Question about 1987 GMC G3500

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How do you set the timing on a 87 3500 GMC van with a 350 cu in eng? I know I will have to disconnect a wire and turn the distributor because the eng is throtle body fuel injection but I don't know where the wire is or what to set the timing to.This van has the computer under the drivers seat. Any help would be appreiciated

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You must disconnect the computer from the distributor, there is a connector that carries the signal in the harness that goes to the connectors to the distributor, it is single wire plug, the wire color is Tan/Black, open up the tubing the wire harness runs in to find the connector, it is very near the distributor body on the engine. Once the wire is disconnected here is the timing procedure and timing spec for the 350 TBI engine.

Set timing under the following conditions:

  • Normal operating temperature.
  • Air cleaner installed.
  • A/C "OFF".
  • Transmission in neutral.
  • Disconnect SET TIMING connector (tan/black wire) located in the harness close to the distributor. DO NOT disconnect the 4 wire connector at the distributor.
  • Connect timing light and adjust as necessary by loosening hold down bolt and rotating distributor.

Base Timing, with Manual and Automatic Transmissions: 00(TDC) That is zero TDC

See diagrams of timing marks below.

  • Tighten hold down and recheck the timing.
  • Stop the engine and connect SET TIMING connector.
  • Clear ECM trouble code by disconnecting ECM power source. Fuses are marked "ECM".

How do you set the timing on a 87 3500 GMC van - emissionwiz_74.gif


Posted on Mar 31, 2011


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