1991 ACURA NSX relay

Fuel Pump

Description

Because of its compact impeller design, the fuel pump is installed inside the fuel tank, thereby saving space and simplify-

ing the fuel line system.

FUEL PUMP

FUEL PUMP BRACKET

FUEL FILTER

FUEL PUMP CROSS SECTION (Side view)

RELIEF VALVE
FEUL

PUMP COVER
FUEL PUMP ASSEMBLY CROSS SECTION (Top view)

DISCHARGE PORT

INLET PORT

IMPELLER

CHECK VALVE

ARMATURE COIL
FUEL

PUMP CASING
IMPELLER
GROOVES
CASING

The fuel pump is comprised of a DC motor, a circumference flow pump, a relief valve for protecting the fuel line systems,

a check valve for retaining residual pressure, an inlet port, and a discharge port. The fuel pump assembly consists of the

impeller (driven by the motor), the fuel pump casing (which forms the pumping chamber), and the fuel pump cover.

OPERATION

(1) When the engine is started, the PGM-FI main relay actuates the fuel pump, and the motor turns together with the

impeller.

Differential pressure is generated by the numerous grooves around the impeller.

(2) Fuel entering the inlet port flows inside the motor from the pumping chamber and is forced through the discharge

port via the check valve.

If fuel flow is obstructed at the discharge side of the fuel line, the relief valve will open to bypass the fuel to the inlet

port and prevent excessive fuel pressure.

(3) When the engine stops, the fuel pump stops automatically. However, a check valve closes by spring action to retain

the residual pressure in the line, helping the engine to restart more easily.

(cont'd)ProCarManuals.com

Testing

Do not smoke during the test. Keep open

If you suspect a problem with the fuel pump, check that
the fuel pump actually runs; When it is ON, you will hear some noise if you hold your ear to the fuel fill port with
the fuel fill cap removed. The fuel pump should run for
two seconds when the ignition switch is first turned on. If the fuel pump does not make noise, check as follows:
1. Remove the seat back panels.
2. Disconnect the C489 (6P) connector (located behind the seat back panels).
CAUTION: Be sure to turn the ignition switch OFF
before disconnecting the wires.
3. Disconnect the PGM-FI main relay connector and connect the BLK/YEL wire and BLK/YEL wire
with a jumper wire.
1. Remove the fuel tank (see page 11-126).
2. Disconnect the connector from the fuel pump.
3. Remove the fuel pump mounting nuts.
4. Remove the fuel pump from the fuel tank.
If battery voltage is available, replace the fuel
pump.
If there is no voltage, check the fuel pump
ground and wire harness (see page 11-122).
4. Check that battery voltage is available at the fuel
pump connector when the ignition switch is turned
ON (positive probe to the BLK/YEL wire, negative
probe to the BLK wire).

C489 CONNECTOR (6P)

BLK/

RED (+)

BLK (-)

JUMPER WIRE

flame away from your work area.

Replacement

Do not smoke while working on fuel

system. Keep open flames away from your work area.

28 N.
m (2.8 kg-m, 20 Ib-ft)

6 N.m
(0.6 kg-m,

4 Ib-ft)

FUEL PUMP

BRACKET

FUEL PUMP

PGM-FI

MAIN RELAY

BLK/
YEL

BLK/
YELProCarManuals.com

Fuel Supply System

Description

The PGM-FI main relay actually contains two individual
relays.

The relay is located behind the passenger's seat backpanel.
One relay is energized whenever the ignition is on which
supplies the battery voltage to the ECM, power to the
fuel injectors, and power for the second relay.
The second relay is energized for 2 seconds when theignition is switched on, and when the engine is running
which supplies power to the fuel pump.
Relay Testing

NOTE: If the car starts and continues to run, the
PGM-FI main relay is OK.
1. Remove the PGM-FI main relay.
2. Attach the battery positive terminal to the No. 4 terminal and the battery negative terminal to theNo. 8 terminal of the PGM-FI main relay. Then
check for continuity between the No. 5 terminal
and No. 7 terminal of the PGM-FI main relay.
3. Attach the battery positive terminal to the No. 6 terminal and the battery negative terminal to theNo. 2 terminal of the PGM-FI main relay. Then
check that there is continuity between the No. 1
terminal and No. 3 terminal of the PGM-FI main

relay.

FUEL

PUMP

RELAY

FUEL PUMP

RESISTOR

FUEL PUMP
PGM-FI
MAIN RELAY

No. 3
No. 7

No. 8 No. 4

No. 1
No. 6

No. 5 No. 2
TO
IGN.
1

TO BAT

TO
IGN.
1

TO GROUND
TO ST. SWITCH

TO ECM
(A7)
TO ECM
(A25.
CD

TO FUEL PUMP
PGM-FI Main Relay
If there is continuity, go on to step 4.
If there is no continuity, replace the relay and
retest.
4. Attach the battery positive terminal to the No. 3 terminal and battery negative terminal to the No. 8
terminal of the PGM-FI main relay. Then check that
there is continuity of the PGM-FI main relay. Then
check that there is continuity between the No. 5
terminal and No. 7 terminal of the PGM-FI main relay. If there is continuity, the relay is OK;
If the fuel pump still does not work, go to
Harness Testing in the next column. If there is no continuity, replace the relay and
retest. (cont'd) If there is continuity, go on to step 3.
If there is no continuity, replace the relay and
retest.ProCarManuals.com

Fuel Supply System
PGM-FI Main Relay (cont'd)
Troubleshooting Flowchart
(To page 11-123)
BLK/

WHT
GRN/

YEL/
BLK

PGM-FI
MAIN RELAY

BLK/

YEL

BLK

YEL/

BLU

BLK/

YEL

BLK/

YEL
BLK

Engine will not start.
Inspection of PGM-FI main

relay.

Disconnect the PGM-FI main
relay connectors.
Check for continuity between
BLK terminal and body

ground.

Does continuity exist?
Measure the voltage between YEL/BLU terminal and body

ground.

Is there battery voltage?

Turn the ignition switch ON.
Measure the voltage between BLK/YEL terminal and body

ground.

Is there battery voltage?
Measure the voltage between BLK/YEL terminal and body
ground.
Is there battery voltage?
Turn the ignition switch START
position with the clutch pedal
depressed.
Repair open in BLK wire between
the PGM-FI main relay and G101
(located at right middle of
engine).
Replace the ACG(S) (20 A)
fuse in the engine compart-
ment fuse/relay box.
Repair open in YEL/BLU wire
between the PGM-FI main
relay and the ACG(S) (20 A)

fuse.

Replace the No. 2 (15 A) fuse
in the under-dash fuse box.
Repair open in BLK/YEL wire
between the PGM-FI main
relay and the No. 2 (15 A)

fuse.

Replace the IG COIL (30 A)
fuse in the engine compart- ment fuse/relay box.
Repair open in BLK/YEL wire
between the PGM-FI main
relay and the IG COIL (30 A)

fuse.ProCarManuals.com

(From page 11-122)
Connect the test harness be-

tween the ECM and connector.
Disconnect "A" connector from

the ECM only, not the engine

wire harness (see page 11-37).
Measure the voltage between BLK/WHT terminal and body

ground.

Is there battery voltage?
Check for continuity between GRN/BLK terminal and A7 ter-

minal.

Does continuity exist?
Reconnect "A" connector to the
ECM. Reconnect the PGM-FI
main relay.

Turn the ignition switch ON.

Measure the voltage between

A23 (-) terminal and the follow-
ing terminals: A25 (+), C1 (+).

Is there battery voltage?

Turn the ignition switch OFF.
Measure the voltage between A7
(+) terminal and A23 (-) terminal

when the ignition switch is first

turned ON.

Is there 1.0 V or less?
(for 2 seconds)
Replace the PGM-FI main relay. Replace the No. 7 (7.5 A)
fuse in the under-dash fuse
box.

Repair open in BLK/WHT wire
between the PGM-FI main
relay and the No. 7 (7.5 A)
fuse.
Repair open in GRN/BLK wire
between ECM (A7) and PGM-FI
main relay. Repair open in YEL/BLK wire between the ECM (A25,
CD and the PGM-FI main
relay.
Replace the PGM-FI main

relay.

Substitute a known-good ECM
and recheck. If prescribed voltage is now available, replace
the original ECM.

Turn the ignition switch off.ProCarManuals.com

Fuel Supply System
Fuel Pump Resistor

Troubleshooting Flowchart

(To page 11-125) FUEL PUMP

RESISTOR

Inspect the PGM-FI main relay
(seepage 11-120).
Engine will not start.
Inspection of fuel pump

resistor.

Disconnect the fuel pump resis-
tor connector.
Measure the voltage between

BLK/YEL (+) (on harness side)

and body ground (-) when the ig-

nition switch is first turned ON.

Is there battery voltage?
(for 2 seconds)

Turn the ignition switch OFF.
Install a jumper wire between
two terminals on the wire harness side of fuel pump

resistor.

Turn the ignition switch to START position.
Does the engine start?
Turn the ignition switch OFF.
Disconnect the C489 (6P) con-
nector (located behind the seat
back panels). Replace the fuel pump resistor.ProCarManuals.com

Intake Air System

System Description

The system supplies air for all engine needs. It consists of the intake air pipe. Air Cleaner (ACL), intake air duct, throttle

body. Idle Air Control (IAC) Valve, fast idle thermo valve, and intake manifold. A resonator in the intake air duct provides

additional silencing as air is drawn into the system.

FAST

IDLE

THERMO

VALVE
ECM
IAC VALVE

TO PGM-FI MAIN

RELAY

THROTTLE

VALVE
INTAKE

AIR DUCT
ACL
THROTTLE

VALVE

DASHPOT

CONTROL

DIAPHRAGM

THROTTLE

VALVE

RESONATOR

DASHPOT

CHECK

VALVEProCarManuals.com

Troubleshooting Procedures

When the Transmission Control Module (TCM) senses an abnormality in the input or output systems, the indicator
light in the gauge assembly will blink. However, when the Service Check Connector (located to the lower right of the glove compartment) is connected with a jumper wire, the indicator light will blink the Diagnostic Trouble Code (DTC)

when the ignition switch is turned on.

When the indicator light has been reported on, connect the two terminals of the Service Check Connector together.
Then turn on the ignition switch and observe the indicator light.
Codes 1 through 9 are indicated by individual short blinks. Codes 10 through 16 are indicated by a series of long and
short blinks. One long blink equals 10 short blinks. Add the long and short blinks together to determine the code. After
determining the code, refer to the electrical system Symptom-to-Component Chart on page 14-52 and 53. SERVICE CHECK
CONNECTOR
Connect with jumper wire.

INDICATOR
Some PGM-FI problems will also make the indicator light come on After repairing the PGM-FI system, disconnect the
CLOCK fuse (7.5 A) in the main relay box for more than 10 seconds to reset the TCM memory.
long short
See DTC 1

See DTC 2

See DTC 14

LIGHT

short
PGM-FI system
The PGM-FI system on this model is a sequential multiport fuel injection system. Disconnecting the CLOCK fuse also cancels the radio preset stations and the clock setting. Make note of the radio
presets before removing the fuse so you can reset them.

NOTE:ProCarManuals.com