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Timing issue


Pete T
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Hi All,

I'm new to canal world. Been reading some of the problems and great to see how so many jump in and help out!!

 

Can you out there help me?

 

I have  a BMC 1.5 DIESEL

the timing dimples on the 2 Cogs is exactly 180 Deg out. No 4 valve is set rocking and it should be No 1 valve i think.

Exhaust is pushing through the inlet take.

What is my solution.

Any help gratefully recieved.

 

Pete

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One normally times on number 1 or the timing marks on the flywheel and on the BMC number 1 is the cylinder at the water pump end of the engine. With number 4 cylinder set to both rockers rocking number 1 will be at TDC compression (more or less).

 

I think the solution is to take the chain off and reposition the camshaft gear, then refit the chan. However, I have no idea how it would run like that so unless you have just rebuilt it how did it happen.

Edited by Tony Brooks
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5 minutes ago, Tony Brooks said:

However, I have no idea how it would run like that so unless you have just rebuilt it how did it happen.

 

This was puzzling me too. Some background to questions like this is always helpful in understanding the bigger picture. My own guess is that this engine is new to the poster, quite possibly acquired cheaply because it has been rebuilt but won't run. 

 

Had the op rebuilt it themselves, I'd have thought the answer you gave would have been obvious, that the chain had been put on with the sprockets in the wrong positions relative to each other. But then i haven't built up an engine from scratch for 50 years! 

 

 

 

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1 minute ago, MtB said:

 

This was puzzling me too. Some background to questions like this is always helpful in understanding the bigger picture. My own guess is that this engine is new to the poster, quite possibly acquired cheaply because it has been rebuilt but won't run. 

 

Had the op rebuilt it themselves, I'd have thought the answer you gave would have been obvious, that the chain had been put on with the sprockets in the wrong positions relative to each other. But then i haven't built up an engine from scratch for 50 years! 

 

 

 

 

Snap - the 50 year bit.

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PS. To take the timing chain off you need to collapse the tensioner (Alen key through the holes filled with a hexagon screw in the bottom of the "block" to set it to "fully in and hold"). Then both the gears need to be slid forward on their shafts until the can gear becomes free. Put the cam gear back but do not secure so you can turn the camshaft to position and then remove it so you can refit the chain and gears. When back on use the alan key to release the tensioner and recheck the dimples.

 

When you refit the timing cover screw the screws in loosely so that when you fit the pulley the cover can centralize itself or put the pulley into the cover before fitting. Put all the screws in before tightening any of them.

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The engine will not run with the cam 180 out from the crank as the injection will be on the wrong cylinder..........Unless........ the injection pump drive gear is also mistimed.  The pump is master splined so cannot be wrong if the gear has been put in correctly.

 

How did it get like this?

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1 hour ago, Tracy D'arth said:

The engine will not run with the cam 180 out from the crank as the injection will be on the wrong cylinder..........Unless........ the injection pump drive gear is also mistimed.  The pump is master splined so cannot be wrong if the gear has been put in correctly.

 

How did it get like this?

 

That raises another point. If it is a result of a muppet rebuild then after putting the valve timing right the OP may well have to pull the pump drive gear and reinsert that in the correct position. That involves removing the injector pump.

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2 hours ago, Tony Brooks said:

 

Snap - the 50 year bit.

 

I must be a younster then, I estimate it was onlt 35 years ago that I last built an engine, an air cooled 1.6 VW.  I somehow got the distributer 180 degrees out. It would not start but filled the brand new stainless exhaust full of unburned mixture. It eventually iginited (valve overlap?) and made the second biggest bang that I have ever heard. I was relieved and impressed that the exhaust stayed in one piece.

 

Filling a baloon full of oxygen and acetylene was the biggest bang.....the wisdom of youth!

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I went to see a muppet one time who had rebuilt a 6/354 Perkins with the fuel pump timing 180 out.......pouring white smoke,and the muppet was running it on ether spray............using the slotted holes for timing adjustment in the timing gears, I was able to get the pump back on the correct timing...and the motor went OK.......If the cam timing is 180 out ,the engine will not turn as valves will have hit pistons stopping rotation.....................what will be out is the skew gear drive for the pump.

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Hi All 

 

Great feedback many thanks.

 

The engine was running OK previously. It had an overheating problem. The heat exchanger pumped out water when the engine got hot. I guessed the head gasket. I changed the head gasket, restarted successfully after two attempts. I only had fresh water cooling so two more starts to prove ok i shutdown to start work on the boat. I then started my repaint program. Anti foul etc. When ready to put into the water I tried the engine to be sure before launching and she would not start. 2 months ago many looking at my problem no success. When i took the pulley cover plate off it was then I noticed the 180 difference. How on earth is this possible. 

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58 minutes ago, Pete T said:

Hi All 

 

Great feedback many thanks.

 

The engine was running OK previously. It had an overheating problem. The heat exchanger pumped out water when the engine got hot. I guessed the head gasket. I changed the head gasket, restarted successfully after two attempts. I only had fresh water cooling so two more starts to prove ok i shutdown to start work on the boat. I then started my repaint program. Anti foul etc. When ready to put into the water I tried the engine to be sure before launching and she would not start. 2 months ago many looking at my problem no success. When i took the pulley cover plate off it was then I noticed the 180 difference. How on earth is this possible. 

 

Have you checked the diagrams in the manual to be sure you know where the dimples should be?

 

So it was left unrunning for a period. Have you checked the valve clearances. Carbon can fall off valve stems and get stuck in the seat. This can give low compression and chuffing through the exhaust. We often suffered this at the spring start up on the ire boats, especially on the engines with the most running hours.

 

My solution was to disconnect the alternator and start at 24 volts but never held the system at 24 volts for very long. I can not recommend that you try this though because it is brutal and bad practice.

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Just a thought, and please disregard if I'm talking complete rubbish, but as the camshaft rotates at half crank speed the dimple on the camshaft gear will be 180 degrees away from the crank gear dimple every second rev of the crank. Is this what is causing the confusion? A photo of the gears would probably clear up the relationship of the two shafts.

  • Greenie 1
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8 hours ago, Tracy D'arth said:

The engine will not run with the cam 180 out from the crank as the injection will be on the wrong cylinder..........Unless........ the injection pump drive gear is also mistimed.  The pump is master splined so cannot be wrong if the gear has been put in correctly.

 

How did it get like this?

 

Sorry, but the cam 180 degrees in error would make do difference. One rotation of the crank would make it right again.

 

I'm wondering if the OP means the crank is 180 degrees out, so 90 degrees at the camshaft? That would never run. In fact I would wager valves would have crashed into pistons.

 

 

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47 minutes ago, Mikexx said:

 

Sorry, but the cam 180 degrees in error would make do difference. One rotation of the crank would make it right again.

 

I'm wondering if the OP means the crank is 180 degrees out, so 90 degrees at the camshaft? That would never run. In fact I would wager valves would have crashed into pistons.

 

 

He says with valves on 4 rocking, when 1 will be at TDC, the marks are out by one crank rev so firing will not be on 1 but 4.

It makes no sense if the motor has run like this, ever.

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14 minutes ago, Tracy D'arth said:

He says with valves on 4 rocking, when 1 will be at TDC, the marks are out by one crank rev so firing will not be on 1 but 4.

It makes no sense if the motor has run like this, ever.

 

 I missed that bit. That confirms that all is well. All the OP needs to do is rotate the crankshaft one whole revolution and hey presto, the marks will line up, and both no 4 and no 1 will be at TDC and the camshaft will be 0 degrees out.

 

What am I missing here?

 

How does he know which is the firing stroke from an injection POV? I suppose if he slackens the HP injection unions he might be able to film the valves and "pumps" together on cranking. Then examine the video frame by frame?

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It depends which piston the OP has designated as No. one. One of my many learning experiences was timing a Renault engine in a Volvo 340.  After much head scratching a much wizer colleague pointed out that on this engine No one piston was at the flywheel end.🙄I

.

Edited by Ken X
Incompetence
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23 minutes ago, Tracy D'arth said:

He says with valves on 4 rocking, when 1 will be at TDC, the marks are out by one crank rev so firing will not be on 1 but 4.

It makes no sense if the motor has run like this, ever.

 

Do you agree that valves on 4 will be rocking when the crank is TDC for both 1 and 4?

 

Simply rotating the crank 1 whole revolution will now make valves on no 1 rock.

 

It also depends on your definition of "rocking". A firing cylinder will have both valves at clearance. On the alternative stroke the swap from exhaust to inlet often overlap such they are tight. My definition of "rocking" is where you can see the change-over from exhaust to inlet. The OP might have a different definition, where the tappets have clearance on the firing cylinder.

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I explained much of what the last few posts are saying in my replay - post 2.

 

It will be far simpler to just rotate the camshaft half a turn once the crank is rotated 1/4 turn so the pistons are away from TDC, and then the crank put back to TDC no1 firing.

 

Not Tracy's post, I agree with that. Our posts crossed.

Edited by Tony Brooks
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6 hours ago, Ken X said:

Just a thought, and please disregard if I'm talking complete rubbish, but as the camshaft rotates at half crank speed the dimple on the camshaft gear will be 180 degrees away from the crank gear dimple every second rev of the crank. Is this what is causing the confusion? A photo of the gears would probably clear up the relationship of the two shafts.

 

That is precisely my presumption. Confusion clouds any problem here. The definition of valves "rocking" is another ambiguity; all the more likely from a novice.

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6 minutes ago, Mikexx said:

 

That is precisely my presumption. Confusion clouds any problem here. The definition of valves "rocking" is another ambiguity; all the more likely from a novice.

 

I think you've put your finger on the problem given the OP says the engine used to run like this. 

 

To me, valves rocking means they are compressing the valve spring and opening the valve. I bet the OP means the rockers are feeing loose and free to rock on the valve clearances. If this is right then there is probably nothing wrong structurally with the engine and it won't start for some other, unrelated reason(s). 

 

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5 minutes ago, Pete T said:

I'll send photos tomorrow. 

Yes rocking i am meaning the tappets are free and rocking.

Just a term we us.

 

 

Mystery solved!

 

So onwards and upwards, it won't start. My money is on the fuel system needing bleeding. Or low compression. Have you checked the compression having replaced the head gasket? But still more likely to be a fuel bleeding or contamination problem.

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12 minutes ago, Pete T said:

I'll send photos tomorrow. 

Yes rocking i am meaning the tappets are free and rocking.

Just a term we us.

 

Valves on the rock is when the inlet and the exhaust are both moving but in the opposite  direction. Both will have no clearance then of course.

 

So there is nothing wrong with the timing!

 

Phew, glad to get that out of the way.  Now if it has fuel, air and compression, spinning it over at a fair wack it will run. Is the stop control fully off?  Is there fuel at the injector? Well charged battery?

Edited by Tracy D'arth
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23 minutes ago, Pete T said:

I'll send photos tomorrow. 

Yes rocking i am meaning the tappets are free and rocking.

Just a term we us.

 

It's not a term anyone else would generally use in the circumstances you now describe. Rocking valves occur when the exhaust valve is closing and the inlet opening. There will generally be some overlap, such the valves will be slightly depressed.

 

Can we rotate the crankshaft one turn, so the camshaft is on the money? There is a direct 2:1 relationship between the sprockets.

 

If everything else is working, it is either fuel, or perhaps poor compression. It might be worth looking at the procedure to prime the fuel system.

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