Mechanics

NO PULSE TO INJECTORS

1991 Chevrolet Silverado • 197,000 miles

91 Chevy k1500 getting spark to all plugs, gas to tbi, continuity from ecm to injectors, but no pulse to injectors please help Every possible part I could test passed just wondering if it is a ecm problem?
Avatar
Bboyett86
January 25, 2012.




Check the fuel injection relay.

Rivermikerat
Jan 25, 2012.
Checked the fuel relays all good. And no injection relay just a fuse for injectors a-b and that's good too. Im stumped

Tiny
Bboyett86
Jan 25, 2012.
ENGINE CONTROLS - SYSTEM/COMPONENT TESTS -1991 Chevrolet Pickup K1500
Page 1 of 2
FUEL SYSTEM (GASOLINE)

FUEL DELIVERY

NOTE: For fuel system pressure testing, see BASIC TESTING article in this section.
FUEL PRESSURE REGULATOR (TBI)

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Question: fuel pressure testing tbi
Tech1
Fuel pressure regulator is mechanically controlled by internal spring pressure. Regulator is adjusted at factory and is not serviceable. If fuel pressure is too low, check for restricted delivery line. Also, check
fuel pump pressure and volume. If fuel pressure is too high, check for restricted fuel tank return line or fuel filter. If no faults are found and pressure is too high or too low, replace fuel pressure regulator.
FUEL PRESSURE REGULATOR (PFI)

Fuel pressure regulator is a vacuum-controlled diaphragm type, which uses manifold vacuum to modify fuel pressure to compensate for engine load fuel requirements. Connect fuel pressure gauge to fuel
pressure service port. Start engine and note fuel pressure. Disconnect vacuum hose from fuel pressure regulator. Fuel pressure should increase 4-10 psi (.15 kg/cm ). If pressure does not increase 4-10 psi
(.15 kg/cm ), check for presence of manifold vacuum at signal line. If vacuum is not present, check for kinked, cut or split vacuum hose or plugged throttle body vacuum port. If vacuum is present and no
pressure change occurred, replace fuel pressure regulator.
2
2
FUEL PUMP OIL PRESSURE SWITCH (BACK-UP CIRCUIT)

To test fuel pump oil pressure switch back-up circuit, start engine. With engine running, disconnect fuel pump relay. If engine stalls, fuel pump oil pressure switch is faulty. If vehicle continues to run, switch is
okay.
FUEL PUMP RELAY

See RELAYS, SOLENOIDS, MOTORS & MODULES.
FUEL PUMP RELAY BY-PASS PROCEDURE

If fuel pump will not energize, relay may be by-passed to test fuel pump. Turn ignition off. Using a
fused jumper wire, apply battery voltage to fuel pump test connector. Fuel pump should turn on. For fuel pump test connector location, refer to COMPONENT LOCATIONS at end of article.

1/25/2012
ENGINE CONTROLS - SYSTEM/COMPONENT TESTS -1991 Chevrolet Pickup K1500
Page 2 of 2
FUEL CONTROL

FUEL INJECTOR(S)

Disconnect fuel injector harness connector. Measure resistance across injector terminals. Resistance should be as specified. See FUEL INJECTOR RESISTANCE table.
OXYGEN SENSOR

See ENGINE SENSORS & SWITCHES.
FUEL INJECTOR RESISTANCE Application
TBI Except 3.1L (VIN D) 3.1L (VIN D)
4.3L Turbo PFI
(1)
Resistance (Ohms) 1.3
1.2
2.0
(2)
(1) Injector resistance specification is at 140 F (60 C).
(2) Minimum reading.
IDLE CONTROL SYSTEM

IDLE AIR CONTROL (IAC) MOTOR

1.
Disconnect harness connector to motor. Check resistance across IAC coil terminals "A" to "B" and "C" to "D". See Fig. 5. Resistance should be 40-80 ohms. If okay, go to next step. If
resistance is not as specified, replace IAC motor.
Check resistance between IAC terminals "B" to "C" and "A" to "D". Resistance should be infinite. If resistance is not as specified, replace IAC motor.
2.
NOTE: Functional testing of Idle Air Control (IAC) motor requires a Scan tester
capable of cycling ECM output devices (bidirectional) or a special IAC
Driver and Node Light Set (222L or J-37027). Flow charts in the TESTS
W/CODES - DIESEL (for Diesel engines) or TESTS W/CODES - GASOLINE (for Gas engines) and TESTS W/CODES - TRANSMISSION (if transmission
codes are displayed) articles may refer to the Tech 1 tester, General Motors' bidirectional tester.
Fig. 5: Identifying IAC Motor Circuits (Typical) Courtesy of GENERAL MOTORS CORP.

1/25/2012
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Rivermikerat
Jan 26, 2012.

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