Complete Fuel Line Replacement - Fuel Injected Bus, 1975-1979

Fuel Line Replacement - '75-'79 Fuel Injected Bus

Job: Complete Fuel Line Replacement

Application: Fuel injected Bus 75-79

Notes:

READ ALL THE WAY THROUGH THIS FIRST

front is front in the engine compartment

Symbols:

m	meters
mm	millimeters
"	inches
rails	metal fuel lines
#_	cylinder noted

Tools and Supplies:

Item	Notes
5 gallon bucket	Fits under my Bus (barely) to drain the gas.
Rags	For gas leaks
Fire extinguisher
Pressure gauge, 35 psi	For testing lines, pump, regulator
Sandpaper	I cleaned the dirt and scum off my rails and they look great

Parts:

Quantity	Item	Notes
4	large injector seals	Spend the money on OEM if you're replacing as the aftermarket ones are ill-fitting
4	small injector seals
3 m	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 and Vanagain.
6"	10 mm low pressure fuel line	I used 5/8". You can also use 1/2" (12mm ID) fuel line or 1/2" emission hose.
30	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.
2	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.
1	New filter	Volkswagen 133 133 511, Bosch (long) 0 450 901 005, Bosch (short) 71013, Wix 33274, or Fram G3743

Procedure:

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.
1. 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.
2. 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.
3. 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.
4. 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!
5. 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.
6. #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.
7. 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.
8. #1/2 rail remove/replace is typical to #3/4 rail, but in a tighter space.
9. #1/2 rail to pressure regulator, not a bad job.
10. That's all for the engine compartment. While here, disconnect the tank supply/return lines from where they enter the engine compartment if you haven't already.
Remove & replace lines under the Bus.
1. 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.
2. 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