Fuel Line Replacement - '75-'79 Fuel Injected Bus
By Billy Price, with suggestions from
Jim Thompson and Nick Palmer. Copyright © 2002, Billy Price.
Job: Complete Fuel Line Replacement
Application: Fuel injected Bus 75-79
READ ALL THE WAY THROUGH THIS FIRST
front is front in the engine compartment
||metal fuel lines
Tools and Supplies:
|5 gallon bucket
||Fits under my Bus (barely) to drain the gas.
||For gas leaks
|Pressure gauge, 35 psi
||For testing lines, pump, regulator
||I cleaned the dirt and scum off my rails and they look great
||large injector seals
||Spend the money on OEM if you're replacing as the
aftermarket ones are ill-fitting
||small injector seals
||7.5 mm high pressure (35psi) fuel line
||Mercedes-Benz P/N 916030-000527 - try M-B dealership or European auto
repair shop. Or Volkswagen P/N N 020 281 1 from list vendors like Bus Depot
||10 mm low pressure fuel line
||I used 5/8". You can also use 1/2" (12mm ID) fuel line or 1/2" emission
||7.5 mm clamps
||NOT "Gates" style with the exposed screw slots in the band. Get the
ones that have a solid band of metal next to the hose (M-B). They're a
dollar each but worth it. Try a M-B dealer or Euro auto repair shop.
||10 mm clamps
||I used the old style here as there's only 2 and you get a good close
look at 'em every time you replace the filter.
||Volkswagen 133 133 511, Bosch (long) 0 450 901 005, Bosch (short)
71013, Wix 33274, or Fram G3743
- Disconnect battery ground strap for fire safety. Make sure the strap
can't fall back against the body and make contact again.
- Drain tank.
If a tank removal/flushing/restoration is in your mind, now is
the time. Why flow old crap into your new lines/filter?
- Remove & replace lines in engine compartment.
Why only engine compartment? I saved the lines to/from the tank
which go through the firewall & under the Bus for last so I'd only have
to go under the Bus once. If you follow the lines like a map, from tank
outlet to tank return, you'll be under there twice, but this may be more
comfortable for some people.
- Behind #3 (left front of engine) a metal rail comes through the
firewall below the F.I. relays; start here. Follow the combination
metal/rubber lines around the engine to see the scope of your task as it
hits #3, #4, the cold start valve (if you have it), #1, #2, pressure
regulator, through the firewall to tank return.
- Unscrew old clamps. Discard these! If the old lines are hard to get
off, grab a Stanley knife and slit them lengthwise from their ends on the
rails. Expect some fuel leakage.
- Replace each piece as you go. Use each piece of your old fuel line as
it comes off as a template for the new line's length. Make nice square cuts
in the new hose. Sand the crud off the metal rails as they become
available, they're shiny underneath.
- When installing new line, place the clamp fully open on the hose first.
Slip the hose over the flares on the metal lines far enough so that the
clamp can slide over the flare with the hose on it (tight!) and have plenty
of hose to clamp on the far side of the flare. Rotate your hoses before you
tighten so that you can use their natural bend in a manner that facilitates
routing. Sometimes the hoses are hard to fit, but stay away from lubricants
as this is your fuel system. NO SOAP!
- Got the first piece of rubber on the firewall supply rail? Good. Don't
attach it to the #3/4 injector rail yet because you should assemble the
injectors to the rail first as a sub-assembly. Don't try this in the engine
compartment, it's too tight. I found getting hose on the injectors
themselves to be the most difficult task. Tight fit, and I had to remove
the injectors from their mounting points to do it. Replace seals if
necessary. I reused mine.
- #3/4 rail connected to firewall rail? Now for the cold start
connections. The cold start valve is sorta delicate, so don't muscle it too
hard. It's also one of the more accessible parts of this job.
- Cold start done? Now we get to the #1/2 cylinders where junk is in the
way bigtime. Remove the airbox for working room. I disconnected my F.I.
harness and some vacuum hoses for working room/routing. Mark everything you
take off for later reinstallation. Be careful here, I knocked the F.I.
computer ground wires off the engine block while doing this and couldn't
start my Bus for three weeks till I found them. Reinstall disconnected
equipment immediately so you don't forget it.
- #1/2 rail remove/replace is typical to #3/4 rail, but in a tighter
- #1/2 rail to pressure regulator, not a bad job.
- That's all for the engine compartment. While here, disconnect the tank
supply/return lines from where they enter the engine compartment if you
- Remove & replace lines under the Bus.
- Remove the return hose coming from the #1/2 side of the engine to the
tank. There are several clips under the Bus that hold the line. If your old
line is hanging down, find the clips so the new line won't be. This is the
longest length of line to replace.
- Finally, the supply from the tank to the engine compartment. This
include the fuel pump and filter, and also has mounting clips under the
Bus. Remove and replace all the rubber and the filter.
- Your fuel path should now be complete. Check ALL the clamps and
connections again. Verify all disconnected equipment is reconnected.
- With a 7mm box wrench, remove the bolt in the fuel rail between #3/4.
This is where you attach your fuel gauge. I had to cut the fitting off the
gauge I bought and shove the hose on it with a clamp.
- Add some gas for a test run. Don't fill up, what if you're leaking
somewhere? I added about 3 gal.
- Reconnect battery ground strap.
- Bus starts? Pressure gauge 28-33psi? No leaks anywhere? Awesome. No
start? Call someone else.
- Shut off the engine and check again for leaks. Remove the pressure
gauge and replace the bolt in #3/4 rail.
- Consider replacing the gas vapor venting system lines, which is not in
the scope of this write-up.
Last updated on Thu Oct 3 17:52:21 EDT 2002