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5thhorsemann

Vapor lock questions for the hotter climate guys

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On ‎12‎/‎16‎/‎2016 at 7:10 PM, siteunseen said:

And a Merry Christmas to us all!  

Please replace the fuel rail with rubber fuel hose.  it's proven to help with percolation of fuel, as per Jeff G an automotive engineer with a race team that uses the 240Z.

Jeff G,

Any picture of your engine bay? I would like to see how you routed the rubber fuel hose far or behind the valve cover....

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My Z is in a friends garage, so I don't have anything handy.  I do plan to go over and work on it this weekend though, so I will try to get some pics.  Keep in mind, my car is a race car and function was far more important than looks when I routed the lines.  For a street car, I would have done things differently.

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On ‎10‎/‎05‎/‎2016 at 3:33 PM, Zed Head said:

Sounds more like percolation, I think.  Basically, fuel getting too hot in the carbs and forcing/finding its way out unmetered, adding extra fuel, I believe.  Still heat-related, so the rubber lines Jeff G described should help.  Progress!

It's been discussed before, part of the saga.  Might even be in previous pages of this thread.  Here's Nissan's take on it. - http://xenonzcar.com/s30/files/1973 240z 1974 260z fuel system modifications.pdf

That document is on the CZCC site also - 

 

This is correct. What i am getting is fuel percolation at both carbs. I even replaced the fuel rail with rubber hoses this weekend and was still getting rough idle under a heavy traffic at 11:00 a.m. bumper to bumper. Car started to hesitate and stalled a couple of times. However i did found this company called THERMO-TEC which provides solutions to wrap the fuel lines and wrap the heat shield extensions:

http://thermotec.shptron.com/c/heat-protection?pp=8&pg=2

Which of all the products they sell can work to wrap the fuel rail and cover the heat shield extensions?

 

 

Heat shield SU CARBS.jpg

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This has been an ongoing problem for a long time and I don't remember all of the remedies you've tried other than fuel pump and fuel lines, so excuse me if you've already tried what follows. 

Have you tried letting the Z idle in a shaded spot with the hood open all the way and an external fan blowing down on the carbs to push  heat build up away and then revving the engine when it gets to operating temperature to see if it stumbles?  That could confirm or eliminate the fuel percolation aspect.  Have you connected with any of the Nissan clubs in Panama?

Dennis

 

 

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On ‎05‎/‎03‎/‎2017 at 5:28 PM, psdenno said:

This has been an ongoing problem for a long time and I don't remember all of the remedies you've tried other than fuel pump and fuel lines, so excuse me if you've already tried what follows. 

Have you tried letting the Z idle in a shaded spot with the hood open all the way and an external fan blowing down on the carbs to push  heat build up away and then revving the engine when it gets to operating temperature to see if it stumbles?  That could confirm or eliminate the fuel percolation aspect.  Have you connected with any of the Nissan clubs in Panama?

Dennis

 

 

I think the 280zx injector cooling blower is the remedy. Anyone differs?

blower cooling.jpg

blower cooling engine 2.jpg

blower cooling engine.jpg

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 Try the fan. You've got nothing to lose except the problem. BTW, If adding choke improves the performance, The engine is running too lean AT THAT POINT IN TIME.

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On 5/3/2017 at 3:28 PM, psdenno said:

This has been an ongoing problem for a long time and I don't remember all of the remedies you've tried other than fuel pump and fuel lines, so excuse me if you've already tried what follows. 

Have you tried letting the Z idle in a shaded spot with the hood open all the way and an external fan blowing down on the carbs to push  heat build up away and then revving the engine when it gets to operating temperature to see if it stumbles?  That could confirm or eliminate the fuel percolation aspect.  Have you connected with any of the Nissan clubs in Panama?

Dennis

 

 

I think the 280zx injector cooling blower is the remedy. Anyone differs?

blower cooling.jpg

...............................................................................................................................................................................................................

Perhaps it's a language problem.  I asked a couple questions about troubleshooting and your ability to connect with other Nissan owners in Panama.  In your response, you quoted my questions and then answered with a question about an injector cooling blower.  WTF! (Spanish translation available upon request). Ya no puedo ayudarte.

Dennis

 

 

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No language problem! I just want your confirmation that asides from the wrapping of the stainless Steel heat shield extensions, the 280zx air injector manifold cooling blower shown could solve the percolation. As simple as that. And by the way, no nissan club in Panama!

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The blower might help.  Odd that the nozzles appear to point directly at each carb.  Could be that they designed it for carbs, then switched to EFI, then finally broke it out for the ZX's.  Wouldn't be surprised if they had all of the tooling ready to go for carbs but avoided implementing it.

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10 minutes ago, Zed Head said:

The blower might help.  Odd that the nozzles appear to point directly at each carb.  Could be that they designed it for carbs, then switched to EFI, then finally broke it out for the ZX's.  Wouldn't be surprised if they had all of the tooling ready to go for carbs but avoided implementing it.

 I didn't notice that. It does look "made to order" for twin hitachi's.

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@jalexquijano, I'm still gathering heat soak puzzle pieces and trying to fit them together. Nissan says that fuel percolation occurs between the f. pump and the carbs and will cause an over rich condition. Vapor lock, on the other hand, occurs on the suction side of the pump. This got me to thinking about heat sources on the suction side of the pump. Taking into consideration all the work you've done under the hood to stop the problem, is it possible that the fuel is actually getting over-heated, in traffic, in the fuel lines under the car in the tunnel? My 240 tunnel used to get very, very hot, in traffic, in the summer. I can't imagine that a new exhaust with larger pipes would help either. BTW, I don't remember if you still have a mechanical pump along with your electric one (both are supposed to help the problem)

 To anyone, Was the fuel line location under the tunnel ever changed through the years? I'm still gathering puzzle pieces.

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PO removed the mechanical fuel pump from my car before i bought it! The Airtex 8012s electric fuel pump i have installed pushes 3psi (i measured it with a gauge last week). So in order to combat this horrible heat soak, i will be installing a 280zx injector cooling blower and using thermo-tec adhesive backed heat barrier: https://www.amazon.com/Thermo-Tec-13575-Adhesive-Backed-Barrier/dp/B00029KC2K to wrap the heat shield extensions. I am just really fed up of trying to solve this fuel starvation during traffic jams.

Anyone has a better solution?? Cant believe i am the only one that has this problem and cant find a way to fix it!

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