1991 ACURA NSX Service Repair Manual

Fuel Supply System

Fuel Injector Resistor

Description

The fuel injector resistor lowers the current supplied to

the fuel injectors to prevent damage to the fuel injector

coils. This allows a faster response time of the fuel

injectors.

ECM
PGM-FI

MAIN

RELAY
Testing

1. Disconnect the fuel injector resistor connector.

2. Check for resistance between each of the fuel in-

jector resistor terminals (B, C, D, F, G and H) and

the power terminal (E).

Resistance should be: 5—7

FUEL

INJECTOR

RESISTOR

B

C

D

F

G

H

E

Replace the fuel injector resistor with a new one

if any of the resistances are outside of the

specification.
FUEL

INJECTOR RESISTOR

FUEL

INJECTORSProCarManuals.com

Fuel Pressure Regulator

Description

The fuel pressure regulator maintains a constant fuel pressure to the fuel injectors. When the difference be-
tween the fuel pressure and manifold pressure exceeds
3.5 kg/cm2 (50 psi), the diaphragm is pushed upward,
and the excess fuel is fed back into the fuel tank
through the fuel return pipe.
CLOSE INTAKE MANIFOLD
VACUUM

DIAPHRAGM

FUEL

INLET

INTAKE MANIFOLD

VACUUM

DIAPHRAGM

OPEN

FUEL

RETURN
FUEL

INLET

(cont'd)

2. Reconnect the vacuum hose to the fuel pressure
regulator.
3. Check that the fuel pressure rises when the vacuum hose from the fuel pressure regulator is
disconnected again.
If the fuel pressure did not rise, replace the fuel
pressure regulator.

Testing

Do not smoke during the test. Keep

open flames away from your work area.

1. Attach a pressure gauge to the service port of the fuel filter (see page 11-106).

Pressure should be:
330–370
kpa
(3.30–3.70
kg/cm2,
46–53
psi)

(with the fuel pressure regulator vacuum hose

disconnected and pinched)

FUEL

PRESSURE FUEL PRESSURE GAUGE

REGULATOR
07406–0040001ProCarManuals.com

Fuel Supply System

Fuel Pressure Regulator (cont'd)

Replacement

Do not smoke while working on fuel Fuel Filter

Replacement
Do not smoke while working on fuel
The fuel fitter should be replaced: every 4 years or 60,000 miles (96,000 km), whichever comes first or
whenever the fuel pressure drops below the specified value
(330-370
kPa
(3.30-3.70
,
46-53
psi)

with the fuel pressure regulator vacuum hose discon-
nected) after making sure that the fuel pump and the
fuel pressure regulator are OK.
1. Place a shop towel under and around the fuel filter.
2. Relieve fuel pressure (see page 11-105).
3. Remove the 12 mm banjo bolt and the fuel feed pipe from the filter.
4. Remove the fuel filter clamp and fuel filter. 5. When assembling, use new washers, as shown.
1. Place a shop towel under fuel pressure regulator,
then relieve fuel pressure (see page 11-105).

2. Disconnect the vacuum hose and fuel return hose.

3. Remove the two 6 mm retainer bolts.

FUEL
PRESSURE

REGULATOR
O-RING
Replace.

NOTE:
12 N.m

(1.2 kg-m,

9 Ib.ft)
SERVICE BOLT

12 N .
m (1.2 kg-m, 9 Ib-ft)
BANJO BOLT

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

WASHER
Replace

28 N·m
(2.8 kg-m,

20 Ib-ft)

WASHER
Replace

10 N .
m (1.0 kg-m, 7 Ib-ft)
WASHER

Replace

system. Keep open flame away from your work

area.

system. Keep open flame away from your work

area.

Replace the O-ring.

When assembling the fuel pressure regulator,
apply clean engine oil to the O-ring and assem-ble it into its proper position, taking care not to
damage the O-ring.ProCarManuals.com

Fuel Supply System

Fuel Pressure Regulator (cont'd)

Replacement
Do not smoke while working on fuel Fuel Filter

Replacement
Do not smoke while working on fuel
The fuel fitter should be replaced: every 4 years or 60,000 miles (96,000 km), whichever comes first or
whenever the fuel pressure drops below the specified value
(330-370
kPa
(3.30-3.70
,
46-53
psi)

with the fuel pressure regulator vacuum hose discon-
nected) after making sure that the fuel pump and the
fuel pressure regulator are OK.
1. Place a shop towel under and around the fuel filter.
2. Relieve fuel pressure (see page 11-105).
3. Remove the 12 mm banjo bolt and the fuel feed pipe from the filter.
4. Remove the fuel filter clamp and fuel filter. 5. When assembling, use new washers, as shown.
1. Place a shop towel under fuel pressure regulator,
then relieve fuel pressure (see page 11-105).

2. Disconnect the vacuum hose and fuel return hose.

3. Remove the two 6 mm retainer bolts.

FUEL
PRESSURE

REGULATOR
O-RING
Replace.

NOTE:
12 N.m

(1.2 kg-m,

9 Ib.ft)
SERVICE BOLT

12 N .
m (1.2 kg-m, 9 Ib-ft)
BANJO BOLT

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

WASHER
Replace

28 N·m
(2.8 kg-m,

20 Ib-ft)

WASHER
Replace

10 N .
m (1.0 kg-m, 7 Ib-ft)
WASHER

Replace

system. Keep open flame away from your work

area.

system. Keep open flame away from your work

area.

Replace the O-ring.

When assembling the fuel pressure regulator,
apply clean engine oil to the O-ring and assem-ble it into its proper position, taking care not to
damage the O-ring.ProCarManuals.com

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