Hard Start - Cold; Hard Start - Hot - GMC G Service Manual

Definition: Engine cranks OK, but does not start for a
long time. Does eventually run. If the engine starts but
immediately dies (as soon as key is released from start
position), refer to "No Start, Engine Cranks OK" symptom.
• Make sure driver is using correct starting procedure.
Refer to Owner's Manual.
• Visual check:
— Vacuum hoses for splits, kinks and proper con­
nections as shown on Vehicle Emission Control
Information label.
— Air leaks at carburetor mounting and intake
manifold.
— Ignition wires for cracking, hardness, and
proper connections, at both the distributor cap
and spark plugs.
— Wiring for proper connections, pinches and
cuts.
• Check the choke valve, throttle and fast idle cam for
sticking. Replace any malfunctioning parts. If caused
by foreign material and gum, clean with suitable non­
oil base solvent. Refer to CARBURETORS (SEC.
6C1).
• Check choke and vacuum break operation and
adjustment. Choke should be closed cold. Refer to
CARBURETORS (SEC. 6C1).
Definition: Engine cranks OK, but does not start for a
long time. Does eventually run. If the engine starts but
immediately dies (as soon as key is released from start
position), refer to "Ignition System Diagnosis" in ENGINE
ELECTRICAL (SEC. 6D).
• Visual (physical) check:
— Vacuum hoses for splits, kinks, and proper con­
nections as shown on Vehicle Emission Control
Information label.
— Ignition wires for cracking, hardness, and
proper connections at the distributor cap and
spark plugs.
— Wiring for proper connections, pinches and
cuts.
• Make sure driver is using correct starting procedure.
Refer to Owner's Manual.
• Check choke valve, throttle linkage and fast idle cam
for sticking.
• Check choke and vacuum break operation and
adjustment. Choke should be open hot. Refer to
CARBURETORS (SEC. 6C1).
• Check for carburetor flooding.
• Check fuel inlet filter; if plugged, replace.
• Check float level using external float gage. Adjust
float to proper specification if required. Refer to CAR­
BURETORS (SEC. 6C1).
HARD START — COLD
HARD START — HOT
CARBURETOR EMISSIONS 6E1-9
• Check EGR system for sticky operation that could
cause valve to stick open.
• Check float level using external float gage. Adjust
float to specification if required. Refer to CARBURE­
TORS (SEC. 6C1).
• Check carburetor fuel inlet filter. Replace if dirty or
plugged.
• Check ignition system. Refer to ENGINE ELECTRI­
CAL (SEC. 6D). Check distributor for:
— Worn shaft.
— Bare and shorted wires.
— Pickup coil resistance and connections.
— Loose ignition coil ground.
— Moisture in distributor cap.
• Remove spark plugs; check for wet plugs, wear,
improper gap, burned electrodes or heavy deposits.
Repair or replace as necessary.
• Check ignition timing per Vehicle Emission Control
Information label.
• Verify proper engine oil viscosity per recommenda­
tions in Maintenance Schedule. Also refer to Owner's
Manual.
• Check fuel pump volume, pressure and vacuum.
• Check fuel pump volume, pressure and vacuum.
• Check fuel line routing.
• Check EFE valve. EFE valve should be open.
• Check EGR for sticky operation that could cause
valve to stick open.
• Check for obvious overheating problems:
— Low coolant.
— Loose water pump belt.
— Restricted air flow to radiator, or restricted water
flow through radiator.
• Check ignition system. Refer to ENGINE ELECTRI­
CAL (SEC. 6D). Check distributor for:
— Worn shaft.
— Bare and shorted wires.
— Intermittent pickup coil or connections, module,
ignition coil ground and condenser. Repair or
replace as necessary.
• Remove spark plugs. Check for cracks, wear,
improper gap, burned electrodes, heavy deposits.
Repair or replace as necessary.
• Check ignition timing. Refer to Vehicle Emission Con­
trol Information label.