I thought I’d post this in XJS forum since it gets the most traffic but the car I’m working on is a Series II XJ12.

I recently decided to go back to the two fuel pump and two switch valve set up on my 6 liter engine swap XJ12. I’d already replaced the fuel lines when I first restored the car with original engine and new original style fuel pumps but had a fuel smell that remained ( and I ignored).

Originally on my engine swap I had a single fuel pump and a tee for the return so that it went to both tanks. That seemed simplest at the time when I was solving so many other problems but after driving the car I realized the drawbacks.

One was the fuel pump was wired to the left hand 12v source and so if anyone ever inadvertently hit the fuel switch on dash the car wouldn’t run. Not a problem for me but I hate leaving things like that. The other problem was it you took a risk filling the tanks as it might overflow. Didn’t happen to me but still.

And so I decided to redo the fuel system and add a second pump and use the original fuel solenoid switch valves.

And so after draining the tanks and trying to avoid saturating trunk with gas, I’ve replaced every fuel hose in the trunk (some new, some stuff bought 2-3 years ago and stored in a dark basement) and still had a fuel smell. Then I tightened every clamp until it felt like it might break and still had a fuel smell. Then I added a second clamp to every connection and still had a fuel smell. And then I tightened every clamp until it felt like it might break and still had a fuel smell. And then I melted hot glue over (almost) every connection and STILL had a fuel smell. JFC.

The pungency of fuel is amazing. Years ago I had an Alfa Spider that had old fuel lines under the car and even on that convertible, that wasn’t even close to air tight, you could smell fuel. And the lines weren’t even leaking. Just old.

So Im starting from scratch and replacing all fuel lines with new low permeation marine fuel hose. Plus buying all new clamps of a variety of types.

I tracked the leaks using this vapor detector I got off Amazon. Here are a couple of videos demonstrating how sensitive it is. If things beeps you will smell fuel. And the amount it takes to register is vanishingly small.
enjoy!
(Gonna follow up with a video after I shrink the file)

 

Video

 

Thought I’d follow up with some pics of what came out of my main fuel line after flushing. This is what came after a 10 micron fuel filter and then a 100* micron filter at the engine.
* yes, you read that right, for some reason I thought I’d installed a 10 micron at the engine but somehow missed the rating at the time. Oops. But technically the trunk mounted filter should’ve gotten everything and maybe it did. But here’s what was in the main line after flushing back to front and then front to back. Pics are in order of flush.

 

Andy
I read somewhere on the Series part of the forum, I think, that there is some sort of breather arrangement or something of that sort, up in the C pillar of the saloons, and that this can somehow make fumes in the cabin.
Maybe your car has such a system, and that is causing part of the trouble?

 

FWIW my xjs still smells vaguely fuelly in the boot, mixed with the order of fluid film I spray inside the trunk lid to slow the inevitable rust out that will happen one day.
When I travel it's just me so I toss my luggage in teh otherwise useless rear seat and there's no smell in the cabin at all amazingly. I did the marine hose
replacement thing too, that stuff is goooood. I wonder if modern fuels, even non ethanol that I still get here easy, just meanders through
the walls of old lines and seals easier than older fuels did. I swear if it goes troublesome again I'm putting a fuel cell and modern plumbing in it.

 

I think I discovered part of my problem.

my car, again a ‘74 XJ12 originally had carburetors and so the fuel pressure was 7lbs(?). And the original hard lines in the trunk had some flares on ends but not the tee for the return line back to the solenoids and the switch solenoids were straight tubing as well. Pics below.

My new fuel system has 40-43 PSI and that maybe was too much for those connections.

BUT! I still had leaks on some barbed joints that absolutely should’ve sealed and so original point remains. Gasoline smell is pernicious.

 

I think I recall seeing a loop in the rear C pillar but if I recall it was all metal. But that's a good tip because I'd forgotten about it (once my interior went back together).

 

It could be that gas liquid or vapor seeped into the carpet or insulation and is slowly dissipating. There is a chance that you could still have a microscopic leak at a joint but you'd need a gas detector to find it.

for the sale of this conversation I'd be curious to see what you'd find with a gas detector in there.

 

So I drained my tanks and took apart the entire fuel system and replaced every line in the trunk with “low permeation marine fuel hose” from Amazon.

And after a day of sitting the fuel smell was stronger than ever. Why? Because every single bit of hose permeates gas vapor according to my electronic detector (and my nose).

I am beyond pissed. The hose is not even remotely impermeable.

 

Here's the garbage hose:

 

Chinese made crap that is not what it is marked

The price it a tip off, good hose will cost you around $8-$10 per foot, not $2 a foot.

Go down to the local auto store and buy some Gates Barricade or Goodyear, SAE J30-R9 or R14 fuel injection hose.

Doug

 

Yeah, I shoulda considered price.

I bought more from a dedicated shop that sells filtration equipment etc etc for diesel engines and industrial equipment. But I may get some local stuff from Napa, seems like they would have decent quality hose.

What a hassle and lesson for the next person!

 

I use this from a local marine supply store. Smell has gone.
type-368 A1-15 non-permeable marine hose

Dave

 

That's what I bought and it is definitely better quality. It is substantially stiffer and I can see the plastic layer that makes it non permeable.