# Timing problems with 99 S 10 4.3 liter



## ReconRooster (Sep 6, 2021)

Recently purchased a 99 Chevy S 10 Extreme, with a 2000 Chevy Blazer 4.3 replacing the original motor, that had been blown. Replaced timing chain with all marks lined up correctly. But still won't start, have tried everything, still can't get it dialed in close enough to start, do I need to replace the computer as well, since the truck is a 99 and the new motor a 00' ??? Any ideas to help? Thanks!!!


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## HotRodx10 (Aug 24, 2017)

Have you checked to be sure the distributor is aligned correctly with the cam? The rotor needs to be pointed at the contact for Cylinder #1 when the timing marks are aligned. If it's pointed the other direction, the crankshaft needs adjusted one full revolution.


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## ReconRooster (Sep 6, 2021)

Should that be with the timing chain on or off?


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## HotRodx10 (Aug 24, 2017)

ReconRooster said:


> Should that be with the timing chain on or off?


I'm not sure with that engine whether the crankshaft can be rotated independent of the timing gear (by removing a shear key or whatever locks the timing gear to the crankshaft). If it can, then you can rotate the crankshaft without turning the camshaft. That is what would be necessary to align the distributor with the camshaft, instead of being 180 degrees off. Have you determined that the distributor is off by 180 degrees?


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## Steve2444 (Sep 28, 2020)

HotRodx10 said:


> I'm not sure with that engine whether the crankshaft can be rotated independent of the timing gear (by removing a shear key or whatever locks the timing gear to the crankshaft). If it can, then you can rotate the crankshaft without turning the camshaft. That is what would be necessary to align the distributor with the camshaft, instead of being 180 degrees off. Have you determined that the distributor is off by 180 degrees?


Once rebuilt a 350 chevy, camshaft heads timing chain etc, had the same problem. Turned out to be the Distributor was off by 180deg. Very easy to make that mistake.


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## Bondo (Dec 8, 2007)

ReconRooster said:


> Should that be with the timing chain on or off?


Ayuh,..... The timin' chain, 'n marks, time the cam to the crankshaft,.....

You still need to time the distributor to the cam,.....


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## Fix'n it (Mar 12, 2012)

those engines have the crab cap. if you don't know what your doing its easy to stab the distributor incorrectly. start there. 

here is my 97 S-10 4.3. 15+ psi, ford powerstroke intercooler, tons more


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## BigJim (Sep 2, 2008)

Fix'n it said:


> those engines have the crab cap. if you don't know what your doing its easy to stab the distributor incorrectly. start there.
> 
> here is my 97 S-10 4.3. 15+ psi, ford powerstroke intercooler, tons more
> 
> View attachment 664008


That is one mean looking engine, love it.


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## Fix'n it (Mar 12, 2012)




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## Nealtw (Jun 22, 2017)

HotRodx10 said:


> Have you checked to be sure the distributor is aligned correctly with the cam? The rotor needs to be pointed at the contact for Cylinder #1 when the timing marks are aligned. If it's pointed the other direction, the crankshaft needs adjusted one full revolution.


Now, who told you that? if it is on the wrong stroke the distributor is out 180.


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## HotRodx10 (Aug 24, 2017)

Nealtw said:


> Now, who told you that? if it is on the wrong stroke the distributor is out 180.


The crankshaft rotates twice for each revolution of the cam and distributor. If the distributor is out 180 degrees, without moving the camshaft, either the crankshaft has to be rotated 360 degrees (which will rotate the distributor 180) or the distributor has to be removed, turned and reinstalled. In my experience, it's easier to turn the crank, even if the timing chain has to be removed. If the oil pump runs off off the distributor shaft, which it does on many engines, it can be difficult to get it to seat properly, and may require finding a way to turn the oil pump shaft 180 degrees (some have a flat side on the shaft). Since the splines are angled, it can also take quite a bit of trial and error to get the distributor to seat in the proper position, since you have to insert it at about 30 degrees off of where it will be when it's seated.

Btw, nobody "told" me that; I know it from studying how ICEs work and from considerable experience repairing and rebuilding engines.


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## Nealtw (Jun 22, 2017)

HotRodx10 said:


> The crankshaft rotates twice for each revolution of the cam and distributor. If the distributor is out 180 degrees, without moving the camshaft, either the crankshaft has to be rotated 360 degrees (which will rotate the distributor 180) or the distributor has to be removed, turned and reinstalled. In my experience, it's easier to turn the crank, even if the timing chain has to be removed. If the oil pump runs off off the distributor shaft, which it does on many engines, it can be difficult to get it to seat properly, and may require finding a way to turn the oil pump shaft 180 degrees (some have a flat side on the shaft). Since the splines are angled, it can also take quite a bit of trial and error to get the distributor to seat in the proper position, since you have to insert it at about 30 degrees off of where it will be when it's seated.
> 
> Btw, nobody "told" me that; I know it from studying how ICEs work and from considerable experience repairing and rebuilding engines.


How many times have you pulled and changed the cam when it was on the wrong stroke?


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## HotRodx10 (Aug 24, 2017)

Nealtw said:


> How many times have you pulled and changed the cam when it was on the wrong stroke?


Never. I rotated the cam until the timing mark was aligned correctly, rotated the crank until the distributor and the crank timing mark were also aligned correctly, removed the crank timing gear, and then installed the timing chain and crank gear.


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## Nealtw (Jun 22, 2017)

HotRodx10 said:


> Never. I rotated the cam until the timing mark was aligned correctly, rotated the crank until the distributor and the crank timing mark were also aligned correctly, removed the crank timing gear, and then installed the timing chain and crank gear.


How about when you have rebuilt the engine?


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## HotRodx10 (Aug 24, 2017)

Nealtw said:


> How about when you have rebuilt the engine?


Same thing.


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## Nealtw (Jun 22, 2017)

HotRodx10 said:


> Same thing.


On occasion I have helped a newbe who set the timing on the wrong stroke the worst you have to do is rotate the plug wires 180 if you can't rotate the distributor.


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## HotRodx10 (Aug 24, 2017)

The cam sprocket only fits on the camshaft in one position. The cam only rotates once per revolution (4 strokes of the pistons - intake, compression, power, exhaust). The distributor also only rotates once per revolution. The crankshaft rotates twice per revolution. The distributor has to fire the spark plug at the end of the compression stroke to begin the power stroke. If the distributor is 180 degrees out, it fires the spark plug at the end of the exhaust stroke, and nothing happens. 

Put another way, the crankshaft timing marks align twice per revolution, but the camshaft timing marks and the distributor only align with TDC of the compression stroke for Cylinder #1 once per revolution.


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## Nealtw (Jun 22, 2017)

HotRodx10 said:


> The cam sprocket only fits on the camshaft in one position. The cam only rotates once per revolution (4 strokes of the pistons - intake, compression, power, exhaust). The distributor also only rotates once per revolution. The crankshaft rotates twice per revolution. The distributor has to fire the spark plug at the end of the compression stroke to begin the power stroke. If the distributor is 180 degrees out, it fires the spark plug at the end of the exhaust stroke, and nothing happens.
> 
> Put another way, the crankshaft timing marks align twice per revolution, but the camshaft timing marks and the distributor only align with TDC of the compression stroke for Cylinder #1 once per revolution.


Now you want to teach me how engines work. Good luck with that. #1 cylinder is at top dead center and you can save a whole bunch of typing. 
Given the mistake can be made I know no one that pull an engine out a VW bug or bus for that.


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## HotRodx10 (Aug 24, 2017)

Nealtw said:


> On occasion I have helped a newbe who set the timing on the wrong stroke the worst you have to do is rotate the plug wires 180 if you can't rotate the distributor.


Well sure, if you want to do a hack job, it might work, but then again, it might not. On older vehicles that worked fine (other than making life difficult for the next person who had to work on it, but that confuse the computer in at least most, if not all, newer fuel injected vehicles with electronic ignition.


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## Nealtw (Jun 22, 2017)

ReconRooster said:


> Recently purchased a 99 Chevy S 10 Extreme, with a 2000 Chevy Blazer 4.3 replacing the original motor, that had been blown. Replaced timing chain with all marks lined up correctly. But still won't start, have tried everything, still can't get it dialed in close enough to start, do I need to replace the computer as well, since the truck is a 99 and the new motor a 00' ??? Any ideas to help? Thanks!!!


Are you getting any spark, back fire anything? 
Did you find top dead center on #1 before setting the chain?


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## Nealtw (Jun 22, 2017)

HotRodx10 said:


> Well sure, if you want to do a hack job, it might work, but then again, it might not. On older vehicles that worked fine (other than making life difficult for the next person who had to work on it, but that confuse the computer in at least most, if not all, newer fuel injected vehicles with electronic ignition.


Enough already.


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## HotRodx10 (Aug 24, 2017)

Nealtw said:


> Now you want to teach me how engines work. Good luck with that. #1 cylinder is at top dead center and you can save a whole bunch of typing.
> Given the mistake can be made I know no one that pull an engine out a VW bug or bus for that.


Well, you seemed to be confused about the operation of a 4 stroke engine.

Who said anything about pulling the engine? If the timing cover is already on, you find TDC of the compression stroke for cylinder #1 by sticking your finger over the spark plug hole while someone manually turns the engine. When the pressure blows your finger off, you're about there. Line up the the timing mark on the crank pulley with the 0 degree mark on the metal tab, try different positions of the distributor until it's pointed at the contact for Cylinder #1, bolt it down, put the cap on, put the spark plug in, make sure the wires are on in the right order, and see if it works.

Btw, what does a VW bug have to do with this? He's working on a Chevy S-10.


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## HotRodx10 (Aug 24, 2017)

Nealtw said:


> Enough already.


More than enough. You were the one asking the questions and making ridiculous suggestions.


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## Fix'n it (Mar 12, 2012)

4.3 high performance time chain.


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## BigJim (Sep 2, 2008)

The way I installed a distributor was bring number one up on compression stroke, the rotor cap will point to number one in the distributor cap. Hold down on distributor cap and turn the engine over, the oil drive will drop into place. lock distributor down and set timing.


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## raylo32 (Nov 25, 2006)

Are you sure you aren't maybe overlooking some other issue? Did you check to make sure you have adequate fuel pressure?


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## Old Thomas (Nov 28, 2019)

Has it run since the engine went in?


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## Brainbucket (Mar 30, 2015)

On the 4.3 distributor, there are 2 timing marks in the base. There is a 6 point for the 6 cylinder and a 8 point for the V8. Put engine on compression TDC, then drop the distributor with the rotor pointing to the #6 point. The timing gear dots is the crank is pointing straight up and the cam gear is pointing straight down, lining them selves dot to dot.


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