Question about 1984 GMC S-15 Jimmy

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How to adjust the timing on 1986 gmc s15? - 1984 GMC S-15 Jimmy

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Below copied from

See Figures 1, 2 and 3
The following procedure requires the use of a distributor wrench and a timing light. When using a timing light, be sure to consult the manufacturer's recommendations for installation and usage.
The vehicle emission control information label, which is found underhood, will often contain specifications or procedures for checking and adjusting timing that have been updated during production. The information contained on the label should always be used if it differs from these instructions.
On most HEI systems, the tachometer connects to the TACH terminal on the coil and to a ground. Some tachometers must connect to the TACH terminal and to the positive battery terminal. Also, note that some tachometers won't work at all with an HEI system. Consult the tachometer manufacturer if the instructions supplied with the unit do not give the proper connection.

WARNING Never ground the HEI TACH terminal; serious system damage will result, including ignition module burnout.

  1. Set the parking brake and block the drive wheels, warm the engine to normal operating temperature.
  2. Shut the engine OFF and connect the a timing light to the No. 1 spark plug (right front 2.8L engine, left front 4.3L engine or front plug on in-line engines):
    1. If using a non-inductive type, connect an adapter between the No. 1 spark plug and the spark plug wire; DO NOT puncture the spark plug wire, for this will cause a voltage leak.
    2. If using an inductive type, clamp it around the No. 1 spark plug wire.
    3. If using a magnetic type, place the probe in the connector located near the damper pulley; this type must be used with special electronic timing equipment.

Do not under any circumstances pierce the insulation of a spark plug wire in order to connect the timing light.

how to adjust the timing on 1986 gmc s15? - 0900c152801c8b8f.jpg enlarge_icon.gif Fig. Fig. 1: A common timing mark scale

  1. Clean off the timing marks, then label the pulley or damper notch and the timing scale with white chalk or paint for better visibility. If the timing notch on the damper or pulley is not visible from the top, the crankshaft should be bumped around using the starter or turned using a wrench on the front pulley bolt, in order to bring the mark to an accessible position.
  2. On early model vehicles not equipped with EST, disconnect and plug the vacuum advance hose at the distributor to prevent any distributor vacuum advance. The vacuum line is the rubber hose connected to the metal cone-shaped canister on the side of the distributor. A short screw, pencil, or a golf tee can be used to plug the hose.

  1. On later model vehicles equipped with EST, the electronic spark timing must be disabled or bypassed to prevent the control module from advancing timing while you are attempting to set it. This would obviously lead to an incorrect base timing setting. There are 2 possible methods of disabling the EST system, depending on the type of engine:

    On 2.5L engines, ground the "A'' and "B'' terminals on the ALDL connector under the dash before adjusting the timing. On all other engines using the EST distributor, disengage the timing connector wire. On a few of the earlier model vehicles, the 4-terminal EST connector must be disengaged from the distributor. Most later model vehicles are equipped with a single wire timing bypass connector. On these later model vehicles the bypass wire is usually a tan wire with a black stripe. The wire usually breaks out of the wiring harness conduit adjacent to the distributor, but on some vehicles it may break out of a taped section just below the heater case in the passenger compartment.
  2. Start the engine, then check and adjust the idle speed, as necessary. The idle speed must be properly set to prevent any centrifugal advance of timing in the distributor.
  3. Aim the timing light at the timing marks. Be careful not to touch the fan, which may appear to be standing still. Keep your clothes and hair along with the timing light's wires clear of the fan, belts and pulleys. If the pulley or damper notch isn't aligned with the proper timing mark, the timing will have to be adjusted.

TDC or Top Dead Center corresponds to 0° mark on the scale. Either B, BTDC, or Before Top Dead Center, may be shown as BEFORE on the scale, while A, ATDC or After Top Dead Center, may be shown as AFTER.
  1. Loosen the distributor base clamp locknut. You can buy special wrenches which make this task a lot easier on certain models. Turn the distributor slowly to adjust the timing, holding it by the body and not the cap. Turn the distributor in the direction of rotor rotation (found in the firing order illustrations earlier in this Section) to ******, and against the direction to advance.
  2. Once the timing is properly set, hold the distributor to keep it from the turning and tighten the locknut. Check the timing again after finishing with the nut in case the distributor moved as you tightened it.
  3. If applicable, remove the plug and connect the distributor vacuum hose.
  4. If necessary check and/or adjust the idle speed.
  5. Shut off the engine and reconnect the EST wire (if equipped), then disconnect the timing light and tachometer.

Posted on Aug 25, 2010

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Posted on Jan 02, 2017

SOURCE: I need a diagram of


Posted on Sep 19, 2010

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SOURCE: firing order for a 1986 gmc s15


To avoid confusion, ALWAYS replace spark plug wires one at a time.

The most important thing to remember about the removal and installation of a distributor, cap or spark plug cable is that all wires MUST be labelled before they are disconnected. Keep in mind that these figures depict a firing order where the distributor cap terminals are relative to EACH OTHER only and they do not necessarily depict the tower positions in relation to the rest of the engine. This is true because any distributor which has been removed and reinstalled may have been installed with the No. 1 spark plug tower at any position (360 degrees) in relation to the rest of the motor, as long as the rotor aligned to the No. 1 tower when the No. 1 cylinder was at TDC of the compression stroke (valves closed, ready for the plug to fire). As long as the remaining wires were connected in the correct firing order sequence (depending on direction of distributor rotation) the engine will run. DO NOT EVER remove more than one wire from the distributor cap at a time unless you tag ALL wires and towers to assure proper installation.


Fig. 1: 1.9L engine . Firing order: 1-3-4-2 . Distributor rotation: counterclockwise


Fig. 2: 2.0L engine . Firing order: 1-3-4-2 . Distributor rotation: clockwise


Fig. 3: 2.5L engine . Firing order: 1-3-4-2 . Distributor rotation: clockwise


Fig. 4: 2.8L engine . Firing order: 1-2-3-4-5-6 . Distributor rotation: clockwise


Fig. 5: 4.3L engine. Firing order: 1-6-5-4-3-2 . Distributor rotation: clockwise

I hope help you with this (remember rated this help) Good luck.

Posted on Oct 05, 2009

  • 17970 Answers

SOURCE: firing order diagram for 1986 GMC S15 2.8L

For this models:
1986 GMC S15/T15 4WD P/U 2.8 liter V-6 VIN "R"
1986 GMC S15/T15 4WD Jimmy 2.8 liter V-6 VIN "R"
1986 GMC S15/T15 2WD P/U 2.8 liter V-6 VIN "R"
1986 GMC S15/T15 2WD Jimmy 2.8 liter V-6 VIN "R"


Hope helped woth this. Remember rated this help. Good luck.

Posted on Nov 24, 2009

  • 316 Answers

SOURCE: My 1986 GMC S15 will start and idle, but wont

fuel pump fuel filter?

Posted on Oct 05, 2009

  • 560 Answers

SOURCE: what is firing order for

Pay a visit to and follow the instructions to enter your vehicle into the system . Then , select vehicle repair info / guides and you will find your firing order in tune up specifications . Also , you will find a lot of other useful information . It's free . Good luck . And be safe .

Posted on Sep 05, 2010

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Hope helped woth this. Remember rated this help. Good luck.

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