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Anonymous Posted on Mar 10, 2015

Fuel line diagram

What are the 3 lines for...delivery..return..and what is the third

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robert wales

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  • GMC Master 4,977 Answers
  • Posted on Mar 10, 2015
robert wales
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Joined: Mar 01, 2011
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The third is probably the vent line.

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1helpful
1answer

The fuel lines are all rusted and broke and i need to know what goes where

Should be one line comes from the fuel tank to the pump and the other line goes from the pump to the carburetor or injector body. Some cars have a third line that relieves fuel pressure from the pump to the return in the tank. This third line is much smaller than the other 2
0helpful
1answer

SE 3.1l. Where can I get a diagram showing fuel lines and part names?

you can visually see the lines. the 3/8" diameter line is the pressure line and the 5/16" line is the return line. you buy fuel lines for it and replace the O rings while you do them. if they are rusty then replace both lines.
3helpful
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Need to know what 3 lines from fuel tank go

The pump line, or feed line, goes to the fuel filter and then to the engine's fuel rail. A return line leaves the fuel rail and sends gas back to the tank. Usually, the feed line is slightly larger than the return line, not always.
The third line is a vent line for emission controls-routing gas fumes from the tank to the charcoal canister, where it is stored and later sent to the engine to be burned.
0helpful
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No power after 4000 rpms

This sounds like a fuel pump or fuel filter problem.
The 1988 Jetta has two fuel pumps. The "main" one under the car directly in front of the gas tank on the right hand side. The other fuel pum is in the tank. You can access that fuel pum by removing the round access panel in the trunk towards the back seat.

You'll need a fuel pressure gauge. You can usually borrow one from a large auto parts chain store.

FUEL DELIVERY & SYSTEM PRESSURES
System Pressure
Connect Pressure Gauge (VW 1318) between line from fuel distributor to cold start valve and
test port connection on lower chamber of fuel distributor, using Adapter Fittings (VW 1318/5).
Test port is sealed by a threaded plug. Bridge fuel pump relay with Jumper Switch (US 4480/3).
1.
Disconnect wiring from Differential Pressure Regulator (DPR). Open valve on pressure gauge
(points at cold start valve line when open) and activate fuel pump. System pressure must be 75-
82 psi (5.3-5.8 kg/cm2 ). If pressure reading is low and fuel pump delivery quantity is good,
replace pressure regulator.
2.
If pressure reading is high, disconnect fuel tank return line from DPR. Repeat test. If reading is
correct, check for plugged return line. If reading is incorrect with line open, replace DPR.
3.
Differential Control Pressure
Close valve on pressure gauge. Activate fuel pump with jumper switch. Leave DPR
disconnected. DPR reading should be 2.9-7.0 psi (.2-.5 kg/cm2 ) less than system pressure. If
pressure is incorrect, disconnect lower chamber return line and measure volume.
1.
Close open port to diaphragm pressure regulator. Activate fuel pump with jumper switch. Fuel
volume should be .14-.16 qts. (.13-.15L) for period of one minute. If volume is correct, replace
DPR. If volume is incorrect, replace fuel distributor.
2.
Close valve on pressure gauge. Install Test Harness (1315A/1) between DPR and vehicle
harness. Set multimeter to DCA 200 mA scale. Connect multimeter to test harness. Disconnect
wiring to coolant temperature sensor. Connect 15 k/ohm side of Test Resistor (VW 1490) to
sensor wiring.
3.
Turn on ignition and fuel pump. Differential pressure should be 10-17.5 psi (.7-1.2 kg/cm2 )
less than system pressure. DPR current should be 50-80 mA. If pressure is incorrect and current
is correct, replace DPR.
4.
If both pressure and current readings are incorrect, remove test harness from DPR. Ensure
resistance of DPR is 17.5-21.5 ohms. If reading is incorrect, replace DPR.
5.
If reading is correct, check ground from temperature sensor to cold start valve. If ground is
good, check power supply fuse. If fuse is okay, check terminals on ECU connector. If connector
is okay, replace ECU.
6.
Residual Pressure & Internal Leak Testing
Open valve on pressure gauge. Operate fuel pump for 30 seconds. Pressure can drop to a
minimum of 38 psi (2.7 kg/cm2 ) after 10 minutes. If pressure drops below specification, inspect
fuel pump check valve and all fuel fittings for leakage.
1.
NOTE: Pressure and leak testing does not include checking cold start
valve.
FUEL INJECTION SYSTEM - BOSCH CIS-E -1988 Volkswagen Jetta Page 1 of 3
http://www.ondemand5.com/mric/common/asp/printart.aspx 11/25/2011
If there are no leaks, check airflow sensor plate clearance. If plate clearance is correct, replace
diaphragm pressure regulator and repeat leak test. If pressure drop is not within specification,
replace fuel distributor "O" rings.
2.
Transfer Pump Delivery Volume
Check voltage supply to pumps. Connect Jumper Switch (US 4480/3) in place of fuel pump
relay, on relay panel. Remove fuel filler cap. Disconnect and plug off Black fuel line from
sending unit.
1.
Connect hose to sender port and place in measuring container. Turn on fuel pumps. Minimum
transfer pump delivery volume should be .42 qts. (.4L) in 10 seconds. Reconnect fuel line to
sender.
2.
Main Pump Delivery Volume
Check transfer pump (if equipped) and fuel filter. Disconnect fuel return line and place in
measuring container. Switch on fuel pump with jumper switch. Check fuel pump delivery
volume for 30 second period. Delivery rates are given with voltage reading at pump as volume
will change with different voltages.
1.
Minimum delivery volume for Fox, Quantum and Quantum Syncro models is .71 qts. (.68L) for
30 seconds with reading of 11.4 volts at fuel pump. Minimum delivery volume for other models
is .62 qts. (.59L) with 11.4 volts at fuel pump.
2.
Fuel Distributor
Check sensor plate adjusting lever and fuel distributor control piston for smooth operation.
Disconnect fuel injector lines at fuel injectors.
1.
Remove fuel pump relay and bridge fuel pump circuit. Use Jumper Switch (US 4480/3) in place
of fuel pump relay. When pressure has built up, turn off fuel pump. Move sensor plate from rest
position to end of travel.
2.
Uniform resistance should be felt during entire movement. No resistance should be felt on
quick return to rest position. Connect injector lines. Install fuel pump relay.
3.
Injector Quantity Comparison
Remove fuel pump relay, from relay panel, and install Jumper Switch (US 4480/3) in off
position in place of relay. Attach Fuel Quantity Analyzer (US 4480) to bumper and secure in
place. Remove injectors from cylinder head with fuel lines attached. Check and replace fuel
injector "O" rings as necessary.
1.
Check tightness of injector insert (2-piece inserts). If inserts are loose, remove and clean
threads. Use sealing compound when installing upper insert. Replace sealing washer that goes
against cylinder head below lower portion of insert. Lubricate injector "O" rings with gasoline
and install injectors, with fuel lines connected, into fuel quantity analyzer tubes.
2.
Ensure lines are not kinked or bent. Loosen fittings to align fuel lines and retighten. Remove
rubber boot from airflow sensor housing above sensor plate. Turn and lift setting screw and
adjusting slide of Sensor Plate Adjustable Holder (VW 1348/1) into upper position. This
simulates full throttle operation. See Fig. 11 .
3.
FUEL INJECTION SYSTEM - BOSCH CIS-E -1988 Volkswagen Jetta Page 2 of 3
http://www.ondemand5.com/mric/common/asp/printart.aspx 11/25/2011
Fig. 11: Sensor Plate Adjustable Holder (VW 1348/1)
Courtesy of AUDI OF AMERICA, INC.
Place sensor plate adjustable holder on airflow sensor housing with holder centered over plate.
Pointer on edge of holder base must point toward center of fuel distributor. Push adjusting slide
of holder down onto stop.
4.
Turn adjusting screw clockwise until magnetic end touches sensor plate retaining bolt. Activate
fuel pump with jumper switch. Turn adjusting screw of holder counterclockwise until any one
injector starts to deliver fuel. Turn off jumper switch and empty fuel quantity analyzer after
taking sample.
5.
Idle injection quantity is measured first. Lifting adjusting slide of holder to first stop simulates
idle position of sensor plate. Activate fuel pump until fuel level reaches 20 ml on scale of any
tube.
6.
Check that all injectors have identical spray patterns that are even and cone-shaped. If not, raise
sensor plate up quickly to full lift position and release. Repeat idle quantity test. Compare
amounts of fuel delivered by all injectors with analyzer held level. Maximum difference in
delivery quantity between injectors is 3.0 ml of fuel.
7.
If fuel delivery quantity differs between high and low levels by more than 3.0 ml, interchange
injectors and repeat test. If difference of delivery quantity changes with injectors, replace
injectors. If difference of delivery quantity does not change with movement of injectors, either
fuel lines are pinched or fuel distributor is defective.
8.
Measure full throttle injection quantity. Empty analyzer into fuel tank and reinstall injectors in
analyzer. Lift adjusting slide of holder to last stop to simulate full throttle position of sensor
plate. Activate fuel pump with jumper switch until fuel level reaches 80 ml on scale of any tube
of analyzer.
9.
Check that all injectors have identical spray patterns that are even and cone-shaped. If not, raise
sensor plate up quickly to full lift position and release. Repeat full throttle quantity test.
Compare amounts of fuel delivered by all injectors with analyzer held level. Maximum
difference in delivery quantity between injectors is 8.0 ml of fuel.
10.
If fuel delivery quantity differs between high and low levels by more than 8.0 ml, interchange
injectors and repeat test. If difference of delivery quantity changes with injectors, replace
injectors. If difference of delivery quantity does not change with movement of injectors, either
fuel lines are pinched or fuel distributor is defective.
11.
Check fuel injectors for leakage immediately after delivery quantity test is complete. Set sensor
plate in rest position. Activate fuel pump with jumper switch for 2 minutes. Injectors should not
drip. Replace injectors that drip.
See image. Fuel filter is probably located on the frame between the engine and fuel tank.
8_24_2012_11_36_10_pm.jpg8_24_2012_11_36_30_pm.jpg
1helpful
1answer

Fuel pump fuel lines

Its kind of a crime that these companys can get away with not making all fuel lines out of stanless steal but they do .So they rust out from the road salt. You don't say what you have but it sounds like an in tank pump. I find the easest way is to replace the metal lines with rubber lines . The pump it self should 3 lines comeing off it. The biggest is 3/8s and thats the main supply then a 5/16 as the fuel return line . It needs this because all of the fuel that is pumped to the injectors is not burned so it returns to the tank. The third line 1/4 or 5/16 is for the EVAP and any kind of rollover shut off system. Your best bet is go to napa tell them your problem and they will have if not everything most of what you need to switch to flexable line that will never rust again and lots of speical fittings and connecters. You can fix it for about 100 dollars in parts but you have to figure out exactly what you will need but if you go to a dealer it would be 2 to 4 thousand on most vehicles .These things are easy to get at GOOD LUCK WITH IT
0helpful
1answer

I can't find where the return line on the fuel system is going. only 1 line comes up to the front where the mechanical fuel pump is located. I can't get fuel to the carb.

on a carcureted engine there is no return line, to check fuel delivery disconnect the fuel line at the carb and turn the engine over, these run at low pressure, like 4lbs
1helpful
1answer

Im looking for repair manual for 1986 chevy k10 pickup. or at least a diagram of where all the gas lines go

Autozone.com has a lot of info on your truck. Just sign up for free account, enter your truck year, model, etc. and look here: http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideMain.jsp .

To answer the question on fuel tank lines, there should be 3. The pressure line goes to the fuel pump, and a return line from the fuel pump. The third line is the evaporation system/vent line. It goes to the evaporation cannister to control gas emissions. Not sure where that is on your truck. The manual doesn't say.

If you have more questions, please let me know.
1helpful
3answers

2001 dodge stratus r/t engine code p0455 evac... what does this mean or how can i fix this essuie??

Or maybe the recall on the fuel return line 2001 Dodge Stratus Recall Date: 10/27/2000 2001 Dodge Stratus Component: FUEL SYSTEM, GASOLINE:DELIVERY:HOSES, LINES/PIPING, AND FITTINGS Potential Units Affected: 13100
Summary: VEHICLE DESCRIPTION: PASSENGER VEHICLES. THE OUTER LAYER ONLY OF THIS 3-LAYER FUEL RETURN HOSE DOES NOT CONTAIN THE DESIRED OZONE PROTECTION DUE TO A PROCESSING ERROR.
Consequence: THIS HOSE IS CONSIDERED TO BE INADEQUATE.
Remedy: DEALERS WILL REPLACE THE FUEL RETURN HOSE.
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