Fuel Hoses

by Richard Atwell
(c) Copyright 2003-2011

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Engine Fire Advisory: The screws on fuel injection clamps can work themselves loose over the years and this can contribute to dangerous top-of-engine fuel leaks. Clamps should not do this but it seems that engine vibration can accelerate the process. If you are using Oetiker ear clamps you won't have this issue.

Note: if fuel hose lasted 25 years I would only recommend using Oetiker clamps.

From my own experience, I recommend that you check your clamps once a year and change your fuel lines every 5 years.


This is one of my first articles after I started to restore my bus. It contains a wealth of information about fuel lines and restoring them. I can't stress enough the importance of changing the original lines before they cause an unwanted fire.


Fuel Injection:

So EXACTLY how much fuel line do you need for a FI bus? It's not 12-15 feet like Bus Boys suggests although a little extra hose is useful to have. These measurement come from the fiche and are confirmed by measurement of my original hoses. In some cases there is no length specified then my measurements of the original hose are used.

Print out this table and cross off each item as you cut the hose and fit it.

Scott Lyons has created a very nice looking diagram showing what goes rubber fuel lines are required:

Note: Older versions of Firefox can't open some of these images for some reason. Update or use another browser.

1975 has a slightly different layout than 1976 because the fuel pump is located outside the frame near the left rear wheel.

Long before any diagrams, I measured various sections myself and created this table for the DIY'er:

Location Length Size Type Comments
Tank outlet to pipe 50mm 7mm ID hose
Tank line 735mm 8mm OD metal pipe 211 221 233F
Tank line to fuel filter 115mm 7mm ID hose 50mm for BA6 gas heater
Filter to Pump 50mm 10mm ID hose 100mm for BA6 gas heater
Pump to 3/4 fuel rail 280mm 7mm ID hose 211 221 245 protective jacket used to protect fuel line
Injector #3 35mm 7mm ID hose photo
Injector #4 35mm 7mm ID hose photo
3/4 fuel rail 50mm 7mm ID hose
CSV inlet fuel rail 330mm 8mm OD metal pipe 039 133 329
CSV inlet 50mm 7mm ID hose
CSV outlet 50mm 7mm ID hose
CSV outlet fuel rail 440mm 8mm OD metal pipe 039 133 330
1/2 fuel rail 50mm 7mm ID hose
Injector #2 35mm 7mm ID hose photo
Injector #1 35mm 7mm ID hose photo
Pressure regulator 160mm 7mm ID hose
Pressure regulator to return pipe 50mm 7mm ID hose
Return pipe 240mm 8mm OD metal pipe 211 221 229A
Return pipe to tank inlet 50mm 7mm ID hose

These length do not include the injector fuel rails. You must have these two pieces and cannot substitute hose in their place. If you only have the two injectors fuel rails then you'll need more hose: 2820mm (9.32 ft.) total.

I'd advise you to get the metal lines from the junkyard if you are missing any: it will cost you less to replace the hose in future. I've provided part numbers in case you locate these über NLA items.

Old metal fuel lines may have fuel residue and varnish inside them. Although I consider cleaning optional, the only effective method of cleaning I've found is to chain them all together, clamp the end, and using a funnel fill with a mild solution of muratic acid for 3 hours or more as required. If your lines look rusty to begin with, you should replace them rather than try to clean them. Carb cleaners, paint thinners and degreasers can take a long time even if you use the fuel pump to recirculate them. Be sure to rinse out the lines before installation.

soaked

Dual Carbs:

I had the opportunity to measure the fuel hose from a 72 bus. With 49k miles it was in very original condition but the PO's receipts show some fuel lines were changed so they are my measurements, not VW specs (although they might turn out to be the same).

Location Length Size Type Comments
Tank outlet to filter 100mm 5.5mm ID hose
Inline filter 65mm n/a filter 131 261 275A
Filter to fuel pump 360mm 7mm ID hose
Fuel pump to tee 380mm 5.5mm ID hose
Tee to right carb filter 190mm 5.5mm ID hose
Right carb filter 80mm n/a filter 131 261 275A
Right carb filter to right carb 90mm 5.5mm ID hose
Tee to right left filter 360mm 5.5mm ID hose
Left carb filter 80mm n/a filter 131 261 275A
Left carb filter to left carb 140mm 5.5mm ID hose

NOTE: I've included the lengths that the filters take up in the system in case you wish to eliminiate them. The factory fuel pump had a built in filter but the reproduction units do not. Even so it was a tiny filter and the inline filter between the tank and the pump nicely lets you adapt the 7mm hose from the pump to the 5.5mm size of the tank opening.

There is also a tiny copper screen inside the tank.


Locating Hose:

Finding hoses can be tough. The VWFLAPS only carry a few sizes and VW used a lot of hose of different sizes. I've included numbers to try at the VW dealer if you prefer to get it locally than wait for an online shipment. I'm sure many sizes are common to modern cars and still available.

Fuel Injected buses use 7mm high pressure fuel line exclusively. Carbureted buses use 5.5mm fuel line but 7mm line from the tank to the filter on 68-71 models and to the fuel pump on 72-74 models (dual carbs with mechanical fuel pump).

Note: black braided hose is for vacuum and gray braided hose is for contact with fluids. If you use the black braided hose for fuel line (such as the section between the filter and pump), it will either crack or swell and be the subject of fuel leaks. The older the hose (so called shelf-wear) the faster the leaks will occur. They won't happen overnight but can take 6-12 months depending on your climate.

Size (ID x thickness) Part Number Source Description Comments
3.5mm x 3 N 020 291 1 VWFLAPS Vacuum line Buy bulk 2 ft.
4mm x 2.5 N 020 361 1 Vacuum line green braid
4mm x 2.5 N 020 361 2 Vacuum line red braid
4.5mm x 2.5 N 020 351 1 VWFLAPS Vacuum line Buy bulk 1 ft.
5.5mm x 3 N 900 996 01 VWFLAPS Fuel hose (carb) Late 74's have 7mm from tank to filter
7mm x 2.5 N 020 357 1 Bus Boys Fuel hose (FI), Breather lines Buy bulk 2 ft.
7mm x 3 N 020 281 1 Bus Boys Fuel hose (FI), fuel lines Buy bulk 4 ft.
7.5mm 916030-000527 Mercedes Benz dealer Fuel hose (FI) Close enough
7.5mm K-181-152-50 Porsche dealer Fuel hose (FI) Close enough (74-75 911)
9mm x 2.5 N 020 359 2 Breather line
10mm 112-476-12-26 Mercedes Benz dealer Fuel hose (FI) 1m of hose
10mm 112-476-12-26-TH Mercedes Benz dealer Fuel hose (FI) 1/10th meter of hose (4")
11mm x 3.5 N 020 300 1 Fuel line
12mm x 3.5 N 020 290 3 Bus Boys Vacuum line Buy bulk 2 ft.
13mm x 3.5 N 101 238 01 Bus Boys Vacuum line
14mm x 4 N 904 023 01 Bus Boys Vacuum line

People use 10.5mm fuel line from the Mercedes Dealer for the short piece of 11mm line that goes between the fuel filter and the fuel pump. If you have a gas heater, you need two 50mm pieces with a tee for the takeoff, otherwise you just need one 50mm long piece of hose. VW lists the lengths to be 80mm and 100mm but it's always appeared shorter on inspection. Order 4" (1/10th meter) from the MB dealer.

The last time I went looking for fuel line, the next best choice when 10mm line was not to be found was to use the 12mm (N 020 290 3) hose. It has the gray braided covering and fits over the 13mm flare of the fuel pump inlet and fuel filter outlet. This seems to be the preferred hose of VW repair shops and the dealer. My local MB dealer doesn't even stock 10mm line anymore and charge $68/m and it has to come from Germany.

The early 75- 76 1/2 busses had the fuel pump mount on a frame cross member instead of the side frame member. You'll have to adjust the lengths I've given to accomodate this change (metal line vs. hose) but you'll still need about the same amount overall. The section of fuel hose between the filter and pump on these models is about 850mm long.

Pelican Parts carries 6mm, 7mm and 8mm fuel hose and 3.5mm, 5mm, 7mm, 8mm, 12mm and 14mm vacuum hose.


Hose clamps:

First and foremost you must use proper FI clamps with the special band. Regular "worm gear" clamps will chew into the fuel lines and your bus will be at greater risk of burning down. Those clamps also lack the raised edges so the band will actually cut the fuel hose over time.

Option 1) Get them from the dealer:

The MB and VW dealers charge a fortune for the factory clamps and you need a lot so decide now if you want to spend the money and save yourself the hassle of shopping around to find a suitable clamp at a suitable price. They are nice clamps although I'm not a fan of the phillips head.

7mm clamp 10mm clamp mb clamp

Option 2) Find them online using the part numbers:

Search online using the 7mm part numbers in the table below if you want to find the stock clamp at a discount.

In 2005, I located an exact replacement for the original clamp (flared edges, Made by GEMI, same markings except for VW logo). Bus Depot now stocks these clamps as 311 133 515 and they have a gold corrosion plating with phillips screw.

gemi clamp

I counted 24 clamps on my bus if you have all of the metal fuel lines in the engine compartment and on the underside below the tank. You'll need another 4 if you want to clamp the injector hose twice for safety and you'll need two larger clamps for the 10mm ID hose that goes between the fuel filter and the fuel pump.

Option 3) Use an SAE clamp:

ideal clamp

The flaps should carry Ideal/Tridon brand clamps which I believe are made by AWAB. The part number that fits is 52F16 (fits 3/8" ID FI hose) and they are sold in packs of 4 and sometimes 10 if you ask at the counter. They will clamp down almost all the way. If you try to use the smaller 52F15 clamps you will find them don't clamp enough (metric->SAE incompatibility). The edges are rounded but not like the original factory clamps but neither are the new VW clamps from the dealer. These clamps are the easiest to find but are relatively expensive.

Option 4) Buy ABA online:

aba clamp aba #15

The best clamps I've found are from ABA of Sweden. It's the perfect clamp in every way especially considering that they are made from stainless steel. The ones I bought didn't have a phillips head screw which is an improvement over the VW clamps but I hear that ABA has changed the design to phillips head. I ordered 50 clamps for $40 (#22015, 33/64-39/64", 13-15.3mm) from Ultimate Garage but they are now $65-75.

aba clamps

I selected this size based on my measurements of the fuel hose and fuel rails:

ABA sells a smaller hose clamp #22014 (15/32-9/16", 12-14.3mm) that would seem to be a closer fit looking at the specs but my own experience has told me to get the next size up 4 times of out 5. Kenneth Wilford of Vanagain sells the same ABA #15 clamps in his hose kits which include 7x3mm hose for the Vanagon fuel rail. He says, "They work the best of any clamps I have used. I have been selling them in kits for over 5 years now". When I tried the #22015 clamps out on some spare VW fuel rail, they were an excellent fit so I have installed them everywhere.

aba loose aba tight

You can see in the chart below that ABA recommends their AWAB hose clamp for FI (ABA owns AWAB and GEMI, the other two major European clamp companies). Their 5/16" FI clamp is recommended for 8mm hose (same size) but we are using 7mm hose so why does it fit? The VW fuel rail is 8mm OD and expands our 7mm hose for a tight fit. Because of this we have to go up one hose clamp size so I chose the stainless #22015 hose clamp.

aba catalog

Jack Hattaway contacted ABA looking for a supplier and they referred him to McMaster Carr part #53175K28. The range in the catalog appears slightly different than the clamps I found but when they were delivered to him they turned out to have the same clamping range labeling. Another person contacted me to tell me that they received ABA #16 clamps from McMaster Carr when they ordered #53175K28 and that part #53175K27 is ABA #14 so it seems that they are not a reliable source.

Part Numbers:

Size Part Number Source Description Comments
7mm clamps 311 133 515 Bus Depot Fuel hose clamps (FI) $0.69
7mm clamps N 024 122 2 VW dealer Fuel hose clamps (FI) $1.91
7mm clamps 001 997 69 90 MB dealer Fuel hose clamps (FI) I forgot but search online (50 cents each)
7.5mm clamps 916002-012100 Mercedes Benz dealer Fuel hose clamps (FI) Close enough
5/16" clamps 52F15 FLAPS Fuel hose clamps (FI) Close enough for 7mm hose cinched down
10mm clamps N 102 582 01 VW dealer Fuel hose clamps (FI) $2.86
10mm clamps 916002-017100 MB dealer Fuel hose clamps (FI) Larger than normal FI clamps
3/8" clamps 52F16 FLAPS Fuel hose clamps Barely and poor fit for 10mm hose
1/4" clamps 52F13 FLAPS Fuel hose clamps Too small for 7mm hose

Other Measurements:


FI Fuel tank:

The hoses on the breather lines for the fuel tank vapor recovery system also need replacing. They are the #2 cause of irritating gasoline vapors after a broken fuel filler neck. If you think a faint fuel smell is not worth investigating, I would recommend that you park your bus in your garage overnight. Often, the vapors will penetrate into the house and of course saturate the garage and then you'll know you've got a bigger problem than you originally thought. Remember that fuel is most combustible in vapor form.

The hose that I've marked in red is partially hidden in the engine compartment and suffers the worst initial wear because of its exposure to the elements and the fact that the two metal lines don't quite line up therefore the hose is kinked and will crack from the extra stress. When it does, it will leak gasoline into the engine compartment during fill-ups or sharp turns.

breather hoses tricky devil

For some reason only known to the engineers, there is no matching hose (the one I marked in red) on the opposite side behind the "paint can lid". My guess is that this has something to do with assembly due to the spare tire wheel well in the back.

The fiche says to use N 020 281 1 (7x3mm) hose. What you'll find available under this number is usually smooth high pressure fuel hose.

The original hose (N 020 357 1) was the braided variety and 7x2.5mm. This is the braided version of the smooth high pressure fuel hose so it's definitely acceptable for the breather lines. The hose I bought with this number was from Continental and was labelled NBR (type of rubber suitable for fuel) so I know it will be ok if it gets wet when the tank is very full and fuel sloshes around.

The real world difference between the two hoses is that the braid is going to fray at the ends overtime whereas the smooth hose is reinforced and has a special jacket that is abrasion and ozone resistant. I've never tried to use "fray-stop" from the craft store to keep the braided hose looking good but it was an idea I had at one time.

For you hose nerds like me, NBR means Buna N or Nitrile which is a synthetic polymer of butadiene and acrylonitrile. The latter component has a high resistance to petroleum based products so it's popular for fuel lines.

comparison

However there is a subtle difference in size as verified by the datasheets. The smooth hose is actually 7.3mm ID which makes it easier to slip onto the fuel rail which has flares to hold the fuel hoses in place even before you apply the fuel line clamp.

Because of this it's slightly too big to be clamped on all of the breather lines. Some are plastic, some metal and there is a plastic tee on later models that I talk about below.

Due to this size difference I recommend using the 7x2.5mm braided hose because it is a better fit. However, this hose is not as heat resistant as the smooth hose and the ends tend to crack (all except the red one interestingly). You'll find the red hose is difficult to clamp and for that I recommend using a coating of seal-all over the hose even if you are able to clamp the ends.

When this happens, you get unwanted fuel vapors. I recommend that you should buy an appropriate sized clamp and clamp both ends of each hose. In a pinch I've used electrical tape and a clamp that was too large but this is better than nothing. While it takes years for the hose to crack, you'll forgot about it and wonder where the smell is coming from and probably find yourself unable to locate the hose easily.

78 hoses cracked clamped

Yes, the clamps look ugly and it's not original but safety is more important don't you think? VW should have used ear clamps at the factory IMHO.

When I talk about clamps I'm including the hoses behind the firewall. Since they are inaccessible unless the engine has been dropped a little, you should use clamps to apply the most permanent fix.

left hose right hose hose to tank tank

The el-cheapo 5/16" fuel hose you'll find at your local flaps will be brittle in a couple of years. One reason is quality and another is that it's very hot under the bus from the exhaust especially the 75-78 models where the u-bend that joins the header to the heat exchangers are located. The fuel lines that goes from the fuel pump to fuel rail gets baked and if you have an exhaust leak there it's even worse. Old hoses down there, may strand you or burn your bus down.

See my fuel tank restoration for tips on replacing the large 2 1/4" hose from the filler tube to the fuel tank.

Also of interest is part #15A in the diagram. This is the 3 way tee that I mentioned above. It used to cracks from age and break and then you were screwed but in the last couple of years reproductions have become available (211 201 405). VW changed the design in 78 and eliminated that style of tee which is why I don't have any photos of it.


Dual Carb Fuel tank:

The 72 tank is a little different. There is a molded rubber elbow at the top center of the tank and this item is NLA. The breather tube it connects to leads to the filler opening.

opening elbow

Spooky has a repair method for this item.

I decided not to remove the elbow and instead coated it with Seal All to keep the fumes inside the tank.

The breather hoses are 7mm just like the FI tank setup but the large hose connecting the filler tube to the tank is much longer.

tank hose other end 72 tank breather hose breather hose

The non-FI fuel tanks do not have two metal "macaroni" elbows on the bottom of the tank but instead this area is threaded for a fuel tap:

tank outlet foam seal filter sock

Inside you will find a brass sock that acts as a simple filter. It may be torn or rusted or missing. The sock is part 111 209 147A and there is an 8mm crush washer (N 011 525 13) that helps to make a tight seal at the fuel tap.


Early FI:

It seems that the early FI buses (74 automatic CA) and 75 have the carb style of fuel hose from tank to the filler opening. This long smooth or braided hose is definitely NLA and choices for replacement mean either using a 76-79 pipe from the junkyard or buying a replacement kit with the bend pipe. German Supply makes this kit but since the filler opening is advertised for 72-73 buses I'm not sure it will fit. Ask them.

75 tank

Fuel Sender:

If you can't pull your fuel tank for whatever reason (chicken is a reason) and have to cut a hole in the body in order to replace the sender here are the instructions:

Here's a photo from Chris Fletcher who made the most tasteful cut into the body to get at the fuel sender without removing the tank. He used a 5" bilge cover from a marine supply store. Chris tells me that a 6" cover will be too large.

cutaway

You do not have to cut a hole to test the sender. You can do that at the back of the fuel gauge.

Jamie Rivers has provided diagnostics for testing the fuel gauge system.


References:

History:

07/24/03 - Split off from Vacuum Hose page
03/19/05 - Added dual carb fuel line measurements
03/21/05 - Added 72 bus fuel breather photos
03/23/05 - Added McMaster part number confusion
04/02/05 - Added more ABA pictures
10/25/06 - Added some fuel line clamp photos
12/19/08 - Added some info about breather lines and clamps
06/03/09 - Thanks to Meghan for the torn fuel hose photo
09/05/11 - Fixed broken photos, added translate button, updated footer