Fuel Delivery Overview

Carbs & F.I.

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Amskeptic
IAC "Help Desk"
IAC "Help Desk"
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Fuel Delivery Overview

Post by Amskeptic » Mon Nov 30, 2009 9:01 pm

Gasoline is a remarkable energy source and flammable. Start your own overview of any gasoline-powered automobile with a thorough inspection of fuel lines for routing and potential hazards of chafing or road debris strikes, and condition of hoses, clamps, and ignition risks like wiring or mechanical heat sources.

When checking a fuel system failure, please have your common sense switched "on". Do not use a hot incandescent light bulb for inspecting fuel leaks down at an injector for example. A cold LED flashlight would be the more sensible choice.

Fuel delivery and distribution is relatively simple. We have to bring liquid fuel to the distribution point and vaporize it in a quantity that ensures reliable combustion.

Fuel delivery comprises all hoses and the pump. A failure in the delivery system rarely causes sudden death, but it can. If the engine dies right out, you will want to first check for correct ignition, since this is the system that will most likely stop the engine dead. If ignition system is firing off nice sparks when you crank the engine briefly, start way up the river of the fuel system with essentials like "is there fuel in the tank?" Go ahead and pull a hose off downstream of the pump, place hose in a safe secure container where you can crank the engine briefly again to see if fuel is delivered.

Distribution problems will only cause partial failure, which will seem as traumatic due to the bucking and hiccoughing and spitting and backfiring, but any time an engine manages to keep running, you are further on the road to solution than if it is not running at all. Dirty carburetors and failed fuel injectors and sudden large vacuum leaks can give your engine just enough of a fuel mixture to fire intermittently. Remember, don't be here unless you have proven your ignition system first.
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Steve
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Re: Fuel Delivery Overview

Post by Steve » Fri Sep 11, 2015 1:37 am

One nice aspect of the fuel injected models that I am familiar with, both air cooled and the later years' water-cooled, is the fuel injection rail test port located on the left fuel rail. This capped (with a small, easily lost aluminum sealing washer under the cap) port allows for a section of fuel injection pressure-rated rubber line to be slipped over it and clamped. To the other end of that I have a gauge scaled at 0-50 PSIG and this set up allows me to trouble shoot fuel pressures without the risk of pressurized gasoline exposing myself to unnecessary risk.

Should you decide to do this, keep mind the fuel rail is supposed to be pressurized as much as 30-35 PSIG... even with engine shut off. So always wear fuel resistant gloves, safety eyewear and place a rag or two under the fuel rail where the cap is before you remove it, hopefully seeing a spray of gasoline emit from under the cap when you loosen it.

Refer to your Bentley Fuel Injection chapter under topics including troubleshooting and test equipment for more information.

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