Rough running when hot, '79 280Z

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- Ed
  
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posted
16 years ago

Tue, Jan 1, 2008 6:05 PM

This question in on behalf of an uncle who picked up this very low mileage Z a year or so ago. It has now developed rough running when hot. He has replaced the fuel pressure regulator and has a fuel pressure gauge rigged so it can be read while driving. The pressure looks good to me, riding at about 30 psig at idle and varying with engine load between 20 and 30.

I have no experience with the Z, but the FI looks similar to the Bosch system on my '76 Jaguar V12. I've advised him to test the coolant temperature sensor, but don't know what the desistance vs. temperature should be. We are both curious about the fan mounted on the right side of the engine with a flat duct taking the air up and over the valve cover and into the vee. Is that to combat fuel rail vapor formation? If so, could a failure of this fan or controls explain the symptoms?

TIA

Ed

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- Clamstrippe Fecadunker
  
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posted
16 years ago

Tue, Jan 1, 2008 7:36 PM

Vee? what vee?

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- Ed
  
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posted
16 years ago

Tue, Jan 1, 2008 8:57 PM

Oops, I guess I used the term loosely. The broad, plastic, flat duct goes up from the fan and curves over the valve cover. The air is dumped into the space to the left of the valve cover and under the fuel rail.

Were all the Z-cars fitted with a fan like this?

Ed

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- NissTech
  
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posted
16 years ago

Fri, Jan 4, 2008 6:28 PM

the V shaped duct you mentioned is to cool the injectors.

the ratio of resistance to temp of the head temp sensor is basically, the lower the resistance the hotter the engine, as the engine heats the resistance drops.

at operating temp, the head temp sensor should read about 260-300 or so Ohms, anything excessive either way could constitute a runability problem you described.