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Unknown vacuum hose


Nevyn
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Hi all....I have noticed a small vacuum hose is off at one end. I have no idea where it goes and need some help.
I can't even say where its coming from as I don't know what its called, but I have included a photo to help with that.
With this hose not connected could it be causing any running issues?

20170209_142440_zpsk4a8de8d.jpg

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You might check the underside of the hood for a vacuum routing diagram, I know there's one on mine. If I'm remembering right and yours is carbureted, it's not going to match the vac routing for US models.

 

The thing on the firewall looks like a solenoid valve to me, but I have no idea what it would be controlling, so I don't know what effect it would have. If you run out of ideas, you might just pull that line towards the motor, see where it ends, and look for anything it could be going to in that general area... carbon can, intake, carb, vacuum advance on the dizzy, something like that. It must've come from somewhere.

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Where's the other end go? And what year is it? Looks different than my 89

 

 

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Didn't think of checking where the other end goes? Will check it out soon.

It's a 1987 model...Z24 with a carburetor, not injected

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You might check the underside of the hood for a vacuum routing diagram, I know there's one on mine. If I'm remembering right and yours is carbureted, it's not going to match the vac routing for US models.

 

The thing on the firewall looks like a solenoid valve to me, but I have no idea what it would be controlling, so I don't know what effect it would have. If you run out of ideas, you might just pull that line towards the motor, see where it ends, and look for anything it could be going to in that general area... carbon can, intake, carb, vacuum advance on the dizzy, something like that. It must've come from somewhere.

Have never seen a vacuum routing diagram under the bonnet, but will double check just in case.

It definitely goes to the inlet side of the engine, so rules out the dizzy vacuum (and that hose is connected anyway)....but I will move the hose around and see where it reaches....

When the engine in running the hose is sucking.

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Have never seen a vacuum routing diagram under the bonnet, but will double check just in case.

It definitely goes to the inlet side of the engine, so rules out the dizzy vacuum (and that hose is connected anyway)....but I will move the hose around and see where it reaches....

When the engine in running the hose is sucking.

If it's sucking, one thing it'll do is probably run your idle higher than normal. I've gotten familiar with the service manual for mine and it has the 4cyl stuff in it. I'll take a look at it and try to find the pages with relevant info and show you.

 

 

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Where's the other end go? And what year is it? Looks different than my 89

 

 

Sent from my iPhone using Tapatalk

The other end of it goes in through the firewall to something in the dash......I can't find anything that is relating to this in my service manual.

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If it's sucking, it's leaning out your mixture, especially at idle. Enough to matter? That I don't know. Good luck finding where it goes.

It does seem to idle higher than it should be, and has started to use more fuel.....

With the weekend here now I am hoping to find time to have a very close look over the whole engine and try and find where it should be.

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Hmm. I don't think there'd be much under the dash that would take vacuum. I know some people install vacuum gauges that are supposed to give some idea of engine efficiency or something. The only other reason I can think of for vacuum in the cab is if Nissan decided to dabble in vacuum operated vents or something, which, AFAIK, they didn't.

 

I seem to remember you swapped the engine in this rig at some point. If you've still got the old engine around, I'd have a look and see if it has a vacuum hookup somewhere that this one doesn't. I know the vacuum routing changed a little on the VG30s when they added the BPT to the EGR system, could be there's some similar small difference that's left you with an extra hose.

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  • 3 weeks later...

Vacuum break switch for turning off the cruise control when hit the brake pedal? Just a guess...

Could be possible, but no cruise control......

 

 

I'm been rather busy lately so haven't had much chance to do anything, but have a pretty free day tomorrow given we have a long weekend over here....I would rather be out up in the mountains but not till I get this hose sorted.

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