I am in the process of replacing the fuel tank, filler neck, etc.. The tank rusted out and I ordered a new fuel pump, just wanted everything new. I ordered the Honda stock pump but the measurements the sending pipe (on the pump hanger/assembly) and return pipe is not what everyone here said it's supposed to be. I'm measuring 13mm (1/2") on the sending pipe and 11mm (7/16") on the return pipe. I'm wondering if the dealer sent me the wrong pump.. All the research here said it's 8mm (5/16") for the sending pipe and 6mm (1/4") for the return line.. someone help correct me.. thanks.

this is for a 1996 civic HX coupe..

 

Are you measuring the inside of the pipes or the outside ?

 

Measuring the outside of the pipe, then I'd know what size of ID (inner diameter) fuel hose to use to fit the pipes.

so I am asking what is the pipe size of the stock fuel pump's inlet/outlet pipes.. I can always dig out the back seat, open the access port, measure the existing stock pump.. but was easier to ask what it's supposed to be

 

so.. does anyone really know the sizing of the pipe from the 96-2000 fuel pump (stock)? Everyone has said in the past on this forum it was 5/16" supply (8mm) and 1/4" return (6mm) but clearly that is not true.. and yes I know how to use calipers to measure distance. Interesting that no one can come up with proof, guess I'll give up and measure it myself (one in the car right now) when it gets a little warmer around here. Sad that the data is not correct on this forum.. I have double checked and I do have the correct stock Honda pump (new I ordered).

 

It's just really unusual to have tubing that big. I have never seen anything larger than 5/16 OD. 1/4-inch (6-mm) tubing is good up to 200 hP. 5/16 (8-mm) up to 400 hP. 1/2-inch (12-mm) would be oversized for anything less than 1000 hP.

 

The factory hose size ID is actually METRIC, so none of the SAE values that you have posted are truly correct... but they are darn close.

The feed line is just slightly larger than 1/4" ID, but it is NOT a hose barb. The pump assembly has an O-ring clip seal and is not replaceable with a conventional hose. The return is slightly smaller than 1/4" ID, but is a normal hose barb and 1/4" hose will fit it. Your focus on the OD is irrelevant unless you are trying to retain the original OE hose clamps. Then you will need to measure the original hose and find an aftermarket replacement that is the same outer diameter.

 

UPDATE/CONCLUSION..
I re-measured the pipes from the new fuel pump and the old fuel pump with a regular metric ruler and found the correct measurement!
I found that the calipers I had used before have incorrect measurement marks on them! (going in the trash)..
The forum was correct, I was wrong, I apologize.

Supply line/pipe from fuel pump (stock honda) is 8mm OD (5/16" hose), if in the future you cannot get the Honda flex supply line.
Return line/pipe from fuel pump (stock honda) is 6mm OD (1/4" hose)

Thanks JRCivic1 for the update and you're absolutely correct. I did supply the english conversion since most of the fuel hose you find at the local NAPA is mostly in english measurements in case someone looks this post up in the future. About the supply flex line from the pump to the hard line, some Honda dealers say it's discontinued but my local dealer could get one so I ordered that. Not cheap but I did not know it had a special o-ring inside the hose, found a used one on ebay and could see what you're talking about. I'll just use that, one less thing to worry about in the future.