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purging the fuel system
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Author:  Frank T [ Wed Aug 06, 2014 8:56 pm ]
Post subject:  Re: purging the fuel system

OK Surf, I fail to find a good diagram showing how the choke works on the SUs, but I have found a picture which kinda shows part of what I'm describing.

The arrow points to the choke on one SU. Either SU has one. That bent metal clip down the side of the carb body pulls or pushes the lower end of that nipple the arrow points to. That's the 'choke' and it's movable up or down.

It contains the fuel jet, into which the tapered "fuel metering rod" (needle) fits from above. Instead of pulling the needle upward to let more fuel flow into the engine like we'd do when the engine was running, we're instead pulling the fuel jet ('donut') down away from the 'traffic cone'.

You may have tightened your choke cables with the chokes ON. Inside the cabin, push your choke lever full-fwd (choke off). Then loosen the cables at the carbs (be careful not to lose those tiny screws and don't ask me how I know that, either :evil: ). Reach under the SU and push up on the chokes. When they move all the way up (choke OFF), retighten the cables. I would first push a big, broad piece of cardboard directly under the engine, to catch however many of those tiny aggravating screws you drop. :evil:

Careful not to turn the mixture adjusting nuts while you're down there. If your car ran great before you took it apart (I still love that), you want to leave it alone the way it was. If they need adjusting later, we can discuss the easy way to do that.

Attachments:
File comment: These housings move up and down, turning the "choke" on or off. All they do is allow more or less fuel to flow.
SU choke location.png
SU choke location.png [ 457.7 KiB | Viewed 10312 times ]

Author:  SurferD [ Thu Aug 07, 2014 7:45 pm ]
Post subject:  Re: purging the fuel system

Frank T wrote:
["During my drive the coolant temp was pegged. I replaced the sensor so it could be low coolant or a bad gauge. Also my oil pressure isn't reading at all"] :shock:

WELL!!! One (the oil) could certainly lead to the other (the water temp). Check all levels before starting the car again, for sure. Hopefully it's just bad gauges or a blown fuse or bad connections (the temp gauge is right there near the distributor, so maybe you bumped it). That same shaft that drives your distributor also turns your oil pump, so if you have one you usually have the other. But you could be out of oil. :oops:

And something else happens to these engines which you should be aware of. Unless the coolant is replaced in a specific manner, an air pocket can form beneath the thermostat, keeping super-heated water away from it. The thermo, therefore, doesn't get the message that it's time to open and can sometimes let the engine overheat (blowing freeze plugs and/or head gaskets).

If you drained (or leaked) your coolant any significant amount (a pint or more), you can rest assured there is now an air pocket under your closed thermostat, which is the highest point in your cooling system. Again, please don't ask how I know about this. :roll:

We had an extensive discussion about this here in Tech Talk last year ~ I'll try to find it rather than trying to repeat it.

Here it is:

viewtopic.php?f=4&t=7529

I changed the oil while it was laid up so I know that wasn't it. Turned out I'm a dummy and with the excitement of it running, didn't refill the coolant. I followed your procedure and now the temp is hovering in the first 3rd of the gage. I also replaced the oil pressure sensor with a slightly used unit. It now reads but seems low. The glass on the gage is loose and if I tap it the needles wave so I think I'll replace it for good measure.

Author:  SurferD [ Thu Aug 07, 2014 7:53 pm ]
Post subject:  Re: purging the fuel system

Frank T wrote:
OK Surf, I fail to find a good diagram showing how the choke works on the SUs, but I have found a picture which kinda shows part of what I'm describing.

The arrow points to the choke on one SU. Either SU has one. That bent metal clip down the side of the carb body pulls or pushes the lower end of that nipple the arrow points to. That's the 'choke' and it's movable up or down.

It contains the fuel jet, into which the tapered "fuel metering rod" (needle) fits from above. Instead of pulling the needle upward to let more fuel flow into the engine like we'd do when the engine was running, we're instead pulling the fuel jet ('donut') down away from the 'traffic cone'.

You may have tightened your choke cables with the chokes ON. Inside the cabin, push your choke lever full-fwd (choke off). Then loosen the cables at the carbs (be careful not to lose those tiny screws and don't ask me how I know that, either :evil: ). Reach under the SU and push up on the chokes. When they move all the way up (choke OFF), retighten the cables. I would first push a big, broad piece of cardboard directly under the engine, to catch however many of those tiny aggravating screws you drop. :evil:

Careful not to turn the mixture adjusting nuts while you're down there. If your car ran great before you took it apart (I still love that), you want to leave it alone the way it was. If they need adjusting later, we can discuss the easy way to do that.


When I took the cables off I just loosened the screws and slid out the wires to be easily replaced later.
I checked the chokes and operated the lever and they are working as they should.
I may have to do a little fine tuning with the cables like you say.
You make common sense explainations of complex procedures, thanks.

Author:  FM6 [ Thu Aug 07, 2014 8:31 pm ]
Post subject:  Re: purging the fuel system

Frank T wrote:
'Murican cars,



You mean like your "Dodge Neon" . . . . . . :shock: :shock: :mrgreen:

Author:  Frank T [ Thu Aug 07, 2014 9:31 pm ]
Post subject:  Re: purging the fuel system

:mrgreen: Not 'my' Dodge Neon!!! I wouldn't even be buried in one of those things.

The oil pressure sensors on the early Zs are notoriously poor. They will scare you with low readings. "Real" Z drivers replace them with mechanical sensors which show accurate readings.

Really glad you've got your Z running now. Maybe we'll zee it at Grossman's next week.

Author:  SurferD [ Thu Aug 07, 2014 9:48 pm ]
Post subject:  Re: purging the fuel system

Frank T wrote:
:mrgreen: Not 'my' Dodge Neon!!! I wouldn't even be buried in one of those things.

The oil pressure sensors on the early Zs are notoriously poor. They will scare you with low readings. "Real" Z drivers replace them with mechanical sensors which show accurate readings.

Really glad you've got your Z running now. Maybe we'll zee it at Grossman's next week.

Me too!
I have to get it registered and brave the drive from Orange to Old Saybrook.
It hasn't driven in about 7 years so I'm a little aprehensive about the 76 mile long round trip.
The brakes are a bit soft but I have speed bleeders so that should be easy enough.

Author:  Frank T [ Thu Aug 07, 2014 10:09 pm ]
Post subject:  Re: purging the fuel system

Well, meet me along the way and we'll cruise in together. I could find you somewhere near New Haven I-95.

Author:  FM6 [ Thu Aug 07, 2014 10:45 pm ]
Post subject:  Re: purging the fuel system

SurferD wrote:
Me too!
I have to get it registered and brave the drive from Orange to Old Saybrook.
It hasn't driven in about 7 years so I'm a little apprehensive about the 76 mile long round trip.
The brakes are a bit soft but I have speed bleeders so that should be easy enough.


It's just 38 miles at a time. :thumbs_up:

Looking forward to meeting you. :thumbs_up: :thumbs_up:

Author:  SurferD [ Sat Aug 09, 2014 9:57 am ]
Post subject:  Re: purging the fuel system

I'm looking forward to you all finally seeing my jalopy. I was doing a shakedown run today but ran out of gas and couldn't restart it with new gas. Luckily I was close to home and could just tow it back with my truck.

Author:  Frank T [ Sat Aug 09, 2014 1:02 pm ]
Post subject:  Re: purging the fuel system

That happened to me in California once. A CHiP stopped and ran a hose from his cruiser carb to my car and pumped a gallon into my Z for free.

Only run hi octane in your Z, and if you do run it dry check your fuel filter for signs of rust. The bottoms of these old S30 fuel tanks are usually awash with a layer of sandy rust from years of condensation. Routinely changing out the fuel filter prevents rust from clogging your system.

What were your impressions of it, before you ran it dry?

Author:  SurferD [ Sat Aug 09, 2014 6:39 pm ]
Post subject:  Re: purging the fuel system

Frank T wrote:
That happened to me in California once. A CHiP stopped and ran a hose from his cruiser carb to my car and pumped a gallon into my Z for free.

Only run hi octane in your Z, and if you do run it dry check your fuel filter for signs of rust. The bottoms of these old S30 fuel tanks are usually awash with a layer of sandy rust from years of condensation. Routinely changing out the fuel filter prevents rust from clogging your system.

What were your impressions of it, before you ran it dry?

I changed the fuel filter a short time ago so I don't think it's clogged yet but will keep an eye on it.
I used 87 octane but will use 93. I forgot it has a fairly high compression ratio.
I got it running again after sitting a few hours.
It's a great ride! The suspension is very floaty so I guess it needs shocks.
But it's really like how it should be, man and machine. I especially like the unassisted steering.
I have a hole in the exhaust pipe that lets in lots of fumes but I'm fixing that tomorrow.
I got insurance yesterday and will register it on tuesday so I'll be legal.
I'm planning on bringing it to classic car show at Heavenly Donuts on Rt34 in Derby tomorrow.
I live about a mile from there.
Anyone else want to meetup before that?

Author:  Frank T [ Sat Aug 09, 2014 8:34 pm ]
Post subject:  Re: purging the fuel system

I might catch you at the Brown/Derby donuts place. Could be fun.

The fumes were part of the car. The rear hatch usually leaked a bit and sucked exhaust fumes into the cabin with the early cars (those with ventilator hatches on the rear deck). Datsun fixed that in the Series-II cars by moving the vents to the B pillars. The flat tail of the S-30 creates a swirl right at the taillights which collects exhaust fumes. They find their way into the cabin at various points around the hatch, including those ventilator grilles.

I never got ANY fumes into my cabin when my car was new, but after it had been repainted (i.e. the tail lights and the rubber hatch seal got R&R'd), it became noticeable.

Author:  Frank T [ Sun Aug 10, 2014 10:38 am ]
Post subject:  Re: purging the fuel system

What time does that donut meeting happen today?

Author:  SurferD [ Sun Aug 10, 2014 11:43 am ]
Post subject:  Re: purging the fuel system

Frank T wrote:
What time does that donut meeting happen today?

Usually cars start showing up around 2 but it goes on until like 7. I'm planning on going around 5. PM me if you're going.

Author:  Paul [ Thu Aug 14, 2014 7:05 am ]
Post subject:  Re: purging the fuel system

Frank I'd have to say that firing order doesn't apply to you anymore, or the likes of most of us.....they're all to young :shock: I don't think you had it 180 out......the dizzy only goes in one way, the shaft is offset. I think you finally drew fuel up to the carbs. Or did one of those accidental fixes.......I do those all the time. Also, I'd say use 89 Octane. Just seems to work the best. Also, I know we can't see inside them, but be aware of the rubber diaphragm is the fuel pump. I tried once, but maybe someone else can shed some light in as to where to get rebuild kits for our original fuel pumps. I've been saving them for this reason. Heck with the aftermarkets.

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