How to reset the timing on a 1991 GMC 5.7

To set the timing on your 1991 Nissan truck, follow these steps:

1. Locate the timing marks on the engine. They are usually located on the front of the engine, near the crankshaft pulley.
2. Remove the timing cover if necessary to access the timing marks.
3. Check the engine's specifications to determine the correct timing setting. This information can be found in the owner's manual or a repair manual.
4. Connect a timing light to the battery and to the number one spark plug wire. The timing light will allow you to see the timing marks more easily.
5. Start the engine and let it warm up to operating temperature.
6. Aim the timing light at the timing marks on the engine and observe the marks as the engine runs.
7. Use a wrench to loosen the distributor bolt slightly.
8. Rotate the distributor slightly to adjust the timing until the marks line up with the specified setting.
9. Tighten the distributor bolt once the timing is set.
10. Recheck the timing to ensure it is still set correctly.
11. Turn off the engine and disconnect the timing light.
12. Reinstall the timing cover if it was removed.

If you are not comfortable performing this procedure, it's best to take your truck to a qualified mechanic for timing adjustment.

if you adjusted timing [which shouldnt have to be done unless distributor was disturbed]] check timing chain for skipped tooth or stretch

No, but you should disconnect the vacuum hose from the distributor and clog it while setting the timing if it has a vaccum advance

You can\'t. GM did away with timing light based ignition timing on the vortec engine family. You can adjust the distributor, but it adjusts something called Camshaft Retard Offset, and can only be read using a scan tool. The only reason you would need to check the camshaft retard offset is if you removed the distributor or intake manifold and accidentally got the distributor off a tooth or two.

Hello theman022002,

Your description would indicate that the timing is off. Possibly when you installed the new distributor you were off a tooth or two. Turning the distributor Will Not adjust the timing.

You will need to reinstall the distributor with every thing set to top dead center, then follow the steps below to set the proper cam retard offset.

Good Luck.

Ignition Timing: Adjustments

TEST PROCEDURE
The ignition timing cannot be adjusted. The distributor may need adjusting to prevent crossfire. To insure proper alignment of the distributor, perform the following:

1. With the ignition OFF, connect the scan tool.
2. Start the engine. Allow the engine to idle until the engine reaches normal operating temperature.

IMPORTANT: Cam retard Offset reading will not be accurate below 1,000 RPM.

3. Increase engine speed to 1,000 RPM while performing the following steps.
4. Use the scan tool in order to monitor the Cam retard Offset.
5. If the Cam retard indicates a value of 0 degrees, the distributor is properly adjusted.
6. If the Cam retard does not indicate 0 degrees, the distributor must be adjusted.

ADJUSTING PROCEDURE
1. With the engine OFF, slightly loosen the distributor hold down bolt.

IMPORTANT: Cam retard Offset reading will not be accurate below 1,000 RPM.

2. Start the engine and raise the engine speed to 1,000 RPM.
3. Use the scan tool in order to monitor the Cam retard Offset.
4. Rotate the distributor as follows:
a. To compensate for a negative reading, rotate the distributor in the counterclockwise direction.
b. To compensate for a positive reading, rotate the distributor in the clockwise direction.
5. Repeat step 4 until 0 degrees is obtained.
6. Turn OFF the ignition.

NOTE: Refer to Fastener Notice in Cautions and Notices.

7. Tighten the distributor hold-down bolt to 3 N.M. (25 lb ft).
8. Start the engine.
9. Raise the engine speed to 1,000 RPM and with the scan tool view the Camshaft retard Offset to verify 0 degrees has been maintained.

Regards,
netvan

I removed the distribitor and the timing is out

could be the crankshaft sensor causing the timing to be off if it has a coilpack type distributor or if it has a gear driven distributor then it could be either the distributor itself or possibly just cap and rotor

0 degrees BTDC would be the spec , there is a brown w/tan tracer wire near the distributor , you have to disconnect the connector before setting timing

no it has a distributor here is the prodeure for the timing sensor under the cap.

1. Disconnect negative battery terminal, disconnect distributor lead wire at the wiring harness connector.
2. Release distributor cap retainers and lift the distributor cap off.
3. Scribe a mark on the edge of the distributor housing to indicate the position of the rotor. Use the mark as a reference when reinstalling the distributor.
4. Remove the distributor hold down bolt and clamp, and carefully lift the distributor out of the engine.

INSTALLATION

1. Clean the top of the cylinder block to insure a good seal between the distributor base and block. If the engine has not been cranked with distributor removed, proceed with step 2. If the engine has been cranked with the distributor removed proceed to step 3.
2. Position the distributor into the engine. Make sure the O-ring seal is in place on the distributor housing. Align the rotor with the mark previously scribed on the distributor housing. Engage the tongue of the distributor shaft with the slot in the distributor oil pump drive gear. Proceed to step 4.
3. If engine has been cranked with distributor removed perform the following:

1. Rotate the crankshaft until number one piston is at the top of its compression stroke. The mark on the crankshaft vibration damper should be in line with the "0" TDC mark on the timing chain case cover.
2. Rotate the distributor rotor until it is positioned pointing at the number one distributor cap terminal.
3. Lower the distributor into the engine, making sure the O-ring seal is in place. Engage tongue of distributor shaft with slot in the distributor oil pump drive gear.

1. Install the distributor hold down clamp and screw and tighten finger tight. Install distributor cap and wires, making sure all high tension wires are firmly secured in cap towers.
2. Connect pick-up leads and negative battery cable lead. Set ignition timing, refer to ADJUSTMENT PROCEDURES for timing adjustment

the firing order is
1-6-5-4-3-2