Hey,

The replacement fuel pump I'm installing (Airtex 2 line) has on outlet connection of 1/4-18 NPSF. Everthing I find locally is NPT. The old pump had the original threaded connection to the 3/8 IF hard line to the carb and it won't screw into the new pump. I've found a references to the NPS online and found an electric fuel pump fitting that seems to be the correct one but is 16 bucks shipped and is a special order item that will take a couple of weeks to arrive. Is there something else that may work for this? Has anyone else had this issue?

Thanks,

Rob

 

From http://www.hydraulic-testers.com/tec...r/pipeconn.htm

 

Almost sounds like you got the wrong pump somehow, providing you have the right hard line.
I have seen parts store computers goof before. Mine (72) was 3/8"... 1/4" seems too small.

 

1/4" pipe thread has an outside diameter of 0.540". Was 3/8" the line size or the thread size on your pump?

 

That's a great link Joe. NPT fittings can be found aftermarket all day long. But it really seemed like the 1/4 NPT fitting I found at the parts store just wouldn't start at all. I didn't even feel close and I didn't want to force it a funk up the pump threads. But I could try again. Would you recommend teflon tape for this type connection?

 

I thought the same thing Rob. I initially purchased a 3/8 NPT fitting but it was too large. Then I tried the 1/4 NPT and while it appeared to be the correct size, it just didn't want to screw in. I contacted Airtex and they replied with the 1/4-18 NPSF connection. This is Airtex #40704 and I got it from RockAuto and that's the same p/no from O-Reilly, Summit, and others. It matched up correctly to the one that was on there which may or may not have been the original. The original set up was a street ell threaded itnto the pump and a 3/8 hard pipe with an internal flare (IF) from the carb going into the ell. The hard pipe looked original as to what I've seen on other cars and for sale as original replacement. The ell may be another story as I've found quite of bit of other jury rigged stuff from PO'S. Thanks for the feedback.
Rob

 

I guess I was thinking of 3/8" line diameter, so 1/4" pipe thread might be right...
Since this is a flair connection, teflon tape will not be required or even recommended.
I do know I had a heck of a time getting my repro hard line to thread into the new airtex pump I got from RA due to the hard line's angles. It had to be just right!
I had to do some careful creative bending of the line to get it to thread in.
I think the carb line was loose while I was going this.
ALWAYS start it in by hand, not by wrench to avoid thread damage.
If you have some silly putty or clay, you could do a little tread comparison with some small impressions.

 

Agreed, it seems that fuel lines need to "approach" their mate at just the right angle to get the threads to start.

Another possibility with any NPT connection is that on one or both sides the threads were not cut deep enough. The last time I bought inch-and-a-half rigid conduit (probably chinese-made) at Home Depot, the pipes would start threading into couplers and flanges, but they would seat after only two rotations. Not nearly enough threads engaged! The same situation could be happening with your fuel pump. If the threads weren't cut deep enough, you might not even be able to get it started.