Fuel System Service Flashcards
How are filters rated?
According to their ability to stop particles of a certain size
What are the 4 basic types of fuel filters?
Screen or Strainer
Surface
Depth
Edge
Screen and Strainers
commonly used in the inlet of fuel tanks and the outlet lines of off-road equipment. Are a surface type filters
Why are spin on filters the most common filter design?
Simplistic design and relatively low cost
Ease of surface
Less chance of dirt entering the fuel system during service
What are the common materials used in depth type filters
Cotton yard
Cloth
Wood fibre
Porous metal
What are the common filter classifications?
Primary
Secondary
Final Stage
What size particle will each type of filter remove?
Primary - larger than 25 microns
Secondary - larger than 5 microns
Final stage - Down to 1 micron
Fuel filters differ from most oil filters in that they do not have?
By-pass valve
What is the function of a transfer pump?
Move fuel from the tank through the filter to the high pressure pumping mechanism. Pumps create low pressure.
What are the 5 basic types of fuel transfer pumps?
Diaphragm Plunger Hand primer Gear Vane or Blade
Diaphragm type transfer pump
May be operated off the engine or injection pump. Will work with cam turning in either direction. Are self regulating. Output usually around 10 PSI. Produce a pulsating output. May include a sediment and/or water separator.
Where are plunger type pumps most commonly used?
On a multi-plunger injection pump
Plunger type pumps
Usually operated by a cam or eccentric on injection pump cam. Will work will drive in either direction. Self regulating. 25-30 PSI. Produce a pulsating output. May have a hand primer
Gear type pumps
Consists of two perfectly meshed gears turning in an enclosed housing. Spur gears are most commonly used. Have a specific direction of rotation. Must have a pressure relief.
Vane type pumps
Commonly used in single or opposed plunger distributor pumps as an integral transfer pump. Will produce a high volume for size
What is first that should be checked when diagnosing a fuel system issue?
Fuel level
High inlet restriction can be the result of?
A plugged tank vent
Restricted fuel lines
A plugged fuel filter before the pump
To check fuel pressure you should?
Install a pressure gauge on the outlet side of the transfer pump after the secondary filter
Low fuel pressure could be the result of?
High inlet restriction Restricted fuel lines a plugged fuel filter Worn transfer pump A relief valve stuck in the open position
What are the two basic methods of checking fuel flow volume?
Measure the return fuel flow with the engine running at a specific RPM for a specified length of time
Measure the output volume of the fuel pump while the engine is cranking
The correct amount of fuel is important to ensure?
A sufficient volume of fuel is available for the injection pump or unit injectors to meet engine requirements
Sufficient cooling of injection system components
“Since pressure is the result of flow and restriction”; how can this be a indication of fuel issue?
Low fuel pressure can be an indication of reduced fuel flow
What are the two basic methods for testing for air in the fuel?
Submerge the return line in a bucket of fuel and watch for bubbles
Install a sight glass in the fuel line before the transfer pump
Air in the fuel system can be the result of?
A cracked or broken fuel tank stand pipe
Loose fittings
Cracked fuel lines or fittings
Missing gaskets or O-rings in primary filter
For every 10F above 100F of fuel temp, power deceases by?
1%
Before a fuel pump is removed you must make sure that?
The dirt around the pump is removed to help ensure that dirt does not enter the fuel system.
Fuel filters are rated according to their ability to stop certain sized particles measured in?
microns
Explain how surface type filters remove particles from the fuel?
They do not allow any particles larger than the holes in the filter medium to pass through
To avoid system contamination, what two methods should be used to fill filters during a service?
Use hand transfer pump
Fill with clean pre-filtered fuel
Diaphragm and plunger type fuel pumps are self regulating because?
Diaphragm or plunger spring tension limits the maximum pressure that the pump can develop
What 5 fuel problems could cause hard starting?
Low fuel level Restricted inlet Cracked or loose inlet pipes Plugged filter (before pump) Fuel system draining back to tank after shutdown
Sealed fuel injection pumps should not be disassembled unless you have?
The proper training
A clean environment
The correct tools
A plunger type pump with a weak or broken plunger spring would have?
Low volume or pressure
What 3 clearances should be checked when inspecting a gear type transfer pump?
Gear to gear clearance
Gear to pump body clearance
Gear end clearance
What are the 5 areas of a vane type pump that should be checked for wear?
Ends of the vanes Sides of the vanes Rotor slots Inside surface of the liner End plate or cover
Wear inside of a vane type pump causes?
Internal leakage and reduces pump output
Some fuel systems must be checked using a special tool called a ________.
flow meter
Clearance of precision parts in an injection pump should be how many microns?
1 to 3 microns
