VW Baywindow Bus - Fuel Hoses
by Richard Atwell
Engine Fire Advisory: Are your fuel hoses showing cracks? You better look before you regret it...
Some of these cracks will be noticeable at the ends and some will be invisible to you because they will be hidden by the cloth braid covering the hose. Sometimes the braided hose is soaking wet to the touch but looks normal from afar.
If you are buying a new bus whether it has been sitting for a long time or not, you can depress the flap in the air flow meter and pressurize the fuel rail if it's equipped with fuel injection. Doing this will pressurize the fuel rail to 35-38 psi and expose obvious leaks before you drive away and risk a fire.
The screws of the original fuel injection clamps can sometimes work themselves loose over many years and this can contribute to dangerous top-of-engine fuel leaks. Clamps ideally should not do this but it seems that engine vibration and hardening of the fuel hoses are likely contributors. If you are using Oetiker-style ear clamps you probably won't have this issue assuming they were installed properly
Regardless, you should be inspecting your fuel lines on a yearly basis and replacing them on a multi-year schedule that is suitable for your climate. I can't stress enough the importance of changing the original lines before they cause an unwanted fire.
This article was one of my first after I started to restore my bus. It contains a wealth of information about fuel lines and restoring them.
Since I originally wrote this article, gasoline has been reformulated worldwide to include an even increasing amount of ethanol as a constituent component.
In recent years, there has been a lot of discussion in online forums, especially those catering to German made automobiles like ours, citing that standard fuel hoses are susceptible to chemical attack from the ethanol, which creates fire and safety issues.
Until the article can be fully updated, I recommend that you research fuel suppliers extensively, before simply buying "German" fuel hose from your favorite VW suppliers. Is this an emergency issue? That really depends on who you talk to but it's hard to go wrong buying the best hose available especially when it is suited to the application.
So EXACTLY how much fuel line do you need for a FI bus? It's not 12-15 feet like Bus Boys used to suggest although a little extra hose is useful to have on hand (with your on-board emergency parts stash).
These measurement come from the fiche and are confirmed by measurement of my factory 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 at German Supply in Canada has created some very nice looking diagrams showing what sizes of fuel hoses are required:
He also sells complete fuel hose/clamp kits.
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:
|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.
I had the opportunity to measure the fuel hose from a 72 bus with 49k original miles. It was in very original condition but the PO's receipts indicated that some fuel lines were changed so these are my measurements, not VW specs (although they might turn out to be the same).
|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 tiny and the inline filter between the tank and the pump allows 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 those fuel tanks.
Finding metric fuel 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 rather 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 in most places, a 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 become 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 (closed)||Fuel hose (FI), Breather lines||Buy bulk 2 ft.|
|7mm x 3||N 020 281 1||Bus Boys (closed)||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 (closed)||Vacuum line||Buy bulk 2 ft.|
|13mm x 3.5||N 101 238 01||Bus Boys (closed)||Vacuum line|
|14mm x 4||N 904 023 01||Bus Boys (closed)||Vacuum line|
Regarding the piece of hose between the fuel filter and pump on a FI bus: some folks 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 to me upon inspection. Order 4" (1/10th meter) from the MB dealer and don't be surprised by the tight fit.
The last time I went looking for that fuel line, the next best choice was to use 12mm (N 020 290 3) fuel 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.
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 traditionally carries 6mm, 7mm and 8mm fuel hose and 3.5mm, 5mm, 7mm, 8mm, 12mm and 14mm vacuum hoses...
First and foremost you MUST use proper FI clamps with the profiled band with raised edges. 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 clamps 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 heads.
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) and they have a gold corrosion plating with phillips screw. Bus Depot used to stock these clamps as 311-133-515.
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 hoses twice for safety and you'll need two larger clamps for the 11mm ID hose that goes between the fuel filter and the fuel pump.
Option 3) Use an SAE clamp (BEST OPTION):
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. The edges are rounded but not quite 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 stainless clamps online:
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 $70.
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" which was about 15 year ago! When I tried the #22015 clamps out on some spare VW fuel rail, they were an excellent fit so I have installed them everywhere and they've worked out great.
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.
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.
|7mm clamps||311 133 515||Bus Depot (NLA)||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|
Over the years, VW used a lot of different fasteners as they saw the need for improvements or cost savings. Some buses had screw clamps on the fuel lines like mine while others had "ear clamps" from Oetiker. These are sometimes called "crimp clamps" as they have to be crimped on using a special hand tool. They are semi-permanent and have to be cut off in order to be removed.
If fuel hose lasted 25+ years I would only recommend using Oetiker fuel hose clamps, however from my own experience, I recommend that you use stainless steel clamps that are secure but can also be easily removed to check on the condition of your fuel hoses or to more easily facilitate fuel hose replacement.
By removing a short piece of hose and cutting it open, you'll have a better idea of the state of your fuel lines. Cracks at the ends from air contact don't always mean that the inner hose is failing. Take a look at this photo of the 12m hose between the fuel pump and filter.
This hose was on my bus for 9 years until I decided to change it with the fuel filter. It was good quality German made hose (either from Cohline or Contitech).
Where the fuel soaks into the hose, the hose looks perfect even with the 5% or 10% ethanol in today's oxygenated fuels.
But look at the areas where the flares on the pipes are located: there are cracks from mechanical stress and clamping forces. The white residue is corrosion from the aluminum fuel pump inlet. The other end is in even worse condition because of the more aggressive flare on the fuel filter even with this 12mm hose which is larger than normally used 11mm hose.
The hose is also cracking from the outside all over which you can't even see under the hose braid! This is where the air, rubber and permeating fuel vapour converges. This is the main reason why you should AVOID braided hoses because actually leaks are often the only indicator that it's going to fail.
My advice is to use a FI rated hose in this area to help outlast your fuel filter. It's usually a good idea to replace this hose every time you change the filter because it's such a tight fit and old may crack during removal of the fuel filter.
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 once in a while. Often, the vapors will penetrate into the house and of course saturate the garage and then you'll know you've got a problem you may not even have noticed. Remember that fuel is most combustible in vapor form...
The hose that I've marked in red in the diagram below 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 can leak gasoline into the engine compartment during fill-ups or sharp turns.
Also of interest is part #15A in the diagram. This is the 3 way tee that I mentioned below. It cracks from age and breaks 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.
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 although I can't say for certain how it is supposed to perform with continuous vapour contact vs. fuel contact.
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.
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 long lasting 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 it cracks, you'll get unwanted fuel vapors. I recommend that you use 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 bad hose.
Yes, the clamps look ugly and it's not original but safety is more important don't you think? VW should have installed ear clamps here at the factory IMHO.
When I talk about adding clamps to the fuel breather lines, I'm including the hoses behind the firewall. Since they are inaccessible unless the engine has been dropped a little, you should use clamps and Seal-All to apply the most permanent fix.
The lowest cost el-cheapo 5/16" fuel hose you'll find at your local flaps will be brittle in a couple of years. I know first hand from making this mistake when I first resurrected my bus and didn't have the time to source the right fuel hose when I lived in Texas and got my bus running after it sat for a few years.
One reason for a shortened life is the quality of the hose and another is that it gets 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 and they are out of sight so check them yearly at least.
See my fuel tank restoration for tips on replacing the large 2 1/4" hose from the filler tube to the fuel tank.
The 72 fuel tank is a little different. There is a molded rubber elbow at the top center of the tank and this item is NLA but people have reported that 321-611-939E works. If you do find hose under the original part number it will probably be an approximation of the original molded hose.
The breather tube it connects to leads to the filler opening:
Spooky has a repair method for this critical part.
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 diameter hose connecting the filler tube to the tank is much longer than on the FI buses.
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:
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 outlet.
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.
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 a 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.
NOTE: 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.
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
07/15/19 - Google update: new adsense code, removed defunct translate button
10/28/20 - Added ethanol fuel warning, updated links and added rotten hose photo