Weird Starting Issue After Putting It Back Together

[mrburitto]

Hey everyone,

I just put my K20 back together with a new intake manifold and carb and its not starting. Just bought a new battery so its not that. It is cranking for a second but then stutters like theres some kind of resistance and then repeats. I have fuel flow I can see it in the filter but I don't think that would cause this either.

Also I thought I smelt some kind of plastic or rubber burning for a second.

 

[legopnuematic]

Got spark? timing? firing order?

 

[mrburitto]

ya theres spark and the firing order is right. the timing should be ok because I put the distributor back in the same position. but im not sure how to check it if its not running

 

[mrburitto]

I did have it at tdc before i pulled of the distributor though and put it back in the same position. thought that would avoid a timing issue

 

[legopnuematic]

What I did on my 79's engine to get it roughly timed before I started it is to set the engine at 10 degrees btdc on compression on the harmonic balancer and then stab the distributor in facing number 1, set the cap on and marked on the main body where the closest post was and lined it up with the rotor, clamped dizzy down. It seemed to work as it fired right up. On my 76 when I swapped the distributor I marked where the old one was in relation to the rotor position to main body and then to the engine itself and when I stabbed the new one in in what visually appeared to be the same spot, when I fired it up it was over 20 degrees btdc without vacuum advance and at idle.

 

[mrburitto]

Ok ive been adjusting timing and got it to run really rough once. Adjusted some more and now theres an awful grinding sound when i turn the ignition... what did I do?

Also when i was checking for tdc it seemed like the marks on my balancer were off. I had a little wood shaft down in the cylinder on the compression stroke and cranked it by hand until the moment the shaft started to go back in. When it was going back in the marks read about 15 degrees advanced. Was my method for checking tdc flawed or are the marks on my balancer off?

I also triple checked my wires and made sure the firing order is right. I didnt remove any wires from the distributor and just marked which was plugged into the #1 cylinder then put it back how it was.

 

[Charlie]

Could possibly have stretched timing chain causing issue. I had timing issue last November due to stretched chain. Installed chain kit, issue solved.

 

[chengny]

Ok ive been adjusting timing and got it to run really rough once. Adjusted some more and now theres an awful grinding sound when i turn the ignition... what did I do?

Also when i was checking for tdc it seemed like the marks on my balancer were off. I had a little wood shaft down in the cylinder on the compression stroke and cranked it by hand until the moment the shaft started to go back in. When it was going back in the marks read about 15 degrees advanced. Was my method for checking tdc flawed or are the marks on my balancer off?

I also triple checked my wires and made sure the firing order is right. I didnt remove any wires from the distributor and just marked which was plugged into the #1 cylinder then put it back how it was.

Unless you know the engine's history, ignore the relationship between the timing tab and the mark on the balancer hub. The method you used to put the #1 piston at TDC is the best when working with an engine that may have been modified. If either the timing cover or balancer have been replaced with a part from the wrong model year...the timing marks (and the use of a timing light) become worthless.

When your stick method shows the piston to be at TDC, pop the distributor cap and confirm that the rotor is pointing at the #1 plug wire post. It helps if you make a mark on the distributor base - that accurately lines up with the #1 post - before you pop the cap.

 

[K201979]

Smelled plastic burning and starter sounding funny, maybe a short or burnt fusible link, hot wire, ect. Stealing power from starter and ignition?

 

[mrburitto]

Smelled plastic burning and starter sounding funny, maybe a short or burnt fusible link, hot wire, ect. Stealing power from starter and ignition?

Only think i can think of is the electric choke on my new carb. plugged it into the IGN fuse port.

 

[mrburitto]

I retarded the timing as far as it would go (vacuum advance hits tranny vac line) and the grinding went away thank god. I didn't know being too far advanced could make a grinding noise? Gonna pull off the distributor cap tomorrow and verify its pointing at #1 at TDC. I don't know how that could have gotten fd up though. I didnt take off the cap or do anything to it but remove the whole thing to change the intake manifold and then put it back just how it was.

 

[chengny]

I retarded the timing as far as it would go (vacuum advance hits tranny vac line) and the grinding went away thank god. I didn't know being too far advanced could make a grinding noise? Gonna pull off the distributor cap tomorrow and verify its pointing at #1 at TDC. I don't know how that could have gotten fd up though. I didnt take off the cap or do anything to it but remove the whole thing to change the intake manifold and then put it back just how it was.

I don't know how that could have gotten fd up though. I didnt take off the cap or do anything to it but remove the whole thing to change the intake manifold and then put it back just how it was.

When you dropped it back down - despite your best efforts to position it exactly as it was before you pulled it - the gear teeth may have engaged one tooth off.

As the distributor is lifted out of the manifold, the shaft is also rotating in the reverse direction. This is due to the helical cut of the cam/distributor drive gears. When the gears are fully disengaged, the rotor will have been indexed about 30 degrees CCW from it's original position. In a perfect world, if you didn't disturb the distributor shaft/gear and also stabbed it in exactly the same position, the gear teeth should align just as they were previously. And then as the distributor drops in - and the gear teeth fully engage - the rotor should rotate CW back to where it was when you pulled it.

But as the saying goes; "Sh*t happens". It is easy - and common - to stab a distributor and have the gear teeth mesh one tooth over in either direction. If it is one tooth off in the advanced direction, the symptoms are much like you describe. Expect erratic starter operation due to kickback and a short attempt by the engine to fire. If you can get better results (like the engine runs, but poorly) by rotating the distributor to the far end of it's adjustable range - usually limited by the vacuum advance can hitting something - that would generally indicate you are a tooth off.

 

[mrburitto]

I don't know how that could have gotten fd up though. I didnt take off the cap or do anything to it but remove the whole thing to change the intake manifold and then put it back just how it was.

When you dropped it back down - despite your best efforts to position it exactly as it was before you pulled it - the gear teeth may have engaged one tooth off.

As the distributor is lifted out of the manifold, the shaft is also rotating in the reverse direction. This is due to the helical cut of the cam/distributor drive gears. When the gears are fully disengaged, the rotor will have been indexed about 30 degrees CCW from it's original position. In a perfect world, if you didn't disturb the distributor shaft/gear and also stabbed it in exactly the same position, the gear teeth should align just as they were previously. And then as the distributor drops in - and the gear teeth fully engage - the rotor should rotate CW back to where it was when you pulled it.

But as the saying goes; "Sh*t happens". It is easy - and common - to stab a distributor and have the gear teeth mesh one tooth over in either direction. If it is one tooth off in the advanced direction, the symptoms are much like you describe. Expect erratic starter operation due to kickback and a short attempt by the engine to fire. If you can get better results (like the engine runs, but poorly) by rotating the distributor to the far end of it's adjustable range - usually limited by the vacuum advance can hitting something - that would generally indicate you are a tooth off.

Ok that makes sense. Thanks for the explanation. Helps a lot to understand what happened when your trying to fix something.

 

[mrburitto]

Just to clarify, I will be finding tdc with my stick again, and then I will take the dist cap off and probably find the rotor not pointing at #1 and I will need to turn it so that it does?

 

[chengny]

Just to clarify, I will be finding tdc with my stick again, and then I will take the dist cap off and probably find the rotor not pointing at #1 and I will need to turn it so that it does?

If by "turn it", you mean the distributor - then no, that is not going to help. You have already tried that and even rotating the distributor as far as possible - till it hits something - you were unable to bring the timing into proper range. Put the distributor back in its normally indexed position (roughly as shown below) and then pop the cap.

If you do find the rotor to be way off the #1 post (one tooth off shifts the rotor about 30 degrees = about halfway to the next post) then the distributor should be pulled and re-stabbed.

This time before you drop it in, manually index the rotor CCW about that 30 degrees because it will shift CW the same amount as the gears fully mesh. And don't forget to get the slot in the oil pump drive shaft lined up with where the tang on the end of the distributor shaft will finally end up. Use a long screwdriver to position the slot to where it needs to be.

The image below shows how being one tooth off effects rotor position. But, in your case it sounds like the gears did engage one tooth off - but the other way and so the timing is overly advanced:

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I had always been curious about the old “one tooth off” theory. Specifically; how many degrees will the timing actually move if the distributor is stabbed one tooth out of it’s proper mesh point with the cam.

Here is what I found:

There are 13 teeth on the distributor drive gear.

So if the distributor is stabbed one tooth out of position, the timing of the spark will be advanced (or retarded as the case may be) about 28 degrees in relation to it’s associated post.

There are 8 posts in the distributor cap spaced evenly around the 360 degree arc.

That works out to 45 degrees of separation between one post to the next.

For the sake of argument, let’s say that being one tooth off in the retarded (CW) direction will cause the rotor to be about halfway between the #1 and the #8 post when it fires the #1 plug.

If you get frustrated trying to get it stabbed correctly, read this:

http://www.junkyardgenius.com/ignition/dist01.html