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Elbocho74

1974 Datsun 620 with Z20 engine dont start.

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Hello Datsun community.  I recently got a 1974 Datsun 620 with a Z20 engine that I can not make it to start. Can I have some insight to make it run?

Engine was rebuilt by a reputable shop:

Engine has a 4 plug distributor, the plugs on the intake side are there but not connected.

I checked timing TDC and looks good. 

I replaced the coil and resistor.  I have good spark.

I have an electric pump with fuel pressure regulator at 3.5 psi.  Good flow.

Comprssion is 150 on all cilynders.

I have a rebuilt weber 32 36 manual choke. 

When I crank the engine it runs for a ew seconds and stalls.  I have not been able to run it and adjust the idle speed.

 

Has any body experienced a similar problem?

 

 

 

 

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Try just turning the idle speed up to get it to stay running.... then once the motor is warm you can adjust it better.....

Also are you using the choke during start up?

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Also I think you want the intake side plugs connected if your not running all 8 and not the exhaust side but that's just a guess....

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3 hours ago, Crashtd420 said:

Try just turning the idle speed up to get it to stay running.... then once the motor is warm you can adjust it better.....

Also are you using the choke during start up?

Chocke is closed during starting.  I tried adjusting the idle jet screw in and out at diferent positions but it cant stay runing.  

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Can you get it to run if you hold your foot on the throttle?

Maybe open the choke up and try..... 

 

If you can get a high idle with your foot on the gas pedal you might have to double check your idle jet isn't clogged....

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Have you checked the air fuel screw?

You did say it was rebuilt.  That could possibly have been screwed all the way in and not reset... should be around  2 turns or so out ... 

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Try adjusting the actual idle screw, not the mixture screw, even if it idles at 1500/2000rpms at least it is running and then you can turn it down slowly and work on the mixture screws then.

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16 hours ago, Crashtd420 said:

Can you get it to run if you hold your foot on the throttle?

Maybe open the choke up and try..... 

 

If you can get a high idle with your foot on the gas pedal you might have to double check your idle jet isn't clogged....

I tried startig the engine with foot on the gas pedal. Same thing ran a few seconds with a cloud of black smoke.  I pumped the pedal up and down, the engine seemed it was getting to run. But it shut down.  

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I would probably have a look at your plugs and see if they are wet or fouled out....

 

Even try a new clean set.....

 

Then maybe try without the choke on.....

 

Check your coil too....

is it getting hot?

 

Your losing something.....

 

Need to determine if its fuel or spark....

 

 

 

 

 

 

 

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21 hours ago, wayno said:

Try adjusting the actual idle screw, not the mixture screw, even if it idles at 1500/2000rpms at least it is running and then you can turn it down slowly and work on the mixture screws then.

I turned the idle screw just before it touched the linkage.  The fuel mixure screw, I set it out two turns.  Fully opened the choke crancked the engine but same thing sounds like if its going to start good but the it shuts.  My timing I believe is good.  

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2 hours ago, Crashtd420 said:

I would probably have a look at your plugs and see if they are wet or fouled out....

 

Even try a new clean set.....

 

Then maybe try without the choke on.....

 

Check your coil too....

is it getting hot?

 

Your losing something.....

 

Need to determine if its fuel or spark....

 

 

 

 

 

 

 

I pulled all plugs out, they were wet with gas but new.  It seems the cilynders are flooding.  I regaped the spark plugs to 35 and the points at 18.  Checked firing order looks good.  Coil is not hot. Voltmeter shows 12.5 v at the resistor

( 6 ohm ) and 6.5V at the coil + stud.   Is 6.5 v normal at the + coil stud?

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1 hour ago, Elbocho74 said:

I pulled all plugs out, they were wet with gas but new.  It seems the cilynders are flooding.  I regaped the spark plugs to 35 and the points at 18.  Checked firing order looks good.  Coil is not hot. Voltmeter shows 12.5 v at the resistor

( 6 ohm ) and 6.5V at the coil + stud.   Is 6.5 v normal at the + coil stud?

I remember something like that with the power to the coil..... I think that's right but I'm not 100% sure,  haven't delt with a ballist resistor in over 15 years.....

 

Couple questions and ideas for you....

 

1 how are you verifying fuel pressure?

2 do you have a timing light?

 

If you don't you should really get one....

 

So my ideas....

How are the points?

New /used.... I know you regapped it but if they are old did you clean the face of the points... 

 

If you have a timing light you could connect it to the plug wire between the coil and the distributor cap.... as your cranking the engine it should keep flashing.....

 

You could even turn the fuel pressure down slightly to 3 but 3.5 should be more than fine.... I'm leaning toward this being a spark issue.....

 

 

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22 minutes ago, bilzbobaggins said:

Out of curiosity, why did you drop the E.I. dizzy and go with points?

That just popped into my head too...

I commented about the points and only now realized this is a z20 motor.....

 

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Doesn't say he replaced it, and all 8 plugs are still in the head. Probably came without the 8 plug distributor. Best thing would be to find an 8 plug Z series distributor and set it up right.

 

An L series points distributor is very unlikely to be pointing at the #1 plug on a Z series engine. Set the engine to TDC compression stroke on #1, use the timing scale near the crank pulley beside the alternator and look where the rotor is pointing to under the distributor cap. Get back to us on this.

 

 

On a side note when running only 4 plugs connect up the intake side not the exhaust side.

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4 hours ago, bilzbobaggins said:

Out of curiosity, why did you drop the E.I. dizzy and go with 

5 hours ago, bilzbobaggins said:

Out of curiosity, why did you drop the E.I. dizzy and go with points?

I got the truck as it is now.  With points.  Im new with Datsuns and didnt know what I got into.  

 

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On 11/27/2019 at 5:12 PM, datzenmike said:

Doesn't say he replaced it, and all 8 plugs are still in the head. Probably came without the 8 plug distributor. Best thing would be to find an 8 plug Z series distributor and set it up right.

 

An L series points distributor is very unlikely to be pointing at the #1 plug on a Z series engine. Set the engine to TDC compression stroke on #1, use the timing scale near the crank pulley beside the alternator and look where the rotor is pointing to under the distributor cap. Get back to us on this.

 

 

On a side note when running only 4 plugs connect up the intake side not the exhaust side.

Rechecked TDC.  I turned the crank pulley to TDC. The notch mark aligned with the 0 mark on the scale.  The rotor pointed towards the rear of the engine Cyl 1.  I pluged the intake side plugs.

 

Someting I noticed the points were closed altough the pulley points on the 0 scale the points were not hitting the top of the corner on the distributor shaft.  I loosened the screw and moved the distributor to the farthes right and regapped the points to 18.  

 

Cranked the engine and IT RAN.  I started adjusting my iddle speed and air mixure screw.  It ran for about 10 minutes.  It sounded good.  But wnen I pressed the gas pedal sounded like if it was stalling.  This might be another issue.  Any thoughts on this.?

 

All of the suden the engine shut down again.  I Checked the coil it was hot.  (Bran new MSD 2 With new 6k Ohm resistor).  

I puled out the coil wire checked it with test light and no spark.  

 

I checked voltage to the resistor I have 12v and 9 v to the + post on the coil.  But no spark.  Any advise to check my coil status. And why it gets hot about 150 F.

 

I thank all of you guys and galls for the imput.  Seemed Im getting close to make this cool truck run again.  

 

I tried to upload pics from my phone but dont know how.  I will have to ask my 9 year old how to do that.  

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On 11/27/2019 at 11:25 PM, wayno said:

Have you ever seen this engine run properly?

After following the advise in this forum, I made it run for about 10 minutes.  It shut down .  

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Cant remember if you still need the ballast resistor with this particular aftermarket coil when running points.

Edited by bilzbobaggins
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I always thought you wanted a 1.5 ohm ballist resistor with a 1.5 ohm coil for a 3ohm load......

I think that blaster 2 coil is .7 ohm and you put a 6 ohm resistor...

Not really sure that is right......

 

And I think you method of setting the points gap and timing is a bit off....

 

You should be setting the points gap by rotating the crank and finding the point that the points open the widest... set your gap ... then set your timing.. if you rotated the distributor to set the points you may have over advanced or retarded your timing.....

 

Do you have an actual timing light?

 

 

Edited by Crashtd420
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Check the points. They may have burned up. The limiting thing here is the points. They can't handle much more than about 4 amps of current. So if you have a 1.5 ohm coil you need a 1.5 ohm ballast resistor to reduce the current. If you omit the ballast the points will draw 8 or more amps, they won't last long and the coil will over heat. It's possible that the after market coil is a lower resistance for an electronic ignition that has no points and can handle the extra current. These coils are from 0.75 to 1.0 ohms and will draw from 5 amps with a ballast to 16!!! without.

 

Not a fan of after market stuff, I go with what worked for Nissan. Inspect the points and if suspect, replace them. Get a ballast resistor if you don't have one or a 3 ohm coil...... if you do have one get a coil rated at about  1.3 to 1.5 ohms.

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2 hours ago, Crashtd420 said:

I always thought you wanted a 1.5 ohm ballist resistor with a 1.5 ohm coil for a 3ohm load......

I think that blaster 2 coil is .7 ohm and you put a 6 ohm resistor...

Not really sure that is right......

 

And I think you method of setting the points gap and timing is a bit off....

 

You should be setting the points gap by rotating the crank and finding the point that the points open the widest... set your gap ... then set your timing.. if you rotated the distributor to set the points you may have over advanced or retarded your timing.....

 

Do you have an actual timing light?

 

 

I checked the specs for my coil MSD 2 is a .7 Ohm and requires a .8 Ohm resistor.

 

Ill try again to set my points.  

 

I got my timing light out after 10 years of no use, but my light bulb is blown will have to get a new one.

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3 hours ago, datzenmike said:

Check the points. They may have burned up. The limiting thing here is the points. They can't handle much more than about 4 amps of current. So if you have a 1.5 ohm coil you need a 1.5 ohm ballast resistor to reduce the current. If you omit the ballast the points will draw 8 or more amps, they won't last long and the coil will over heat. It's possible that the after market coil is a lower resistance for an electronic ignition that has no points and can handle the extra current. These coils are from 0.75 to 1.0 ohms and will draw from 5 amps with a ballast to 16!!! without.

 

Not a fan of after market stuff, I go with what worked for Nissan. Inspect the points and if suspect, replace them. Get a ballast resistor if you don't have one or a 3 ohm coil...... if you do have one get a coil rated at about  1.3 to 1.5 ohms.

You are right my points are fouled.

My coil is .07 ohm and requires a .8 ohm resistor.  Now that I saw the engine running.  Im considering set it up with an electronic ignition system. 

What set up could I use for electronic ignition.  Could you list the part numbers.  I would like something reliable but not too expensive. 

 

You mentioned on a previous reply to find the 8 plug distributor for this z20 engine.  Do you know the part number so I can look the parts.  I would like to set it up as it should.  

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