Fuel Hoses

by Richard Atwell
(c) Copyright 2003-2005

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 comfirmed 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:

• 1976
• 1977
• 1978-79

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:

• Total Hose: 1095mm (3.59 ft.)
• Total Metal Pipe: 1745mm (5.73 ft.)

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 uber 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.

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 meaurements, not VW specs (although they might turn out to be the same).

• Total 7mm Hose: 360mm (14.2 in.)

• Total 5.5mm Hose: 1260mm (4.2 ft.)
• Total length of filters in system: 225mm (8.8 in.)
• Total of above two: 1485mm (4.87 ft.)

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).

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 it's two 50mm pieces with a tee for the takeoff. 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 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.

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.

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.

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:

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:

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.

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

• The Bus Boys FI hose (7x3mm and my favorite) is 13.5-13.75mm OD
• On the fuel rail the hose measures 13.5-14.5mm OD
• On the cold start valve barb the hose measures 13.5-14.25mm OD

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.

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.

Part Numbers:

Other Measurements:

• The MB 10mm hose measures 17.16mm OD (10.5mm ID)
• On the fuel filter the hose measures 17.52mm OD and on the pump 17.82mm

FI Fuel tank:

The breather lines for the fuel tank vapor recovery system need replacing also. The one I've marked in red in the engine compartment suffers the worst wear because of it's exposure to the elements and can leak gasoline into the engine compartment during fill-ups or sharp turns.

There is no small hose matching the red one I marked in the diagram on the opposite side behind the "paint can lid" (thank goodness).

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 was braided and N 020 357 1 is the 7x2.5mm braided variety. 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 so I know it will be ok if it gets wet with fuel when the tank is very full and the bus turns corners.

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

The basic difference between the two hoses is that the braid is going to fray at the ends overtime whereas the smooth hose 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, 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.

• Continental braided fuel hose data sheet
• Continental "smooth" fuel hose data sheet

It appears that the smooth hose is actually 7.3mm ID which makes it easier to slip onto the fuel rail.

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 bus 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.

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.

Spooky has a repair 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.

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 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 definately 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 advertized for 72-73 buses I'm not sure it will fit. Ask them.

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:

• VW instructions
• Spooky Patrol Group
• Speedy Jim's Plans

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.

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:

• My fuel tank restoration
• Spooky tank repair

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