SC Timing Issue

chrisorbics

Registered User
My 1991 sc will only start with the cam sensor unplugged. It usually starts on the second crank. I had two used ones then I got a new one and still the same issue.

With it plugged in the engine turns and then bangs as it stops. So bad that I thought the engine had internal issues until I unplugged the cam sensor.

I just installed a bhj harmonic balancer and a different timing cover due to a broken stock balancer and seized water pump stud.

The balancer is timed at 28 degrees after tdc. I did this by cutting a 1.3 inch long piece of masking tape as the instructions show. So 1.3 inches from tdc towards the drivers side.

Then I installed the synchronizer with the alignment tool pointed towards the front passenger side corner. It matched the picture I have from Mitchells manual.

Now I am at a loss. I have a spare DIS module and I installed that at my friends place. It ran ok but rough idle and then it stalled 20-25 minutes later and I pushed it to the side of the road. It finally restarted after five minutes.

I am assuming the tach runs off of the cam sensor because it does not work when the car is running. It move sometimes which cranking.

I am not sure where to go next.
 
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You ran the 1.3" tape clockwise looking at the engine from the front of the engine bay on the balancer and lined it up to that mark? That's what it sounds like when you mention you ran the tape to the drivers side from TDC mark, which would be clockwise. 26 degrees ATDC, is the other way you should run the tape counter clockwise on the balancer to get After TDC, anything clockwise of the balancer is before TDC. My SFI BHJ actually has a timing mark right at 26 ATDC for this purpose. If you set the timing accidentally to 26 degress BTDC that would probably explain your issue.
 
Really? My manual says otherwise.
In addition, when my tach failed, replacing the DIS module fixed the issue
 

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You ran the 1.3" tape clockwise looking at the engine from the front of the engine bay on the balancer and lined it up to that mark? That's what it sounds like when you mention you ran the tape to the drivers side from TDC mark, which would be clockwise. 26 degrees ATDC, is the other way you should run the tape counter clockwise on the balancer to get After TDC, anything clockwise of the balancer is before TDC. My SFI BHJ actually has a timing mark right at 26 ATDC for this purpose. If you set the timing accidentally to 26 degress BTDC that would probably explain your issue.

Ok that makes sense. So the mark with the line all the way across the balancer is cylinder 1 TDC(I hope it is because I pulled the plugs and I seemed like it to me)?

So looking at the car standing in front of the engine I should set it 1.3 inches to the left of the tdc mark(or counter clockwise)?
 
Maybe I need a new DIS too. The cheapest I saw so far was rock auto for 150 something. Is that good?

I will most likely get the car timed right before I spend the money on the DIS.
 
This diagram may help to understand how the coil and the tach work together. The manual has also a good description regarding the required input of the tach for the WMV to work correctly, including a test sequence.

The manual does not have any indication regarding the 1.30" tape to find the 26 degree ATC. I assume you got the info from the following
http://www.tccoa.com/articles/mn12how-to/BHJ/BHJ-install.html

This link may help to understand a little more about the cam setting. Watch the second video too !
http://www.youtube.com/watch?v=AmYehbDwuHw

http://www.youtube.com/watch?v=hf1IVbxDchw
 

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Ok that makes sense. So the mark with the line all the way across the balancer is cylinder 1 TDC(I hope it is because I pulled the plugs and I seemed like it to me)?

So looking at the car standing in front of the engine I should set it 1.3 inches to the left of the tdc mark(or counter clockwise)?

yeah tdc should be makes by the groove that goes all the way across the bhj balancer. Now it seems the older bhj balancers did not have the 26 atdc marked but on mine it counts 10 degrees atdc then stops and there is a lone mark at 26 atdc. Short answer is yes you should be aligning to the left of the tdc mark that goes across the balancer by 26 degrees or off the measurement method 1.3" left/counter clockwise from tdc.
 
I'd pull the #1 plug, make sure its at TDC, then set the Cam Sensor Stalk correctly...there are several threads with pictures showing exactly how it should be set. once thats done you should fire.

The balancer will be at correct either way so I wouldn't get to excited about that. As for the DIS, keep in mind it can be tested for free at any chain parts store ie Auto Zone, Advance, Napa etc....whatever you have in the area.

If the car will fire (and run correctly) with the Cam Sensor unplugged I would think that's your culprit. Keep in mind the car will fire without it hooked up usually within 3 tries.

Also for what its worth the tach will act up when a cam sensor is on the way out, or unplugged - my '89 did this when I had a cam sensor going bad...so regardless of what any books or manuals say I can vouch that a cam sensor can cause it to die as well.


-Tim
 
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Tim is right. Most likely you have the crankshaft off 180 deg. You have to make sure it is on the compression stroke when aligning the sensor. Remember, two rotations crankshaft = one rotation camshaft.

Also, regardless of what the diagrams seem to indicate, the tach is fed off the cam sensor. Unplug the cam sensor - no tach. Anytime you have a complete loss of tach then the cam sensor is the #1 cause. Since the coils are a passive device, a completely bad coil will not fire the engine at all. A partially bad coil will take out 2 cylinders at a time which would be pretty obvious to a casual observer. A bad DIS can generate just about all of these faults as well as it can cause the tach to read at 2/3 and 1/3 normal rpms as well. The DIS is by by far the most difficult to diagnose as it's failure modes are a long list which I will not get into. Best bet is if you doubt your DIS, have it tested.
 
I'd pull the #1 plug, make sure its at TDC, then set the Cam Sensor Stalk correctly...there are several threads with pictures showing exactly how it should be set. once thats done you should fire.

The balancer will be at correct either way so I wouldn't get to excited about that. As for the DIS, keep in mind it can be tested for free at any chain parts store ie Auto Zone, Advance, Napa etc....whatever you have in the area.

If the car will fire (and run correctly) with the Cam Sensor unplugged I would think that's your culprit. Keep in mind the car will fire without it hooked up usually within 3 tries.

Also for what its worth the tach will act up when a cam sensor is on the way out, or unplugged - my '89 did this when I had a cam sensor going bad...so regardless of what any books or manuals say I can vouch that a cam sensor can cause it to die as well.


-Tim


Ok you are saying to set the balancer to tdc but it thought it was supposed to be set to 26 degrees after tdc? Also the cam sensor is new. Thanks.
 
Ok you are saying to set the balancer to tdc but it thought it was supposed to be set to 26 degrees after tdc? Also the cam sensor is new. Thanks.

I'll try to make this very simple terms; Afterall I am a very simple guy myself.

1. Install the balancer - it only goes on 1 way because of the key way...done deal, move to the next step...you're overthinking it.

2. Remove spark plug on #1 Cylinder - Front Passenger side plug. put the tip of a screw driver in the spark plg hole...turn the engine over with a wrench on the crank to get #1 at TDC (the peak of the upwards stroke). You'll be able to get a feel of when its at its peak with the screw driver tip in the cylinder.

3. Position the cam stalk in the same position as this picture: http://www.sccoa.com/forums/showthread.php?133363-cam-sensor-and-timing&p=1065686#post1065686 - The half moon aligned as shown.

4. Bolt everything up - reinstall the plug etc.

5. The engine will be set at the correct timing...no need to screw with the balancer markings, taping stuff etc.

Hope that was simple enough...the books honestly make it more complex than it truly is.

-Tim
 
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