Howdy folks.

TLDR: If you ever need flexible rubber hose for inside your fuel tank, you need it to be SAE j30r10 rated.


The scoop:
A few months ago, I put a new fuel pump (Delphi FE006911B1 for Bosch systems) from Napa auto parts into my 1990 740. I just had it apart again because I was getting air in the line again.

This car is Regina but I hacked in a bosch fuel pump arrangement because the original configuration was all hacked up and I couldn't find the exact right way to do it. Nobody seemed to know and parts diagrams had like 7 different configurations, none of which matched what I have.

Anyway, the reason I was getting air bubbles in my line is that I trusted these chintzy little plastic clamps that came with the pump like these https://www.directindustry.com/prod/hcl-fasteners-ltd/product-61072-572743.html. I replaced them with these "fuel line clamps" from harbor freight rated for 13-15mm and had to tighten them almost completely down. (https://www.harborfreight.com/mini-fuel-injection-style-hose-clamp-kit-40-piece-58150.html)

In the 6-8 months since I put the pump in with one of the accordion hoses like IPD sells - https://www.ipdusa.com/products/21189/In-Tank-Fuel-Pump-Outlet-Hose-200-700-900-MTC-VR406-Volvo-3514360 - the rubber swelled slightly and the top of the hose started leaking air into the fuel it was feeding to the main pump. At first, it was occasional and I could purge the air out, but last week it became constantly noisy.


When I bought the kit from Napa, the hose that came with the Delphi fuel pump for the upper section was too short and I had to buy new fuel line. Submersible fuel line is very hard to find locally and VERY expensive (like $25/foot). I needed some and I found that I needed (I'm pretty sure of the diameter) 6 inches of 1/4 inch fuel line with the SAE rating j30r10. There are many ratings for fuel line that are common like j30r7, but only j30r10 appears to be resistant to being exposed to gasoline on both sides most of the time and to high pressure. So if you ever need flexible rubber hose for inside your fuel tank, you need it to be SAE j30r10 rated.


In my particular car, the metal tube that mates with the accordion hose from the in-tank pump does not have any kind of "wrinkle" (flare, lip, bulge, etc) that you would put a clamp behind. If I have to take the thing apart a 3rd time, I will be putting a flare on that and eliminating that very thin accordion hose. As far as I can tell, the metal tube and the fuel pump outlet never change shape or distance from each other. The accordion is entirely to make it easy to assemble. IPD says this is 7.3mm ID, which is a little larger than 9/32" ID. An important thing to notice is that the fuel pump outlet and the metal tube are slightly different diameters. The metal tube is smaller, so a flare would definitely help.

I know this sounds like a Napa ad, but they have a tool that lets you put flares in brake lines for like $35. It would work for adding flares to tubes, but I'm not sure it would work for this section because there isn't much of a stub on the end of the line. I really hope I don't have to find out.


Hope this helps someone later (maybe me hah!)
Will