original fuel line from gas tank on '71 Westy

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When I installed the larger, later-model fuel tank in my '65 I fitted it with an aircraft finger-strainer and shut-off valve going to a standard 37-degree flare fitting. Down stream, it's 1/4" 3003 aluminum tubing with standard aircraft fittings, all the way to the forward breast tin, where I have a bulkhead fitting.

To pull the engine, just close the valve and open the line.

Inside the engine compartment I've used metric-sized steel fuel pipe, properly bent and secured. I prefer the old style fuel pumps (ie, threaded fittings) but have a cone-top on there right now.

(Older pumps can be rebuilt... if you can find the kit for them.)

VW fuel pump (and most other mechanical pumps on cars) is the toggle type. Engine pushes the rod, rod actuates the rocker, rocker pulls DOWN on the toggle, which is connected to the diaphram, which sucks some gasoline into the lower camber of the pump. If everything's working right the PUMPING action is provided by the spring that pushes the diaphram UP. Spring only provides a few ounces of pressure. (Max spec is something like one pound. Truth is, you don't even need a pump with a bus. Gravity feed from a can on the rear deck will get you home.)

When the diaphram goes UP it pushes some gasoline past a check-valve into the upper chamber, which also has a diaphram and a spring and which acts as a PRESSURE REGULATOR, insuring the carb sees a fairly constant flow of fuel. The float in the carb has no trouble overcoming the few ounces of pressure provided by the springs.... so long as everything is working okay.

But when you have a really bad day, the toggle snaps off and the diaphram rod gets locked to the rocker and your innocent little variable-output, ounce-pressure pump becomes a POSITIVE OUTPUT pump capable of producing several pounds of pressure... more than enough to blow that silly filter after-marekt out of the line and spray gasoline all over the engine compartment.

But hopefully not on the later-model pumps, which are supposed to fail safe.

What wears out? The springs rust. The one-way valves start to leak. The diaphram tears. The toggle breaks off. The rocker pivot gets ovaled out. The ends of the push-rod wear down.

All of which is easy to fix or replace.

Major chore is rebuilding the ovaled-out pivot-pin bore in the pot-metal casting of the pump's body. Proper repair is to re-bush the hole with a bronze bushing, replace the pivot pin with one made of stainless steel. Old model usta be secured cy circlips.

Diaphrams, springs & valves are in the repair kit; just replace them. But if the pump is REALLY old you may need to re-thread the holes (insert Heli-coils if you know how), use larger screws. (The pot metal wears out.)

Worn ush-rod needs a dot of weld on each end, then polished back to its specified length. Protrustion (through the plastic heat insulator) is adjusted by adding/subtracting gaskets, a few of which you should keep in your kit. (Fuel pump push-rods come in three lenghs, reflecting changes to the pump over the years. Long rod can be cut down to a shorter size but a worn short rod has to be welded then polished.

Old style pumps had a filter, supposed to be cleaned every time you changed the oil. Nobody does. I don't know why. Instead, they spend two bucks for one of those ten-cent after-market filters. And then never change it either. (I think it has something to do with watching too much television.)

Carb bowl has a drain plug. Same place you gain access to the main jet. Water & crud will collect in the bowl. Supposed to be drained every time you change your oil. Nobody does, of course.

VW fuel system is sooper-simple, even the later ones with their vapor recovery system.

Early style carbs & pumps were designed to be rebuilt/repaired. Later model stuff is throw-away junk, lasts a couple of years then leaves you stranded somewhere. Progress.

I can't afford to own a vehicle I can't maintain myself. And I'm not just talking money.

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Easy answer on the hose: Stop over-tightening the clamps. Snug to the OD of the hose is all it takes to keep them on. The flare of the fitting and the elasticity of the inner lining of the hose is what provides the seal. The clamp is only there to prevent the hose from being pulled off.

Some early VW fittings were straight. No flare. The only suitable hose for that type of fitting is the original VW design with the elastic outer cover. Later stuff (look at a Brazilian carb or fuel pump) has the flare, is meant to be used with straight hose secured by a clip or clamp.

Got an early carb or pump? Then either replace the brass ferules with threaded fitting or add a slight flare to the end. Why? Because the proper size hose is no longer commonly available. If the pipe has no flare AND you use straight hose, no matter how tightly you clamp it, it'll eventually come off. Less worrisome (for me) to simply replace the hose with pipe and threaded fittings. Do it once -- and do it right -- you don't have to worry about it later.

Your option. It's your ride and you're the Mechanic in Charge.

-Bob Hoover

Thanks for this article, Bob. I personally appreciate it when you share your deep knowledge of how these things work.

Thanks. Aircraft-level fuel safety is exactly what I had in mind. Do you know of a quality source for a bus gas tank with the modifications you suggested? snipped-for-privacy@naxs.com v I think I can stand the press-on fittings in the engine compartment [have applied light clamping anyway] , although I had *not* recently considered the spectre of an over-pressure fuel pump. I'm glad you brought that up; I remember my last fuel pump having flared fittings[emergency aftermarket purchase on-the-way-to-work], but I'll have to check my carb fitting. My carb has to be pulled out soon because the vacuum line is believed to be clogged. v Is the gas tank fitting usually flared? I'm assuming brazing of the fuel tank fitting is required. That [plus my fuel guage has finally started jerking back and forth] has me thinking about pulling the gas tank out. Do you know of a quality source for a bus gas tank with the modifications you suggested?

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