Wandering Ignition Timing

OK update I think I fixed the problem. My carb is running so rich it was fouling the plugs. No matter where I put the idle mix screw the plugs came out black. I bought a new idle air mixture screw and it seems to run a lot leaner than before, a nice toasty brown. It starts fairly easy and idles fine after warmed up. its amazing what one tiny little screw can do.

Also I fixed the wandering timing issue with the new magnet from hotspark. Seems I had a couple of different issues playing against each other.

Thanks for all the suggestions, I know now that my coil is new and fine, all my ignition is the way its should be, my dizzy and alternator are working fine as they should be.

Well its back. I had everything timed and adjusted to a "T". I put 30 hours on it on our vacation. Half way through the trip I noticed I couldn't open it up without knocking and pinging and coughing at WOT. It cruised fine at 3500RPMs where I usually cruise anyway (big heavy boat does not plane well) I got home and threw a timing light on it and noticed it was 20 degrees off again. It was idling at 30 BTDC and advancing from there! I reset the timing again (have done this many times) and made sure it was advancing and it was, to 30+ BTDC at 3000 RPMs. So I know the advance is working. I've decided to keep a timing light in my tool bag for the boat at this point.

Question: I was researching how the dizzy actually is connected and powered off the counter shaft (more swedish engineering) but what keeps the counter shaft from slipping? Is it driven off the timing belt or the crankshaft? If it's driven off the T-belt I may have to dive in there and see if the pulley isn't slipping some how. If its gear driven off the crank shaft I doubt the counter shaft is slipping. Its got to be something else.

Hi, Pugetsounder.

Since only the ignition timing seems to be the problem, I would venture to say that the belt is not slipping; for if it did, the valve timing would also be off. So let's look at something else.

Look at this picture.

http://www.marinepartseurope.com/en/volvo-penta-explodedview-7742860-21-15890.aspx

What keeps the countershaft from slipping is pin part 24. That pin secures the wheel 26 to the countershaft 23. You may want to make sure that the pin is not missing or sheared. As you can see in this picture

http://www.marinepartseurope.com/en/volvo-penta-explodedview-7742860-21-15894.aspx

the crankshaft has sprocket 16 attached to it, so when the crankshaft turns, the sprocket 16 moves the timing belt and the timing belt moves the countershaft and camshaft wheels.

However, something else could be causing your problem. Make sure that bolt 13 is not bottomingh out and that the washer 14 is in place.

http://www.marinepartseurope.com/en/volvo-penta-explodedview-7742860-30-15916.aspx

Pugetsounder, Eduardo is correct.
Short of the timing belt slipping on the driven pulley...... in order to the counter-shaft to become "Out-of-Phase" with the crankshaft, sump'n ain't right.

On that note...... a counter-shaft that is "Out-of-Phase" may not affect the Camshaft phasing if the Camshaft and Crankshaft have remained OEM phased.
The fuel pump and and oil pump won't know the difference, unless someone told them.

However, the factory indexing of the distributor gear-to-counter-shaft (on this engine) does align much better when the OEM phasing is used.
The adjustment slot in the distributor housing is only so long, and it only allows for XY degrees of adjustment.

Question for you:

When you say that your BASE has ended up being @ 30*, and that you have to re-time or re-set the timing, what/how are you re-setting this?

• Are you able to move the distributor housing, and correct it? (as in the slot allows for this much correction).
• Are you needing to lift the distributor, and re-index it with the counter-shaft?
• If you installed a new timing belt, did you also install a new tensioner, and adjust the tension correctly?

.

Thanks El Pesc.

el_pescador said:

Hi, Pugetsounder.

Since only the ignition timing seems to be the problem, I would venture to say that the belt is not slipping; for if it did, the valve timing would also be off. So let's look at something else.

Look at this picture.

http://www.marinepartseurope.com/en/volvo-penta-explodedview-7742860-21-15890.aspx

What keeps the countershaft from slipping is pin part 24. That pin secures the wheel 26 to the countershaft 23. You may want to make sure that the pin is not missing or sheared. As you can see in this picture

Click to expand...

The belt is new and I have checked the timing marks on all three pulley wheels a couple of times and the belt and timing are spot on. If the pin is sheared the wheel itself would stay timed to the belt but wouldn't the counter shaft ( and dizzy) be able to move seperately form the wheel? Can I access and check the pin from outside the motor?

el_pescador said:

http://www.marinepartseurope.com/en/volvo-penta-explodedview-7742860-21-15894.aspx

the crankshaft has sprocket 16 attached to it, so when the crankshaft turns, the sprocket 16 moves the timing belt and the timing belt moves the countershaft and camshaft wheels.

Click to expand...

See above on belt timing.

el_pescador said:

However, something else could be causing your problem. Make sure that bolt 13 is not bottomingh out and that the washer 14 is in place.

http://www.marinepartseurope.com/en/volvo-penta-explodedview-7742860-30-15916.aspx

Click to expand...

The bolt is holding fine I have chnaged the timing and tested the dizzy it does not move. This is helping me understand how the whole thing works.

Thanks Ricardo.

RicardoMarine said:

Question for you:

When you say that your BASE has ended up being @ 30*, and that you have to re-time or re-set the timing, what/how are you re-setting this?

Click to expand...

Timing strobe set on number one cylinder. It seems to move back and forth; either advanced or retarded. Funny it only seems to change after a WOT run. Getting this pig up on plane is pretty close to WOT. At least I've narrowed that down. When ever I have reset the timing I take the boat out for a test run and it runs perfect. I got it up to 17 KPH which is flying for this boat. It runs smooth as butter. No knocking or pinging. Then after few hours of run time it changes.

RicardoMarine said:

Are you able to move the distributor housing, and correct it? (as in the slot allows for this much correction).

Click to expand...

Yes I have done this many times in the past year.

RicardoMarine said:

Are you needing to lift the distributor, and re-index it with the counter-shaft?

Click to expand...

I have had to on a couple of occasions. not all the time.

RicardoMarine said:

If you installed a new timing belt, did you also install a new tensioner, and adjust the tension correctly?

Click to expand...

I did intall all new but I will recheck the tension on the belt and retension the pulley. If anything just to eliminate those to concerns.

Other than this annoyance of the timing change everything else seems to be dialed in or new components. We really enjoy the boat and this problem doesn't keep us land locked but it would be nice to fix it. On a couple of occasions I have wanted to step up on plane to beat a current and all of a sudden I get the knocking and pinging and coughing and sputtering and I know the timing changed again. I know its not good for the engine. I'm sure its not good for the engine to even cruise lower RPMs being 10 or 20 degrees out of igition timing. What a PITA.

As stated before I have tried new ignitor parts, another dizzy that was in good shape out of a running boat. I have checked the timing belt on the marks. I am thinking it has something to do with the counter shaft possibly being loose from its pulley. At least I can eliminate that but at this point that's what it seems like.

PS.... if I may chime in again.
And just to be clear....... in no way am I as up to speed as Eduardo is on these little OHC engines.

pugetsounder said:

Thanks El Pesc.

The belt is new and I have checked the timing marks on all three pulley wheels a couple of times and the belt and timing are spot on.
If the pin is sheared the wheel itself would stay timed to the belt but wouldn't the counter shaft
Correct!

but wouldn't the counter shaft ( and dizzy) be able to move seperately form the wheel?
Not only the distributor, but the counter-shaft AND the distributor indexing will have changed relative to the crankshaft.

IOW, the relationship between the counter-shaft and distributor will have remained in tact... but the two will not remain in phase with the crankshaft if this key has sheared off as Eduardo is eluding to.

Can I access and check the pin from outside the motor?
The aluminum cover will need to be removed ..... but yes..... no major engine disassembly would be required.

Now... here's a question for Eduardo.
If this key has sheared off, and if the belt cog/pulley is no longer phased to the counter-shaft..... what's the liklihood of difficulty in getting this bolt to loosen from the actual counter-shaft????
IOW, will loosening this bolt simply want to spin the counter-shaft???
And if it does, what method is used to hold the counter-shaft while removing the bolt????
Or.... is this even an issue?



See above on belt timing.

The bolt is holding fine I have chnaged the timing and tested the dizzy it does not move. This is helping me understand how the whole thing works.

Click to expand...

Here's a view of the automotive engine and belt cogs/pulleys/wheels.



With the Marine version, the counter-shaft belt cogs/pulley/wheel is concealed from view.

I was posting as you were posting.

pugetsounder said:

Thanks Ricardo.


I did intall all new but I will recheck the tension on the belt and retension the pulley. If anything just to eliminate those to concerns.

Click to expand...

Again, I'd have to refer to Eduardo here.... but see if this makes sense.

The timing belt makes very good and solid connection with the crankshaft wheel and with the camshaft wheel..... almost a 180* +/- wrap, so to speak.
But take a look at the "wrap" on the counter-shaft wheel.
This appears to be less than a 45* wrap.

My thoughts are.... if the belt tension is rather weak, perhaps it's slipping right at the counter-shaft wheel, yet remaining phased correctly at the other two wheels.
Like said..... the fuel pump and oil pump won't know the difference... but the distributor's ignition timing certainly will.

Ricardo has got a point, but if the belt tensioning is incorrect I would expect it to slip in the smallest cog. That is, the one attached to the crankshaft. It won't hurt checking the belt tension to remove that possibility.

el_pescador said:

1. Ricardo has got a point,
   
   
2. but if the belt tensioning is incorrect I would expect it to slip in the smallest cog. That is, the one attached to the crankshaft.
   
   
3. It won't hurt checking the belt tension to remove that possibility.

Click to expand...

1. Eduardo... in grade school, my teacher told me that same thing ("Rick, you have a good point").
   But she went on to tell me that if I put my hat on, I'll cover it.
   
   
2. I'd normally agree on this....... but... look at the degree of belt contact with the crankshaft wheel.
   I don't know..... just a commnent.
   
   
3. Ditto.

OK I went out and ran the motor. I did notice some slop in the T belt. Not alot but there was slop I tightened it up so we will see. I can see Ricardo's point: All the slop and slap I saw and the direction of the belt I could see it possibly jumping teeth on the counter shaft since the slop happens just before that pulley wheel. We are headed out for the weekend so it will definitely get a test run. As far as checking the counter shaft alignment that will have to wait for next week till we get back on land.

So I think I fixed the problem. After tightening the T-belt the problem has dissappeared. yesterday I noticed a drip from the seawater pump so I pulled it off to reseal it. While I was in there I decided to check the belt timing on the counter shaft wheel and sure enough it had jumped a couple of teeth from when I originally installed the T-belt last year. Reset it, re-tightened the belt as tight as I could. I think the tensioner pulley needs a bit of help for this. All is good. Thanks for all the help and advice.

Duane

pugetsounder said:

So I think I fixed the problem. After tightening the T-belt the problem has dissappeared. yesterday I noticed a drip from the seawater pump so I pulled it off to reseal it. While I was in there I decided to check the belt timing on the counter shaft wheel and sure enough it had jumped a couple of teeth from when I originally installed the T-belt last year. Reset it, re-tightened the belt as tight as I could. I think the tensioner pulley needs a bit of help for this. All is good. Thanks for all the help and advice.

Duane

Click to expand...

Look. the belt isnt slipping and or jumping that problem, although the thread never completes, is distributor. Period. Anyone following this thinking it may help you find your own problem I feel sorry for the time you are about to waste!