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510 Sputters and dies


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OK, gang,  Here are the symptoms:


Drive 510 for approximately 20 minutes at 50 mph on country road.  After twenty minutes or so the car starts to slowly lose power. 2 more minutes and carbs sounds clogged and will not rev.  Pull over, wait 20 minutes.   Car will restart and run (back home) for 20 minutes then die as before, hopefully as I'm rolling up the drive.


L20b with 1100 miles since rebuild

dual DCOE 40s 

Matchbox dizzy/'79 coil

electric fuel pump

fresh gas


Amb. temp 72 degrees

Water temp < 200 degrees

Oil pressure nom.



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soon as it dies. Tap on the carbs where the gas line goes in. maybe the needle valve is getting stuck thus you running out of gas. then start the car. or have 2 poeple one tapping as one is trying to start.


loose power . Im winging this one but ck the valve lash . I just make sure the valves wiggel when the lobe is pointing up. Dont have to pull out the feeler gauges. Usually the exhaust valve gets tight and youll loose a cylinder.


I assume you got a fuel reg for those carbs as most electric fuel pumps are OVER 5pounds pressure. You want like 3-3.5.



maybe try soem starter fluid also. when it dies

partly open carb shoot fluid iin. and start. if fires right away then you kow its a carb issue and your elelctrical is fine.



alway ck for intake tightness and the spcers inbetween carbs for cracks

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Thanks hainz,


I do have an adjustable pump set at 3 lbs.  


Upon further review of the archives, I understand this could also be the dreaded 'Vapor Lock".  I do not have a return line.  Its a little unclear to me how that would work.  I'm reading some of those old post now.  Lots of flame; not much data.

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If this were summer in El Paso, maybe. Has to be awful hot to vapor lock when driving. It mostly affects re start.


Is it just above freezing and damp in El Paso this time of year? If yes it could be carb icing.

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Back to basics. Fuel and spark.


Next time it quits pull coil wire off and hold near ground while cranking... spark???


If yes then ignition can be assumed good.


That will leave fuel. Can you hear the electric pump when it quits?

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I do hear the fuel pump on after the car dies.  I can't tell if it changes pitch.


I will pull off the coil wire and check it.  I'll go drive around tomorrow morning 'till it dies and check it.


Can I assume either the coil's overheating or the fuel is?


One other clue:  I have Spal fan on the front of the radiator, and no fan behind so there's not a lot of air circulation under the hood.  

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Yes.  Its a "pusher" fan and it does blow through.  Coolant stays cool; < 210 most of the time.  I have no issues on the engine itself overheating.


And I agree; assume nothing.  Test.  Preferably, one thing at a time.

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Should have a 180 thermostat so I wouldn't expect the engine temp to be more than 185 or so. 210 is close to boiling point of water. Gas, depending on the many additives, boils between 100F and 400F. If an alcohol blend then the alcohol boils off around 180F. If your under hood temps get anywhere near 200F that may be enough to cook the gas in that  8 foot long fuel line.

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Given the dew point of your climate, this is a bit of a long shot, but I would say when it falls down, another thing to check would be how cold your carbs are to the touch. If they feel like a block of ice, you may have found your problem.

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In my my 81 280zxt I had issues in the summer where the fuel pump would overheat and kill the engine. I would have to sit beside the road for 20min or so. Then it would start up just fine. I would have close to the same symptoms you are having except that I had efi.

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  • 10 months later...

I can't believe it's been a year since I started this post.  Life intruded last year and I had to walk away from my Datsun.  It sat under its cover since then.  I've visited the forum, but mostly to see what VTR posted in some of the other areas.  In any event, I'm back at this problem. 


In reading fuel pump posts and related older posts, I have sorta decided to heed Datzunmike's advice about the most reliable Datsun being a stock Datsun and return to a mechanical fuel pump.  But the L20b didn't have one when I bought it.  So do I need a spacer?  If so what depth and if anybody has a recommendation on a replacement mechanical pump, I'd love to know.


Any help is appreciated. 

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if elelctgric pump shoots gas and you got 3 pounds on the reg should be fine.


a stock mexico replcement pump comes with a spacer I believe. Mine was 29.99 at O rileys.


like I worte before the needle can stick and make it run out of gas.

also ck the funnels inside for loosen and ck the jets if they back out.

This is a 1/2 hr to 1 hr to figure out not a year. Now the gas is old in the car. but 1 yr shouldnt be bad as i le mine sit also.

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Thanks Hainz,


Off to O'Riley for the pump.


Actually the tank is bone dry.  I thought to attack this and be as thorough as possible.  I drained the tank and took it to be cleaned.  It only had a couple of gallons in it anyway that I can use in the lawn mower.  By removing the tank, I had access to the electric pump I put in 14 years ago.  I am going to disconnect it and then hook up the "new" mechanical pump.  I'll need to eliminate several feet of fuel line under the hood and turn the pipes around on the DCOEs.


Trust me, the year off of Datsun fun was NOT intentional. 

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Hay hope that fixes it.

If you dont get that spacer you can still use the pump. My old pump never had one and when I put the new one on I guess it pumped more fuel. my carbs would flood until I mounted a regulatory.

Its a cheap ORiley one so I still have to set it at 4 but it works.

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