fuel line size?

[bicolour]

tryint the find out the size of fuel line i need on 2l Aircooled?

seems to vary from 5.5 -7

[billybigspud]

8mm from petrol tank if it has the right one.

[ronsrecord]

What would be REALLY REALLY helpful is a definitive guide on fuel line sizes for different models. It's a question often asked, and seems to have lots of variations. Maybe we could record what size we're putting where, on what engines?

[bicolour]

well did my engine bay to pump today in 6mm, 5mm was to small but think 5.5mm would of been best

i took of a 8mm on there but was loose very loose

[bigherb]

You should always use a slightly smaller diameter hose than the fittings never relying on just the hose clamp to seal the hose. Petrol tank outlet is 8mm so use 7.6mm id hose to the filter, then from the filter the rest of the pipe and fittings are 6mm so use 5.6mm id hose.

[benlawlor85]

Found this really helpful, Thanks big herb.
After buying 7mm from various places after reading the wiki i am now going to order some 5.6mm.
Think the wiki needs an update.

[CJH]

What would be REALLY REALLY helpful is a definitive guide on fuel line sizes for different models. It's a question often asked, and seems to have lots of variations. Maybe we could record what size we're putting where, on what engines?

I was feeling rather smug, having replaced the hose from my fuel tank to the fuel pump at the weekend, as well as fitting a new fuel filter. I simply replaced what was there with the same stuff - 7mm SAE J30 R6 from a local motor factors. They didn't have big enough fuel hose clips, so I bought jubilee clips.

THEN.... THEN I came across various threads and the wiki article about fuel hose sizes, clip types, fuel hose spec etc, and figured I'd have to do it all again, maybe with smaller hose (5.6mm?), maybe the proper clips, definitely a higher spec hose (SAE J30 R9). I also learned that there was a return line from the carb to the tank (who knew?!), and that would need changing, and so would the short line from the fuel pump to the carb. So before going out and buying more hose I decided to get out and measure the O/D of all the fittings.

I found it's essentially what Bigherb said - 8mm on the tank inlet and outlet, 6mm everywhere else, EXCEPT the inlet to my pump is 8mm (while the outlet is 6mm). The fuel filter I bought from Brickwerks is stepped - first step 6mm, second step 8mm.

So it makes sense to me to use 7mm I/D all the way from the tank to the pump (about 3m - less probably but I like a bit of spare to work with for routing and squaring up the ends), and 5.6mm I/D everywhere else (3m should be plenty again). I assume I'll need some sort of adapter to convert from 5.6mm to 7mm for the fuel tank return.

Oddly, and hopefully someone can say if this is good/bad/standard, the return pipe on my van at the moment seems to have a length of 8mm semi-rigid plastic in the middle, but this is NOT functioning as a size adapter, since it's 8mm at both ends. It also doesn't seem to be there to get through bulkhead holes and stop chafing, as it's rubber at all the bulkhead points. When I replace this return hose, should I put new semi-rigid plastic in, or should I use SAE R9 rubber hose for the full length?

[AdrianC]

SAE J30 specs are the US standards - some fuel hose over here fits them, some doesn't. R9 is the ethanol-safe spec. We're on 5% ethanol now, 10% will be available in the UK soon (has been elsewhere in the EU for a few years). There's other "bio-fuel safe" pipe available, and whilst I suspect stuff that doesn't say it is will probably be OK, I'd certainly be looking for stuff that definitely claims it.

Really good fuel pipe's most critical on injected engines - because there's a fair bit of plumbing running at full injection pressure, which is about ten times that of the fuel pressure between pump and carb.

I've got to get around to replacing the pipe on our DJ-engined van soon, as well as dropping the tank for the cooling pipes - I'll try to remember to make a note as to how much of what diameter there is.

[bigherb]

CJH, the sizes I quoted where for the original poster with a 2.0ltr aircooler, different engines had different set ups some had return lines some didn't, but as yours looks to be a conversion I would replace the tank lines with a semi rigid line just coupling at the ends with rubber hose.

[CJH]

CJH, the sizes I quoted where for the original poster with a 2.0ltr aircooler, different engines had different set ups some had return lines some didn't, but as yours looks to be a conversion I would replace the tank lines with a semi rigid line just coupling at the ends with rubber hose.

Thanks Herb. Just a thought - since my fuel tank return pipe needs to fit the 6mm fitting on the carb and the 8mm fitting on the tank, AND because the pipe needs to go through a bulkhead hole that doesn't seem big enough for a grommet, can I perhaps kill two birds with one stone? Is there perhaps such a thing as a bulkhead-mounted adapter, so that I could use 5.6 I/D hose in the engine bay and 7mm hose from the bulkhead back to the tank?

[CJH]

SAE J30 specs are the US standards - some fuel hose over here fits them, some doesn't. R9 is the ethanol-safe spec.

Adrian - do you know what the equivalent European (DIN?) spec is? Is Brickworks' DIN 73379 hose suitable for 10% ethanol content?

CJH, the sizes I quoted where for the original poster with a 2.0ltr aircooler, different engines had different set ups some had return lines some didn't, but as yours looks to be a conversion I would replace the tank lines with a semi rigid line just coupling at the ends with rubber hose.

Herb, sorry, I didn't understand what you meant by "yours looks to be a conversion" - can you clarify? Which bit of my setup has been converted? And what would you recommend for the semi-rigid sections? Is all plastic fuel pipe suitable for all fuel types, and where can I get it from?

[AdrianC]

SAE J30 specs are the US standards - some fuel hose over here fits them, some doesn't. R9 is the ethanol-safe spec.

Adrian - do you know what the equivalent European (DIN?) spec is? Is Brickworks' DIN 73379 hose suitable for 10% ethanol content?

A quick google suggests DIN73379-2B is equivalent to R7, and "not recommended" for biofuel or for injection-pressure hose, whilst -3D is the R9 equiv.

[CJH]

And what would you recommend for the semi-rigid sections? Is all plastic fuel pipe suitable for all fuel types, and where can I get it from?

This (8mm cupro nickel (KUNIFER) fuel pipe) seems to be the stuff for semi-rigid fuel pipe. I'd say I could run this from near the tank return fitting and up through the hole in the engine bulkhead via a grommet, and then I'll just need a short 8mm to 8mm rubber hose link (7mm I/D hose) at the tank, and a short rubber hose link in the engine bay between the carb and the other end. Just the step from the 8mm Kunifer pipe to the 6mm carb outlet to worry about - not sure if I really need an adapter or whether the 5.6mm I/D rubber could be (safely) persuaded to push over the 8mm semi-rigid pipe.

I'm not sure what the life of the Kunifer pipe will be, but I suspect it'll be a lot longer than the rubber hose, so for the next few hose replacements I'll only need to buy very short lengths for these linkages.

[AdrianC]

I'm not sure what the life of the Kunifer pipe will be, but I suspect it'll be a lot longer than the rubber hose, so for the next few hose replacements I'll only need to buy very short lengths for these linkages.

Have you had a look at what's on there already? It's _very_ unlikely it'll be rubber all the way along. I don't think I've ever seen that on any vehicle. Normally, it's harder plastic or steel for the majority of the run, with rubber for the joints and where flexibility's needed to allow engine movement. That's certainly the way it is on our van, too.

[CJH]

Have you had a look at what's on there already?

Yes - the return from the carb to the tank has a length of distinctly old looking straight plastic, but the total run is still a good 50% rubber hose, and it's still hose where it passes through the sharp-looking hole in the engine bulkhead. The line from the tank to the fuel pump is 7mm hose all the way, clipped to the chassis at regular intervals. I already replaced this last weekend, like-for-like, but with SAE J30 R6. Replacing that is now another job on the list, but it's moved down the list of priorities, since I'm assuming the R6's lesser resistance to ethanol will show up over time and is not an immediate problem. When I do replace that run I'll probably go for the Kunifer semi-rigid on that side as well.