Fuel Pump to Accumulator Connector Leak

Check the banjo bolt for cracks.

 

Just a side question -- is that some non-Bosch fuel pump with some sort of adapter fitting between the check valve and the fuel pump?

Gasoline is very non-viscous so migrates so easily that I'd still suspect every joint in the area (even the brazed tube into the banjo fitting). The joint between the thin hex of the check valve and that adapter fitting seems to have a copper washer in it but looks a little strange...

 

I just don't like having that extra fitting and joint between the fuel pump and check valve, and think maybe someone might have used the wrong check valve. This picture shows the silver Bosch 1587010536 check valve on the left used on some MB and the goldish Bosch 1587010532 check valve used on the F fuel pumps on the right. They use the same banjo fitting and cap nut, but have different sized threads to screw into the fuel pump:

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Just a thought...

 

No, that would be fine (keeping things parallel). You could also go to a 2mm thick copper washer as the extra thickness gives more deformability to seal up imperfections (and make sure you always use new, soft copper washers -- or you can anneal the old ones in a pinch, but that's sort of a hassle for such an inexpensive washer).

 

Very common. Even the factory had that problem when the cars were new. Due to the design of the fitting at the pump its difficult to counterhold. the pump to tighten them. Often some rotational stress is created and in use it relaxes slightly, enough to cause a leak. I tighten all fittings with both pump and accumulator mounting clamps loose so they rotate freely and tighten them last.

 

100% agree on this, it's super important to do it that way. The pipe connects to the centerline of the fuel pump, but off-center on the accumulator. For a given spacing between the pump and accumulator, here are two "equilibrium" rotational positions the accumulator can be in (+/- up/down angle) to avoid putting stress on the pipe or connections. When I assembled my new fuel pump and accumulator on the mounting sled, I left the mounting clamps loose and gently snugged up the pipe fittings to get the pump and accumulator in whatever relative positions they needed to be in before tightening the fittings all the way. Then tighten up the mounting clamps. There is a small amount of slop where the mounting clamps attach to the sled, which will accommodate the final arrangement of the pump, accumulator, and fuel pipe.

 

It's very likely that the banjo fitting is not seating well because it started out cockeyed. The shape and design of the rigid pipe doesn't help here. It's very optimistic to think that mounting alignment of the accumulator and pump on the sled (when you lock down those clamps) is going to match whatever the pipe wants to do at both fittings. I suspect you are crushing the sealing washers down before properly aligning/seating the banjo surfaces.

So yeah, I would be highly suspicious that your procedure introduced a misalignment. It may even be possible to notice this if you undo the clamp on one of the components and see if the pipe springs into a different alignment.

Next time around, mount the two components into their clamps and to the sled, and just barely snug up finger tight so that both components can still rotate within the clamps and the clamps can still pivot on the sled. Basically you are fixing those components to the plane of the sled and a loosely parallel alignment, but not constraining them in other dimensions. Then attach the pipe to the fittings loosely and eyeball everything. Pay attention to the banjo fitting and make sure it's aligned onto the check valve surfaces. Move the accumulator and pump as needed to make it perfect. Then gently snug up the fittings by hand. I think you'll notice that everything settles into whatever arrangement is necessary to align the fittings. Once satisfied, snug up the fittings all the way, and only then tighten down the mounting clamps.

If at any point before final snugging of the fittings, you notice that it's not possible for everything to settle into place, it suggests that the pipe is maybe bent or cockeyed. Might be possible to carefully correct that by tweaking the pipe, but I'd be wary of anything that requires serious manhandling. May also be possible to enlarge the holes on the mounting sled or clamps to let the clamp brackets move slightly, and you can also shim the clamps with washers if needed.

If the pipe is really messed up, there are Ferrari-specific kits to replace it with stainless braided flex tubing. Then you remove the "rigid" misalignment effect of the pipe completely. I think I have one of those kits in my parts bin, bought as insurance in case I ran into issues with the pipe when replacing my 328's fuel pump and accumulator. I can dig it out if you want more info.

I don't know that I've ever seen torque specs for fittings with sealing washers. Normally I go by feel. After the parts all make contact, a gentle twist of the wrench is usually enough. You should feel the copper washers "yield" as everything comes together. I've never paid attention, but estimate it's no more than 1/4 turn after contact is made. Perhaps someone else has better guidance on that. But for sure, having the fittings aligned before you tighten down is super important. The washers are there to make a final seal, not to compensate for misalignment.