is facing down, tomorrows after work I’ll try and post a photo. But it spit out the carb like triple H had water in his mouth. Wonder if the plugs are fouling? Since they smelled like gas?