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4.3 vortec timing

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Old 12-19-2009, 11:36 AM   #1
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4.3 vortec timing

Ive got a 4.3 that came in a 93 s15 jimmy the distributor was removed & its back in & running but not right, my first instinct is that the timings off my service book says set timing per the instructionson a emmisions sticker under the hood the jimmy dosent have these any more another service book for the next generation s-10says I have to unplug a tan /black wire to stop timing from advancing while checking it . I dont find that wire but I find a white wirew/a black plug in the area Ive been told to look but its unpluged It is conected to the distribiutor I would think to disable the timing advance its some how got to be conected to the ecm.
in putting a timing light on it I see 2 timing lines on the harmonic balancer & it will run while I turn the distributor til either one is close to 0
questions :
1 what should the timing be set at ?
2 do I need to somehow disable the timing advance ?
3 if so any idea how?
4 which (&how do I tell?)timing mark on balancer do I use?
any help would be great
Old 12-19-2009, 12:44 PM   #2
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Re: 4.3 vortec timing

yes you have to disconnect a wire to do the base timing.
I think eveyone says it's somewhere in the cab behind the kick panel on the passenger side.

but from what I've always seen it's a single brown or tan wire and located neer the firewall on the passenger side.
give this post a few more days...I'm sure more people will help. because I honestly don't have any experience with a 93.
Old 12-19-2009, 12:48 PM   #3
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Re: 4.3 vortec timing

I got this info from autozone's website..





Set the parking brake and block the drive wheels, then warm the engine to normal operating temperature.
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):
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 allow a voltage arc.
If using an inductive type, clamp it around the No. 1 spark plug wire.
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.




Fig. Fig. 1: A common timing mark scale





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.
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.







Fig. Fig. 2: Aim the timing light at the mark and scale, but be careful not to contact the fan or drive belts






Fig. Fig. 3: Timing marks are often difficult to see; this engine is equipped with a magnetic probe holder which may be used with special equipment

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. This 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.
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.
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.

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 retard, and against the direction to advance.
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.
If applicable, remove the plug and connect the distributor vacuum hose.
If necessary check and/or adjust the idle speed.
Shut off the engine and reconnect the EST wire (if equipped), then disconnect the timing light and tachometer.


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Old 12-19-2009, 01:07 PM   #4
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Re: 4.3 vortec 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.
I think this might answer one of my questions. I think this is a fairly early vortec
Old 12-19-2009, 02:50 PM   #5
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Re: 4.3 vortec timing

I tried unpluging the 4 wire conector on dist & it dosent runso thats not the answer .
Old 12-19-2009, 08:17 PM   #6
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Re: 4.3 vortec timing

try this.


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. This 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.
Old 12-19-2009, 08:28 PM   #7
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Re: 4.3 vortec timing

behind the kickpanel.
Old 12-19-2009, 09:36 PM   #8
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Re: 4.3 vortec timing

,
Quote: Originally Posted by a4x4spit
Ive got a 4.3 that came in a 93 s15 jimmy the distributor was removed & its back in & running but not right, my first instinct is that the timings off my service book says set timing per the instructionson a emmisions sticker under the hood the jimmy dosent have these any more another service book for the next generation s-10says I have to unplug a tan /black wire to stop timing from advancing while checking it . I dont find that wire but I find a white wirew/a black plug in the area Ive been told to look but its unpluged It is conected to the distribiutor I would think to disable the timing advance its some how got to be conected to the ecm.
in putting a timing light on it I see 2 timing lines on the harmonic balancer & it will run while I turn the distributor til either one is close to 0
questions :
1 what should the timing be set at ?
2 do I need to somehow disable the timing advance ?
3 if so any idea how?
4 which (&how do I tell?)timing mark on balancer do I use?
any help would be great

I have a 1993 Jimmy 4x4 with a 4.3l engine and went through a process similar to what you are experiencing. Here is what I found out (with lots of forum help):
  1. Timing is to be set at 0* TDC. This should be the largest/deepest notch in the timing tab (see pic)[IMG]file:///tmp/moz-screenshot.png[/IMG]
  2. You have to disconnect the tan/blk wire under the HVAC case just to the left of the transmission tunnel (passenger side) inside the truck prior to attempting to set the timing. You may have to pull back the carpet a bit to see this connector. Do not disconnect the 4 pin plug on the distributor.
  3. See #2.
  4. The First mark on the balancer is the one for setting timing. If you use the Second mark it will run but poorly and overheat.
Attached Thumbnails
4.3 vortec timing-timing.jpg  

Last edited by Licklog; 12-19-2009 at 09:40 PM. Reason: Clarity
Old 12-20-2009, 03:14 PM   #9
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Re: 4.3 vortec timing

I HAVE LOOKED AS HARD as I can for a tan & black wire inside the jimmy I have computer loose & wiring harness hanging & can follow it to fire wall the only plugs are one that goes to data link plug and a single white wire that wasnt pluged into anything but i found the other end of the plug under the carpet heading toward guaged in dash.
can I just cut the tan & black wire that goes between dist & ECM and put in my own disconect plug?I would be easy to do & I cant see a problem if it dosent work Illplug it in & forget about it
Old 12-20-2009, 03:35 PM   #10
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Re: 4.3 vortec timing

thanks for help still havent got it but now am sure 0 deg is the # & where 0 is on the scale I also rolled it to tdc & marked the harmonic balancer line that lined up so thats the line to set the timing with sound right?
Old 12-21-2009, 11:48 AM   #11
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Re: 4.3 vortec timing

ok I put a spade connector in the tan w/black wire near distribitor after checkin that it actually goes to the ecm at the pin that is called the ic bypass I checked timing before unpluging it and could barly see the mark I unpluged my new plug & the timing dropped to about 4 deg so I set it to 0 and it seems to run fine
Old 12-21-2009, 06:22 PM   #12
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Re: 4.3 vortec timing

awesome.
Old 12-21-2009, 09:45 PM   #13
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Re: 4.3 vortec timing

Yea!
Old 12-30-2009, 04:13 PM   #14
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Re: 4.3 vortec timing

I've got the same problem...can't find the tan/black wire. The one that you put the spade connector in was part of the 4 wire plug to the distributor?
Old 12-30-2009, 05:01 PM   #15
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Re: 4.3 vortec timing

yes
Old 12-30-2009, 05:31 PM   #16
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Re: 4.3 vortec timing

Thanks for the reply. My wire does not break out of the harness anywhere. Guess I need to take care of that. Thanks again.
Old 12-08-2011, 10:22 AM   #17
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Re: 4.3 vortec timing

Quote: Originally Posted by harveydean
I've got the same problem...can't find the tan/black wire. The one that you put the spade connector in was part of the 4 wire plug to the distributor?
On my '94 s10 Vortec, the black and tan connector for the timing advance is outside the wire bundle running to the onboard computer. To access, take the panel directly below the glove box and carefully extend the harness, (it will be outside of wire bundle).
Old 01-23-2014, 05:40 PM   #18
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Re: 4.3 vortec timing

This old man has a similar but worse problem. My 1990 S10 4.3L just quit running. Drove it home and next time I went to use it I would not run. It cranks, has spark (tested #1 with a spark tester light. I did get it running once after priming the carb with raw gas and cranking the heck out of it. But she only ran that once and it was ROUGH, like it was badly out of time.
I will try the info above you guys gave "a4x4spit" = disconnect the cited wire (if I can find it) and then try to set timing to ZERO with my Inductive Timing Light. My manual is useless. I'd never have guessed zero for the base timing. That is a new one for me.
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