2F Asian carb fuel line fittings and tubing OD

[cruiserb0b]

Hi folks.....

Want to install a fuel pressure gauge at the Asian carburetor input. It's a '77 FJ40 built in New Zealand (I don't think that matters....). The thread on the compression fitting really looks like 1/4" NPT and the fuel line tube looks to be 5/16"OD. AM I NUTS? Can anyone confirm this?

Thanks

Bob

 

[Pighead]

Hi folks.....

Want to install a fuel pressure gauge at the Asian carburetor input. It's a '77 FJ40 built in New Zealand (I don't think that matters....). The thread on the compression fitting really looks like 1/4" NPT and the fuel line tube looks to be 5/16"OD. AM I NUTS? Can anyone confirm this?

Thanks

Bob

I'm thinking that nothing on an Aisin carb is NPT. There may be metric or British threads but no NPT. I bet the hard fuel lines are metric too.

 

[charliemeyer007]

If its a carb, the fuel pressure is very low, a nearly meaningless number -i.e. it will run or not, maybe a small chance of interment pumping - fuel injection on the other hand requires the correct amount of higher pressure to work correctly.

 

[Grayscale]

I thought that compression fittings were sealed with National Pipe Straight threads, not tapered-pipe threads, in a manner similar to British or Japanese Industrial Standard (Cruiser).
Apparently there are NPTF National Pipe Thread Fuel, and those are really close to NPT like you find on the manifold, maybe fuel pump.
In terms of measuring OD of the tube, then, it is time for calipers or a micrometer, as the compression fitting will seal on the OD. I have to dig under the hood to get confirm it one way or the other.

 

[charliemeyer007]

Yea it is a PIA with all the "Standards" You would think that in this day and age we could have a free world standard and let the commies have their own.

 

[mattressking]

Don’t waste your time/money or ruin a perfectly good system - your gauge is the fuel sight glass, no reason for a gauge because of aforementioned low fuel pressure.

Is the fuel in middle when running? Great move on. If not, fuel pressure gauge won’t fix . This isn’t a high horsepower FI or NA race car, it’s unnecessary.

 

[mattressking]

I'm thinking that nothing on an Aisin carb is NPT. There may be metric or British threads but no NPT. I bet the hard fuel lines are metric too.

Corrrct since these are manufactured in Japan they are all JIS. If you look at the JIS specifications you’ll find pipe threads are all BSPP/BSPT.

 

[Grayscale]

I'm thinking that the tapered pipe fitting the OP is looking at resides between the fuel pump and the carburetor?

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I had a hard time on the rebuild unit, pulled over when it was running bad, and realized that I needed to go home and readjust my float position, again. That was a long time ago, but, I think that the lowered position was too low, thus the fuel pump could exhibit pressure on the float itself by pushing the needle too far down, iirc. The float adjust, and maybe omission of the carb-dip, were the mistakes that I made on the carb rebuild - everything else was slow, but simple.

The first spec. in the book that I skipped was the first spec. - fuel pump pressure, which has a range of 3.4 to 4.8 lbf/in2. Apparently, you gotta hack the system to test the system?

Ahh, for most other things in life, a big enough hammer, and a roll of teflon tape is all you'll ever need. Like my friend from work, a couple cigarettes and a cup of coffee = lunch break.