Author Topic: General Motors Pickup Trucks  (Read 41 times)


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General Motors Pickup Trucks
« on: January 24, 2022, 04:27:37 pm »
General Motors Full-Size Trucks 1980-87 Repair Manual
Gasoline and Diesel
Chilton's, An American Tradition Since 1925

The smog control gear on the vehicles of this era are extremely complicated.  I think it got easier when they went to sequential fuel injection and everything behing handled through the computer.  But to understand where it all came from, the extreme complexity, is why I picked up the book.  So let me go straight to the emission controls section.

Positive Crankcase Ventilation
to evacuate the crankcase of vapors
PCV valve meters the air flow rate, to maintain idle quality.  Valve sits in grommet in top of left valve cover.

Crankcase breather hose goes from right side valve cover to air filter housing.  Has its own little filter.  In some "abnormal" situations it would send crankcase vapors back up and into the intake.

Air Injector Reactor (A.I.R.)
the smog pump.  Injects air near the exhaust valve.  Has diverter valve, check valve, and its own filter

Pulse Air Injection (PAIR)
exhaust gas pulses siphon fresh air into the exhausts. Has check valves.  Mostly on I6 engines.

Thermostatic Air Cleaner (Thermac) on all gasoline engines.  Uses damper controlled by vacuum motor.  Preheats cold inlet air.

Evaporative Emission Control System  (EECS)  about 3 vacuum control valves.  Must use special EVAP rubber tubing.

Early Fuel Evaporation (EFE) valve on flange of exhaust manifold.  For heat rising.  Uses Thermal Vacuum Switch (TVS) which has 3 vacuum control lines

Throttle Return Control (TRC) tries to interdict supper rich mixture you get when you quickly take your foot of the gas and let the throttle close.  This slows it down.

Oxygen Sensor, must never be expose to silicone, can't use silicone sealants on exhaust or intake manifolds.  Do not touch sensor.  If it looks white, it is trashed.  Do not modify pig tail connector, do not solder other stuff to it.  Might have to have exhaust manifold heated to 120 deg F to unscrew.  Don't use regular anti-sieze, because that insulates it.  Use special GM anti-seize for O2 sensors.

Catalytic Converter, gets super hot.  Install with suitable sealants.  (ceramic?)

Trapped Vacuum Spark, prevents drop in vacuum to distributor advance when cold.  Uses Thermal Vaccum Switch (TVS)

Exhaust Gas Recirculation (EGR), feeds back a small amount of exhaust gas.  Seems to have special mid throat port on carburetor.  Purpose is to diffuse peak ignition temperature to prevent oxides of nitrogen from being formed.  Sometimes use ECM (Electronic Control Module)

Electronic Spark Timing (EST) System (California or fuel injected only)

Explains diagnostic codes

Goes into diesel engine

Diesel has vacuum pump

Huge set of vacuum diagrams

Uses Rochester Carburetors

Might have to install grease gun nipples.  Use special grease for power assisted steering, not the same as chassis ball joints.  Don't over fill ball joints so they screw up rubber booties.

For manual transmission and rear axle use 80w 90 GL5.  For automatic use Dextron.  For power steering use special GM fluid or Dextron II.

Has two tie rod adjustments.  But you can get steering wheel of with puller.  Can adjust camber (roofer's square on smooth flat concrete floor best )  Can adjust castor

Shows two Delco Alternators with internal voltage regulators.  These are better than the old two wire externals.  On Chrysler the Drain Charge Ammeter was iconic.  But because of better voltage regulation, and it gets even better, those ammeters are hard to buy now.  Volt meter is sufficient.

One of the Delcos is 3 phase delta, and the other is 3 phase Y.  One has in addition a module of 3 exciter diodes.  The other does not.  There is always a wire for the dashboard warning light.  On the one with the exciter diodes it back feeds to keep the light off.  The other has some internal box to which a schematic is not supplied.

Open front wheel bearings you need to grease.
They say to replace inboard side grease seal every time.

They show cross torque lug nut patterns for 5, 6, and 8 studs.


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